Overly complex cutting path

I have been cutting a battery holder which involves about 60 deep holes of various diameters in a piece of beech. Most of these holes cut quickly in 1mm slices, but a few have the bit cut a slice, bring the bit up the centre of the hole, move to the edge and go back down before cutting the next slice and repeating the process. These holes take over twice the time to cut as the other holes. The process seems to be random and does not show on the tool path generator. Has anyone got any suggestions as to what causes this frustrating problem?

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What are you using to generate the Gcode?

Not sure about Easel, but in HSM you can typically order by islands and specify retract heights. Also choosing a pocket operation vs a 2D adaptive clearing can result in very different paths that still yield the same result. Likewise, ramping, weather helical or straight, vs plunging can result in less travel.

If you backplot the g code you should be able to see exactly where the tool will cut and travel, and many backplot tools will also give time estimates for each operation.

I am using easel to generate g code and as far as I know there are no options available to change the tool path. The CAM software just does what it thinks. I am simply curious as to why two identical holes next to each other have very different tool paths, one of which is much slower than the other. There is no difference in the resulting cut quality.

I had the same issue with four identical holes in walnut (.625" in diameter with a depth of .27"). On the first hole, the bit would retract after each slice just like you describe. The other three holes cut much faster without the bit retracting after each slice. My workaround involved selecting that first hole. Next I wrote down its position as indicated on the Shape tab. Then I deleted it. Next I selected one of the good holes, copied it and pasted it. Then I changed its position on the Shape tab to what the deleted first hole was. Now, all four hole are cut without retracts after each slice. I realize this may be a pain with 60 different holes, but maybe my solution will spark something similar for you.

Thanks Chris, I think you are on the right track with this. I’ll do a bit of experimentation along these lines and see if I can work out what causes the complications.