Variables when Laser Cutting PETG

PETG, or Polyethylene terephthalate, is an incredibly versatile resource for manufacturers that gets a lot of attention from Vytek. It’s a lightweight thermo-plastic that has high impact strength, an appealingly glossy finish, and a purity that makes it perfect for packaging food and pharmaceuticals. PETG products are easy to die-cut and thermoform without upsetting structural integrity.

Simply put, it looks good and is highly durable. However, it poses some interesting challenges when it comes to laser cutting thicker sheets, and that’s where Vytek’s experts come in. We wanted to find out for ourselves what the best methods are to work with PETG.

To complete our tests, we used a ½” sheet and examined a wide range of variables to see what would yield good results. Our main goals were to reduce burning on the edges and to mitigate the resins from the back side of the material. We found that there were three main variables that allowed us to meet those goals: Masking, Pressure, and Fume Extraction.

Masking
With the initial tests, we found that masking both sides of the material produced the best edge. What we didn’t realize until later was that the masking on the top surface was contributing to a burning effect that occurred on the edges. Thankfully, the effect is easily removed with a solvent wipe, which means the issue appear to only be on the surface of the material.

Pressure
We also quickly discovered a high pressure assist gas was crucial to the process of cutting the thicker sheets of PETG. This was a tricky finding however, because as the pressure got higher past a certain point, the results got poorer. Anything over 60 PSI was unusable.

Using nitrogen, our best results were when the gas pressure was set to 40 to 60 PSI. However, even within that range we saw a rather undesirable swept effect on the edge with the higher pressures. This could have been a result of the nozzle type we were using, or the fact that we used a 7.5” optic. While those are variables we didn’t have the time to play with, we think it’s possible to achieve workable results within the 40 to 60 PSI range with a few modifications.

Fume Extraction
The final variable we attempted to perfect was the fume extraction method. In general, we found that the use of our updraft fume extraction was actually a detriment overall. Using the updraft fume only resulted in a further burning on the edges of the cut. From what we could tell, pulling the fumes back through the kerf was a factor in causing the burning effect

Final considerations:

There are a few more variables that can be considered to help when cutting PETG which we think can affect the quality of the cut and mitigate any burning effect, but were unable to fully test. If what we’ve talked about isn’t quite getting things done for you, consider some of the following:

  • Reduce the spot size, which may result in a better edge or faster cutting.
  • Consider using a 9.4 um wavelength, which may be better absorbed by the material. The downside here is that it is likely to require higher power, about 500 watts.
  • Downdraft fume removal could help with burning effect.

If you’ve got expertise with cutting PETG, we’d love to hear your input in the comments bellow!

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