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Electrical Discharge Machining And Mold Making

   The use of electrical discharge machining is so essential that it is almost impossible to imagine a modern shop without an EDM machine. Many of today’s products simply could not be produced without it. Think of all the cell phones, calculators, IPods, cameras, medical devices and the endless amounts of high tech equipment that are made out of plastic!

Besides the essential role it plays in plastic injection mold making, EDM is used for the precision machining of medical parts, aerospace parts, and other highly specialized products. Electrical discharge machining, including Wire EDM, has also completely changed the way molds are made, as well as other specialized parts.

This is your information source for the EDM die sinker

Graphite  Copper EDM Tooling EDM Oil
EDM Filters Specialty Electrodes Carbide EDMing Surface Finishes

Check out the pages dealing with graphite, graphite dust, copper, dielectric fluid, electrode holders, and machinery.

What about jobs in EDM?

Find out what kind of personality it takes to have electrical discharge machining as a career job. See what the future holds in this high-tech profession.

You can also find educational material that attempts to explain this rather mysterious process. Not so long ago, it was as much black art as science. Today, however, much of the mystery is removed due to CNC controls.

Most shops send their operators to classes put on by the manufacturer of their EDM machine. It is foolish to invest so much money in a machine and skimp on the training! But it happens all the time.

What about EDM and stress?

EDM is quite a stressful occupation, to put it mildly. It may not appear difficult, but the stress levels can be exhausting. Nearly every mold component that is EDM’d is in the final stages of manufacturing. The slightest mistake can become very costly, very quickly.

There is nothing quite like the feeling of coming to work in the morning and seeing your supervisor leaning over the EDM machine staring at your workpiece. Then you find out that you had mixed up two locations and the completely finished cavity block is now completely useless!

Injection Molding Process

Process of Injection Molding

The process of injection molding process is best explained as heating up a type of plastic and under a forced type or pressure is poured into a predesigned mold, after the hot liquid is poured into the mold the mold is clamped shut to prevent any air from getting in. After the initial work is done, the mold hardens and takes the shape of the mold.

Then the next step in the process is when the resin (hard plastic) which is now in the shape of a small pellets are poured into the feed hopper, the hopper is a large open bottomed contained and what it does is that is filters the pellets into the screw.

As the screws turn the resin pellets are moved into the screw and then they go through a very intense pressure. Then friction is created and when that happens heat is generated to melt the pellets. There are heaters on both sides of the screws and there is temperature control during the melting process.

The oil gets pumped from the tank to the injection molded parts that run along the tie bar equipment, then that’s when the liquid plastic gets injected into the mold. Then the water-cooling technique is applied in assist in cooling off the mold. The process is complete when the mold is pulled from the pre-designed mold.

Custom Molding Jobs

Custom Injection Molding Jobs

In the industry of injection molding, things work on a very specific scale. The molds must be right, the specifications must be right. That is true for the molds that are already designed. When a company wants and needs brand new design molds the process must be handled very delicately.

When an plastic molding company gets contracted by a new company to design and fill molds. The company needing the molds must be very accurate and very specific when it comes down to doing a custom job. One slight imperfection and the whole project could be worthless. Time is money and that is not something that either can afford to be wasted.

The injection molding process is a specific one, there are certain stages and certain things that have to be done and if your design has a flaw in it then there are going to be set backs. When a mold comes out after it hardens, it looks great a little rough around the edges, but it looks what it is supposed to.

Molding produces great products and there is a science to the skill in making the molds and producing the injection molds. If you are a company who is looking for a custom design, make sure the specs and designs are not flawed and you will get an unbelievable product.

Contract Injection Molding

Contract Injection Molding

When you are looking for a company to do a terrific job handling your custom injection molding contract. You want to make sure that they can cover your needs. If at all possible, tour the facility of where you are interested in having your work done. But you want to make sure their facility can handle the load.

You want a company that handles both a large and small volume of work. Some companies only will do a certain amount of work therefore they turn down small amount jobs. You want them to provide samples, you want to be able to see what kind of job they will do for you before you contract a huge order and do not like the work.

You want full production abilities, process optimization, and Insert molding and over molding, PPac capabilities. You also want packaging and domestic and international shipping capabilities. The company that you contract for your work, you want to handle the type of job you have for the price that you want.

That is why it is important to tour the facility to see first hand how the company will handle your job load. You want a guarantee that the job you give them will be nothing less than spectacular. This is what contract Plastic molding is all about.

Injection Molding Machines

Injection Molding Machines

One type of injection molding machine is the Milacron LIM, Liquid Injection Molding; there are many benefits in having this machine over the traditional LIM. This machine has its own controls and especially made soft ware for this product only. It has a low pressure set up for injection setup and it has a closed loop control.

Unlike the traditional LIM this machine has an increased power ejector force, so it can inject the mold quicker. It has a standard injection screw, a cooling plate on both sides, eight new pneumatic valves, and two heat zones on each paten, a 3-stage air ejector. The improvements from the standard LIM also include a revised rear seal on the injector screw and also a revised seal that is on the nozzle.

These machines have a thermo set process that uses a silicone rubber material that is used to be injected into the heat plastic molds. The best part about these Milacron machines is that no other machine can use their software is designed just for their machines and no one else’s. The Milacron also has a complete design line of Fluid Auto meter mixers.

Milacron is one of the best in the business of injection molding and if your company needs to replace a machine, consider this one, it is one of the best.

Injection Molds

Injection Molds

The designs of the mold are predetermined by whose company is requesting the parts. A lot of thought has to be put into making the molds, the molds have to be designed so that the molds don’t get stuck inside the mold and ruin the piece. The molds are designed that when the resin (hard plastic) is complete that the mold can be taken out and polished to be the piece that the mold was designed for.

If any air gets into the plastic molds or any kind of condensation the mold could get ruined and must be done again. This is not very productive, so the molds must be made to the exact specifications. The molds come in tow parts called the core and the cavity, the core is the middle of the mold and the cavity will encase the core when the mold is complete. Each part must be removed with care, any imperfection and the mold has to be tossed out.

There are molds that they are considered easy and then they have what they call the more complex molds. Some molds are very complex that they have different parts to them such as slides as well as a core and a cavity. Remember, you can create a car door with injection molding so you have to know that the mold for that is going to be very complex.

When you get a mold that is very heavy, the core and the cavity in conjunction with cooling hoses working together they form a molding tool. Sometimes when the tools are heavy they have to be lifted into the molding machine. When the tool needs to be cleaned or maintained they can hoist it back out again. So far, these are the basics of injection molds.

Injection Molding Glossary

Injection Molding Glossary

Injection Molding: this is a technique used to fabricate parts made from thermoplastic materials.

Thermoplastic materials: are materials made out of plastic that are able to melt into a liquid when heated at a high enough heat and when it freezes it will be in a glassy state when it is cooled.

Polystyrene is a polymer that is a liquid hydrocarbon that is commercially made from petroleum.

Polypropylene is a very hard plastic that is used for many different uses such as food packaging, reusable containers and textiles. It is a very durable and rugged unusually.

Resin is comes from many plants especially from the Coniferous tree that is used for its chemicals. You can use resin for adhesives and incense and some perfumes.

Solidify is to become hard or firm.

Pellet is a small compressed piece of material or a substance.

Nylon is a chemically resistant, it is also heat resistant, but it is tough and very flexible.

Injection Molding Questions and Answers

Here are some frequently asked questions when there are problems in the process of injection molding, here some of the most popular ones and their solutions.

What happens when the molds are brittle and delaminate? The cause may be an improper injection screw. The screw that is used for molding at a low-pressure ratio fro the amount of resin being used; causes the plastic’s molecules to form incorrectly. Basically, a weak molecular structure can cause brittle parts. When this happens de lamination can occur as well. The result will be a to take a pressure reading and record the ratio. This should be performed once every six months.

Another problem may be discoloration; the possible cause for this may be excessive dwell time or what they call residence time. When a part has been discolored or changed the problem is usually found in the residence time. The material stays in the barrel too long, the base will become discolored. What can be done is the heat sensitive materials have to be set at a certain ration. After every injection shot clean out the barrel.

Discoloration may also be caused by an improper plastic mold temp. The hotter the mold is it will keep the material melted for a longer period of time. The temp of the mold should be adjusted to the supplier’s specs on material and cycle times.

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