Hello all, Sorry if this is post is duplicative but I couldn't find another post that had this specific question. My issue may be weird in that the z axis is gradually increasing during my cuts. It is strange because the cuts themselves might have an increase of up to 2mm over 200mm. Some facts: LEAD 1515 The wasteboards are dead level compared to the x and y axis. I confirmed this by checking the distance between the z-axis and the stock over the surface area of the cuts. However, when the spindle returns to (0,0,0) after the cut, it actually looks like the z is maybe a millimeter above 0. Maybe I should turn down the acceleration or z speed slightly? I don't think it is a collet issue, partly because of what I mentioned above but also because the bit sits as far back in the spindle as it will go. No third-party parts All screws are nice and tight (from the frame to the gantry to the spindle mount) Entirely default grbl settings Stock is 0.75" thick red oak but the same thing has happened on 0.5" MDF and 0.75" plywood and similar slippage (up to 2mm, but no more) even over the full 48" range of the machine. Here is a photo for reference. You can see the outlines where no additional light comes through. I also circled one area where the cut almost made it all the way through and another area close by that did not. Thanks in advance for any help!
"The wasteboards are dead level compared to the x and y axis. I confirmed this by checking the distance between the z-axis and the stock over the surface area of the cuts." Have you actually done surfacing of the entire wasteboard before using the machine?
Thanks, Christian. I have not. I checked it by making sure z-zero was consistent (within about a millimeter in 9 spots). I'm not opposed to resurfacing it (I even have the bit already), but hoping there is something else to try before it comes to that... especially since the z isn't quite returning to the correct spot anyways.
1 mm is a lot. That can be the difference between cutting through and...well being 1 mm from cutting through depending on where you zeroed your z. Just shave off a 0.5mm layer with your surfacing bit and see if it has cleaned up the entire cutting area. If not, shave off another 0.5 mm.
Thanks, Craig. Perhaps I'll try that soon. I should specify that it's just under a millimeter across the entire 48x48" cutting area. The difference in the picture is about 1.5mm over 150mm (managed to measure it with calipers), so it seems odd to me. When just jogging the gantry over the same area, the difference in Z is less than the width of a sheet of printer paper. I still think there's something about the movement of a job that is making it increase. But all advice is noted. I'll try to resurface. Thanks again.
Well, even if there is another problem, it's imperative that you start with a perfectly uniform spoil-board. So far, we can only go on the evidence of the pic you uploaded which does look like the spoil-board is a bit higher on the left. Try the job again after you've surfaced and lets see what you get. BTW, check the Z axis extrusion first by lifting it up from the bottom - there should be no play whatsoever there and the axis itself MUST be constrained by the upper and lower lock collars and must NOT be supported by the flexible coupling.
