Tag Archives: EDM machine

How to Increase the Process Speed of Die Sinking EDM

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Developments in the EDM process and its technology along with improvements in accuracy, automation and micro-mold making technology can pay enormous dividends to the domestic mold making industry.

 

Speed Is Not the Solution

Increasing drive speed is one solution to improving the speed of die sinking EDM. In this way the unproductive times for lifting movements are reduced; however, the gain in speed is limited to small electrodes and very deep cavities. In addition, above a certain speed the electrode wear is considerable and very high axis speeds result in extreme strain on the mechanism, make the machine more expensive and shorten its working life. Therefore, it is wrong to believe that a general increase in the process speed is only to be achieved by rapid lifting movements. The contribution of fast axes to the machining process is just one supplementary aspect to a complex interaction that encompasses the generator, process control, gap width regulation and the mechanism. And die sinking EDM requires intelligent flushing.

 

Potential Lies in the Flushing

You can imagine the EDM process as being a balance between the EDMed and evacuated material in the gap. If this balance is not present, then either you flush the machining area unnecessarily—involving a loss of time and additional instability of the process—or you EDM the same particles several times, which cannot be removed from the gap sufficiently.

 

Die Sinking EDM

Before the material can be evacuated from the gap you must remove it from the workpiece. So how can you achieve more removal? As in the case of all optimization problems, the greatest gain potential lies where the efficiency is smallest. The efficiency of a single discharge with a cathodic poled workpiece is theoretically about 25 percent.1 In addition there are some factors that make the efficiency even worse (e.g., process control problems, non-ideal flushing conditions, small gap width), so that realistically you must reckon with an efficiency of less than 10 percent.

 

Removal and Surface Quality Determine the Time Requirement

In the case of EDM, the objective is always to optimize the removal performance of the machining on one hand, and to achieve the surface quality of the workpiece to be machined on the other hand. The workpiece, when machined, is intended to display a certain final roughness and a certain form precision. In addition, two conditions are called for:

 

  1. As small a thermally influenced area of the workpiece surface as possible
  2. As low an electrode wear as possible.

 

These marginal conditions determine the machining time and costs for workpiece production. In practice, a sequence of technological parameters is used because starting out from the roughing to finishing settings, the pulse energy is gradually reduced until the required technological results are achieved. Once again the law of nature applies: you can quickly achieve results of modest quality, but only slowly results in high quality.

 

Physical Processes Show a Solution

The approach toward an ideal state means moving the characteristic curve in the direction of the arrow. That means faster EDM with the same gap width, roughness and wear. If, up to now, the discharge energy of the EDM pulses was increased, regrettably you also only had greater roughness and a greater gap width so that the gains in speed during roughing were lost again through longer finishing. You will find a way to a solution if you return to the basics of EDM theory—to the physical processes leading to the formation of the spark and metal removal.

 

During the discharge, you can identify three main physical phases in succession:

 

  1. The Build-Up
  2. Discharge
  3. Fade Phases

 

In the first phase the discharge canal is built up. After passing through the working medium, the current flows almost exclusively on the surface area of the discharge canal and the anode is partially evaporated by the electron bombardment. The electrode wear mainly takes place here. Every pulse—whether contributing intensively to removal or not— causes microscopic wear. In the discharge phase, the electrical energy supplied causes melting or evaporation of material mainly on the workpiece. The fade phase begins with the switching off of the power supply. The plasma canal collapses and the partially evaporated, partially liquid material is ejected.

 

When to Interrupt Pulses

During the discharge, a crater forms in the workpiece. Fundamental studies of discharges have shown that the growth of the crater in the workpiece stagnates from a certain time. This is because a balance forms between the energy supplied and the energy lost, as well as energy that is used for the maintenance of the plasma and the heat loss to the workpiece and dielectric. This asymptote of the crater growth can be recorded in real time from the spark voltage and current.

 

However, why is the asymptote of the crater growth so important? Because this is the right moment to interrupt the pulse. It is unnecessary to let a pulse last longer if the target radius of the crater and the required roughness have been achieved. You can begin with the next pulse immediately. The time required by the pulse to reach this state also is not constant, as the speed with which a discharge reaches a certain spark base diameter depends on the macroscopic situation in the gap and the local geometry in the spark discharge area. With this first measure alone, you will optimize the number of discharges per unit of time and increase the removal rate.

 

When to Increase the Current

If you now observe the charge’s fade phase you will see that the removal from the workpiece is caused by the collapse of the plasma canal. The sudden drop in pressure—triggered by switching off the power—causes the evaporation and ejection of superheated material. The plasma canal has a very high temperature and pressure. The gradient of its collapse influences material removal. The more abruptly the energy disappears, the better the crater material will be ejected. In order to enhance this effect, a special trick is employed: before the pulse is interrupted, the current is increased briefly. The idea of increasing the pulse current is not new, the innovation is the definition of the point in time when this increase is to take place. The increase in the pulse current has no consequences for the roughness, wear or gap width, but does increase the removal. In addition, as the removal per pulse is greater, you need fewer pulses for the machining, and therefore the wear sinks.

 

Removal Rate Doubles in Part

This new machining strategy (asymptote detection, current increase and pulse interrupt) is the subject of a patent application for its use in new EDM die sinking systems. The results are in accordance with the theoretical reflections, especially where good flushing is guaranteed (e.g., pre-machined workpieces). For these machining jobs removal rates have doubled.

 

Generator Brings Striking Improvements in Performance

The innovative generator offers an increase in productivity of approximately 30 percent; however, up to 100 percent with pre-milled molds that occur increasingly nowadays through synergies with HSM. This refers to all roughing and finishing using copper and graphite electrodes. The advantages are particularly great with good flushing conditions and pre-milled workpieces. These convincing results explain that it is possible to increase the speed and productivity of die sinking EDM, and the potential for improving this technology is still considerable.

 

If you need more information about die sinking EDM, please try to visit the website of Excetek Technologies Co., Ltd. – the company is the well-known brand for its EDM machines. Get more details about Excetek, welcome to check out their product pages and feel free to send inquiry to them.

 

Article Source: MoldMaking Technology

EMO Hannover 2017 : Taiwan Excetek Technologies Is Going to Attend This Grand Event

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More than 2037 exhibiting companies from 41 nations will be seen participating at EMO Hannover. With exchange of industrial knowhow and specialized networking events as the highlights of the show, the entire business community benefits from it.

 

The products and services demonstrated in this show are as follows, Turning machines, Drilling machines, Boring machines, Milling machines, Flexible manufacturing cells and systems, Transfer machines, Grinding machines, Tool grinding machines, Planning, shaping, slotting and broaching machines, Gear Cutting and finishing machines, Sawing and cutting off machines …etc.

 

Taiwan local company Excetek Technologies Co., Ltd. is also going to attend this grand event. Excetek is famous for its Wire Cutting Machine, Small Hole Drilling Machine, and EDM Machine. If you will enjoy this B2B event, try to visit the booth NO.D88 HALL13 of Excetek to obtain more information about their company and machinery.

 

Pack your bag and get ready to attend this exciting B2B event – EMO Hannover 2017. Related information please check out here: http://www.emo-hannover.de/
EMO Hannover 2017

What Are the Different Types of CNC Machining Tools?

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The most common types of CNC machining tools are the vertical milling machine, lathes, and drilling or boring machine. Other types include EDM machines, laser cutting machines, and water jet profilers. These are just a few of the examples used in the manufacturing industry today.

 

The acronym CNC stands for “computer numerical controlled.” In these tools, a computer or “controller” drives the machine according to G-code instructions. The machines are designed to quickly perform repetitive tasks accurately at high speeds. Common tasks include cutting, grinding and drilling.

 

Fabrication of modern CNC machining tools began as early as the late 1940s by John T. Parsons to produce wing sections for the United States Air Force. Today, the range of products made with these machines is vast. CNC machining tools produce highly specialized parts for machine and automotive industries around the globe. Other types of industries that utilize CNC machining tools are the woodworking and granite or stone industries.

 

The main component of CNC machining tools is the machine control unit. This unit reads and decodes instructions, generates axis commands and feeds motion commands to circuits that drive axis mechanisms. It also controls the spindle, coolant and tool change functions. Other components of CNC machining tools are a program input device, which installs a part program into the CNC control, and a part program, which controls the movement and functions of the machine.

 

Various types of machinery use CNC as a controller. A lathe or turning center is a common type of CNC machining tool. This type of machine is capable of performing various lathe-cutting operations automatically. Laser cutting CNC machining tools are another type, and use a focused beam of laser light to cut a wide range of materials.

 

CNC EDM machining tools operate by using a thin wire as an electrode. The resulting erosion caused by the arc is what does all the cutting. CNC controls the table movement, as the wire remains stationary during operation.

 

A machining center is the latest type of CNC machining tool. It is capable of performing various tasks such as milling, boring and drilling in a single setup. Pallets or worktables automatically exchange work pieces as needed. The machining center automatically changes tool heads to perform the specific tasks as needed.

 

OCEAN Technologies Co., Ltd. is the manufacturer of specializing in CNC EDM machines. We provide EDM machines include micro EDMs and CNC drilling EDMs…etc. If you are interested in learning further details about OCEAN’s EDM machine series, welcome to browse our website or contact with us directly to obtain more information!

 

Article Source: http://www.wisegeek.com/what-are-the-different-types-of-cnc-machining-tools.htm

EDM 101: Electrical Discharge Machining Basics

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EDM (electrical discharge machining) has long been the answer for high accuracy, demanding machining applications where conventional metal removal is difficult or impossible. Conceptually, it is very simple; electrical current passes between an electrode and a workpiece.  The spark discharge erodes it to form the desired final shape.

 

The whole process takes place in a dielectric bath such as oil or deionized water. EDM was developed during the Second World War by the Lazarenko Brothers in the Soviet Union and has since evolved into a major industry with several types of machinery. Electrical spark discharges have long been a method for achieving extremely high temperatures. In EDM processes, the plasma-like 10,000 C temperatures can create a complex environment at the microscopic level on the workpiece surface.

 

While it is generally understood to be a high temperature melting process, what is actually happening on the workpiece surface is still a subject of research. The major challenge in efficient EDM processing is control of electrode. There are other parameters, including electrode shape for some processes – issues which made computer numerical control a breakthrough technology for widespread adoption of EDM.

 

Three major types of EDM machines

 

While there are numerous specialty forms of electrical discharge machining, industrial machines are commonly grouped into three categories:

 

  • Wire EDM
  • Die sinker or ram EDM
  • Hole drilling or “hole popper” machines

 

As the name implies, wire EDM uses a thin wire as the electrode, which carries the spark inducing electrical potential. It is programmed to move in a carefully controlled pattern roughly analogous to a woodworker’s scroll saw. Control of the wire movement in an XY plane is similar to other CNC-driven technologies, but with the unique conditions of EDM and special requirements. Logical discharge erodes the electrode as well as the workpiece, so typically a spool of wire is used for the electrode, passing continuously by motor drive to present a fresh discharge path in the cut.

 

Also, during the process an unstable discharge can be created if the dielectric breaks down in the cut region, or wear debris contaminates it. Control electronics can compensate to a certain extent, but clean dielectric fluid must be pumped continually to flush the cutting zone.

 

The “cheese cutter” wire EDM technology is popular, but has one important limitation: wire must pass entirely through the workpiece, making essentially a two-dimensional cut in a three-dimensional part. Complex cavity shapes that are needed in many tool and die applications, such as metal stamping dies and plastic injection mould can be EDM processed using “die sinker”  (sometimes called “ram”) EDM.

 

In this process, an electrically conductive graphite electrode is machined precisely to form a “positive” of the desired cavity that is carefully plunged into the workpiece. Logical spark occurs over the surface of the graphite electrode. The ability to produce complex, three-dimensional cavities is a major advantage. Disadvantages include the need to machine the electrode, more complex electrode wear control issues and occasional difficulties in flushing the cut.

 

EDM can also be used in hole-making operations. If a small pilot hole is pre-drilled in the workpiece, wire can be threaded through, and conventional wire EDM used. Where this is impossible – in blind hole applications, for example – a specialized EDM hole making machine can be used. Commonly called a “hole popper,” these machines use a rotating conductive tube as the electrode, with a continuous flow of dielectric (usually deionized water) to flush the cut.

 

This technology is also used with wire EDM machines to create the pilot hole necessary for wire threading. Accurate, precise holes are possible and have allowed for several advanced technologies. Perhaps the most important is the use of EDM created cooling holes in high temperature alloy turbine blade sections. This permits a “film cooling” process, which allows jet engines to operate at higher temperatures for greater durability and efficiency.

 

Why EDM?

 

In practical terms, Electrical Discharge Machining overcomes a major issue with conventional machining: hardness.

 

In traditional machining processes, metal workpieces are typically made from special grades of hard enable tool steels, which are machined in an annealed or soft state to facilitate cutting.

 

After the desired shape is machined, the parts are then hardened by one or more heat treatments. This adds time, cost and can alter the finished parts’ dimensions, especially if a poorly controlled heat treatment process is used. EDM, however, can cut hardened materials and exotic metal alloys and as a bonus produces excellent surface finishes, frequently reducing the need for post machining grinding or surface treatment steps.

 

Like all machining processes, EDM is a balancing act between speed and surface finish. In wire EDM processes for example, it is common to use a faster, rough-cut followed by the finishing or skimming cut, which uses a less aggressive flushing profile to minimize wire deflection. Material removal can be precisely controlled, typically measured in “tenths.”

 

If you need further details about electrical discharge machining, welcome to visit our website and feel free to contact OCEAN Technologies Co., Ltd. – the professional EDMs manufacturer in Taiwan.

 

Article Source: http://www.engineering.com/AdvancedManufacturing/ArticleID/10100/EDM-101-Electrical-Discharge-Machining-Basics.aspx

 

What is Electrical Discharge Machining (EDM)?

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Electrical discharge machining (EDM) is a type of machining operation used for shaping conductive workpieces into geometrically complex parts. Electrical discharge machines are particularly ideal for machining components that have complicated contours or subtle cavities that would be difficult to produce with other conventional machining equipment. The process involves supplying electricity to both the shaping tool as well as the workpiece and then bringing the tool into close proximity with the workpiece, which is completely immersed in a dielectric fluid bath. This proximity causes the electrical field intensity between the tool and workpiece to overcome the strength of the dielectric fluid, and produces a series of electrical discharges between them. These electrical discharges remove material from the workpiece, and the pattern or shape of material removed is dependent on the shape of the tooling electrode. After the machining operation, the dielectric fluid is replaced between the electrodes. Apart from acting as a dielectric between the two electrodes, the fluid also plays a key role in the machining process, as it is used to flush away the removed material and cool the machined area. The nature of the process is such that, while material is being removed from the workpiece; the tooling electrode is also gradually eroded, making periodic replacement necessary.

 

The electrical discharge machining process is extremely precise and generally used in the production of components that are typically complex and require extreme accuracy. In addition, another area of application that EDMs perform above par is in the machining and shaping of hard or exotic materials such as titanium, Hastelloy, Kovar, Inconel, as well as hardened steel. However, the only caveat with the electrical discharge machining process is that it can be only be used with conductive materials.

 

There are essentially two types of electrical discharge machines, which differ in the type of tooling electrode that they are outfitted with. They are sinker EDMs and wire EDMs. The sinker EDM, also known as a ram EDM uses a shaped tooling electrode to facilitate the machining process. This tooling electrode is formed by conventional machining into a shape that is specific to the application it is used for and an exact reverse of the shape to be machined into the workpiece. The tooling, typically machined from graphite, is used with an insulating fluid such as oil or other dielectric fluids. This shaped tooling is connected to a power supply and made to approach the workpiece electrode, creating electrical discharges between them, which cause erosion in the desired shape. This type of EDM is typically used for precise machining of complex 3D parts, such as injection molding, die tooling, and other components that require exceptional accuracy.

 

The wire EDM, on the other hand, is an electrical discharge machine that uses a fine metallic wire, usually made from brass, which acts as a cutting electrode to accurately shape intricate, complex components from thick metal plates. The wire and workpiece are both supplied with electricity and when the wire approaches the workpiece, electrical discharges occur between them. These discharges remove material from the workpiece in a shape that is similar to a cutting or slicing action. As the wire electrode is eroding along with the workpiece, it is continuously fed into the workpiece from a spool to ensure uninterrupted cutting operation. The wire is fed through two guides, typically made from diamonds, each placed above and below the workpiece electrode. These guides are movable on a 2-axis x-y plane and are CNC controlled for cutting. The cutting operation occurs on a workpiece that is completely immersed in a dielectric fluid bath, normally de-ionized water, which is used as a coolant and to flush away the removed material. This machining process is used to cut complex and intricate 2D shapes on thick metal parts, especially components from hard and exotic metals such as Inconel and titanium. Some components commonly machined using wire EDMs are stripper plates, custom gears, and other parts that need to be intricately cut out. However, the advent of upper guides and multi-axis freedom of movement in the newer wire EDMs, allows these machines to cut intricate tapers and transitional shapes as well.

 

Welcome to visit EXCETEK, the leading manufacturer of wire cutting machine, established in 2006 specializing in various series of wire cutting EDM machines (Electrical Discharge Machining). We insist to provide only the best electrical discharge machines and related accessories to our clients around the world, and we have also earned well reputations by high quality wire cut machines we manufactured. For more specification, please browse our product list and feel free to contact us, the superior EDM machine manufacturers to get more wire cutting machines and electro discharge machining.

 

EXCETEK TECHNOLOGIES CO., LTD.

No.10, Fenggong 3rd Rd., Shengang Dist., Taichung City, Taiwan

TEL：+886-4-2520-0688

FAX：+886-4-2520-0111

E-mail：info@excetek.com.tw

 

Article Source: http://EzineArticles.com/3778819