Tracking issue during cutout

[Dale]

I have a problem when doing a cutout in that the first pass is exactly where it should be on a .75" thick board with multiple passes of .25". However on the second pass it follows the track fine width wise but length wise on the far righthand side of the design it cuts about 1/8" short of where it should. This is on a 16" project. Luckily I was standing there watching it so was able to hit the stop button before it ruined the project. The exact same thing happened previously using a different design.
I am using Dan's Universal Carrier Board, have tape on the bottom of carrier board, head pressure 80 lbs, a new cutting bit and the board is still tight up against the stops on the carrier board.
Is the tracking encoder bad?

[bergerud]

I have not had tracking issues since using the UCB. I believe that the UCB actually solves the tracking problem. If I am wrong, I would like to know.

Maybe you could check some other things for me. Is the head level? Could the O ring on the brass roller be rubbing on the front rubber belt? Is there a piece of wood jammed in the belt system somewhere? Could the x drive system have a gear tooth missing?

(I assume you did clamp down the head, with both rollers on the board, after the measuring stage and before the bit touch on the board.)

[Dale]

Thanks, I'll check out those items. Yes I did camp down the head (I made that mistake once when I first started using the carrier board on a fairly large piece of cherry, won't do that again!)

[Dale]

OK, I checked head for being level, it is. The O ring is not rubbing on the belt, pulled the cover off the x gear system and no teeth are missing on any of the gears, and there is nothing interfering with the belt system. Any other suggestions?

[bergerud]

Gee, I do not know. Out feed tables too high?

[Dale]

No, out feed tables are adjusted correctly. Guess I could let the machine do the first pass then finish it with a scroll saw until I figure it out.

[bergerud]

A picture would be interesting to see.

[SteveNelson46]

Try running the project on a piece of scrap without the carrier sled.

[Dale]

Sorry I do not have a picture of either project, but i was able to salvage both of them. I will try running it without the carrier board but it will be a few days before I can get to it. Will let you know what happens. Thanks for all the help

[Dale]

OK, found the problem. Ran the project without using the Universal Carrier Board and it came out fine so knew it had to be something with the UCB. Then I remembered that when placing the board on the UCB for both projects that I had a problem with, I had noticed the jam nut on the left hand threaded rod on the key board side was loose. I did not have a wrench with me at the time so just got it finger tight, at the end of the carve the nut was loose again. I tightened it with a wrench (like I should have the first time) and carved both projects with no problem. Guess the loose nut let the UCB "rack" enough to throw the cut path off. Just to make it clear to everyone, I am not blaming the UCB for this. It was clearly my laziness to get a wrench that caused this problem.

[bergerud]

Thank you for the explanation. Interesting. (I was beginning to worry!)

Do you have sandpaper on the UCB rails?

[Dale]

Yes I do but it is extremely course 80 grit I think.