Eleven Hour Carve Ruined

[Cgav34]

Nothing like having an 11 hour carve get ruined in the last few minutes cause of the machine throwing the cut path off!

As the machine was making it's cutting pass on a 10"h x 36"w project, I watched and noticed that it wasn't following the path correctly. It appeared that the cut path had been shifted to the left about half an inch. I immediately aborted the project and attempted to cut the object out myself with a coping saw, but the damage had already been done.

I double checked the file, thinking I had inadvertently moved the cut path during a move or resize, but it was spot on.

Any ideas as to why the machine would have decided to shift the cut path over on it's own?

[fwharris]

Most often it is a tracking issue, board moving away from the squaring plate, head pressure to low, dull bit, no out feed support for the board, outfeed trays set to high or not staying under the rollers.

[bergerud]

I know how that feels. That is why I always cut out in 1/4" passes. Large forces and vibration can screw up tracking. Could you post a picture?

[jaustin]

Saw dust under rollers could also throw off the cut path, I think that is what happened witth my last project. After cooling off and not being P.O i re-looked at the issue and believe that is what happened.

Dust collector came unconnected and let saw dust build up under the rollers.

[Cgav34]

Thanks. In going back to check, it appears the built in outfeed tables had lowered a bit (I guess do to the continuous vibration), and I didn't have any roller stands or anything to support the board. Just seems weird that the carving went fine, the 6 cutouts I had in the interior of the design went fine...it wasn't until the outline of the entire project was being performed that it started getting off track. I was using 1/4" passes in 3/4" stock, but it was still too late.

No pics of the project...I was P.O.'d, so it immediately went into the burn barrel :rolleyes:

May be a topic for another post, but...anyone ever build a cart for their machine Something like a miter saw stand with folding outfeed wings? Thought about removing he built-in outfeed tables and building something like the this:

84172

[DickB]

I would not build a table like that - it would only work if all of your stock is completely flat. In my experience I have had to adjust the outfeed tables (and supplementary rollers for longer boards) often as I run the next board through the machine. If a board is even slightly warped just a fraction of an inch the outfeed roller may not touch (if warped upward) or cause the tracking roller to disengage (if warped downward).

How close to the edge of the board is your cutout? bergerud theorizes that vibration from the cutting bit near the tracking roller causes problems. I have had much better success with cutouts when using a sled. The sled adds mass which I believe reduces vibration, and the rails of my sled are 1" wide which keeps the cutting bit at least that far from the tracking roller.

It would help to see your mpc and actual board dimensions. Did your board stay under the rollers?

[bergerud]

Dick's question, "Did your board stay under the rollers?" may be the important question. The problem is not just that the board needs the support. When a roller drops, the controller stops using the brass roller data to track the board and uses only the x motor encoder. This seems to always lead to cutout tracking problems.

[Digitalwoodshop]

A picture of the failed wood would give us some ideas. Like above, I believe the board lost it's home position as in the brass roller loosing contact with the bottom of the board...

How much wood on each side in length letting the rubber rollers push the board flat to the brass roller.

Masking tape on the under side of the board? Giving the brass roller something soft to bite into.

Board not under both rollers at the end of the carving then cut path went bad...

Support rollers under the long board...

Condition of the Y Gearbox Bearings.

Head Level? Did the board shift from the keypad to the other side slightly loosing contact with the brass roller?

Sled?

AL