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EPP’s Alex Curtiss featured in Sensors Magazine

Why Using A Plastics Machining Specialist For Instrumentation Equipment Is The Best Choice

January 29, 2016 By: Alex Curtiss, Engineered Plastic Products Corporation

 Alex Curtiss

Initial Gander

At first glance, it’s hard to see why it’s best to choose a plastics specialist to make a machined plastic part in your instrumentation product, rather than just having a metal machining company, maybe one you know and trust, do the work. A metal machining company may be able to make your plastic part. The part may look fine to the naked eye and it may also seem to work well when it’s put into a product and tested out. At first, it may even perform as it should—until something goes wrong and everyone is left scratching their heads looking for answers.

Here’s What Can Go Wrong

That’s exactly what happened to one company in Ohio who manufactures precision scientific instrumentation. A new $2 million dollar machine that they manufactured for one of their top customers was delivered and installed but soon developed an electrical problem and no one knew why. Finally, they took the whole machine apart and examined it piece by piece. Finally, in one of the plastic parts, they noticed a tiny sliver of metal embedded in the plastic.

That tiny spec was the culprit creating an electrical short circuit and that was the reason the machine had stopped working. The plastic part was machined by the company’s vendor that produces their metal components. That is one problem that can happen when a metal machining company produces plastic parts rather than an experienced plastics only specialist.

Why That Happened

This example is not a fluke. It is very difficult to adequately clean a machine that has been working on metals parts. The process can lead to contamination.

If the plastic material is soft, residual metal fragments can become embedded in the plastic machined parts. Depending on what the part is used for, the metal fragment may not cause a problem initially, but, over time, it can cause the plastic to degrade and eventually stop performing properly.

What Else Can Go Wrong

There’s another contamination risk with metal machining companies. Metal parts, unlike plastic ones, typically require the use of oil-based cutting fluids. Because of this, equipment used to manufacture metal parts, even if used for metal only occasionally, can contaminate plastic parts with those oil-based cutting fluids.

Many plastics are highly sensitive to petroleum-based cutting fluids and will degrade if they come into contact with them. Also, many plastics are hydroscopic and will absorb the cutting oils. Additionally, if these parts are being manufactured for FDA-approved uses or medical applications, they will not meet their standards.

Who Is Plastic-Materials Knowledgeable?

Generally there is not an abundance of knowledge about what plastic to use for different component applications. To say plastic is like saying vehicle. There are many types of vehicles from dump trucks to Ferraris. Both are vehicles but the quality and use is not the same. The same applies to plastic.

plastic partsPlastics specialists are knowledgeable of the variety of plastics and which are the best to use for a given application.

Metal shops are experts in metal and cannot be expected to have knowledge of the differences between the many types of plastics. Metal machining companies rarely have any in-depth knowledge of the performance characteristics of different plastics. On the other hand, a good plastic machining specialist know what plastics are best for each function and can produce the plastic part needed without risk of failure.

Ensure The Plastics Vendor Is The Correct One For The Project

Even if you do choose a plastics expert rather than a metal machining company, there are still some points to consider.

First, experience matters. Make sure the supplier you choose is familiar with each machining process you need for your application, as well as with the specific plastic material you will be using. Ask them to share information such as property charts or plastic material handbooks. Specialists in plastic machining should have a wealth of up-to-date information.

A company that specializes in only machined plastic parts not only brings expertise in dealing with plastics to the table, but can help avoid problems that might arise from contamination or simply not understanding the subtle differences between working with plastic, as opposed to metal parts.Machining metal versus plastic.

Second, check for certification. The plastic machining vendor who makes the fewest errors the first time around should give you the highest quality at the lowest cost. Plastic machining vendors can keep errors to a minimum if they are highly process driven The best ones are ISO Certified, use documented statistical process control (SPC) procedures, and own the proper inspection equipment such as coordinate measuring machine (CMM) or video inspection systems.

Remember, experience, more than anything else, will ensure a supplier can manufacture the most cost-effective part with the best quality.

About the Author

Alex Curtiss is President and CEO of Engineered Plastic Products Corporation (EPP) in Elk Grove Village, IL. The company has specialized in producing high-precision machined plastic parts for the aerospace, medical, instrumentation and water treatment industries since 1976 and has been ISO certified since 2002 and ISO compliant since 1994.

Plastic Machining: Design Guide for Plastic Parts

How to use the Plastic Design Guide

  1. Refer to the Design Considerations at the bottom of this page. Consider whether each item on the checklist is a factor in the application or affects performance requirements for the component design.
  2. Select the categories that have the greatest affect on your application.
  3. Review the materials in the Free Plastic Properties Handbook and make a list of possible material candidates.
  4. Contact our technical support to discuss options or ask additional questions.

Custom Plastic Machined Components

Plastic Machining Design Considerations

  • Thermosensitivity – tolerance can change in different temperature conditions
  • Sensitivity to humidity and hygroscopic absorption affects tolerance
  • Sensitivity to chemicals and oils
  • Notch sensitive corners and square ID’s
  • Tolerances
  • High loads
  • High impact
  • Fatigue loading or cycle loading requires consideration of flexing, deflecting, and compression
  • Temperature – max/min extent of time
  • Electrical considerations such as insulating properties
  • Wear resistance or abrasion resistance
  • Dimensional shape retention (load, cold flow, temperature)
  • Regulatory requirements (FDA, UL, etc.)
  • Appearance (color, texture)
  • Optical requirements
  • Outdoor use

Now that you’ve identified the important factors in your application, evaluate material specs in the Plastic Properties Handbook and select your material!

Plastic Machining: Selecting a Plastic Machining Vendor- Looking for the Best

Selection of a truly qualified plastic machining vendor is extremely important in today’s business environment. The time it takes to ask the right questions will pay big dividends – helping you obtain high quality machined plastic parts. And even though the rules for service and quality seem to be continually evolving, getting the best part at the lowest possible price is still the golden rule of purchasing.

If you’re looking for a plastic machining supplier, don’t settle for anything less than the best. Request a Quote from EPP Corporation today.

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Plastic Machining: Selecting a Vendor Looking at Quality & Price

Quality, of course, is directly related to price. Make sure the vendors you interview can provide the highest quality part at the lowest price. Plastic machining vendors can keep errors to a minimum if they are highly process driven, are ISO Certified, use documented SPC procedures, and own the proper inspection equipment such as CMM or video inspection systems. The plastic machining vendor with the fewest errors will produce the highest quality and at the lowest cost.

Make sure the supplier is familiar with each machining process you need for your application, as well as with the specific plastic material you will be using. Experience, more than anything else, will help make sure a supplier offers you the most cost-effective part with the best quality.

If you’d like to see how a process driven, high quality machining vendor compares to your current supplier, Request a Quote from EPP Corporation.

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Plastic Machining: Selecting a Plastic Machining Vendor- Equipment

Ask about the type of equipment the potential plastic machining vendor uses. The well-equipped plastic machining vendor will look pretty much like a metal machining shop, but the true plastic machining specialist will have equipment that has been adjusted or re-built expressly for machining plastic material. The right equipment will machine plastic using the correct speeds, feeds and tooling, and won’t pose the threat of contamination faced when metal-machining equipment is utilized. The right equipment will also insure higher quality plastic machined parts with better finishes and less chance of chips, burrs and other imperfections.

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Plastic Machining: Selecting a Plastic Machining Vendor- Purchasing Practices

Just as a metal machine shop is unlikely to have the material knowledge you need, neither are they going to be able to purchase plastics in large enough quantities to provide you with the best price.

Likewise, find out if the plastic machining vendor candidates you are considering can purchase materials directly from material manufacturer. If they rely on plastic distributors for materials, make sure their vendors are up on the latest material technology. Plastic technology is constantly changing with new materials introduced all the time.

One of your goals should be to make sure that your plastic machining firm’s materials purchasing practices are as good as yours.

To find out more about EPP Corporation’s purchasing practices, contact us today!

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Plastic Machining: Selecting The Right Plastic Machining Vendor For Your Custom Plastic Machined Parts

Not all plastic machining vendors are equipped to offer all parts. Others may not be able to give you the best prices. The following guidelines can help you locate a fully-qualified, cost effective plastic machining specialist for all your plastic machined components:

  1. Material Knowledge
  2. Purchasing Practices
  3. Equipment
  4. Quality and Price
  5. Looking For the Best

Be sure to ask potential plastic machined parts vendors how they comply with these guidelines.

If you have a need for plastic machined components, request a quote!

Plastic Machining: Custom Plastic Components- Molding vs. Machining

With every project that includes plastic components, you will need to answer the question, “Should I machine or mold this part?”

The two major factors needed to reach your conclusion are quantity of parts and level of dimensional tolerance. As a general rule, you should consider plastic machining when lower volumes are needed or tighter tolerances on the dimensions are needed – or both.

Quantity of parts is significant because of the tool cost of a molded part. If you are injection molding your part, the molding tool will typically cost several thousand dollars and tooling for complex parts can cost hundreds of thousands of dollars. Tool costs can make injection molding unfeasible for a low volume run.

Quantities between 100 and 1,000 – on some parts even up to 5,000 – are usually good candidates for conventional or milled plastic machining. Screw machining of plastics can be practical and cost effective from 500 pieces all the way up to 100,000 pieces or more.

Tolerance is a factor because plastic machined parts can typically be produced at a tighter tolerance than molded parts. Each plastic material behaves differently, but you can generally achieve tolerances +/- .005” for molded parts. Plastic machined parts can be produced +/- .001” or better depending on the material and design. This is why critically precise industries – like instrumentation, medical equipment, aerospace, fluid power, telecommunications, and many others – have turned to plastic machining for component needs.

One last advantage to plastic machining is flexibility of design. Once an injection mold has been produced, it can create only that design and any modification to the design requires expensive changes in the mold. Design changes to custom plastic machined parts are immediate and have virtually no impact on tooling costs.

Plastic Machining: Selecting a Plastic Machining Vendor- Material Knowledge

Quiz potential vendors on their knowledge of various materials and applications. Ask them to share the information they have from their material manufacturers. Do they have any property charts or plastic material handbooks to give you? Specialists in plastic machining should have a wealth of up-to-date information.

Material knowledge is a critical area. Good plastic machining firms must be willing to educate you before you finalize your choices, and help you find the best material for your application.

If you need assistance selecting a plastic material for your current project, EPP Corporation is happy to help! Contact us today!

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