I did some measurements of the gantry height at both ends after homing Z and discovered a slight slope to the gantry - upwards by a few mm. I adjusted with M666 and got the difference down to about .2mm, then I cut a project in 3/8” MDF (about 9.5mm). The area was about 18”x 19” at full depth. Because I was using blue tape and CA glue for work holding I added a touch to the stock thickness in Estlcam and set it at 0.380”.
The photo tells the tale - the side closest to X0 is just barely skimming the spoil board leaving a whisker thin remainder that came right off (yes!). As the core moves to higher values of Y the cut gets less deep - by as much as 0.93 mm which you can see on the left side edges.
I measured the Z heights again after the cut, doing a Z home with the core at about 200,300 and the ends were still less than 0.3mm different.
If anyone can offer me any thought about why I’m not getting a close to full depth cut on the high Y side, I’d sure appreciate it.
Notes -
My bed size is about 600mmx1000mm
I’m using a SKR board - not a jackpot
The spoil board is level, and the set screws on the Z leadscrews are tight.
I lubed the leadscrews before doing this
That’s usually because the table has variations in height at different locations. The recommended fix is to either surface the table (cut away the high points so the whole table is flat), or increase the depth of cut (DOC) so that through cuts go all the way through the material.
0.93mm isn’t really bad, I had to remove almost 4mm from parts of my table to get it completely flat.
Thats correct, OP beeds to surface his table, but i would add: cut through operations should have an extra mm of depth, that way he is sure to ve cutting all the way and not just the tip of the bit and have better edges
Thanks for the suggestion, but bear with me while I ask a few questions. This is a valuable learning experience for me….
Is a straightedge a good option for checking the spoilboard for high/low spots?
It would seem that if it cuts through at X=0, and not at X > 100 (approximately) that suggests the spoil board is lower as X increases, correct?
I did a test as follows. I mounted a V engraving bit (sharp point) and drove to x550 y450. I probed for Z 0 at the spoil board, move to x0 y450 z0. The bit was approx. 0.4mm high - above the spoil board. So x=0 is lower than x=550 right? But if x=0 is lower, why am I cutting through at x=0 but not at at x=450?
Just doesn’t make sense.
I’m OK running a surfacing job, but if it lowers the side that I’m already not cutting through, that would seem to be a wast of effort (and spoil board!). Wouldn’t it?
I did, but I ran it again and got it down to a difference of about 0.3mm. I ran my part again, and still have a bit left on the higher X side, but not nearly as much - comes off pretty easy with sandpaper.
I’m going to consider this solved - and order a jackpot board. My SKR is just acting flaky. I had to reboot it multiple times to recognize the SD card slot, and to get beyond the dreaded “no printer attached” message.
