Machining UHMW Plastic: A Complete Guide

Explore the ultimate guide to UHMW plastic machining. Elevate your skills for seamless fabrication.

Thermoplastic polyethylene includes ultra-high-molecular-weight polyethylene (UHMWPE or UHMW). It is also called high-modulus polyethylene (HMPE), and its molecular mass is usually between 3.5 and 7.5 million AMU. It has very long chains. The longer chain helps the polymer backbone carry more weight by strengthening molecule bonds. This creates a solid material with the best impact strength of any thermoplastic.

UHMW Material and Properties Options

UHMW Liners—The UHMW sheet is frequently used to line funnels and hoppers, safeguarding metal surfaces and keeping solid substances like sand, chipped wood, and coal moving smoothly.
UHMW Pieces: UHMW is easy to work with, so it is also used to make parts for machines that package, transport, and handle food. These parts include star wheels, idler sprockets, and under-chain wear strips.
UHMW Wood Replacement—UHMW doesn’t absorb much water, so it’s often used in marine buildings for dock fender pads, pile guards, and non-slip walkways. UHMW doesn’t rust, rot, or break as wood does.
UHMW is x-ray detectable and made visible by x-ray inspection equipment, is Polystone® M XDT. It can withstand impacts, wear well, and doesn’t slide easily, making it great for processing food and drinks.
UHMW Grades: There are different grades of UHMW, such as reprocessed, improved bearing and wear, and FDA-compliant.

Machining Parts of UHMW Plastic

When UHMW polyethylene is used to make parts, it has a great mix of fantastic qualities.

UHMW has high abrasion resistance, a low coefficient of friction, self-lubrication, a surface that doesn’t stick, good chemical fatigue resistance and impact resistance, is easy to machine, and has good noise-dampening qualities. It has many great qualities, like being very resistant to wear and damage and working well at very low temperatures (like liquid nitrogen, which is -259 degrees C). When the temperature reaches 185 degrees F, UHMW will soften and lose its ability to fight wear.

Because UHMW expands and contracts a lot when the temperature changes, it’s not a good choice for close-tolerance applications in these environments.

But Vanderveer Industrial Plastics’ CNC machining skills make it easy to create custom UHMW parts with tight manufacturing tolerances.

Process of Machining UHMW Plastic

As part of our plastic machining services, we cut, turn, shape, mill saw, anneal, and do other things to the plastic. We use automation for jobs that are done repeatedly and need to be done perfectly and consistently, no matter how many there are. This ensures the form, size, length, and so on are correct.

The problem comes from the fact that UHMW has a low melting point (270°) and a high COF (120 x 10″ IN/IN/ÜF). Our machining process for UHMW plastic:

Limit heat

It’s essential to keep heat from building up for the best results. The machining itself creates friction, which leads to heat. When heat builds up, it changes how things are measured, and the cutting tool can turn into a “melting tool.” Think about these ways to avoid this problem:

To drill:

Drills with twist angles between 12° and 18° and lots of flutes will help remove chips and heat from the cutting hole.
Grinding relief into the drill can also reduce friction. The angles will depend on the material, but 20° to 50° is an excellent starting point.
Pecking means taking the drill out of the hole often to remove chips and allow the material to cool.

Cutting and milling

Climbing milling is better than standard milling.
Use vacuum systems or mounting clamps to reduce chatter marks caused by shaking and moving. We also use double-sided tape to hold things together.
Sharp tools are essential, and avoid ones used to drill metal because they are dull and will affect the surface finishes and standards.

Sawing

Rip and combination blades with 0° rake teeth and 3°–10° set teeth are best for reducing heat from contact.
Hollow-ground circle saw blades that haven’t been set can make clean cuts up to 3/4″ thick.
Tungsten carbide blades last a long time and have good finishing.

Speeds and feeds

Rates can be anywhere from 10 to 40 FPM.
Cutting rates must be between 600 and 1,000 FPM.
To get rid of chips, use high-speed steel bits with a higher RPM.

Cooling agents

Avoid water- and oil-based fluids for a better finish and to prevent stress cracks and moisture absorption.
Pushing air through a hoover is best for a tight tolerance. The Hoover helps keep the cutting tools cool and reduces dust from the chips.

Contamination

Contamination is a significant worry when machining polymer parts for highly technical fields like aerospace and medical sciences. To ensure the highest level of cleanliness down to the sub-molecular level, our machining designs, heat-treats, and machine plastics are used. Any sub-manufactured metal work is done outside of our plant. This removes the chance of metals getting mixed up in the process.

Final Words

UHMW plastic is one of the most popular plastics for industrial parts. If finding a professional and trustworthy supplier of machining UHMW parts is difficult, contact UVTECO. We stock the frequently used UHMW plastic sheets, rods, and tubes for fast delivery.