Foamboard testing 3/16" thick 20x30" Readi-Board

Before cutting full sheets I created a simple template to see which settings where optimal for the foam-board with minimal foam melt.

I am using 3/16" thick 20x30" sheets of “Readi-Board” made by “R. L. Adams Plastics” and sold in many dollar stores for (surprise, surprise) $1 a sheet. This can be easily cut down to 20x12 sheets to fit the Glowforge giving two full sheets and a 20x6 scrap sheet that can be used for smaller parts and tests.

The problem with cutting foam-board is that the foam melts very easily in comparison to cutting the paper on either side. In an ideal world I would expect that a 3 pass cut would give the best results with:

  • 1st paper cut at ~ Speed: 200, Power: 5, Pass: 1
  • Foam cut at ~ Speed: 200, Power: 2, Pass: 1
  • 2nd paper cut same as first.

Unfortunately the Glowforge app does not give this level of control.

So I tested what can be done easily and prints quickly.
Here are the results:


Had a dyslexic moment and wrote the settings wrong on the test pieces (above) switching Power and Speed in picture. Actual settings below (pieces aligned left/right by total depth of cut)

  • Top: Power 5 to 23 using 2 step increments. Speed 200 using 1 Pass. “P: & S:” text using way to high engrave setting.
  • Middle : Power 5 to 23 using 2 step increments. Speed 200 using 2 Pass. “P: & S:” still using too high engrave setting. This test was to determine whether the Glowforge would halve the power on 2nd pass, or use half power on each pass. As you can see by visible collapse it used the latter.
  • Bottom: Power 19-28 using 1 step increments. Speed 500 using 3 passes. Engraved text using Speed 500, Power 5, 1 Pass which was spot on.

Here is the more informative pic that shows how the foam melted away when GF cut all the way through: (again aligned by total cut depth)

  • Top: 1 pass - Speed 200, Power 23, made it through but really melted the foam.
  • Middle: 2 pass - Speed 200, Power 9. Same depth but noticeably less foam melting.
  • Bottom: 3 pass - Speed 500, Power 28. Did not make it through but was very close. Took longer to cut overall and appeared to be worse than 2 pass.

Best results (for my foam-board):

  • Cut through top paper and not foam: Speed 200, Power 5, 1 Pass (for marking edge of bevel cuts)
  • Cut through top paper and foam: Speed 200, Power 5, 2 Pass (for score cuts on A, B, C joints and other edge of Bevel cuts)
  • Cut though everything: Speed 200, Power 10, 2 Pass (for normal cuts)
    *** Engrave text: Speed 500, Power 5, 1 Pass (for marking pieces)**

Engrave:


Engrave text, looking under magnifying glass, was optimal at last mentioned setting as it did not cut all the way through top paper, but provided good contrast to read.

  • The big “A,B,C” fold type text is already an outline path (not font) and does not require conversion.
  • The numbers in the circle are text, require conversion to paths, and are useful to identify pieces. This took minimal time to convert.
  • The remaining text (right of circle) is not useful and takes a long time to engrave. This also requires highest engrave DPI and is not worth the time in printing as it takes so long.

Conclusion:

  • Scaling total throughput does not equate same results. e.g. Power 5, Speed 200, 1 Pass is not equal to Power 5, Speed 100, 2 Pass. Second pass requires a slight bump in Power.
  • Your foam-board may vary, but it may be a tiny Power amount that leads to different result (±1).
  • Best to test using power increments of 1 once you are close to optimal settings.
  • 2 & 3 Pass (double or triple power) - this results in reduced total power control as steps are 2 or 3 times output. You may be better off at 1 Pass to fine grain cutting control.
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Great info! Thanks for going in-depth

BTW,

You can absolutely have this level of control by drawing your cut lines in different colours which will show up as different functions on the left, set the individual levels, then put them in order and voila :slight_smile:

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Also, there is a palette addin or whatever you call it around here some place. that has the colors in order of GFUI processing.

Yep, I thought about doing this but its tedious. Would be nice if we could set power level per pass using a single step. I got good enough results using 2 pass and did not think I would get much better results using 3 steps. Might try this when I have more time. Have you done this? Was it worth it?

Thanks, got the palate going in Inkscape. Does save a little time in organizing the steps.

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It would be if I were doing a whole bunch of the same cuts. Currently I’ll leave the item in there, alter the settings, and then send the job again - but I’m always doing one-offs so I’m not a good candidate for it :slight_smile: I have done it once when I was in full-on-testing mode

agreed, and the ability to specify focal depth per pass would also help.

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FYI, I was curious what this stuff was made of and couldn’t find an SDS on their site, but I did find this on another laser forum where someone said they e-mailed the company:

Good morning, Dan and thank you for your inquiry. Our foam board does not contain any PVC and we have a variety of users that laser cut our boards. I hope this helps. Have a great day!

Regards,

R.L. Adams Plastics, Inc.

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Other brands are typically made of polystyrene, which is safe.

Polystyrene is a hydrocarbon, so its combustion products are mostly just carbon dioxide and water vapor, although because of its high ratio of carbon to hydrogen it tends not to combust completely and as a result it emits a certain amount of soot. Nothing that you won’t also get from wood.

FWIW, polystyrene foam is one of the banned materials in my work’s makerspace because it’s considered a fire hazard. Your mileage may vary in the comfort of your own home/workshop.

It’s like corrugated cardboard or anything else with a lot of air pockets. Use low power, watch it carefully, and have appropriate fire suppression nearby.

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Did further test strips to see if I could speed up cutting. The following settings work well when cutting medium detail parts. If parts have tight arcs less than 1/4" then settings from top post work better. There seems to be an issue with acceleration/deceleration which is amplified by this very delicate material.

Cut top paper only:
Speed 500, Power 15, 1 Pass
Power could be further reduced if it is too deep.

Cut top paper and ~75% foam:
Speed 500, Power 35, 2 Pass
Decrease speed for deeper cut. Do not increase power.

Cut through entirely:
Speed 300, Power 42, 2 Pass

Engrave text:
Speed 500, Power 2, 1 Pass

Power setting above 45 @ 2 pass at any speed will destroy the foam or start burning the paper on underside.

Dark/Black foam-board requires slightly more power + 3-5. This goes for original top post settings too.

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