Strange depth change

[dehrlich]

See pics. This is a plaque I carved for my girlfriend. As you can see, there is a depth change in the middle of the pattern, but only on the bottom of the carve region. There was no effect on the graphic. The change appears on both sides of the graphic in about the same spot. Also attaching the MPC. That i could see there is nothing different. Any thoughts?

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[RogerB]

Looks like your bit slipped

[DocWheeler]

Was it on a sled? Was there material under both rollers all of the time?

[Digitalwoodshop]

Is the depth change 3.5 inches from the end of the board as it was in the machine? If so, the board came out from under one roller and since it was not being held FLAT to the table TILTED UP into the bit. Bit stayed the same depth but board moved closer to bit. A classic 7 inch rule of wood. It will do it on each side 3.5 inches from the end in X.

I tape scrap boards on the end and use place on end to get the location correct. That way even with a short board the end of the board is still being held by both rollers. I draw a rectangle in my artwork to show the size of the scrap and keep the artwork in the good wood.

AL

[dehrlich]

No it was supported under the rollers. I had extensions attached with pocket screws so that shouldn't have been a problem. Bit slip doesn't make sense either since it changed back to the original depth on the other side of the region. Like it made a bump in the center of the region. The only thing I can think is perhaps it was due to a difference in the thickness of the material and the extensions that would cause the head to change slightly... could that be it? But do the rollers not have spring adjustment that would allow for this slight difference?

[Digitalwoodshop]

No it was supported under the rollers. I had extensions attached with pocket screws so that shouldn't have been a problem. Bit slip doesn't make sense either since it changed back to the original depth on the other side of the region. Like it made a bump in the center of the region. The only thing I can think is perhaps it was due to a difference in the thickness of the material and the extensions that would cause the head to change slightly... could that be it? But do the rollers not have spring adjustment that would allow for this slight difference?

So you are saying the extension was slightly thinner than the plaque? You could do a test, make a shallow circle carve region 3.5 inches from the thickness difference and see it the bump shows up in the middle of the circle...

AL