I added a secondary spoilboard and proceeded to make a profile cut/contour and withing 50% of the cut complete the endmill had gone through the material and about .125 into the secondary spoilboard.
I did tram and surface the new spoilboard. I stop the cut.
Was I suppose to make any changes when I added the secondaty spoilboard?
My zero is set at the surface of the material
Is your retract height actually set to 25 or 0.25? I assume you are working in inches and it is 0.25 but want to clarify. If you have it set too high and you have a new higher spoil board you may be reaching the top of the Z-axis travel and it is losing steps causing you to drive lower every time it hits the top and loses steps.
Can you share the file you are having trouble with? Generally you need to make sure that the top of your board plus the retract height won’t cause the z-axis to reach the top. With a 0.25 inch retract it is not likely but it depends on your material and how high the second spoil board is. If you share they file it will help confirm a few things just to make sure. Also if you can send a picture of the bit in the spindle positioned above the material. Be sure it also includes the top or the Z-axis in the image so we can see how close to the top it is.
And what is your depth of cut on the profile and as @Brew asked do you have an offset or are you cutting the profile the same width as the diameter of your bit? That puts more stress on the bit which could lead to the bit pulling out if it isn’t tightened with both wrenches.
When you calculate it out, that may be the issue, “Z” is probably losing steps. You could reduce the retract height to make your clearance within spec, loose the additional spoil board which will give you the clearance you need.
If you think your running out of Z height just raise the router / spindle a little higher in it’s mounting clamp. If you using a .750" supplemental spoil board, raise it that much. Also, be sure to check that you have clearance between the lowest part of your Z axis and your work piece.