Category Archives: Industrial Supply

High Voltage Capacitors – Global Market Outlook (2017-2023)

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According to Stratistics MRC, the Global High Voltage Capacitors market is estimated at $154.56 million in 2016 and is expected to reach $296.56 million by 2023 growing at a CAGR of 9.7% from 2016 to 2023.

 

Some of the factors responsible for the market growth include rising demand for electricity, new technological up gradations from the power market and increasing electricity demand in developing economies. In addition, rising demand from the diverse application industries are generating several exciting opportunities for high voltage capacitors in the market. However, high cost of raw materials is the key factor restraining the market growth.

 

Amongst Application, capacitive voltage divider segment is anticipated to be the most attractive product due to its application in high voltage, extra high voltage and ultra-high voltage transmission which are anticipated to boost in near future. Asia Pacific is anticipated to register sustainable growth during the forecast period owing to rising electric demand in developing economies such as India and China which are expected to enhance their grid infrastructure to increase the electricity accessibility to the region’s population.

 

Some of the key players in the market include ABB, Walsin Technology, Vishay Intertechnology, Transgrid Solutions, Taiyo Yuden, Yuhchang Electric, Sieyuan Electric, Siemens, Samwha Capacitor, Samsung Electro-Mechanics, RTDS Technologies, Murata Manufacturing, Maxwell Technologies, General Atomics, Epcos, Eaton and Alstom.

 

Applications Covered:

  • Power Generation
    • Grading Capacitors-GIS
    • P D Sensors
    • TRV Capacitors-GIS
    • Grading Capacitors-AIS
    • TRV Capacitors-AIS

 

  • Testing
    • Reference Capacitors
    • R C Dividers

 

  • Transmission
    • TRV Capacitors-GIS
    • TRV Capacitors-AIS
    • Thyristor Valve Capacitor
    • Grading Capacitors-GIS
    • Grading Capacitors-AIS
    • Filter Capacitor
    • Coupling Capacitors
    • Capacitive Voltage Dividers
    • Capacitive Dividers for EVT

 

  • Distribution
    • Coupling Capacitors
    • Capacitor for Lightning Overvoltage Monitoring
    • Capacitive Voltage Dividers
    • Capacitive Dividers for EVT

 

Access the complete report at:

http://www.strategymrc.com/report/high-voltage-capacitors-market

 

 

Article Source: https://www.reuters.com/brandfeatures/venture-capital/article?id=12502

Methods for Adhesion Bonding of Polyphenylene Sulfide

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Polyphenylene Sulfide (PPS) is a high-temperature, semi-crystalline engineering thermoplastic. Within the industry, PPS is known as THE plastic that performs like metal. Arguably, it’s one of the most challenging polymers to bond to itself or dissimilar materials, such as aluminum and titanium. To be successful at bonding PPS requires an understanding of its chemical and physical properties, thus making resin grade moduli different and critical for each application. This paper presents field proven case study techniques to achieve high-strength adhesion bonding.

 

Properties of PPS

The properties of PPS, similar to other high-temperature performance plastics including PEEK and LCP, depend on its crystallization behavior. PPS is chemically inert with low surface energy and offers the broadest resistance to corrosives of any advanced engineering plastic. It is used in thousands of automotive, aerospace, medical and industrial applications where high-temperature, solvent-proof, electrically-shielded parts are needed. PPS is inherently flame retardant, making it the perfect material for aircraft structures, under-hood power train and fuel system components, water pump impellers and more. While these characteristics are ideal for performance, poor surface wettability is the bonding challenge for manufacturers.

 

Two distinct forms of PPS are sold: “Branched” molecular structure and “Linear”. Among the most recognizable brands are Ticona Fortron® and Chevron Phillips Ryton®. The branched version tends to be more rigid. The linear usually offers better mechanical and flexural strength, as well as higher melts stability. Linear PPS also has fewer ionic impurities1. Glass-filled fibers (30 percent and 40 percent) and glass fiber/mineral mixtures to standard PPS allow for specialized and demanding applications. Electronics manufacturers commonly select 40 percent glass-filled PPS for insulation and connector products. Designers carefully examine the selection of branched or linear, filled or un-filled, relative to field performance properties, joint-tool design and primary processing. Unfortunately, less emphasis normally is given to the impact of these selections upon secondary manufacturing operations, specifically adhesion bonding processes.

 

Primary Processing

Proper processing of PPS is critical in order to achieve the stated properties of this material. PPS products are not hygroscopic, and therefore, do not experience dimensional expansion problems like nylon (polyamides). Yet it is important to use dry resin in molding parts. Moisture, in and of itself, is problematic. High moisture levels can create voids, which could adversely impact part performance, affect adhesion and alter aesthetics. The time between drying and processing should be as short as possible. PPS should be dried in dehumidifying hopper dryers. Hot-air ovens are not recommended, although they may be used if extreme care is taken. The reasons such ovens are not recommended are: a) if the trays are filled too high (more than 1-1.5 in.), the material on the bottom of the tray is not properly dried; b) if several different kinds of materials are being dried in the oven (on different trays) at the same time, pellets can easily fall onto a lower tray, causing contamination of the material on the lower tray2.

 

To achieve a fully crystalline state, mold temperatures of at least 275 to 300 degrees Fahrenheit are required. When PPS is molded below 275 degrees Fahrenheit, the moldings are amorphous, or semi crystalline, and remain in this state until they are exposed to higher service temperatures (including heat curing of adhesives). If the service temperature exceeds the molding temperature, the parts will become more crystalline, resulting in dimensional and property changes. For example, the Heat Deflection Temperature (HDT), @264 psi (1.8 MPa), of 40 percent glass-filled PPS molded in a non-crystalline state is only 350 degrees Fahrenheit, but increases to >500 degrees Fahrenheit (260 degrees Centigrade) in the crystalline state. This is critical for calculating the optimal adhesive cure temperature and time (a function of the number of parts in the oven, total mass) necessary to achieve full chemical crosslinking. Further, mold temperature has a dramatic effect on the surface appearance. Bonding processes should be performed as soon as possible following molding operations, or package parts tightly in non-poly bags.

 

Surface Cleaning

For PPS products, surface cleanliness and plasma pretreatment are critical prerequisites to achieving high-strength bonds. Surfaces must be contamination-free from dirt, grease and oils. Low molecular weight materials (LMWM) such as silicones, mold release and anti-slip agents inhibit bonding. To solvent clean PPS surfaces and remove LMWM materials (in accordance with company policy and state law), acetone or methyl ethyl ketone (MEK) are suggested. Weaker solvents such Xylene, Toluene and Alcohol (IPA) can be used to remove superficial dirt, but not hydrocarbon contamination. Avoid using excess solvent because it can create weak boundary layers of un-removed chemicals, leaving a haze build-up inhibiting bonding. Use proper technique at all times, including lint-free cloths and wearing powder-free protective hand gloves. Solvent cleaning is effective for exposed accessible surfaces, but is generally not practical for remote isolated areas such as small diameter holes found in electronic connector applications. Plasma treatment processes have varying degrees of effectiveness to simultaneously clean and pretreat all surfaces.

 

Surface Oxidation Pretreatment

It’s important to understand why pretreatments are needed and the mechanisms for how they improve adhesion bond strength. The underlying reasons why many plastics are difficult to bond are because they are hydrophobic non-polar materials, chemically inert and possess poor surface wettability (i.e., low surface energy). While these performance properties are ideal for designers, they are the nemesis for manufacturers needing to bond these materials. As a general rule, acceptable adhesion is achieved when the surface energy of the plastic substrate is approximately 8-10 dynes/cm greater than the surface tension of the liquid adhesive, coating or ink. In this situation, the liquid is said to “wet out” or adhere to the surface. A method for measuring surface energy, “wetting” is the use of calibrated dyne solutions in accordance with ASTM D2578.

 

The surface energy of untreated PPS is approximately 38 dynes/cm (calculated contact angle with water is 80.3°). The surface tension of compatible epoxy resin adhesives is 45-50 dynes/cm. Therefore, the calculated post-treatment surface energy must be in the range of at least 48-54 dynes/cm. In this situation, the liquid is said to “wet out” or adhere to the surface. Practically, the most robust bonding of PPS is achieved when the surface energy is 60-70 dynes/cm. This higher plasma treatment level has an additional benefit of extending the pretreatment shelf-life, two years or longer. This typically is not the situation with other polymers.

 

Due to its non-polar hydrophobic nature, PPS adhesion bonding applications normally require plasma surface pretreatment immediately following solvent cleaning to increase the surface energy and provide chemical functionality. Common pretreatments for PPS include Electrical Corona Discharge, Atmospheric Blown Ion, Flame Plasma and RF Cold Gas (Low Pressure). These processes are characterized by their ability to generate “gas plasma”, an extremely reactive gas consisting of free electrons, positive ions and other species. Chemical surface functionalization also occurs. In the science of physics, the mechanisms in which these plasmas are generated are different, but their effects on surface wettability are similar. Each method is application-specific and possesses advantages and/or limitations4. Considerations include part geometry, material handling automation and the conductive properties of the substrate. Black colored PPS is commonly selected for a variety of reasons. Since carbon black can have varying degrees of conductivity, careful evaluation of electrical pretreatment methods is important to ensure that electrical arcing during the treatment process does not occur. Arcing can degrade the insulation resistance material properties that are essential for electronic components.

 

Classical Electrical Corona Discharge is obtained using a generator and electrode(s) connected to a high-voltage source, a counter electrode at potential zero and a dielectric used as a barrier. That is, high-frequency, high-voltage discharge (step up transformer) creating a potential difference between two points requiring earth ground 35+kV and 20-25 kHz. Custom electrode configurations allow for treating much different surface geometry – flat, contoured, recessed, isolated, etc. One specialized application example is a corona discharge treating system for electrical connectors in which a combination of pin and ball electrodes concomitantly treats 3D small diameter holes (= 0.0305″) and flat exterior surfaces in multiple planes, US Patent US5051586 (1991). For PPS military connectors, the pretreatment shelf-life is over two years. Ozone is produced in the plasma region as a result of the electrical discharge. Corona discharge has virtually no cleaning capabilities.

 

Atmospheric Plasma or Electrical Blown Ion Plasma (also termed Focused Corona Plasma) utilizes a single narrow nozzle electrode, powered by an electrical generator and step-up transformer, and high pressurized air in which intense focused plasma is generated within the treatment head and streams outward. This pretreatment process can clean dirt, debris and some hydrocarbons from the substrate, but not most silicones and slip agents. New research indicates that fine etching of the surface can create new topographies for increased mechanical bonding. Ozone is not a byproduct, but nitrogen oxides (NOx) are produced which may have deceivingly similar odor.

 

Flame Plasma Treatment uses the highly reactive species present in the combustion of air and hydrocarbon gas (to create the plasma). While flame treatment is exothermic, heat does not create the chemical functionality and improved surface wetting. Flaming will clean dirt, debris and some hydrocarbons from the substrate. Flaming will not remove silicones, mold releases and slip agents. Flame treatment can impart higher wetting, oxidation and shelf-life than electrical pretreatments due to its relative shallower depth of treatment from the surface, 5-10nm. Ozone is not produced. When procuring flame treatment burners, compare ribbon versus drilled port and the benefits of zero balanced regulators.

 

Cold Gas Plasma, also termed “Low Pressure Cold Gas Plasma”, is conducted in an enclosed evacuated chamber, in comparison to atmospheric (air) surface pretreatment methods. Industrial-grade 100-percent Oxygen gas (O2) commonly is used. Gas is released into the chamber under a partial vacuum and subjected to an RF electrical field. It is the response of the highly reactive species generated with the polymers placed in the plasma field, on inner conductive electrode aluminum shelves or cages, breaking molecular bonds that results in cleaning and chemical/physical modifications (including an increase in surface roughness, which improves mechanical bonding). A significant benefit of cold gas plasma processes is the removal of hydrocarbons, thereby eliminating solvent cleaning. Atmospheric pretreatments do not remove/clean all poly-aromatic hydrocarbons, so solvent cleaning (prior to pretreatment) may be necessary.

 

Adhesives and Curing

Optimal joint design is critical in any adhesive bonding app­lication. Bonded joints can be subject to tensile, compressive, shear, peel or cleavage forces, often in combination. For many PPS applications, two-component, heat-curable structural epoxy adhesives are ideal. Uniform, thin bond line thickness (0.002 to 0.007″) is preferred for optimal shear and tensile strength properties. Also, the air cavity concentration is less. Whenever possible, particularly for unsupported joints, the substrates should be clamped while the adhesive cures/cools.

 

For glass-filled PPS applications, the Heat Deflection Temperature in the crystalline state is >500 degrees Fahrenheit. Therefore, the oven cure temperature safely can range between 300 and 350 degrees Fahrenheit. It’s important to note this is the temperature of the parts reached during curing, which may be different from the oven set point. Avoid stacking of parts. Parts should remain at temperature until completely cured, assuring full crosslinking of the adhesive. Insufficient cure (temperature/time) is one of the most common problems that results in adhesion failure. By definition, “adhesion failure” occurs at the interface between the adhesive and the adherend (substrate). Visually, there is residual adhesive remaining at any location on only one surface and not the second substrate adherend.

 

In addition to solvent cleaning and plasma pretreatment, a textured surface, as molded, will increase mechanical interlocking adhesion. Texture can be accomplished within the mold tool or manually using a Scotch-Brite pad. For example, NTMA mold cavity Finish “40-Diamond buffed 1200 Grit” likely will improve bond strength vs. Finish “10-Fine Diamond 8000 Grit” (0-3 micron range). Even slightly textured surfaces are beneficial. For connector products and other recessed-hole applications, etched core pins in the mold are highly effective.

 

In summary, to achieve high strength adhesion bonding of PPS (30-40 percent glass-filled fibers) and heat-curable epoxy adhesives, I recommend the following:

 

  • Ensure the PPS resin is properly dried before molding and processed at 275 to 300 degrees Fahrenheit
  • Conduct bonding processes as soon as possible following molding
  • Solvent-clean part surfaces
  • Use plasma pretreatment to increase surface wetting and chemical functionalization
  • Apply a uniform thin adhesive bond line
  • Oven cure at 300 to 350 degrees Fahrenheit

 

Additional benefits are gained if product surfaces are textured. Consider, plasma oxidized surfaces can deleteriously effect downstream assembly processes, such as poor heat sealing/welding, when overtreatment occurs. Plasma treated surfaces age at different rates and to varying extent relative to the surrounding environmental factors, including temperature and humidity.

 

To achieve robust adhesive bonding of PPS products requires a total solutions system approach involving design, material properties and primary and secondary operations. Plasma oxidation solves many adhesion problems, but the selection of the best method is dependent upon many factors, including equipment manufacturers. Pretreatments – chemical, mechanical or plasma – can be combined to enhance the bonding results and minimize process variability.

 

If you need more information about polyphenylene sulfide, I recommend that you can visit Prochase Enterprise Co., Ltd. – the company as professional plastic raw material manufacturer can provide customers liquid crystal polymer, Polyamide 46, thermoplastic elastomer, etc. Feel free to contact with Prochase for more details.

 

Article Source: http://www.plasticsdecorating.com/stories/110813/adhesion-bonding-polyphenylene-sulfide.shtml#.WvzUqqSFOvE

How to Locate Your Gas Shut Off Valve

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How to find and operate shutoff valves for gas and water pipes? Don’t wait until you have a home emergency to try and find your gas or water shutoff valves. This article will help you locate them now. Taking the time to familiarize yourself with the valves can help you avoid a disaster later.

 

Finding The Shut Off Valves

Some things in life are worth learning before it’s too late—like the locations of your water and gas shutoff valves. Now granted, these shut off valves are often hidden in some dark, creepy corner of the house. But if a water pipe springs a leak, knowing where the shutoff valve is could save you thousands in water damage repairs. What’s more, you can’t make those major plumbing repairs or improvements unless you first turn off the water. The same goes for turning off the gas—though with some strict safety precautions, which we’ll talk about later.

 

Home water and gas systems contain two types of shutoff valves: main or master shutoff valves for stopping the flow of gas or water to the entire house, and individual or supply shutoff valves for specific appliances and fixtures. We’ll look at both types and tell you how to identify them (since they often look similar), where they are and how to operate them.

 

You’ll notice this story contains a lot of “oftens,” “usuallys” and “almost always’s.” That’s because valves vary greatly in location, shape and number, depending on the age of your house, the local codes and which part of the country you live in. This article covers the basics of each system.

 

Gas Shut Off Valves

Houses with natural gas have a main shutoff valve located just before the gas meter. This valve, often called the street-side valve, is normally a rectangular nub. When the long side of the nub or handle is parallel to the incoming gas line, it’s open and the gas is flowing. When it’s turned a quarter turn, perpendicular to the incoming pipe, it’s closed.

 

The street-side main shutoff valve must be opened and closed with a wrench, and, truth be told, gas companies don’t want you operating this valve; they only want their own employees, plumbing and heating contractors and fire department personnel to use it. They’d rather you use the house-side main shutoff valve located after the meter.

 

This house-side valve—usually a ball valve—may be located where the pipe first enters the house or farther down the line, but it will always be located before the first appliance. If iron pipe is transporting the gas, it’s often black; this differentiates it from similar-shaped, gray galvanized water pipe.

 

If your home is newer and you find a flexible copper pipe running from the meter into your utility room, you probably have a higher pressure gas system. In this case, your inside main shutoff valve is probably near your furnace or water heater, just before it enters a flying saucer–shaped doodad called a pressure regulator. There’s also a chance your home—especially if it’s older—doesn’t have a house-side main shutoff valve.

 

Well, don’t just sit there; get up and locate those valves! In addition to the house-side main shutoff valve, individual gas appliances should have a service or appliance shutoff valve that’s immediately accessible, in the same room and within 6 ft. of the appliance. These valves allow you to stop the flow of gas to your dryer, oven, furnace, water heater or gas fireplaces to make repairs or new installations without cutting off gas to your entire home.

 

Most service valves are single-lever ball valves; again, handle parallel to the line means gas is flowing, perpendicular means it’s cut off. On dryers and ranges, this valve is usually hidden behind them and can only be reached by sliding the appliance out from the wall. This service valve will usually be at the end of a fixed pipe and connected to a flexible supply pipe called an appliance connector. Take care not to kink or pinch this flexible pipe.

 

When you repair or replace a gas appliance, use these shutoff valves to stop the flow of gas. (Most pros replace the flexible connector when they replace the appliance.) If you discover you have a faulty supply valve, or your system doesn’t have one, turn off the gas using the house side main shutoff valve.

 

For those with propane or liquefied petroleum gas, there’s a main shutoff valve on the tank itself, and usually a main shutoff valve somewhere before the first appliance. Some valves (both gas and water) manufactured before 1980 contain a lubricant to help the valve seal better and operate more smoothly. In many cases, this lubricant will have hardened or reacted with the gas to make the valve difficult to turn. Applying gentle heat with a hair dryer and working the valve open and shut in stages will usually free it up again. Sometimes you need to use pliers to free the stuck handle.

 

Important! Now that you know where your gas valves are, also know this: it’s not always safe for you to turn these valves off in an emergency. When gas reaches a certain concentration in a room or house, the slightest spark can set off a tremendous explosion. A light switch or telephone—even static electricity from your clothes—can produce such a spark.

 

If you’re working near the main or individual gas valve and clearly know the source of the gas leak and that gas hasn’t been leaking for long, shut off the valve and get out. But if you’re uncertain of the source or how long the gas has been leaking, clear yourself and your family out and call the gas company or fire department from a neighbor’s house (not your own—remember, phones can generate sparks!). Always err on the side of caution.

 

It’s a good idea to get ready for gas emergencies before they happen, because sometimes projects involving gas lines don’t go as planned. When a gas project goes bad, that’s not the time to be searching for the right tool to shut the gas off at the meter. A good strategy is to buy an emergency gas meter wrench shutoff tool and secure it to the meter.

 

Also note: When you shut off main or individual gas valves, you’ll be extinguishing the pilot lights to certain appliances. Many newer appliances have “pilot light–less” electronic ignition systems, but if you have older appliances, you’ll need to relight the pilot lights. Most appliances have clear relighting directions on a label near the pilot light or in the instruction manual.

 

But some pilots are pretty darn hard to reach. If you’re uncomfortable with relighting the pilot light, hire a plumber or call your local gas service company.

 

If you need more information about automatic gas shut off valve, I recommend that you can visit the website of Alpha Brass Controls – the company specializes in kinds of brass gas valves and control thermostats. Contact with ABC for more details.

 

Article Source: The Family Handyman

How A Manual Chain Hoist Works?

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From What Parts A Manual Chain Hoist Consists

Manual chain hoist is a pretty simple device considering the large amount of weight such a tool can lift. Chain hoists are made from durable, high grade steel to ensure safety and reliability when lifting couple of tons heavy loads. Manual chain hoist can be separated in three different part categories: lifting chains, lifting mechanism and hooks.

 

Chain hoist has got two chain loops – hand chain and lifting chain. Hand chain sits on a wheel located in the lifting mechanism; it needs to be pulled by hand in order to lift a load. The wheel inside the lifting mechanism has got special pockets that allow the hand chain to move the wheel. Lifting chain also loops the lifting mechanism and lifts or lowers a load. At the end of the chain there is a grab hook, where you can attach lifting chains or slings, a load leveler or load itself. There is also a hook on the top of the chain hoists housing. This hook is used to attach the hoist to a ceiling mount, trolley system or other construction that can withstand the weight a hoist will lift. Most chain hoists have swivel hooks, meaning that they can be turned 360 degrees around to allow for easier mounting. The lifting mechanism consists of a cog, axle, drive shaft, gears and sprockets. There is also a chain stopper or brake on most chain hoists that prevents load from lowering under a load.

 

How A Manual Chain Hoist Works

The physics behind a chain hoist are very simple and have been used for lifting heavy objects for a long time. Chain hoist uses a mechanical advantage to transform small force over a long distance to large force over a short distance; this is possible by using multiple larger and smaller gears in the chain hoist mechanism.

 

To lift a load, chain hoist operator needs to pull down the hand chain; this turns the cog and axle which goes through the lifting mechanism. Inside the lifting mechanism are multiple gears which increase the mechanical work applied when pulling the hand chain for dozen times using gear ratio, allowing to easily lift loads with multiple ton capacity.

 

So when the hand chain is pulled, the cog which is rotated by the hand chain turns the drive shaft and gears which turn the load chain sprocket, this also rotates the load chain that is looped over the load chain sprocket and lifts a load. Larger gears move slower than smaller gears, but create more force; this is why chain hoist lifts load very slowly when compared to a hydraulic hoist. At the end of the lifting chain is a grab hook, which allows easily attaching and detaching a load. Also, most chain hoist lifting mechanisms have a ratchet or braking system that prevents the load from slipping back, but allows lowering a load by pulling the other side of the hand chain.

 

Manual Chain Hoist In Comparison With Other Hoist Types for Engine Lift

Chain hoists have different uses, for example in construction sites, shops, warehouses, also in car service stations and other application, where precise lifting is required.

 

The Disadvantages Of Manual Chain Hoists For Engine Lifting Are:

 

  • They are slower than other type of hoists;
  • They have special requirements for installation areas, which limit places these hoists can be used, in opposite hydraulic hoists just need a solid and level ground.

 

However, There Are Also Some Advantages For Using Manual Chain Hoists For Engine Lifting:

 

  • They don’t need electricity, oil or other additional resources to work;
  • They are cheaper than electric or hydraulic hoists;
  • They are simple to use and easy to repair and maintain.

 

If you need more information about manual chain hoists, try to visit Cheng Day Machinery Works Co., Ltd. – the company specializes in producing wire rope hoist, electric chain hoist, crane components, chain hoist trolley, etc. Get more details please send inquiry or contact with Cheng Day Machinery.

 

 

Article Source: http://www.knockoutengine.com/how-a-manual-chain-hoist-works/

How to Decide Between Electric, Pneumatic and Hydraulic Actuators

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Fluid power is a well-established technology; but in case you haven’t noticed, electric actuators have come a long way in the past ten years. But does that mean that fluid power systems are obsolete?

 

To answer that question, I spoke to experts from automation suppliers Festo and SMAC. Festo carries both electric and pneumatic technology, while SMAC specializes in a variety of types of electric actuators from ball screw-driven devices to linear motors.

 

According to Jim Ackert, applications specialist at Festo, fluid power systems may not be going anywhere. In many applications where they were once ubiquitous, however, electrics are pushing in.

 

“For the time being, I think all three technologies have their place in industry,” said Ackert. “But, the flexibility of electric drives, coupled with the fact that the price of electric components has been steadily coming down over the years, makes them more popular and affordable than they once were.”

 

Tradeoffs Between Electric, Pneumatic and Hydraulic Actuators

 

It may sound frivolous, but choosing the right actuator motor technology is a lot like choosing a role-playing game character: the Fighter, Mage and Thief are classic character archetypes in video games, with trade-offs in damage, health and speed. When it comes to actuators, the trade-offs are force, positioning accuracy and speed.

 

In general, the overlap between the force and speed capabilities of fluid and electric actuators is growing. Electric actuators are even making their way into heavy equipment presses and other traditionally hydraulic-dominated markets.

 

Flexibility

Some applications require more flexible equipment than others. Similarly, the different types of actuators vary in flexibility. Because of this, considering flexibility is often a good place to start when deciding on an actuator.

 

For this consideration, you need to look at your application. Will your setup need changes in the future? How many positions will your actuator need to reach?

 

For example, if you are picking objects from one conveyor and placing them onto one of two conveyors, you need three positions. With pneumatic cylinders, this would require at least two cylinders, either set against one another or set up separately, one for each conveyor. With electrics, a position can be set at any point along the device, and you can easily program multiple points.

 

Taken as a whole, electrics are also the most flexible when it comes to force. Take this Curtiss-Wright ballscrew-based actuator, which pushes up to 40 short tons. At the other end of the spectrum, linear motors breeze by at up to 10 m/s (in the case of Festo’s toothed belt actuators). This broad range of specifications means that whatever your needs are, there is an electric device out there that fits them.

 

If your application is high-mix, in the sense that your setup will need to handle extremely high forces as well as lower forces, it can make sense to choose a hydraulic system, ensuring that your actuators will be able to handle any force you throw at it.

 

In terms of flexibility, the primary benefit to pneumatics is that they are simple to install and operate. If you need to change from a 6” stroke to a 12” stroke, it will be relatively simple to swap the cylinder. However, this wouldn’t be preferable in a real-world situation—and if more complex changes are needed, the time and cost will start to add up.

 

Cost

The biggest disparity between what you see at trade shows and what’s really in use on shop floors across the country is the practicality of cost. Sure, that collaborative robot tending a 3D metal printer while streaming data to an iPad is cool, but is it practical?

 

For manufacturing engineers, the name of the game is to get the job done efficiently and on budget. That’s part of the reason pneumatic actuators probably aren’t going anywhere, despite being made technically obsolete by advances in electric technology—and electric motors and drives are getting cheaper every year. Still, comparing Bimba’s original line of pneumatic and electric linear thrusters shows that the electric version costs approximately five times more.

 

Hydraulic systems are the most expensive, and require the most maintenance and equipment to operate.

 

Types of Electric Linear Actuators

Mechanisms of electric linear motion range from ball screws to rack and pinion gears, to linear motors. Each has different strengths and weaknesses.

 

  • Screw Driven Actuators

According to Helix Linear Technologies, there are two main types of screw-driven actuators: ball screw and lead screw. Ball screw-driven actuators convert the rotary motion of a stepper or rotary motor to linear motion by means of a ball screw and ball nut arrangement.

 

In essence, this mechanism takes the principle of a nut riding on a threaded rod and adds ball bearings to decrease friction. However, these mechanisms are not self-locking, and depending on the application may need additional braking mechanisms, such as vertical installations. Ball screws also require regular lubrication.

 

Where a ball screw uses bearings to decrease friction, the lead screw uses a low-friction polymer or bronze nut. The lead screw is therefore much less expensive than other types of linear actuator, but the friction is higher. This means you may need higher motor torque to drive the same load on a less-efficient lead screw mechanism than for a comparable ball screw actuator. The added friction also increases wear and operating temperature, and lead screws need to be replaced more frequently than other types of actuators.

 

Screw drive actuators can deliver extremely high forces, because the force is distributed along the entire helical path of the nut around the screw. They can also be highly accurate. However, drawbacks to this system include faster wear than non-contact systems. According to Ed Neff, President of SMAC, you can reasonably expect a ball screw to wear out in the same time frame as a pneumatic cylinder in certain applications.

 

  • Belt and Gear-Driven Actuators

Belt-driven actuators are like conveyor belts. According to Misumi, belts are typically made of fiber-reinforced elastomer, and usually have teeth for interfacing with the pulleys to eliminate slippage. A carriage rides on top of the belt to carry the payload.

 

The interesting thing about belt systems is that they scale in travel distance more efficiently than screw drive systems. All you need is a longer belt, rather than a longer precision machined helical screw. Another advantage of belt-driven actuators is that they have fewer moving parts, so maintenance is simpler. However, belts will require re-tensioning as part of scheduled maintenance.

 

Belt-driven systems are not ideal for high loads due to the need for thicker belts and their susceptibility to shock loads. Because belt materials are often prone to elongation over time, accuracy eventually suffers.

 

While belt drive systems win out over screws on travel distance, belt tensioning becomes difficult at longer distances. In these situations, according to Danielle Collins of LinearMotionTips.com, rack and pinion systems win out. Rack sections can be laid out to virtually any length.

 

Some rack and pinion systems use a fixed rack and moving pinion, while some use a fixed pinion and moving rack. At longer stroke lengths, moving pinion systems are more efficient because the moving mass is lower. However, cable management is essential in these cases.

 

In gear systems, backlash is always a consideration, but today’s high-precision machining can deliver micron accuracy in gear mating, so the accuracy is comparable to belt driven systems. Some systems also use a split or dial pinion system to remove backlash.

 

In both belt and gear driven systems, the guidance components usually require regular lubrication.

 

  • Linear Motors

Linear motors are typically the most expensive type of electric linear actuator, and they’re also the fastest and most dynamic.

 

Where an electric motor consists of a rotor inside a stator, a linear motor is a motor unrolled. Because linear motors have lower friction than other devices, some linear motor products can last well over a hundred million cycles, according to Neff of SMAC.

 

When the payload mounting surface is precision-machined steel or granite, the device is called a stage. Across the industry, the term “stage” refers to a higher-accuracy device.

 

Simple Hydraulics vs. Servo Hydraulics

 

According to MachineDesign.com, while intermediate-stroke positioning is possible with simple hydraulics, it requires manual control by an operator. The same goes for speed and force control. For computer-controlled or automated position, speed and force control, servo drives are required.

 

With hydraulic systems, the total footprint of the system is much larger than comparable electric systems. Hydraulic systems require hoses, fittings and valves, as well as a hydraulic power unit (HPU) which has a large footprint. While hydraulic cylinders save space at the cylinder, they more than make up for it with the bloated footprint of their control systems. Servo hydraulics requires even more space, with a control cabinet or PLC.

 

How to Choose the Right Actuator for Your Application

Now that we’ve gone over the basics of the different types of actuators, choosing an actuator all comes down to your specific application. Consider the following questions:

 

Force/Payload

  • High Force – Thousands of Pounds

For extremely high forces, such as a press application or a gantry system for heavy equipment, it comes down to hydraulic or electric. The next question to consider is the cycle rate, to determine which option would wear faster and require more maintenance over the life of your system. Ask your vendor about the maintenance and wear of each product.

 

The next factor to consider is that hydraulic oil is messy. If a spill occurs, cleaning up large volumes of oil can be costly and time consuming. Even if a leak does not occur, oil may creep and slowly film surfaces of your machine. In clean environments such as electronics or food processing, the possibility of oil leakage may eliminate the hydraulic option.

 

  • Medium Force – Tens to Hundreds of Pounds

When your required force is within the range for all three options, consider your positioning needs.

 

Will the motion require more than 2 stop positions? If so, a pneumatic system will be complicated to implement, and require manual adjustment. However, pneumatics may still be the least expensive option. The next question to ask is the level of accuracy required. In assembly tasks, for example, you may require fine-grained accuracy, in the tenth-millimeter range. If so, electric actuators may be the best option. Pneumatic systems are typically accurate to a few millimeters.

 

The last thing to consider is the cycle rate of your application. While linear motors are more expensive than other types of actuators, over many cycles (100 Million+) they keep going strong, while other systems will need replacement.

 

  • Low Force

Consider the accuracy and dynamic motion requirements of your application. As Ed Neff of SMAC says, “dumb” motions, such as a simple push, may require no more than a simple pneumatic cylinder. However, any time you want more control over the position or speed of the device, you should consider electrics.

 

Which Actuator is Best?

When making a decision between electric and fluid-power actuators, the key considerations are positioning accuracy, speed and payload.

 

Fluid power systems excel in traditional applications where the main advantages of electric systems are overkill, making their higher cost unjustified. However, electrics are still developing, with the technology advancing every year. Costs are coming down for even the most advanced electromechanical actuators, and some experts believe that one day fluid power systems will be completely obsolete in the linear motion industry.

 

However, today it’s common to see a mix of technologies, even on one machine. A large press, for example, could use a large hydraulic cylinder, with electric actuators for loading/unloading and pneumatic actuators for gripping parts.

 

If you have any interest in learning more information about actuator motor, please try to check out the site of Hsiang Neng DC Micro Motor Manufacturing Corp. – the company specializes in kinds of DC motors, micro motors, gear motors, etc.

 

Article Source: engineering.com

Keep Your Screen Changer In the Flow

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The screen changer plays an essential role in generating quality extrudate. Here’s what you need to know to keep it functioning properly.

 

There are many different designs of screen changers on the market today, from manual slide plates to constant-pressure and continuous backflush or scrapper designs, and each one comes with its own set of strengths and weaknesses. As a processor, you need to know these in order to make the best choice of screen changer for your particular application.

 

This article will focus more on general process troubleshooting as opposed to machine-specific issues, but it’s important to note that a large percentage of problems that extrusion processors have with their screen changers occur because the screen changer they’re using is not the best design for their application. Each specific extrusion filtration application should be closely examined prior to specifying a screen changer for the project.

 

FILTRATION MESH

Every processor wants the best filtration they can get for the area of filtration they have. Very few, however, utilize a screen-pack configuration fully optimized for their process. Take as an example a situation in which an operator is attempting to extend a production run between screen changes. As the screen becomes occluded, head pressure rises and eventually causes the wire cloth to fail. A simple operator solution is to pile on additional 20-mesh screens for increased strength.

 

A better solution would be to increase the support strength of the base screen, using a heavier-gauge 10-mesh screen layered with a single 20-mesh screen. The 10- and 20- mesh screens will support each other by working at two levels. The end result is the ability to run longer between changes, but without the unnecessarily high pressure drop and resulting increase in shear heat. Any increase in pressure-induced shear is best avoided, since this will generate higher melt temperature at the discharge end of the extruder, creating a higher demand on downstream cooling capacity and potentially reducing output.

 

Most screen-changer suppliers offer process-support services that include pressure-drop calculations. These are simple to perform and factor in material viscosities, breaker-plate open area, and screen open area to arrive at the best screen-pack configuration for the process and operating environment. This service is normally a free and simple means to optimize polymer flow performance.

 

TEMPERATURE CONTROL

Another issue occasionally attributed to screen changers is temperature fluctuation. Best practice is to stay alert to gauges, heaters, and heater circuits. Monitoring these on the screen changer may not be as critical as checking the extruder and feed screw, but it can help spot an issue before it becomes catastrophic.

 

Another tip is to optimize the number of heat zones necessary to balance temperature across the screen changer. More specifically:

 

  • Hydraulic slide-plate screen changers are best served by three zones—a body zone and independent zones for the each end of the slide plate. Many processors wire these machines into a single control zone, resulting in too much or too little heat to the slide plate. This can destabilize the melt profile and cause material burning in the off-line breaker plate.

 

  • Continuous bolt-type screen changers are normally best served by a single control zone, but as these machines increase in size, additional body zones help balance the heat. Bolt-type continuous screen changers heat the bolts by conduction from the body. If heat is unbalanced, the body can shrink onto the bolt and generate high enough clamping forces to prevent movement of the bolt.

 

  • Machine adapters are also normally best served with independent heat control. This, however, will vary with size.

 

PRESSURE FLUCTUATION

Streamlining the polymer flow through the screen changer will also affect process stability. For sensitive materials or those with unique flow characteristics, CFD (computational fluid dynamics) modeling software can be utilized to optimize screen-changer flow passages and minimize material residence time. Along this line, adapter length, steps and transitions, and polymer inventory between the screw tip and screen pack can be critical to establishing best flow while minimizing polymer degradation points and thermal stratification.

 

Vent cycles on continuous screen changers can influence pressure stability. Most bolt-type screen changers can see up to 50% of the available filter area removed from the process for screen change. While this naturally causes a rise in head pressure, the flow rate and die pressure normally remain relatively stable. The issue arises with the reintroduction of the clean screen. Vents machined into the bolts divert a small portion of the polymer melt to prefill and purge air from the incoming screen pocket. The resulting slight drop in die pressure can be minimized by operator finesse or more precisely by PLC control. Constant-pressure screen changers, such as rotary wheel designs, are not normally subject to these issues. One auxiliary that can help tremendously with fluctuating pressure is a gear pump, which can tolerate upstream pressure swings while holding the die pressure stable.

 

LEAKAGE

Leakage is a problem with almost all screen changer designs as they age, but most noticeably with slide-plate models. This type of screen changer relies on manually adjusted or pressure-activated seals and is subject to wear and tear from the movement of the slide plate, degradation of the seal-pressure ring, and damage from dislodged screens. Seal maintenance for these machines can be required as often as weekly to once a year. Maintenance can lead to tear down and reassembly, which can be a time-consuming, expensive process. Even before it reaches this point, the housekeeping required keeping the slide plate clean and preventing polymer from leaking onto wiring and other equipment is significant.

 

One way to minimize leakage on a system like this is to increase the head pressure. Your intuition might tell you lower pressure would be better because it would put less strain on the system. However, because the seals are designed to respond to pressure in the extruder, they are only working at their peak when the pressure is higher. At a lower pressure, the seals will relax slightly. When the extruder is idle or running at drool speed and there is very little pressure being exerted on the seal, it becomes easy for lower viscosity material to leak out. One newer slide-plate seal, an all-steel, segmented pressure-ring design, addresses these problems and caries a lifetime leak-free warranty regardless of temperature and low viscosity, making this seal the first to operate leak-free on high-temperature coating applications.

 

Material leakage on bolt-type or other close-tolerance rotary wheel machines that operate without a mechanical seal can likewise occur over time; but with these designs, leakage is almost always caused by mechanical damage. These precision-machined screen changers are typically designed for a fairly narrow material viscosity range.

 

As such, you should not apply a machine designed with clearances for high pressure and high viscosity to a low-viscosity process without approval or modification from the supplier.

 

RESIN CONTAMINATION, DEGRADATION

The primary purpose of a screen changer is to filter out contaminants from the melt stream; but the fact is, screen changes almost inevitably introduce contaminants, some of which get into the die. These result from imperfect cleaning of the slide plate, bolt, or wheel. For example:

 

  • This can occur on a slide-plate screen changer as the upstream and downstream seals scrape material residue into both sides of the oncoming screen pocket. Upstream contaminants are caught on the screen. Downstream contaminants flush out into the die.

 

  • A continuous or constant-pressure screen changer can experience this as well, but to a much smaller degree. The gap between the bolt or wheel and housing is measured in microns on the downstream side. The rare contaminant that makes it through this clearance to enter the melt flow is only consequential to the most demanding of applications, and for these few occasions, secondary, long-life canister filters will catch anything that comes through.

 

Many processes do not have to run continuously or require 100% quality and can overlook contaminants during screen change. However, if your customer has zero tolerance, you’ll need a different kind of screen changer. There is no way to continue using a slide-plate screen changer without introducing some level of contaminants or material degradation from the offline breaker plate. To solve this, a continuous bolt-type or rotary-wheel screen changer is a better solution.

 

LOCK-UP

Continuous screen changers that use no mechanical seal utilize precisely machined clearances to affect a polymer seal. These same clearances provide lubrication between the bolts or wheel and housing and must be maintained to avoid locking up the machines. Lock-up (jammed bolt or wheel) can be a result of various things, usually preventable with correct operator usage. The leading cause of lock-ups occurs when the bolts or wheel are not cleaned and lubricated regularly.

 

Many processors with a bolt-type or rotary-wheel screen changer have bought these continuous-process machines because they have no mechanical seals and run reliably and leak-free for years on end. While these advanced designs certainly require less upkeep than a slide plate, maintenance during screen change should not be neglected.

 

Over time, excess buildup of polymer can plate onto the bolt or wheel surfaces, reducing required clearances and eventually requiring more hydraulic pressure to shift than is available from the power unit or mechanical drive.

 

This stuck bolt or wheel is easily preventable with regular cleaning. A lock-up requires a shutdown and reheat process that can take up to 8 hr or more. Doing daily maintenance and cleaning of the piston takes 5 to 10 min and can save a considerable amount of downtime. “The biggest issue is getting into the mindset of cleaning the whole bolt,” says Marty Danco of Verity Resins, a recycler and compounder based in Forest City, N.C. “When you lock it up, there’s no way home, it’s locked up for good. Using proper copper gauze, the bolt should be cleaned every day—not just the top, but underneath it and on the sides.”

 

The necessity of regular maintenance also holds for breaker plates. Over time, material will carbonize on them, closing off the holes, which raises head pressure and eventually compromises output. Breaker-plate clogging is also easily preventable. The best solution is to make sure to have a clean spare. Swapping these breaker plates out even once a week is great preventive maintenance to ensure it never reaches the point where the process or the final product is impacted.

 

Most leading screen-changer suppliers are excellent resources to refer your troubleshooting issues to. Doing so, instead of relying solely on your maintenance crew, can often reduce your downtime and repair expenses, eliminate some problems before they occur, and potentially point you to a better process solution than the machine currently in service.

 

If you need more information about plastic extruder screen changer, please do not hesitate to check out the website of Hsin-Long Thread Rolling Machine Co., Ltd. – the company provides kinds of blown film extrusion machines, die head, air ring, bubble cage, etc. Learn further details, please feel free to send inquiry to Hsin Long.

 

Article Source: Plastics Technology

Common Types of Pneumatic Valves

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Pneumatic valves are one of an array of components responsible for controlling the pressure, rate, and amount of air as it moves through a pneumatic system. Pneumatic systems, which depend on the force of compressed air to transmit power, can be found in countless industrial applications, from pneumatic pressure power tools to diesel engines. Based on other components within a given application and the type of pneumatic system used, one of several types of pneumatic valves may be found at the heart of the device. Functional directional control valves, those that control the direction of air flow or inhibit flow all together, are a large class of pneumatic valves that houses multiple variants.

 

Functional Directional Control Valves

 

Many functional directional pneumatic control valves are classified based on the number of entry and exit ports they possess, the number of flow paths they create, and the mechanism by which ports are opened and closed.

 

Two-Way Directional Valve

 

A two-way directional valve passes air in two directions, through two ports which can be open or closed. If the valve ports are closed no air can flow through the valve. If the ports are open, air may move from the first port through the valve and through the second port or in the opposite direction.

 

Three-Way Directional Valve

 

A three-way directional valve has three ports, each of which serves a different purpose. The first port is used to connect the valve to an actuator or another device. The second port is connected to an air-flow. The third port is used as an exhaust exit. When the first and second ports are open and the third is closed, air moves through the valve to the device. When the first and third ports are open and the second port is closed, the actuator can vent exhaust.  Three-way valves are often connected to actuators in cylinders, or used in pairs and connected to double-acting cylinders.

 

Four-Way Directional Valves

 

A four-way directional valve has four distinct ports, two of which connect to actuators, one that connects to a pressurized air-flow, and one that serves as an exhaust pathway. They are among the most common types of valves found in pneumatic systems because the four distinct paths allow the valve to effectively reverse the motion of a motor or basic cylinder. An additional port is sometimes added to a four-way valve, making it a five-ported four-way valve. A four-way valve with an additional port is often used to provide dual pressure, meaning the valve can apply one of two kinds of pressure and alternate between the two depending on what the application requires. Alternatively, the valve can use the other port as a secondary exhaust port.

 

Spring Offset

 

This type of pneumatic valve classification refers to the manner in which air-flow direction is switched. For example, in a two-way directional valve, the valve is either open (air-flow is enabled) or closed (air-flow is prevented). In order for each port to assume an open or close position, an actuator moves a valve spool into position. To release the valve spool and return the pneumatic valve to its previous position, a spring releases the spool. A two-way directional valve that functions in this manner is also called a spring offset valve.

 

Resting State: Open v. Closed

 

In two-way directional spring offset valves, there are two positions they can assume when the connected actuator isn’t active: open or closed. In devices where an open resting position is standard, air moves freely through the valve. In a closed resting state, the air-flow is blocked. In three-way valves, one port is always open. In such cases, a closed resting state usually results in blocking the air-flow port, so pressure isn’t moving unless the device is turned on.

 

If you need more information about directional control valves and more pneumatic valves, welcome to check out the website of Ashun Fluid Power Co., Ltd. – the company specializes in kinds of valves and cylinders. You can find modular valves, directional control valves, pressure control valves, flow control valves, lift hydraulic cylinder and more products here. Get further details please feel free to send inquiry to Ashun.

 

Article Source: https://www.thomasnet.com/articles/pumps-valves-accessories/pneumatic-valves

Get Some Information About Bubble Cage Before Buying…

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Why Do You Need Bubble Cages?

Blown film extrusion is the process that involves extruding a tube of molten polymer through a Blown Film Die (Single or Multi-Layer), which is a vertical cylinder with a circular opening. Air is injected through a hole in the center of the die creating a bubble, several times its initial diameter. The bubble is pulled upwards and an Air Ring blows air onto the film to cool.

 

Bubble cages reduce the turbulence caused by the cooling air stream when it hits the bubble. The Bubble Cage reduces movement that the bubble would otherwise have and prevents the bubble from losing stability. More stability results in increased production as well as improved quality.

 

Recommend Bubble Cages Supplier

If you have any interest in Bubble Cage, I recommend that you can visit the website of Hsin Long Thread Rolling Machine Co., Ltd.

 

Hsin Long Bubble Cage

Hsin Long Bubble Cage

 

  • The wires of stabilizing ring with SUS304 for increased.
  • Easy to adjust.
  • Single or double layer assemble easily.
  • Mass production, competitive prices.
  • Choice of various ring diameters.

 

Learn further details about bubble cage or other blown film extrusion machine, please do not hesitate to check out Hsin Long product pages and send inquiry to them.

 

 

Article Source: Mark One Machinery

What Is A Spanner Wrench?

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Maxclaw Hook Spanner Wrench

A wrench is a tool that provides a grip for tightening or loosening a fastener, such as a nut or bolt. The term spanner wrench is redundant; Americans consider this kind of tool a wrench, while the British refer to this tool as a spanner. While there are many kinds of wrenches, Americans refer to the type of wrench that contains pins or tabs around its circumference as the spanner wrench. These wrenches are made of steel for strength and are often chrome-plated to protect against corrosion.

 

There are many types of spanner wrenches, each with a distinctly shaped hook. In addition, some spanners are multi-tools with double-sided hooks. The most common type of spanner wrench is the C spanner. Its head is open in the shape of the letter C, and its jaws are meant to correspond to the similarly sized nut. The obstruction spanner is similar to the C spanner, except its jaws are angled more steeply to enable you to reach nuts in confined spaces. The ring spanner, on the other hand, has a completely enclosed ring that fits precisely over a hexagon or square bolt. While it can take some time to correctly place the ring spanner, it provides stronger leverage than open spanners. Make sure your spanner wrench is the correct size and is sitting properly around the nut before twisting. Otherwise, it could slip from the wrench and damage the tool or injure your hand.

 

Spanner wrenches are often used in plumbing to help repair leaky pipes or faucets. They are smaller and lighter than pipe wrenches, allowing flexibility to work in hard-to-reach areas. In addition, they provide enough turning force to open pipe connections that have been untouched for many years. Similarly, spanner wrenches are commonly used in gas repair to open gas pipes.

 

If you need more options of wrenches, please do not miss Maxclaw Tools Co., Ltd. – the company can provide basin wrench, hook spanner wrench, plumbing wrench, and drum wrench series for you. Now, check out Maxclaw’s product pages to get your right wrench!

 

Article Source: https://home.howstuffworks.com/spanner-wrench.htm

How to Specify and Apply Precision Gearboxes with Servo Systems

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A servo system and gearbox can provide precise motion control, but care must be taken in design, selection, and implementation.

 

With the many industrial gearboxes available today, it’s important to match the proper type of gearbox with the drive, motor, and load. When a machine needs a servo system (drive and motor), the gearbox type is critical for accurate and repeatable motion. Planetary gearboxes fit the bill for servo applications.

 

High-precision helical planetary gearboxes are an excellent choice for applications that need accuracy and reliability. Planetary gearboxes have very low backlash ratings (typically ranging from one to nine arc-min), and when sized correctly offer a service life of over 20,000 hours with virtually no maintenance. Helical planetary gears also provide very quiet and more efficient operation as compared to competitive products.

 

Precision gearboxes are carefully machined to high tolerances – think clockmaker, not blacksmith. They offer power densities that translates to small package size and efficiencies of 90% and greater.

 

Why Use A Gearbox?

Servo motors often drive loads directly without the need for a gearbox, but in many applications it’s advantageous to use a gearbox between the motor and load.

 

One main reason to use a gearbox is torque multiplication. It lets designers use smaller servo systems that consume less energy. Instead of buying relatively large servo drives and motors, designer can use smaller components, saving space and money.

 

Output torque increases in direct proportion to the gear ratio, and top speed of the output shaft decreases. If an application can withstand the reduced speed, a relatively small servo system can supply high torque.

 

Gearboxes can also address inertia mismatches. For high performance servo systems — those with high dynamic responses or low overshoot, for example – the ratio between the reflected load inertia and motor inertia should be as low as practical, ideally under ten-to-one. A precision gearbox reduces the reflected inertia by the square of the reduction ratio. For instance, using a 25:1 gearbox reduces the load’s reflected inertia by a factor of 625, a significant improvement.

 

In some cases, gearboxes simply resolve issues relating to mechanical fit. For example, if directly mounting the motor interferes with another mechanical component, a right-angle gearbox may solve the problem.

 

Compared to most other gear reducers, a precision gearbox provides better accuracy and repeatability. Furthermore, the gearbox’s high efficiency lets it deliver maximum power available from the servo system—features often a necessity in servo applications.

 

Comparing Types of Gearboxes

 

Gearboxes use a variety of power-transmission methods including, but not limited to, planetary gears, worm gears, spur gears, helical gears, and shaft-mount gear units. In servo applications, planetary gearboxes are often the most suitable.

 

Worm gears use a worm or screw gear to turn a larger transverse gear. They can provide high gear reductions in small packages but aren’t that efficient, on the order of 70%. Worm gears aren’t reversible either and thus can’t be back driven, so they cannot be used to increase speed.

 

Spur gears use straight-cut teeth on parallel shafts for power transmission. They are available in a wide range of ratios and are cost effective, but they can be noisy and prone to wear.

 

Helical inline gearboxes also use gears on parallel shafts, but the teeth are cut in helical shapes to allow gradually increasing contact between mating teeth.

 

Helical inline gearboxes and spur gears typically have more backlash than planetary gearboxes, and there is undesirable thrust acting along the gear’s axis. Helically cut gear teeth are quieter and are used in other types of gearboxes because of this.

 

Shaft-mounted gear units are popular for parallel shaft gears, such as spur and helical gears. They are well suited to conveyors and other material-handling applications, and are easy to mount. However, they suffer from the same disadvantages as their constituent parts.

 

Planetary gearboxes are named for their resemblance to a simple solar system. They consist of a ring gear, several planet gears, and a sun gear. The ring gear is typically fixed and is often part of the gearbox’s outer casing, and the input shaft drives the sun gear.

 

Rotation of the sun gear drives the planet gears to spin about their own axes and revolve about the sun gear. A carrier attached to the planet-gear shafts harnesses output. This arrangement creates a balanced and compact design that is concentric about the shaft. If multiple stages are needed, it is relatively simple to connect the output of one set of planet gears to the sun gear of a secondary stage.

 

High efficiency, low backlash, and high power density make planetary gearboxes the best of these alternatives in high-precision servo system applications.

 

Selecting Gearboxes and Servo Systems

 

A servo system coupled with a planetary gearbox is expected to provide precise motion, but this requires all components be carefully matched. Although it’s possible to buy the servo drive, motor, and gearbox from different suppliers, it’s not recommended as this requires a great deal of research and comparison to ensure all components will work together. Purchasing components from a single supplier — especially one that has carefully matched the components and will stand behind the specific combination of parts in question—offers several advantages.

 

The supplier has done all the research and confirms compatibility. Most suppliers will extend a more favorable warranty on such purchases. Plus, they can provide the approved mounting hardware to connect the components.

 

Some suppliers provide online tools for selecting servo systems and compatible gearboxes, easing the specification effort. These selection guides aid the design and provide specific recommendations for closely matched components that can be purchased as a system. In these cases, engineers can be certain the systems they specify are compatible in all critical areas, and that the components will come with the required mounting bushings and keys.

 

In fact, some selector tools let designers enter their torque and speed requirements, and then automatically filter a list of available motor-and-gearbox sets. Engineers can enter torque data in metric or imperial values, or the designer can select a particular servomotor size. Designers enter speed data as discrete values, or pick a gear ratio. Finally, the engineer can choose a preferred physical orientation—inline, right-angle gearing, or both.

 

The resulting list of available systems includes pricing information, a factor often critical to the selection process. After choosing a motor/gear combination, the designer moves to a page with full specifications for the selected servo system, the gearbox, and the combination.

 

One caveat: Even though a selector can make the specifying process easier, engineers and designers should always verify that a system meets their needs and gets applied correctly.

 

Best Practices and Common Pitfalls

 

Although gearboxes help reduce mismatches between the motor’s inertia and that of the load, the gearbox’s inertia must be included in the calculation:
Best Practices and Common Pitfalls
When high dynamic responses are required, engineers need to carefully tune the servo systems, preferably with loads attached, for the most responsive performance. Tuning can provide faster moves and minimize spongy motion while reducing overshoot or ringing after moves is complete.

 

Designers must also pay attention to radial-load and axial-thrust-load specifications. Axial-thrust load is the force acting along the output-shaft axis; radial load acts perpendicularly to the output shaft.

 

The force of gravity acting on the load is perhaps the most common source of radial loads, but other sources are possible, depending on the mechanical apparatus attached to the output shaft. Additional external bearings may be required with some loads to minimize these forces and prolong the life of the gearbox’s internal bearings.

 

A common way to minimize backlash is to approach all target positions from a common direction. In the event a reversing move is required, some designers let the load go past the desired position and return to it from the common direction.

 

Gearbox Applications

 

One classic example of a precision gearbox application is an indexing table with several stations for machining or assembly. Precision gearboxes and servo systems fit well when the table is relatively heavy and needs to be accurately positioned and when high-speed operation is not as important.

 

In this case, the gearbox is being used simply for accurate torque multiplication. The servomotor’s top speed of 3,000 to 5,000 rpm is not required at the load, so the gear reduction ratio and corresponding torque multiplication can be large. This allows a relatively small servo system to handle the task. The servo system might even use its built-in indexer to control the motion based on discrete I/O signals from a PLC, or even a simple selector switch, depending on the required level of automation.

 

Another example of a gearbox application is a high-speed pick-and-place device, such as part removal from an injection-molding machine. The cycle time of these machines is often critical to meet production quotas, and the designer typically wishes to remove parts as quickly as possible after the mold opens.

 

The moving arms of the pick-and-place device are designed to be as lightweight as possible, but inertia mismatch can still be a factor. The gearbox can minimize the mismatch so that the pick-and-place mechanism is extremely responsive.

 

The PLC in this example might be much more involved in controlling the motion, commanding moves with pulse and direction signals. In some cases, the PLC also passes recipe tuning values to the servo drive when the motion profile or the picked-part’s inertia changes.

 

Precision gearboxes and servo systems can be used to meet a wide range of automation challenges. Machine builders should purchase the required components from a knowledgeable vendor who will stand behind their products. Using online selection tools can simplify the choices, although the system will require tuning after installation. When properly designed, specified, and tuned, these systems provide accurate, repeatable results for many years.

 

If you need more information about planetary gearboxes, please do not miss the website of JIA CHENG Precision Machinery Co., Ltd.

 

The company can provide high quality and precision reducer, gearbox, and coupling for you. Feel free to send inquiry to let JIA CHENG know your requirements.

 

Article Source: MachineDesign