[nk27]

HI, i have a weird Spoilboard inconsistency: i clean spoilboard and even after that router bit cuts to about 0.25 deeper on one side

[nk27]

here is picture

[Khalid]

Have you kept shims under the spoil board?

[txcncman]

Is the spoil board pulling up after facing it? Did you check machine alignment?

[nk27]

spoilboard is holding strong, no problems with it. I was thiking i dont need shims since i clean it before on the same router. Will shims help? i didnt find any other adjustment places

[Khalid]

No, dont use shim..i just asked because if the spoil-board is initially supported with shim then after machining will behave the same problem..

It seems to me that your Z-axis is loose at higher depth...

[louieatienza]

Also possible your spoilboard is swelling up from moisture or humidity? MDF is a lot less dense when you cut the outer "shell" off...

[nk27]

no its in good shape and it happens all the time and on the same side

[nk27]

so if shimming wouldnt help, what's the solution?

[louieatienza]

It could be other things... Z axis coupler slipping? Bit slipping in the collet? different speeds? Have you checked with an indicator if both sides are same distance from collet to table?

Since the Z doesn't move during spoilboard cutting, my guess would be a mechanical issue?

[adprinter]

HI, i have a weird Spoilboard inconsistency: i clean spoilboard and even after that router bit cuts to about 0.25 deeper on one side

Have you tried reversing the cut order? (So that it BEGINS the cut on the side of the board Opposite the normal cut order, and ENDS the cut at the side the normal cut order begins on)? Does the .25" difference also swap ends in doing this? What this could ascertain, is that your Z axis is drifting from vibration. If you are using a ballscrew on the Z axis, gravity, and vibration could cause it to slip down. But this will generally be an accumulative result. (Cuts a little bit deeper with each new pass). If everything is tight, then your holding torque on the Z axis just ain't holding! (You need a stronger motor).
But the more likely suspect, will be something as simple as loose mounting bolts on the Z axis Nut assembly. Or the tool is slipping in the collet. After mounting the tool in the collet, measure the actual distance from the collet surface, to the tip of the tool. Measure this distance again, at the end of your flawed cut cycle. If the distance has changed, your tool is slipping in the collet!
There are many variables to check: worn bearings on the Y axis trucks, or damage to the Y axis rail(s) on the side of travel in question. Same thing to check on the X axis trucks/rails. Is your table height adjustable? Check the distance from collet to table all across the table. It is easiest, to mount a dial indicator in the spindle collet, and turn the spindle by hand to check perpendicularity of the spindle in relation to the table surface.

If the table has T slots, you will have to construct slats to be temporarily inserted into the T slots to bring all surfaces up to a consistent level for checking with the dial indicator method. Which won't be perfect. But .25" difference should be fairly obvious.

Is your G code retracting the tool, before stepover between each pass? If so, you could be losing steps on the Z axis (I.E. commanded upward movement FAILS to complete at some point, all subsequent Z movements from that point, on would be cutting DEEPER than called for in the G code).

Hope that some of these tips help you to discover the problem, I know how frustrating it can be sometimes. Especially when it seems to occur "at Random". It can be a real devil to track it down!