Category Archives: Industrial Supply

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

Something You Should Know About Rubber Oil Seal…

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What is Rubber Oil Seal?

 

If you ever notice dark smoke coming from the tail pipe of your car, chances are the rubber oil seals in your vehicle are leaky. The rubber oil seals are also called as oil seals, car oil seals, automotive oil seals and oil seal rings. Leaky oil seals fail to prevent liquids and gases from escaping, and thus oil begins to leak into places in your vehicle where it is not supposed to be. For instance, oil enters the fuel mixture and burns, resulting in the smoky combustion. Thus, we see that these rubber oil seals or oil gaskets are nothing but components that fit on valves and pipes for sealing oil inside the required compartments in your vehicle. Their design features a flexible lip that rubs against a shaft or housing and prevents the leakage or ingress of fluids and dirt from/ into the sealed compartment.

 

Advantages of Rubber Oil Seals:

 

Now rubber oil seal rings perform two important functions: they hold the oil in place, lubricating the moving machine parts, thus reducing friction, grinding and heat in the process. Additionally, these car oil seals keep foreign contaminants from entering and ruining the oil in your car. However, though these automotive rubber seals are popularly referred to as “oil seals”, they are used to retain or confine any form of fluid inside a particular device, especially devices such as hydraulic systems that feature a host of moving parts.

 

Types of Rubber Oil Seals:

 

  • U-Ring Seals
  • V-Ring Seals
  • Rotary Oil Seals
  • Labyrinth or Clearance Seals
  • Bearing Isolators
  • Spring-Installed Seals

 

Why Rubber is the Preferred Material for Oil Seals?

 

Though oil seals also come in materials like plain felt, leather and metal, the best ones are the oil seals made of different varieties of rubber. Seals fashioned from Nitrillic rubber is used with mineral oils, grease, diesel and water. Polyacryllic and silicon seals on the other hand are used for sealing motor oils, while flour elastomer rubber oil seals that have the capacity to withstand a wide range of temperature are normally used in different variety of fuel-related oils. Enlisted below are a few reasons that make rubber the most suitable material for manufacturing oil seals or oil seal rings:

 

  • Can easily withstand high temperature and pressure.
  • Have superior ozone resistance.
  • Feature excellent mechanical strength.
  • Can be easily shaped into different contours and patterns.
  • Are comparatively easier to install.
  • Require less maintenance and provide years of hassle free service.

 

Factors to Consider While Buying Rubber Oil Seals:

 

  • Type of polymer used in manufacturing
  • Shaft outer diameter
  • Seal inner diameter
  • Maximum operating speed
  • Maximum operating temperature
  • Maximum operating pressure
  • Vacuum rating

 

Are you going to look for the high quality rubber oil seals manufacturers and products? I recommend that you can try to visit Chain Yeeh Industrial Co., Ltd. (PHLE). They provide many kind of materials and types rubber oil seal for your choosing, and they also doing customize according to customer’s requirement.

 

 

Article Source: http://www.silentblocbush.com/rubber-oil-seals.html

Fan and Air Circulator Buying Guide

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When researching ways to cool your home, you can consider getting a fan. Fans, also known as air circulators, can be the perfect solution to meet light cooling needs. In more temperate climates, they are an excellent alternative to having an air conditioner that may not see much use. In hotter or more humid climates, fans can help ventilate and dry an area while cooling it, or they can supplement existing air conditioning systems.

 

Size, cooling capacity, intended use, style, and operational noise will all influence how effective a fan will cool your environment. Hence, understanding how fans and air circulators work to keep you comfortable is a key component to choosing the right one for your needs.

 

About Fans

Though fans may seem simple upon first glance, they have more recently become sophisticated cooling systems that help you save on cooling costs, meet versatile needs, and promote energy efficiency. Fans were arguably the first cooling devices created by humans. Today most fans are operated by an electric motor, which turns the blades within a housing unit. Several variations in fan design and intended purpose have greatly enhanced their functionality.

 

Fan Types

There are three main types of fans:

  1. Residential fans are generally meant for personal use.

 

  1. Heavy-Duty fans are found in offices, warehouses, and other workplaces to meet practical needs as well as keep employees comfortable.

 

  1. Water damage restoration fans help dry structures that have sustained water damage and tend to be versatile and powerful.

 

Fan Style and Design

Additionally, fans can be further categorized based on style and design. Fan styles include:

 

  • Tower fans have a long, vertical housing unit that includes a cooling apparatus that runs the length of the fan. They conserve space and offer greater blade protection than more traditional fans.

 

  • Pedestal fans feature a conventional fan design perched on a long stand to reach higher areas than a floor or table fan. They are useful for cooling areas off the ground without needing a desk or shelf for support.

 

  • Table fans can rest on a table, desk, shelf, or other stationary object. These desk fans are generally smaller air circulators that are convenient and mobile.

 

  • Floor fans sit on the floor and have a variety of uses. They tend to be larger than other types of fans and are often used in commercial and industrial applications.

 

  • Personal fans keep you cool in everyday situations. These fans are often placed in bedrooms, workshops, and even cars with a primary purpose of cooling one occupant.

 

  • Misting fans generate water droplets that are then released into the environment and evaporated, cooling the area in the process. These fans are generally used outdoors.

 

Many fan models will fit into more than one of the above categories. If you are just starting to investigate what kind of fan you will need, you should first narrow down the type and style of fan you prefer.

 

Fans vs. Air Conditioners

Fans have a variety of advantages over air conditioner systems. While air conditioners have an overall better cooling capacity than fans and offer a greater degree of control over your cooling experience, fans are more ideal for managing specific cooling tasks and allow for increased portability and convenience. Below are some of the more common benefits of using a fan instead of an AC.

 

  • Cost — As a rule of thumb, fans usually cost less than air conditioners, especially for residential usage. If you are trying to spend economically and wouldn’t necessarily benefit from the added capacity of an air conditioner, purchasing a fan may be the perfect route to take. Fans also cost less to maintain than air conditioners, since fans do not have filters, exhaust systems, and drainage concerns associated with them.

 

  • Efficiency — Fans consume less energy than an air conditioner when cooling a similar-sized same space. Whereas air conditioners create a low volume of air at a high pressure, fans create a high volume of air at a lower pressure. If you are looking to save on energy costs or only need a temporary cooling solution, you would do much better with a fan. Combined with a central air conditioning system, fans can help you save on your energy costs each month.

 

  • Green Living — Because fans don’t require refrigerant and conserve more energy when compared to an AC, they are far easier on the environment than an air conditioning unit. Running a fan is one of the cleanest ways to reduce your carbon footprint as you cool your home or workplace.

 

  • Setup — Air conditioners may involve elaborate exhaust and drainage systems, complicated installation processes, specific window or location requirements, and even professional assistance to setup. Fans operate out of the box. Merely choose a location for your fan and plug it in. Most fans do not require any assembly on your part, and those that do are easily put together.

 

  • Maintenance — Air conditioners often need air filters cleaned and replaced, refrigerant recharged, water drained, and pumps maintained in addition to the regular cleaning and upkeep any home appliance would require. Maintaining a fan involves keeping the blades clean and keeping the fan clean. Wiping it down with regular soap and water will get the job done, and you won’t have to purchase additional items not included with the fan to make sure it lasts. Fans are also far more convenient than ACs to repair and replace should a major incident befall it.

 

  • Portability — Because fans weigh less, require little or no installation, and have fewer external components than most ACs, they can be easily moved from room to room or put away for storage purposes.

 

Maintenance

Compared to other appliances, fans are relatively low-maintenance. The most significant issue related to fan upkeep is preventing dust, dirt, grime, and other buildup on the fan blades. When too many particles accumulate on the blades, the fan will spin slower, spread dust and dirt throughout the room, won’t move air as fast or as far, and will generally reduce the fan’s effectiveness. Too much dust buildup may cause the fan to stop spinning altogether.

 

The best way to avoid particle buildup is to regularly clean the fan blades, housing unit, and any air intake mechanisms. If your fan can be disassembled, simply take it apart and wipe down the various components. Refer to the manufacturer’s user manual when disassembling your fan, as the screws may be hidden or there may be easier methods to reach the blades. If your fan cannot be easily taken apart, try using brushes, sprays, or canned air to remove internal buildup. Take care not to get water on the motor or any other electrical parts.

 

Other measures you can take to prolong the life of your fan include placing it out of reach of children or pets, not running it when it’s not needed, using the fan only as it was intended, securing it from falling over or on top of other items, and giving the fan enough space to provide maximum benefit. Should it become necessary, fans are one of the easiest household appliances to replace.

 

Looking for Best Fans Manufacturer? I Recommend You…

King Fortune Electrical Co., Ltd. has become the most trusted name in industrial desk fan products. To meet the customers’ maximum satisfactions, the company has committed to its uncompromising insistence on excellence, quality and innovation. The superior quality of every King Fortune desk fan is backed by the most dedicated technical service support in the company.

 

If you have any questions or have an interest in King Fortune desk fans, please do not hesitate to send inquiry or contact with King Fortune immediately.

 

 

Article Source: https://www.sylvane.com/fan-buying-guide.html

When Should I Use A 3 Piece Ball Valve?

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The options for ball valves are seemingly endless. To select a ball valve, decisions have to be made. Which seat material? What kind of end connections? Full, reduced, or standard port ball? 2-way or multiport? What about packing? Finally, how many pieces?

 

What Is A 3 Piece Ball Valve?

Ball valves come in one, two, or three pieces. One piece ball valves are inexpensive and generally not repaired. Two piece ball valves consist of two separate pieces, with the connection between them being either threaded or a bolt and flange assembly.

 

As you may have guessed, a 3 piece ball valve consists of three pieces, two end caps and a body. The end caps are welded, threaded, or flanged to connect to the pipe on either side.

 

Why Use A 3 Piece Ball Valve?

For processes that put heavy demands on valves, having a 3 piece valve is more convenient than one or two piece ball valves. When seats and seals need to be routinely replaced, having three pieces allows for easy disassembly, servicing and reassembly without having to do major cutting on the pipe.

 

Three piece ball valves also allow for elastomers to be changed accommodating different process conditions, temperatures, pressures and flows.

 

Need to weld the valve in place? Another benefit is being able to move the body with trim out of the way while welding, ensuring the internals stay intact.

 

What’s The Big Difference Between 2 And 3 Piece Ball Valves (Other Than The Obvious…)?

Two piece ball valves were also designed with maintenance in mind. The big difference between the two is that the body on the 3 piece valve can be taken out without disturbing the two end caps. A two-piece ball valve doesn’t often allow this to happen, and it’s not possible at all with a one piece ball valve.

 

There’s also a price difference. As noted earlier, one piece valves are generally of the throw away variety. Three piece valves tend to initially cost more, but can save money in the long run in terms of time spend maintaining, and ability to change seats and seals vs. replacing the valve in its entirety.

 

Not sure how many pieces you should select for your ball valve application? If you have any interest in 3 piece ball valves, welcome to visit the website of Wellgrow Industries Corp. – the company is one of professional pipe fittings manufacturers in Taiwan. Feel free to send inquiry or contact with Wellgrow.

 

Article Source: Crane Engineering

Precision CNC Machining of Medical Implants

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Machining parts with complex geometries and fine surface finishes is common in the aerospace and automotive markets, but medical implant manufacturing takes it to a whole other level. A common saying in manufacturing for space applications is, “there is no repair shop in space.” The quality, precision and reliability of each part must be perfect because once it leaves this world, it just has to work since millions of dollars are on the line. Arguably, the same holds true in medical machining. If an orthopaedic implant doesn’t work correctly, the health and well-being of a patient is affected. When the surgery is complete, it just has to work.

 

Global demographic trends indicate that the need for medical implants will grow, and so will competition in the market. According to Seco Tools, approximately five major suppliers claim 85 percent of the orthopaedic component manufacturing market, with more than 200 companies fighting for the remaining 15 percent share.

 

Materials

Just like in any other engineering discipline, material is a critical consideration for medical implants. The two characteristics of material performance are biofunctionality and biocompatibility. Biofunctionality is more of a consideration for things such as plastic materials—the functionality of bone and joint implants is well-served by most metals. With metals, biocompatibility is the main consideration—examining corrosion properties of the metal and interaction of the corrosion reaction and the body’s tissues.

 

According to a recent article co-authored by Jan-Willem van Iperen and Ruud Zanders, engineers at SECO tools, the most common materials for knee and hip implants are cobalt-chrome alloy, such as CoCr28Mo6, and titanium, such as Ti6Al4V. Titanium is less popular but growing. Stainless steel also is used for temporary implants, as it is less corrosion resistant than cobalt-chrome or titanium.

 

Bar stock, forgings or castings are typically the starting point for machining operations, which are followed by grinding and polishing. Machining these materials can be challenging due to the same characteristics that make them functional in the body—their high strength and stiffness.

 

For example, cobalt-chrome is hard, abrasive and highly elastic. This can cause intense tool wear, compounded by the material’s low heat conductivity. Titanium, on the other hand, has the lovely property of work-hardening, as well as poor heat conductivity. During machining, heat builds up at the cutting edge and tool face.

The usual response to these types of materials is to dump plenty of coolant into the cut. However, traditional coolants can contaminate medical implants, requiring expensive and time-consuming cleaning processes. For this reason, Fusion Coolant Systems developed a coolant system using supercritical carbon dioxide. For more information about scCO2 dry-cutting technology, visit Fusion Cooling Systems.

 

Machining Operations

Like other manufactured parts, orthopaedic implants can involve several machines or computer numerical control (CNC) cutting operations, including grinding and even potentially metal 3D printing. On the machining center, operations for a typical knee implant can include roughing, tray base roughing, tray base finishing, chamfer milling, T-slot undercut machining, wall finishing/chamfering and undercut deburring. The goal is to achieve the required surface finish on the machine, reducing the need for time-consuming manual finishing.

 

Five-axis milling and grinding machines provide advantages to working with the complex shapes and contours of orthopaedic implants.

 

Cutting Tools

Seco Tools has introduced a line of cutting tools designed to shorten knee implant cycle times through high-speed machining and other aggressive milling strategies.

 

The Jabro medical range includes nine geometries and 39 tools, most of which are part of the Jabro Tornado high-speed cutting family. Each geometry is designed for particular applications in the machining of tibial tray and femoral knee implant components. Additionally, because these new dedicated tools are targeted for the machining of CoCr (cobalt-chrome) and 3-D printed Ti6Al4V ISO-S12 parts, they can be used for other medical implant components as well, including parts used in hip replacements and bone plates.

 

Should You Get into the Medical Machining Market?

If your machine shop already does high-precision or 5-axis machining for aerospace, it could be worthwhile to look into this lucrative, albeit highly competitive, manufacturing market. If your shop is eying the medical implant market, consider the following factors:

  • What is your capability for small-scale or micromachining? Some medical devices require very small components.
  • What is your capability to machine titanium and other challenging materials?
  • Can you efficiently manufacture small-batch or custom one-off complex parts?
  • Can you shop meet FDA certification standards for your machining processes?
  • Can your equipment handle the complex geometries required?

 

For more information on the equipment required for medical machining, check out this article from Mazak about its 5-axis machines’ applicability in this market.

 

By the way, if you have any interest in precision CNC machining, I recommend that you can visit Champion H&C Inc.: www.hc-aluminum.com. The company can provide a variety of CNC machined products for you. Get more details, welcome to check out Champion H&C product pages.

 

 

Article Source: https://www.engineering.com/AdvancedManufacturing/ArticleID/16486/Precision-CNC-Machining-of-Medical-Implants.aspx