Depth of carve problem

Acquired a C machine. Did overall maintenance and all seemed well. 1 prob I can't resolve. Pattern doesn't inset the high end below the surface of the board. Attached pic of boards, copy of MPC, running version 3.106. Have run MPC's using the same card on another machine with no prob. Pic is of both carves. I have tried adjusting the depth and the MPC height up and down and the result is the same. Tried a calibrate thickness and used the result from measuring the board with a micrometer with the same result. Tried calibrating and adjusting the depth thicker and thinner than the micrometer numbers with the same results. I placed a .24 shim on the sliding plate where the bit touches with the same results. Removed that and placed the shim on the squaring plate by the tracking sensor with the same result. Know I'm missing something, just hope somebody else can show me what I'm missing. Appreciate any help.
Thx, Rick H

Still looking, cut a piece of wood. Measured thickness on known good machine, measured same piece on problem machine , adjusted calibration to the same depth and measured again getting the same thickness as the good machine. Carved with the same result as before, still a flat spot on the carve for on the front side of the carve. Will try to do other tests as I think of them?

Update: Measured a board using the machine that carved the MPC ok, then set the depth calibration in the C machine to match exactly when measuring the board. Still had the flat spot. Did the Z axis test on machines and got almost identical numbers. Checked the Z position on the sensor menu on multiple machines and found the C machine showed a larger number when I touched the square and sliding plates.. Was surprised to find I had different length bits. Have 5 of the 1/16th carving bits for the Carvetite chuck and 2 are shorter on the cutting end by approx 1/8 in, put the longer bit in with same result. Decided to try changing the depth in the MPC again. Original MPC had a depth of .500 and I had tried it at .530 and still had a flat spot. Ran a carve with it set at .560 and the carve ran ok, no flat spot.
The question I still have is why???? What can cause there to be that much difference in how the machine sees the wood and places the MPC on it when it works ok on other machines. Have the same problem with other MPC's. just using this quick one for a test. I'm starting to run out of ideas.
Anybody have a theory ??
Thx, Rick H

How does this pattern carve on the other machines? When I mouse over the pattern I do get a zero depth reading as I get towards the center.

How is the bit plate? Is it held out straight and flat or does on drop towards the end?

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Originally Posted by fwharris

How does this pattern carve on the other machines? When I mouse over the pattern I do get a zero depth reading as I get towards the center.

How is the bit plate? Is it held out straight and flat or does on drop towards the end?

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Pattern does carve ok on other machines, noted above that another pattern had the problem which is where I found the problem. Using this pattern to test things due to the shorter carve times. Am currently running multiple carves on another machine to correct the problem and not waste the boards and they are coming out ok. The rattleback MPC is one I got from the forum years ago. I inserted a tapered 'shim' in the space above the bit plate on the machine approximately in the middle of its length and it appears to fit as close to the same as I can tell.
Thx for the feedback. Still baffled. Probably overlooking something.
Rick H

ps: will try to thoroughly check out the bit plate today. Thx again

Floyd,
Bit plate feels tight, can wiggle up & down very little and looks ok. Used the Z sensor test and got a 1.129 when the bit touched the plate on the C machine. Did the same on my B machine and got 1.152. Don't know enough to understand what the difference means Placed a string level on both plates while it was actuated and the bubble was inside the lines on both machines. Really hoped your ideas might point to the prob as I hadn't done a lot of checking there.
If you happen to have another idea it would be appreciated.
Thx, Rick H.
another PS: just for grins I taped a .030 feeler gauge to the top of the bit plate to see what impact it might have. Used a previous board that had the flat spot on it. Stopped the carve after a couple of minutes and found the depth was the same

Wondered if it be caused by the encoder on the Z pack. Opened it up and found a light grayish/black dust inside the cover. Used a Q-tip and touched it lightly to the disc and moved the truck down to rotate the disc. Had a small amount of the dust on the swab. Reassembled and ran the carve with the same flat spot appearing on the project. Moved the board to another carver with the same card and project came out correctly. Back to the drawing board.
Rick H

You indicated this was an acquired machine. Perhaps someone made a mistake when upgrading to or replacing rubber belts. I am given to understand that the spacers added to the squaring plate are mission critical for precise operations. Have you investigated the squaring plate and its relevant spacers?
I have also had a head alignment problem before that left the far side of the machine slightly lower resulting in a similar problem with a flat top.

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Originally Posted by sjmoore69

You indicated this was an acquired machine. Perhaps someone made a mistake when upgrading to or replacing rubber belts. I am given to understand that the spacers added to the squaring plate are mission critical for precise operations. Have you investigated the squaring plate and its relevant spacers?
I have also had a head alignment problem before that left the far side of the machine slightly lower resulting in a similar problem with a flat top.

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Checked with the previous owner and the machine was bought new with the rubber belts in place, not an upgrade. Agree with your thought process, why I contacted him to ask the question. Hadn't thought about the level being a cause. Cleaned and lubed the posts along with everything else but not the level. Will doublecheck the squaring plate.
Will check tomorrow and let you know.
Thx for the ideas.
Rick H