Delrin® Laser Cutting and Bonding

Delrin® is the DuPont Polymers, Inc. brand name version of the engineering thermoplastic polyoxymethylene (POM), also known as polyacetal or simply acetal. Delrin is an excellent alternative to metals in some applications due to their high strength, low density, excellent dimensional stability, and broad range of operating temperatures. While products made from Delrin are typically manufactured using a pelletized resin by injection molding or extrusion, Delrin can easily be cut or engraved with a laser—so long as the right equipment and laser settings are used.

This article will discuss the laser cutting of Delrin plastic, including: the best laser cutter to use, the laser cutting process, and recommended machine settings.

What Are the Characteristics of Delrin?

Delrin, a POM (polyoxymethylene) resin manufactured by DuPont, is a tough, durable, low-density engineering thermoplastic that offers exceptional wear and warp resistance, and high tensile strength. Delrin can have a tensile strength of anywhere between 60 and 90 MPa, depending on the particular grade. Delrin has superior chemical resistance and low moisture absorption. Unlike other plastics, such as PVC (polyvinyl chloride) or Teflon™, laser cutting Delrin does not produce toxic fumes. These characteristics make Delrin a superb alternative to many of the traditional metal parts commonly found in the automotive, aerospace, and industrial industries. This material is also used in the medical, food packaging, and consumer product industries. Figure 1 is an example of Delrin sheet material:

Which Laser Cutter Is Best for Delrin?

CO2 laser cutters are considered the best option to use for Delrin cutting. They are the easiest to use and are the most cost-effective option when it comes to cutting Delrin compared to using fiber optic or neodymium laser cutters. Fiber optic lasers are better suited for cutting reflective materials (such as metals) because they absorb the material being cut and prevent reflection. Neodymium lasers, on the other hand, are powerful systems that are suitable for cutting tougher and thicker materials. They are significantly more expensive than CO2 lasers. 

CO2 lasers use a gas mixture consisting primarily of carbon dioxide and nitrogen to produce a powerful beam of light. A series of mirrors focus the light generated by the excited photons in the gas. While laser cutting metal with a CO2 laser can be difficult, CO2 lasers are perfect for cutting non-metals, including wood and plastics like Delrin. 

How to Laser Cut and Engrave Extruded Delrin

Laser cutting and laser engraving extruded Delrin are relatively straightforward processes. "Cutting" means the laser will remove material through the entire thickness of the workpiece, completely separating the pieces on either side of the beam path. This process is often used to produce the external geometric profile of a part.

"Engraving," on the other hand, only marks the surface of the part with a series of adjacent shallow laser cuts that can outline and fill the shapes of superficial logos, motifs, item codes, and descriptions onto a workpiece. 

Ensure that your laser cutter is properly installed and ventilated according to the manufacturer's instructions. This is important because cutting Delrin releases formaldehyde, which is a skin and lung irritant, and may cause long-term health effects. The list below describes the general steps required to laser cut and engrave extruded Delrin:

1. Develop a drawing of the intended design to be laser-cut using CAD software or use a predefined image.
2. Determine whether a vector cut/engrave or a raster cut/engrave will be used. Vector cuts/engraves produce a crisper image using a narrow laser cut path while raster cuts produce a broader, more diffuse, pixel-based path.
3. Import the CAD drawing or image into the laser cutter’s software to create the laser cut file.
4. Cut blanks of appropriate size from your raw Delrin stock material.
5. Set the laser system parameters to the manufacturer's starting point recommendations for cutting Delrin.
6. Conduct as many test cuts as necessary to determine the optimum cutting parameters.
7. Make the final cut or engraving on the part once the optimal settings have been established. 

How to Laser Cut and Engrave Cast Delrin

Cast Delrin laser cutting and engraving is only slightly different from cutting and engraving extruded Delrin, but requires a little more finesse. This is because cast Delrin parts will likely have more intricate shapes, profiles, and features that can make laser cutting and engraving more complicated. The list below shows the steps for completing cuts and etching on cast Delrin:

1. Develop a drawing of the desired design to be laser-cut using CAD software (vector cut/engrave) or use a predefined image (raster cut/engrave).
2. Import the developed CAD drawing or image into the laser cutter's software.
3. Modify the laser system’s parameters for Delrin cutting (reference the laser-cutter system’s manual and recommended cutting parameters to ensure proper preparation).
4. Set the workpiece on the laser table in the correct orientation so that the desired cuts and engraves occur on the correct faces of the part. 
5. Conduct a few test cuts to determine the optimum cutting parameters for the particular laser system and Delrin grade.
6. Complete the complete cut or engraving on the part once optimum settings have been found. 

What Are the Differences Between “General Part” and “Presentation Part” Cutting of Delrin?

General part cutting emphasizes cutting speed over final cosmetic appearance and high precision. Dimensional accuracy and level of detail in a “general” part will not be as high as with a “presentation” part. The presentation part cutting emphasizes a slow cut to ensure that tolerances are met and cuts are made cleanly, with a high priority on aesthetic appearance. 

What Effect Does Delrin Sheet Thickness Have on Laser Cutter Power Requirements?

The thicker the Delrin sheet to be cut, the more laser power is required to cut it. The thickness of the workpiece influences several laser cutting parameters, including cutting speed and minimum turn radius. When cutting thick Delrin sheets, there are two methods that can be used to accomplish a clean cut. The first method is called “pecking,” or “slow pierce.” This consists of slowly cutting deeper into the material in a stepwise fashion.

The second method is called “blast pierce.” It is a more aggressive, but faster approach to cutting thicker sheets. This method consists of using a fast speed at a higher power to “blast” material away. However, blast piercing will result in a larger kerf (larger width cut). Consider whether appearance and accuracy or cutting time are more critical to your project and then pick an appropriate cutting method.

What Is the Best Speed for Laser Cutting Delrin? 

The best speed for laser cutting Delrin depends on the power of the particular laser cutter being used. Generally, faster speeds must be used when laser cutting Delrin to help prevent the burning of the material and to limit the potential for the work material to catch fire. For 35 W systems, use a laser cutting speed of 30% of the maximum speed allowed. For 50 W systems, use a speed of 40% of the maximum speed allowed. 

The particular Delrin grade being laser cut does not have a profound impact on the best speed and power settings. However, for systems with power ratings different from 35 W or 50 W, start with a slower speed and iteratively make cuts to determine the best speed for a particular laser-cutting system. 

What Is the Best Power Level for Laser Cutting Delrin?

Because of Delrin’s high melting temperature, high powers are required to effectively cut the material. For both 35 W and 50 W laser cutting systems, use a power equal to 100% of the maximum allowed power. With higher-power laser cutting systems, start with lower power during the setup phase and iteratively increase the power until the workpiece is cut and within desired requirements. 

What Are the Drawbacks of Laser Cutting Delrin?

While laser cutting Delrin can be an effective fabrication process, it also has some drawbacks. The list below highlights some of those disadvantages:

1. Warping can occur because internal stresses are introduced into the Delrin sheet during the extrusion process. Although generally, Delrin has exceptional wear and warp resistance, uneven cooling causes internal stresses to be higher at various locations throughout an extruded Delrin sheet, leading to laser-cut parts becoming warped should cutting occur at those particular locations. 
2. Laser cutting tight-tolerance holes typically requires a certain degree of post-processing to obtain correct dimensions. It is difficult to obtain ultra-precise dimensions for thicker materials when using a laser cutter due to the increased contour size of a cut. Therefore, holes are usually cut undersize and are reamed to size in post-processing.

Delrin is less stiff than metals. This leads to parts with large spanning features being thicker or supported at consistent intervals to prevent deflection in the part. 

What Are the Best Tips for Laser Cutting Delrin?

Here are several tips to use when laser cutting Delrin:

1. Make the minimum feature width  equal to or greater than the sheet thickness. Doing so will ensure a strong, rigid part, whereas distances smaller than the material thickness may cause the part to break easily while in use.
2. Optimize the resolution of your CAD drawing or image for the best balance of resolution vs. cutting speed for your application. Having a detailed, high-resolution drawing or image will lead to slower cutting times. However, slightly lowering resolution can have a profound effect on total processing time. Find the optimum resolution that strikes a balance between dimensional accuracy and cutting time.
3. Control the tool path of the laser cutter by assigning different layers to the CAD drawing or image. This will help to optimize the XY travel of the laser and thus decrease total cutting time.
4. Refrain from overlapping lines on a CAD drawing. Instead, include a small gap between two features that meet. For instance, the line that joins two adjacent squares will be interpreted by the laser cutter as two lines leading to burnt edges and a rough-cut surface. By adding a small gap, total cutting time can be decreased and part accuracy is improved.

What Are the Differences Between Machining Acrylic and Delrin?

Machining acrylic and machining Delrin are not that different. However, acrylic has a lower melting point than Delrin, so the acrylic will not require as much laser power as Delrin to cut a given material thickness. Acrylic has a higher tendency to melt and has a coefficient of thermal expansion of 4.0 while Delrin has a coefficient of thermal expansion of 6.8. This means that extra care must be taken when laser cutting acrylic as it will both melt faster and expand if it becomes too hot. Additionally, be cautious about using coolant while machining acrylic, as some coolants may react with the material and cause cloudy spots on the workpiece’s surface.

What Delrin Applications Can Be Laser Cut?

Many applications can be fabricated from Delrin using a laser cutter. Some examples are listed below:

1. Gears
2. Wheels
3. Pulleys
4. Rollers
5. Pump and valve components
6. Bearings
7. Fittings
8. Electrical insulator parts
9. Food containers
10. Sports equipment

What Are the Alternatives to Delrin for Laser Cutting?

There are a few alternatives to Delrin. These materials have similar tensile strength, similar thermal properties, and can also be laser cut. Often, these materials are used interchangeably with Delrin—depending on the application where the part is used. These alternatives include:

1. Polycarbonate
2. Acrylic
3. Nylon

Is Delrin Stronger Than Polycarbonate?

Yes, Delrin can be stronger than polycarbonate, but it depends on the particular grade of the material. Delrin has a tensile strength of 60-90 MPa, while polycarbonate has a tensile strength of 28-75 MPa. Depending on the application, this allows Delrin and polycarbonate products to be used interchangeably since both exhibit high tensile strengths and high heat-deflection temperatures.

Is Delrin Stronger Than Nylon?

Yes, Delrin is generally stronger than nylon, though it depends on the particular grade of the material. Delrin has a tensile strength of up to 90 MPa, while nylon can have a tensile strength of up to 83 MPa. These characteristics make nylon a potential alternative material to Delrin—it has similar or higher strength, heat-deflection temperature, and flexibility.

Is Nylon Laser Cutting the Same as Delrin Laser Cutting?

No, nylon laser cutting is not the same as Delrin laser cutting. Nylon laser cutting usually entails the cutting of fabrics, not thick extruded sheets as is the case with Delrin cutting.

What Is the Difference Between Polyamide and Delrin?

Polyamide is a polymer that is linked together by amide bonds while Delrin is the polymer polyoxymethylene which is formed by polymerized formaldehyde bonds. Nylon is a type of polyamide. The primary difference between the two is that polyamide (nylon) is better suited for textile fibers, while Delrin is better suited for mechanical parts or parts requiring high tensile and impact strength.

Summary

This article presented laser cutting and bonding with Delrin, explained what it is, and discussed when to best use Delrin. To learn more about Delrin laser cutting, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities, including sheet cutting and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

Copyright and Trademark Notices

1. Delrin® and Teflon™ are registered trademarks owned by DuPont Polymers, Inc.

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