Hey all. I need some help on an issue I’m experiencing with the ShopBot. The short of it is: on long operations, the Z-axis seems to cut deeper and deeper.
I’m new to v-carving, but have had plenty of success with the ShopBot with other projects like cutting out templates from plywood. I used Easel to generate the g-code for the project. I homed all 3 axis on the bottom left corner of my workpiece:
However as the machine continued to cut, it progressively cuts deeper and deeper on the z axis. Here’s the same letter, but 90 minutes later near X=50:
I’m happy to run more tests and collect more information if anyone has ideas. I think I can work around this by splitting my project up into smaller jobs, but that’s not ideal. It’ll mean a lot more set-up time and slightly less efficient use of materials and I’d like to avoid both.
Thanks in advance for the great support this maker community always provides.
I haven’t used the ShopBot, but I assume you’ve checked that the collet is tight enough and the bit isn’t working down so it’s hanging farther out of the collet? I’ve seen that before on other CNC equipment.
It looks like a problem that I tried fixing years ago; the z-axis spring is carrying too much. The online recommendation i found to double the support spring did not work like they suggested. I’m starting to think we just need a lighter spindle.
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On Mon, Sep 23, 2024, 11:38 AM Michael Champlin via MakeICT Forum <noreply@talk.makeict.org> wrote:
Hey all. I need some help on an issue I’m experiencing with the ShopBot. The short of it is: on long operations, the Z-axis seems to cut deeper and deeper.
I’m new to v-carving, but have had plenty of success with the ShopBot with other projects like cutting out templates from plywood. I used Easel to generate the g-code for the project. I homed all 3 axis on the bottom left corner of my workpiece:
First letters cut as expected:
However as the machine continued to cut, it progressively cuts deeper and deeper on the z axis. Here’s the same letter, but 90 minutes later near X=50:
After this I jogged the machine back to the corner I zero’d on and here we see the z-axis is off:
I’m happy to run more tests and collect more information if anyone has ideas. I think I can work around this by splitting my project up into smaller jobs, but that’s not ideal. It’ll mean a lot more set-up time and slightly less efficient use of materials and I’d like to avoid both.
Thanks in advance for the great support this maker community always provides.
This was actually my 2nd failed carve. After the 1st failure I suspected bit pull-out. I used a combination square to record the bit protrusion before running the machine. Bit was in exactly the same position afterwards.
I figured you probably checked that, but I guess it doesn’t hurt to ask. Have you had any other helpful advice on the problem? It’s always frustrating when something like that happens and you don’t see the fix, or what’s causing the problem. Good luck with figuring it out. I know there are lots of members with a lot of experience with the ShopBot, so someone should be able to help.
There are things we can do both with the Shopbot and with LinuxCNC. If it’s OK with the Woodshop Lead (isn’t that @doug.wilson now?), I’ll check on several possibilities the next time I am there and come up with some suggestions.
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