Problem matching two sided cutting

[trivejb]

I have a problem trying to get a two sided carve to match (right side aligned over the left). This is a shotgun style butt stock and is cut from a solid 16x7x1.75 walnut block. The pattern is from a model I made and scanned in. I scanned in the left side and made the right side by flipping it over to create separate left and right patterns, centered both directions so they should be identical. I also tired the two sided pattern but with same results. The problem is that the right side is always .125” lower than the left. I currently use a sled, but by reducing it to half size, have cut it from a solid piece with the 3.5” on each end, same result. I have checked the squaring plate with the z-truck and adjusted as needed. I have marked a square line on both sides of the block and made sure the z truck tracked straight across before cutting each side. I mark the center of the bock on both sides and "jog" to center to position the block. Goodness knows what else I have tried but all with the same results, the right side is always lower than the left and is most noticeable at the recoil end (see pictures). I realize the recoil pad end is 8” from the center, where I squared the piece, so a small error at center means a big difference 8” away. 1/16 each side equals 1/8” overall. I have tried tilting my pattern but cannot come up a resolve. Any suggestions would be appreciated. I would prefer not to send the pattern file but could if that is what it takes to resolve this. Pictures attached.
Thanks, Jerry

[mtylerfl]

Hello,

Sorry you are having a problem. It's pretty tough to "guess" what's wrong without seeing the MPC, unfortunately. Could be a tracking issue or simply that the patterns are not lined up in the MPC. That's my two guesses!

[ibewiggin]

Could this be another situation that comes from not placing the pattern on edge or corner? I have heard of many problems with centering the piece. worth a shot. Sounds to constant to be a tracking problem to me.

[bergerud]

I have this problem twice now and it was because the y offset in the calibration menu had spontaneously changed from the default. I do not know if this is your problem but it is easy to check. If I were you I would do a double sided test by drilling a small hole half way through from each side of a board and see how they line up. Also check your mpc by changing the board size so that you can see a cross section and make sure the sides are lined up.

[bergerud]

The files look fine to me. They line up fine when I put them both on the same board. Check that y offset.

[trivejb]

Thanks for the ideas. I shortened the the wood on the half size double sided model and both sides line up, so it appears that is not the problem. I had checked the y offset earlier and made an adjustment (no change) but needs to be checked again. Thanks.

[DickB]

If it is consistently off by .125" you could just jog to center .125" offset from true center on the second side carve. More of a work-around than fixing the problem, but it might let you finish your piece.

[Digitalwoodshop]

Do you have any Constraints or Restraints turned on as in the numbers are yellow? That can give you problems.....

When I did the 2 sided Deer, I picked some key points and placed Dill Holes on the front of the board and then flipped the board. I used the drill holes to line up the back side.


I flipped it back over and removed the Drill holes and cut it....

Yes, this is the 3rd time I posted this Girl this week... But it shows a good cut out of a 2 sided deer. It can be done...

Skipping the Xmas Show this year... too busy.... I am at $16K and want to reach $20K double my last year's Gross.


AL

[mtylerfl]

Could this be another situation that comes from not placing the pattern on edge or corner? I have heard of many problems with centering the piece. worth a shot. Sounds to constant to be a tracking problem to me.

I doubt it...I do all my two-sided carvings using Center (no manual jogging whatsoever, and no placing on edge or corner) and they line up 'perfectly' every time...on both my machines.

[cnsranch]

Lots of ideas, but here's the first thing to do.....

Open your MPC, and move the front pattern of the stock just off the edge of the board. Then do the exact same thing to the back pattern. Just take both of them just off the virtual board (keep the vertical centering "on", but release the "horizontal" so you can move the patterns).

Then, look closely at the edge of the virtual board and see if the two patterns line up, or are offset the way they're being carved.

Something tells me that you're getting the result due to the way your reversing/flipping the pattern for the back side of the carve.

AW's probably on to something regarding restraints - you should be able to center the pattern on the front, then take the pattern to the back, flip it so it's in the same orientation as the front, center it as well, and off you go (as MT said).

But a "restraint" will change the "centering" some - and with it "exactly .125", that sounds like the culprit.

All that said, dragging the patterns off the edge and then looking at both at the same time will tell you if you have a design issue, or a mechanical issue (learned that from either Kenm or Redneck Blues (sorry, Mr, H., I can't resist).

Expensive error - that walnut's not cheap.