Carving acrylic question

I’ve made 3-4 attempts at engraving then cutting out a shape for an edge-lit sign. 90-95% of the way through the outline cut, something goes haywire and the spindle heads off in a straight line - sometimes into the engraved section, sometimes off to the outside, sometimes it wanders off along the X-axis, sometimes along the Y-axis, but always in a straight line. I’ve used a vacuum to suck up chips, I’ve reversed it to blow away chips - no difference It is really starting to tick me off.

I don’t have the problem with any other material. All I can figure is that I’m either overheating and one axis is stalling, or maybe acrylic chips are jamming the drive wheels. Has anyone else run into this situation? What the heck is going on? Thanks

Can you tell us your settings for the outline cut?

Oh yeah, the important details (oops).

I’m using a 1/8" up cut bit. The feed rate is 40 inches/min, and the depth per pass is 0.0175". I haven’t moved to a multi speed spindle yet, so I’ll assume it is somewhere around 12.5k rpm. The acrylic is 3/16" thick, and the outline was a 10" diameter circle.
Is that what you need?

You could be getting a build up of burnt material in front of the bit causing it to go off. I am not a pro at this but i cut the acrylic for my dustboot and looked around the forums before i did and i think i ran around 85 to 90 inces per min. I think maybe you are going to slow and burning the material and getting a build up in front of the bit. Just my thoughts.

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The deeper you go the more precut chips remain inside the slot. I bet they get recut/things heat up and things go south real quick from there.
Chip clearing is vital, decent sized chips aswell - like Wayne I suggest you increase the feed rate some.

Worth considering:

  • Acrylic have a low melting point compared to cast acrylic (Plexiglas etc) causing it to be more tricky
  • Hold-down, if the plate is allowed to lift during carving this can cause a lot of trouble
  • Changing tool path strategy to allow for wider slotting / greater space for the chips to clear.
  • Go agressive when cutting actrylics :wink:
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Thanks for the advice, I’ll try it out.

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