How to Buy Pastic Parts
by Dean West
Most of the world’s fasteners are produced from metal, but many users have switched to plastic as a better material for their application. If you’re considering plastic fasteners… There are several pieces of information you’ll want to have to insure that you end up with what you need.
What Are The Options?
Many prospective customers contact Craftech for help in determining what options would best suit their applications. We’ve been helping engineers find the right plastic fasteners in the right material for over 50 years. We enjoy guiding them to good solutions for their toughest applications. Having supplied many markets, including Semi-Conductor, Marine, Automotive, Medical, Construction, Aerospace and Communications – and each has unique requirements.
Below is a list of important things to consider as you choose a plastic fastener:
- What are you looking for?
First, you’ll need to know the kind of fastener you’re interested in. What dimensions do you need? Is there a range of dimensions that could work? If a part drawing is available, it will clear up a lot of questions.
What’s your application?
Do you need to be concerned about any of the following ?:
–Chemical resistance – There are plastics available which can hold up to almost any chemical exposure. This is a major benefit of using plastic over metal. Swimming pool parts exposed to chlorine is a good example.
–Extreme temperatures – Plastics have maximum service temperatures up to 300 degrees Celsius.
-Low outgassing – This is a big concern in the semi-conductor and aerospace industries, where there are high vacuum environments.
-UV ray exposure – Some materials hold up very well to UV rays. For others, a UV inhibitor can often be added to help lessen their effect.
-Wear – This is an obviously important issue for bearings. Certain plastic have excellent wear resistanace.
-Weight – Different plastics vary appreciably in weight. But most are less than metal especially where weight in the application is an issue.
-Strength – There are plastics as strong as stainless steel. While the addition of glass or carbon fibers can make the materials much, much stronger. There are several measures of strength to consider – depending on your application. These include tensile, compressive, and impact
-Dielectric properties – These are important in the electronics industry. Factors that affect dielectric strength in applications include temperature, part thickness, and rate of voltage increase.
-Non-conductivity – Plastic materials with low conductivity are used as thermal insulators.
-Color – Each plastic material has its own natural color. Parts can be molded in almost any color, and some can be made transparent.
-Cost – There is a wide cost variance between plastic materials. Recycled material can sometimes be considered at savings.
-Non-flammability – This could be important for parts potentially exposed to flames. Flammability tests measure combustibility, smoke generated and ignition temperatures of materials. Additives can make plastic non-flammable
-Water absorption – If the product will have exposure to water, this could affect the weight of the part. Mechanical, electrical and dimensional properties can also be affected.
- What are your quality requirements?
Do you need parts that fit the ANSI or DIN standard? What testing is required? Do you require an ISO certified supplier? Will you want certification of the material used? Does the part require particularly tight tolerances? Craftech can offer all of the above.
- What plastic material is best?
Choice of plastic is critical, as it affects function, longevity, appearance and price. You may or may not know what material you need. Craftech routinely uses dozens of them, and we can guide you to the best plastic for your need. Some materials can be machined, but not molded. The opposite is also true.
- When do you need parts?
If your need is urgent, it would be best to find a supplier who already makes the part – and hopefully has it in stock. We inventory thousands of different plastic fasteners at Craftech, and can often ship right away.
- How many parts are needed?
As with many things, higher quantities can translate to lower part price. Quantity can also dictate the manufacturing process that is most appropriate. For small and moderate volumes, machining is often the right approach. For higher volumes, molding parts is often more cost effective – and consistent. If a mold needs to be built for your part, there are associated costs and a time commitment.
As with any important purchase, choosing a good supplier for plastic components is very important. You will want one who can offer good technical support – particularly with material selection.
At the end of the day, we all want good value. Craftech’s value proposition includes competitive price, quality, customer service, technical expertise and on time delivery. Our customers have rated us highly on these important factors.