Material Matters: Delrin
While Delrin is a household name in the world of machining materials, the name itself is actually a brand name of the company DuPont. The engineering thermoplastic behind the name is polyoxymethylene (POM), an exceptionally strong, stiff, versatile, low-friction material that is easy to machine and known as the most metal-like plastic. Delrin is ideal for high-load mechanical applications, such as gears, ski bindings, and car door lock systems.
Delrin is an acetal homopolymer resin, as opposed to an acetal copolymer resin, the former having a larger crystalline block structure with better internal bonding and superior strength. There are a number of other companies with their own POM formulations and brand names, including Duracon, Celcon, Hostaform, and Ultraform. DuPont’s Delrin is the most popular — so popular, in fact, that the brand name is often generically used to refer to all varieties of POM. It’s also one of our favorite materials to machine.
HISTORY
German chemist and Nobel Prize winner Hermann Staudinger is credited as having discovered POM in the 1920s, but it wasn’t thermostable enough to be commercialized. In 1952, DuPont chemist R. N. MacDonald synthesized high-molecular-weight POM, and in 1956, DuPont filed a patent for a heat-stable POM homopolymer, credited to inventor Stephen Dal Nogare. By 1960, DuPont constructed a dedicated plant in West Virginia to produce Delrin.
PROPERTIES
- Low friction
- High resistance to wear, fatigue, and creep
- High tensile strength, stiffness, and toughness
- Lightweight and enables thinner part designs
- Low cost
- Dimensional stability during high-precision machining
- Withstands moisture, gasoline, solvents, and neutral chemicals at room temperature
- Challenging to bond
- Not very resistant to strong acids, oxidizing agents, or UV radiation
SPECIFICATIONS
Delrin has 83 materials in the MatWeb database of data sheets. There are many different grades of Delrin, each with slightly different properties. For instance, there are medium-high viscosity grades (such as Delrin 300CPE), low VOC emissions grades (such as Delrin Delrin 100CPE), and UV-resistant grades (such as Delrin 527UVE).
Below are the specifications for Delrin 100.
- Density: 1.42 g/cm³
- Rockwell hardness: 90–121
- Tensile strength: 71.0 MPa
- Melting point: 178°C/352°F
- Specific heat capacity: 3.00 J/g-°C at 215°C/419°F
- Electrical resistivity (volume): >= 1.00e+15 ohm-cm
USES
With its low friction, strength, and host of other useful properties, Delrin is perfect for high-load mechanical applications and precision parts such as:
- Gears
- Safety restraint components (e.g., seat belt hardware)
- Door system components
- Conveyor system components
- Medical delivery devices
- Ski bindings
- Zip fasteners
- All-purpose industrial equipment like bearings, pumps, and meters
Interestingly, Delrin is also the material of choice for a number of musical instruments such as:
- Irish flutes: Delrin flutes sound similar to traditional wooden flutes, but are more resilient in varied temperatures.
- Guitar picks: Delrin’s durability wins compared to traditional materials like nylon and PVC (which is known to crack).
- Harpsichord: Delrin has been used to replace the standard bird quills traditionally employed to make harpsichord plectra, the part that plucks the string when a key is pressed.
Due to Delrin’s properties, you can effectively replace many metal parts with it and have thinner, lighter parts that can be produced faster and at a lower price. When compared to certain metals, Delrin parts offer a better strength-to-weight ratio and corrosion resistance, making it particularly useful in marine, moist, or corrosive environments.
Fun facts:
- A number of the Bantam Tools Desktop PCB Milling Machine’s parts are made of Delrin, notably the bearings and anti-backlash nuts used in all the carriages.
- From 1968 to 1972, Mattel used Delrin to produce the low-friction wheel bearings found on redline Hot Wheels.
CNC SPOTLIGHT
Best bits: In general, larger tools like 1/4”, 1/8", and 1/16" single- and 2-flute end mills are better because they cut through material the fastest and are least likely to break. For 3D shapes, a 1/4”, 1/8", or 1/16" ball end mill produces the smoothest contours.
Hot tips: For best results, keep a set of end mills specifically for Delrin and other plastics, and never use them to cut metal. This allows for increased milling speeds and a better finish.
Cool Projects
At Bantam Tools, we build desktop CNC machines with professional reliability and precision to support world changers and skill builders. For the latest Bantam Tools news, sign up for our newsletter. If you’re interested in adding a Bantam Tools machine to your workflow you can order directly from our online store or request a quote.
