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2 min read

UHMW 101: From Molecular Weight to Machining

By Dave Biering on March 20, 2018

UHMW 101: From Molecular Weight to Machining

UHMW remains a hot topic here on Tech Talk, and on our Ask the Experts portal, too. Why is this true? For one, the material offers great value over other plastics, and has good abrasion-resistance properties, plus it is processed via a unique control (no molding, only machining). This trifecta of properties values make for a distinctive material, read on for more top FAQs:

UHMW is short for ultra-high molecular weight polyethylene; or a semi-crystalline polymer. As a point of reference, high-temperature polymers are classified based on their molecular structure. Semi-crystalline polymers are solid until heated to certain temperatures, where they will quickly turn to liquid. Amorphous polymers do not exhibit any crystalline properties and resist liquid melting. UHMW is a considered a high-density polyethylene with a median molecular weight (falling within a range of 3.1 to 5.0 million).

1) UHMW has a low melt point, but a high COF

Like all polyethylenes, UHMW has a low melting point (270°) and a high COF (120 x10” In/In/°F). It gives one of the lowest wear rates (even better than steel, nylon or fluoroplastics) to resist most forms of abrasive media. These qualities give the material good impact resistance.

2) Molecular weight = better abrasion resistance

Molecular weight has a direct impact on a material’s ability to resist abrasion. For instance, a molecular weight grade of 4 million has an abrasion resistance of 100 when measured using a sand slurry test. Yet when you increase to the molecular weight to 6 million, the abrasion rate goes to 75, or an improvement of 25%. Compare this with steel, which has a resistance of 160 and it becomes clear why the material is a good choice for abrasive wear environments.

3) No molding, machining only

Though known as a tough material, UHMW cannot be molded; machining is the best processing method. In fact, waving and warping are common to large sheets of virgin UHMW, so molding is nearly impossible without compromising the integrity of the material. And unless you use the right tools and techniques (revealed in this technical guide), your machine cutting tools are known to actually become melting tools instead! Coolants are critical to maintaining the right heat levels.

4) Beware of expansion to avoid deformation

When machining UHMW, special attention must be paid to how quickly the material expands (up to 20x the rate of steel expansion). Anytime you machine UHMW, or any material with instability, it’s critical to consider the final operating conditions of the part and machine accordingly. Materials that are fabricated in a warm climate will expand and contract and otherwise behave differently when installed and operated in cold-weather environments, and vice versa.

5) Inert to most chemicals

Most liquid solutions are compatible with UHMW, including various forms of alcohol, ketones, and acids. But one should beware of chemicals with high-oxidation, like bleach, and hydro carbons like gasoline.

UHMW is available in many variations, including glass or moly-enhanced or cross-linked. Submit your specs to our team, and we can walk you through the pros and cons of each.

Custom Plastic Fabrication: Get the Guide!

Topics: UHMW
2 min read

Machining UHMW: Why Is Holding Tolerances So Difficult? (GUIDE)

By Dave Biering on October 10, 2017

Machining UHMW: Why Is Holding Tolerances So Difficult?

Ever tried to machine UHMW? It’s no easy task given the material’s instability. In fact, UHMW has 12x the expansion rate of steel. Controlling heat with the right coolant and tools is critical. Let’s review some techniques:

Ultra High Molecular Weight (UHMW) polyethylene is a semi-crystalline polymer that offers good abrasion and impact resistance plus a low coefficient of friction. It’s flexible enough to excel in both wet and dry environments with good wear and service life. These are the pluses.

But one of the negatives that we often hear about is that the material is incredibly hard to machine; particularly for those shops who are new to plastics. Yet machining is a must, since the material is impossible to mold. Like all polyethylenes, UHMW has a low melting point (270°) and a high COF (120 x10” IN/IN/ÜF), which all contribute to the challenge.

Limit heat!

For best results, it’s critical to reduce heat buildup, since the very act of machining generates friction, and thus, heat. An accumulation of heat presents dimensional challenges where your cutting tool can instead become a “melting tool.” To avoid this challenge, consider these techniques:


  • Drills with twist angles of 12°-18° and with large flute areas will help remove chips and heat from the drilling hole
  • Grinding relief onto the drill will also reduce friction. Angles will vary by material, but 20°-50° is a good starting point
  • Remove the drill from the hole (pecking) frequently to remove chips and give the material a chance to cool slightly

Milling and Cutting: 

  • Climb milling is recommended over conventional milling
  • To reduce chatter marks from vibration and moving, use vacuum systems or fixture clamps. Double-sided adhesive tape is another option to keep parts stable. 
  • Sharp tools are critical, and avoid tools that have been used to drill metal, as they are dull and will impact tolerances and surface finishes


  • Rip and combination blades with a 0° tooth rake and 3°-10° tooth set are best to reduce frictional heat
  • Hollow ground circular saw blades without set will yield smooth cuts up to 3/4" thickness
  • Tungsten carbide blades wear well and provide optimal surface finishes

Speeds and feeds:

  • Feed speeds can range from 10-40 FPM
  • Cutting speeds of 600-1,000 FPM are required
  • Use high-speed steel bits with a higher RPM to clear chips


  • For a premium surface finish, avoid water- and petroleum-based fluids to reduce stress fractures and moisture absorption
  • Vacuum air blowing is preferred for a tight tolerance. Vacuum keeps cutting tools cool, plus helps reduce dust from chip evacuation.

Without the right heat levels, you risk an uneven surface finish and an accumulation of plastic debris (burrs). For more UHMW machining techniques, get the Guide to Machining and Custom Fabrication!

Custom Plastic Fabrication: Get the Guide!

Topics: UHMW
1 min read

Trilon Modified UHMW – Ideal for Custom Components

By Dave Biering on April 10, 2014

Trilon AR and FRA question was recently posted to our portal asking about Trilon as a custom component.  Trilon is a modified-UHMW that gives superior wear in highly-abrasive environments. The material is available in variety of formulas, and can be fabricated in the field, or easily customized in-house using carbide or diamond tools.  Trilon excels in industries where durability and longevity matter; including mining, pulp and paper, and timber handling.  Explore our Railroad White Paper to review how custom Trilon FR components delivered superior fire resistance to a mass transit system.

Both Trilon AR and FR give nearly double the wear life of virgin acetal, and up to four times the wear  of nylon.  And since Trilon has a dynamic friction of just .07, the material requires less energy to drive systems ― which can help lower your operating costs. 

Look to Trilon for:

  • Lightweight alternative to stainless steel (8x lighter)
  • Self-lubricating properties that “polish” mating materials to reduce friction
  • Abrasion, moisture and all-weather tolerance
  • Lower operating costs

Ask our design Experts for a quote on Trilon custom components today!

Topics: UHMW Trilon Custom Bearings