Rotary jig: Bit suddenly gouges into part-off

[dominulus]

Carve began normally, but after a few minutes, the belt suddenly jerked, sending the bit gouging into the uncut piece -- and all the way through the part-off.

I stopped the porject, started again and the carve behaved normally through that spot. (Left image)

At 38%, the same thing happened again. (Right image)

Any solutions?

[Digitalwoodshop]

I have not worked with the rotary at all.... but... It looks like it is related to the brass roller loosing contact with the carrier or drive board... Because it looks to me like it was driven into the wood under power.... and that tells me that the brass roller was not happy and the computer moved the drive board trying to make the brass roller happy.... The brass roller is the feedback to the X Drive and tells the computer where the X is....

So a pressure thing or even a broken gear from taking too big a bite in the wood.... ?

Then it looks like the Y slipped and that is why it cut into the sides....

AL

[bergerud]

My guess is that you are using the 1/16" deep bit. It bends into the grain and all hell breaks loose.

[dominulus]

Yes, using the deep bit, but it's gouging across the grain.

I've also learned to use a shield to protect the surface of the tracking belt from the sawdust that appears to affect the friction between the belt and the rotary belt (Built-in dust collector isn't enough to prevent this.)

If I get to it in time, I hit stop, lift the bit out of its gouge, hit enter -- and the belt and bit follow the same errant path, jerking the x-axis forward and back. (Left new image) As it repeats this jerking x-axis behavior, it slowly smoothes out and returns to straight passes along the y-axis. As the carving continues, the pattern on the y-axis has shifted. (Right new image)

Ran the .stl through MeshLab and created new .mpc file to ensure that no surfaces were inside out. The freakout continued to happen.

[bergerud]

I am sorry I did not explain well enough. The 1/16" deep bit cannot be used with the rotary jig. (It cannot be used to carve with the grain.) When the bit cuts to the right, the tip bends and dives under the grain. The 1/16" deep bit is just too flexible. You can only use the 1/8" deep bit with the rotary jig.

See the text in red: http://store.carvewright.com/product.php?productid=24690&cat=&page=1

[dominulus]

Aha! Thank you!

[dominulus]

Question: With the rotary jig, would it be possible to rough-out first with the 1/8" deep-carve bit, then go back over the piece with the 1/16" for better detail -- or is that asking for trouble?

[bergerud]

You could rough out with the 1/8 bit and then go back over it with the standard 1/16 bit (or even the 1/32 bit). As long as it reaches, it would work. (The problem with the 1/16 deep bit is flexibility near the tip so I do not think it a good idea to use it at all.)

I have not thought too much about it but one might have some trouble lining up the two carves. How to make sure they both start in the same place?