The Importance of Machining Delrin

From cars to consumer electronics to kitchenware, Delrin is everywhere: This high-strength thermoplastic is used to make great consumer products and is favored by machinists for its good material properties and high machinability.

This article covers the basics of machining Delrin: what Delrin is, the benefits of machining Delrin, the limitations of machining Delrin, common applications for machining Delrin, and tips for designing and machining Delrin parts.

1.What is Delrin?

Polyoxymethylene (POM) is a semicrystalline engineering thermoplastic that exhibits stiffness, excellent dimensional stability, hardness, and strength.

Also known as acetal, polyacetal, or polyoxymethylene, polyoxymethylene is best known by its brand name Delrin and is manufactured by the chemical company DuPont. (Other brand names for POM include Kocetal, Ultraform, and Celcon.) Note that Delrin is an acetal homopolymer, but POM can also be made into copolymers.

Although Delrin is essentially opaque, it is available in a variety of colors. It has a density of 1.410–1.420 g/cm3 and a hardness of -40°C. It has a crystallinity of 75–85% and a melting point of 175°C.

Delrin is suitable for machining processes such as milling and turning, and for this purpose is supplied in the form of sheets or extruded rods. The material can also be cut with a laser cutter, and in granular form it can be used for injection molding and plastic extrusion.

2.Advantages of machining delrin

Delrin is a popular engineering thermoplastic for CNC machining, both because of its material properties and its machinability.

Its main advantages are:

1. Machinability: Delrin is an easy-to-cut plastic with excellent dimensional stability. This makes it easy to cut to tight tolerances.
2. Strength, toughness and impact resistance: Delrin is a tough, high-strength material suitable for demanding applications.
3. Resistance to moisture and chemicals: Delrin is resistant to solvents, gasoline, alcohol and other chemicals, as well as moisture.
4. Creep resistance: Delrin has good creep resistance, making it suitable for manufacturing long-life end products such as automotive parts. In addition, Delrin has good fatigue resistance.
5. Electrical insulator: Delrin is a popular machining material in consumer electronics due to its electrical insulation properties.
6. Natural lubricity: Delrin has a high level of natural lubricity, making it a good choice for low-friction applications where the part is in contact with other plastic parts.

3.Limitations of machining delrin

Delrin machining has some limitations that make it unsuitable for certain parts and applications.

Its main limitations and weaknesses are:

1. Adhesion: Due to its chemical resistance, Delrin does not react well to adhesives and is difficult to bond – although Delrin is slightly easier to bond than POM copolymers.
2. Flammability: Delrin is not self-extinguishing and will continue to burn unless oxygen is depleted. A Class A fire extinguisher is required to extinguish a POM fire.
3. Heat sensitivity: Machining Delrin at too high a temperature can cause deformation. While this is manageable, it does require some attention.

4.Applications of machining delrin

From the automotive industry to consumer electronics, machined Delrin parts can be found everywhere.

Some common applications for machining Delrin include:

1) Mechanical/Industrial Parts

Delrin mechanical parts include gears, housings, springs, fan impellers, valves, bearings, rollers, and scraper blades.

2) Electrical Parts

Delrin parts for electronic applications include insulators, connectors, bobbins, connectors, and consumer electronic parts such as keyboard covers.

3) Automotive Parts

Delrin automotive parts include door locking systems, hinged housings, and fuel sensor units.

4) Medical Parts

Delrin medical parts include inhalers, insulin pens, and medical devices.

5) Furniture

Delrin can be machined into furniture components such as handles, locks, hinges, and hardware.

5.Delrin Machining Tips

Delrin is widely considered one of the easiest plastics to machine, so no strict precautions are required. That being said, it is more amenable to certain design considerations and machining methods than other plastics.

1. Design for Delrin: When designing parts for machining from Delrin, try to keep wall thicknesses consistent and add fillets and ribs where necessary. Large parts may warp more easily.
2. Keep it cool: Delrin is sensitive to temperatures above 121°C. Air coolants perform better than liquid coolants and also speed up chip evacuation.
3. Keep tools clean: Although machined Delrin produces consistent and easy-to-handle chips, chips should be removed quickly to avoid a buildup of gunk on the tool.
4. Break apart Delrin: To avoid contamination, it is best to use cutting tools that have not been previously used to cut aluminum or other metals.
5. Keep it sharp: When machining Delrin, sharp cutting tools with larger clearance angles will provide better results, and using a cutting lubricant may also help.
6. Don’t clamp too tight: Delrin is not particularly hard, so care should be taken when clamping the workpiece. Light clamping force should always be used.

6.Delrin machining, Delrin 3D printing, or Delrin injection molding?

Delrin is a versatile CNC machining material that is not limited to machining projects. Delrin 3D printing filament can be used to make 3D printed Delrin parts, and Delrin injection molding can also be performed.

3D printed Delrin has geometric flexibility and is suitable for a very wide range of prototyping applications, but its limitations include poor print bed adhesion, possible delamination, and a limited temperature range.

Injection molding Delrin is suitable for larger parts and is more reliable than 3D printing. POM pellets (Delrin or polyoxymethylene copolymer) for injection molding are also more widely available than Delrin 3D printer filament. However, the semi-crystalline nature of Delrin can increase shrinkage in molded parts.

In general, if the desired geometry and size of the Delrin part is machinable, machining is the best option of the three.