A small trick for melty plastics

I’ve been doing a bunch of detail work using melt-prone plastics, and consequently I need to avoid pieces fusing back together because I’ve dumped too much laser energy into a given area.

I first arranged my cut path sequences to give more time before the laser comes back to fire in any given area, but when that’s not sufficient a further trick I’ve found useful is to insert a “delay” operation in the GF command sequence.

To do this:

  1. place a piece of scrap material (I use wood castoffs) to the bed of the laser, as far as possible from your workpiece.
  2. upload a “delay shape” to your workspace. I generally use squares or circles of varying sizes.
  3. set the “delay shape” operation to be as slow as possible, and as low power as possible.
  4. put the “delay shape” operation in your command sequence wherever you need time for things to cool down.

Net result, the laser does your work, but then drives off to a corner of the bed doing pointless work for a while before coming back to continue your work. Plan it right, and you’ll avoid dumping too much energy into one region of your workpiece.

You can fine-tune the cooling by choosing larger or smaller delay shapes. If you want to be really clever, you can put multiple delay shape targets on the GF bed, and sequence them such that the head has to pass all the way across your cooling region, possibly more than once.

It’s not a flawless solution, but I’ve found it does help when cutting tiny details out of melty plastics, so FWIW… You could skip the scrap target material, and just fire into the bed, but I’m paranoid about such things so personally I prefer to have the laser hit something.


I think it’s a great idea!

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^^^^ ditto
John :upside_down_face:

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Seems similar to the trick on 3d printers, of using a separate tower to let the plastic cool between layers, when printing narrow objects. Good thinking.