Incorrect engraving depth with imported image using two-color HDPE

I’m having trouble getting the proper cutting depth for a project where I’m engraving two-color HDPE using an image I imported. The depths that are actually engraved are greater than what I set in Easel. Originally, I set Easel to engrave to 0.06" to just get into the middle layer of the two-color HDPE. I understand the outer layers are 0.05" thick. However, the X-Carve engraves much deeper than that. I’m wondering if there’s something about the imported image that I don’t understand. Any ideas?

PS While I’m at it, does anyone have engraving bit, feedrate and depth/pass recommendations for two-color HDPE?

@DavidBurger Hey David, sorry you’re having issues. Do you have a set of calipers to measure exactly how deep its cutting? If its ~2x deeper, this could mean Easel thinks you have the wrong lead screw.

It could be an issue with the flat-ness of your material (there could be a slight hill in the material compared to where you’re zeroing). It could also be an issue with your zero-ing technique. With such small distances, setting the zero slightly low could cause the material to be cut noticably deeper.

Pictures help, too!

Hi, Eric,
Thanks for the help. I double-checked my machine set-up and I have the correct lead screw selected. I think, though, your second thought might be the issue. I checked a few spots on my waste board and there’s more variation than I had thought. I think my next step is to make a level surface before placing my 12"x12" sheet of HDPE. Do you have any suggestions for engraving bits to use. The design is pretty intricate so I need one that has a fairly sharp tip (maybe 0.3 or 0.4 mm).

I don’t do a ton of engraving, but for a soft plastic like HDPE, I imagine the “standard” v-shaped engraving bit would work just fine. As for speeds/feeds, i’d imagine you have to go slow, check the 1/32" bit settings for HDPE and that will probably work fine.

This is good advice and a handy link…thanks! I believe my particular problem was due to a waste board that just wasn’t level enough. Since making a level surface on which to put my HDPE sheet I’ve gotten better results. All I have left to do is finally decide on a mill, RPM and feedrate. Since the image I’ve trying to engrave is intricate I plan on using a 2-flute, 1-mm cutting end mill. I am getting good results using a 50 in/min feedrate with the Dewalt 611 spindle set to its lowest speed. No apparent melting and the chips are small distinct pieces.

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