"Y" stall at the end of every litho

[myshop1044]

the last few 5 x 7 lithos I have had a "Y" stall just as the bit starts to do the 1/8" feather at the end
of the carve. I wait for it every time. it seems when the bit leaves the picture and starts the first pass of the deepest
part of the bottom feather going up to the top. it gets into a bind and the bit stalls causing a "Y" stall , I am able to stop it then and clean
up the feather my self.
any ideas.
see attached.

[bergerud]

Is this a 1/32" carving bit? On optimal? Have you tried a new bit? Is it possible that the litho moves a little when the bit plunges in?

[myshop1044]

In this case, I used a new bit 1/16" bit, because of the repeating problem. The litho is very tight in the sled?

[bergerud]

It looks as if the bit took an extra bite. If the litho was held tight in the sled, maybe the truck is a little loose? Give the bit a wiggle and see if there is any slop in the system.

[Digitalwoodshop]

Cutting a Litho is the hardest thing you can ask the machine to do... It is just NOT designed to cut plastic as the feed rate is faster than the machine and bit can cut the plastic.. Once is starts to LAG from what it is actually cutting and where it SHOULD be cutting due to the dense plastic the machine faults....

It is possible that the bit has dulled too.... very quickly.... and a new bit should be tried on the same project.

I would tune up the Y gearbox too... replace the 2 bearings early... It could be a case of the high torque of the cut is causing the big plastic gear to move and RUB in the U shaped slot of the machine frame... See the rubbing at the bottom of the picture...

AL

[bergerud]

When cutting plastic, the bit can pull up pretty hard on the work piece. Is it possible that the litho lifted up from the sled?

[myshop1044]

Checked the truck and there is no looseness, have used that machine many times with no problems, it just seems to be litho or its material, I am still using the candlestone 5 x 7 material, and it only happens at the very end around 94% of the
carving. I am just going to watch it during the entire carve next time.
Here is the end product, this one will be very personal for me, he's is my nephew who passed away a few weeks ago. His wife has not seen the end product yet.
Perry B.

[SteveNelson46]

Perry,

That's a very nice looking litho. In spite of the problem.

It could be that the bit is getting hot enough to melt a small amount of the material and getting stuck on the bit. Try pausing the carve around half way or so and inspect the bit.

[sunmiztres]

I am having the same problem using Candlestone. I think this product is very hard and very rough on the bits. I did 2 lithos no problem but after 2 it dulls the bit that I begin to get the y axis error as soon as the carving starts. It costs way too much to use a new bit after only 2 lithos. I have used 1/32 bit and 1/16 bit with the same problem although the 1/16 does last farther into the 3rd carve than the 1/32. I am using optimal setting and still get the error on the 3rd carve. Not to happy considering I bought 20 pieces of the candlestone, got 2 good carves and messed up 3 pieces and at $5 a pop plus the bits ruined I'm out $55 and 14 pieces of candlestone I can't use without buying a new bit.

[bergerud]

Are you sure the bits are dull? It does not compute in my mind that plastic can dull carbide that quickly. I do know that the bits have to be sharp for plastic. I have a two flute bit that I use only for plastic. I never use it on wood. It has lasted years and still seems new. Could it be a chip clearing problem? Maybe the bit gets "sticky" and plugs up. Have you tried cleaning the bit with some high powered solvent?