Uneven Surfacing Issues

Let me start by appoligizing if this has been covered previously. I didn’t see any posts with the same issue.
I am new to CNC and after ALOT of research purchased the MK 2. I’ve had my MK 2 for 8 months now and have yet to be able to get the surfacing of my spoilboard done right. I use the G Sender surfacing program and what i get is the left side of my spoilboard is gettung surfaced, then when it gaet about center the bit isn’t hitting the spoilboard. I have checked to be sure the table surface is level, and tram seems good. I have my LM mounted on same .75 MDF as spoilboard. I’m not ready to pull my hair out yet, but my projecte are cutting different depths when the size entaials the majority of the cutting surface. I have checked and replaced 4 wheels, and riding in the groove, ensured that the adjustment nuts are good. Not sure what else to check. Any help would/is greatly appreciated!!!

@Slvrbullit Hello Bob! Welcome to the group sir!

How big is the difference between the left and right sides and is your machine 30x30 or 48x30. I ask because I don’t think it’s uncommon for the bit to not touch everywhere when first surfacing if your only taking off a small thickness. That is why we surface, to keep removing a small amount each pass until it does a pass that touches everywhere. After that your surface plane should end up parallel to the XY plane of the machine.

That said I wouldn’t expect it to be a large difference between different areas of the spoil board. I would check to see how far off things are before surfacing again. To do this I would take measurements with the machine itself. Visualize the surface area as 9 squares like a tic-tac-toe board and then pick the center of a square and move the router there and set Z zero to the spoil board using the paper method. Then check each square in turn by moving to the center of the square and lowering the Z, like using the paper method, but don’t reset Z zero. Don’t use ‘Go to’ for Z because if the spoil board is high for that square you might break a bit. Anyway when the bit is touching the spoil board for that square check the Z value in gSender, if it is negative that square is low by that amount and positive is high for that square. The difference between the lowest and highest square should be the amount that would need to be removed from the spoil boards highest point to make it flat and parallel to the machine. If that number is more that 1-2mm there is probably something wrong somewhere that we will need to find.

I hope this is helpful and not too confusing!

EDIT: I should also mention that depending on table material and construction the table can move. My wood table developed a high spot in the middle last summer due to humidity. Then it moved back as it dried during low humidity. I even remember someone having inconsistent results and he discovered that when he would check the progress of the machine he was resting some of his weight on the table and that caused slight bending of the table and led to visible imperfections in the carve.


That was a very good explanation.


Sorry for the long wait for my reply - issue solved!! Thanks so much!