What caused this?

[tcough3475]

I'm doing a 6" x 70" carve and the first 60" turned out great. Then the carve error started and I stopped the project. I thought it was a dull bit as I'm carving in white oak and know that oak has a lot of silica in it. I salvaged what I could from the board, changed the bit to a brand new one, and started carving again. The second carve started wrong from the start. The pictures show what it is supposed to look like and what I'm getting now. Like I said, I thought I had a dull bit but I now know that wasn't the problem. Any ideas what may be going on?

7882878829

[henry1]

your bearing any bad one

[bergerud]

My guess would be a loose encoder disc on the y motor. The slow drift in the y direction looks too continuous to be a slipping y belt. (I suppose it could also be a slipping gear in the y motor.)

Also, I assume you did not get any y slip error message.

[tcough3475]

No error messages at all. Machine just kept carving and drifting.

Will check the bearings tomorrow, but noticed the truck moved smoothly just before the carve.

Thanks for any and all help.

[fwharris]

I agree with Dan on the Y encoder possibly bad. Also look at the Y gear on the bit plate end of the Y belt, I had one break and caused the Y tracking to get out of sink.

Side comment, are you using any end blocks to keep the carving under the roller? 7 inch rule!

[bergerud]

No error messages at all. Machine just kept carving and drifting.

That means it did not know it was slipping. That eliminates things like dull bit or other types of drag.

[unitedcases]

I've had a few y belts lately that the teeth have worn down on causing a slip.

[Digitalwoodshop]

Replace the two 685ZZ Y Bearings.... And look for a worn thin shaft...

AL

[tcough3475]

Finally got some time to tear into this and here's what I found. Bergerud you hit the nail on the head in regards to the Y-encoder being the problem. It was rubbing on the sensor and wore away some of the encoder marks. Don't know how/why it did this, but here's a photo of the Y-encoder disk.

Al, I didn't tear apart the gear assembly, but there is some play in it. Not enough to slip from the Y-motor gear, but as I have this torn apart, I might as well replace them too.

Does anyone know if LHR sells just these parts or am I looking at purchasing a whole new Y-motor assembly? LHR is closed and the exploded parts diagram don't show them, only the assembly.

Bergerud and Al, you guys always seem to be able to identify these type of issues and I thank you both for your willingness to share.

BTW, this is a C model with only 287 hours on it.

[bergerud]

What you could do is buy a board tracking sensor just for the encoder disk. (The encoders in the tracking sensors and all the servo motors are the same.)

[tcough3475]

Did some digging in my spare parts box (old "A" machine) and found an old Y-drive assembly. Swapped out the encoder disk and Y-drive gear/bearings and back up and running. I noticed though there isn't much room between the encoder and the sensor. If I slide it just about a 1/32" for clearance, it's not very well secured. Wasn't sure if it was all going to work so I didn't super-glue it in place. After I get some much delayed carvings done, I'm going back in.

Thanks again Dan & Al.

[CarverJerry]

Just for knowledge here, how many hours did you have on your machine when this happened?

[tcough3475]

I had 287 hours on it, "C" model. The "A" model I took the parts from had over 1,500 hours on it and I never had to replace the encoder or Y-drive gear. The shaft on the "C" model was very badly worn, but the bearings looked pretty good.