clean y rail

Need some help or suggestions, when carving lithophanes this weekend the machine stopped and a message to clean Y rails came up, I did, let the machine keep going and broke the tip of my first bit. Did a wood project no problem then attempted another litho different picture and the same message and same result broken bit number 2. I know not to bright! Different spots on the litho run 1st one about 1/4 of the way thru 2nd one about 3/4 thru. I am pretty sure its slight high spots on the litho boards but can't be positive. However I stopped the litho runs and ran two more wood projects no problem. I am using a sled that's .25 inch's deep to set my material in. This would be my 6 and 7 litho's using the sled no problems on the first ones. Any suggestions?

First thought on the clean Y rails would be a dull bit, corian chips in the y belt / y rails / y gears.

Are we talking 1/32" carving bits? Were you carving on optimal? What material are you carving? Do you have dust collection?

My guess would also be plastic chips sticking to the bottom y rails and rollers. It would explain the y message and could also make the y movement jerky explaining the broken bits.

Actually I was using a 1/32 on the first attempt and them a 1/16 bit on the second bit, was carving on best, I do have a dust collector. The y rails are extremely clean

You joined in August so my first question is how many cut hours? If near 250 then I would replace the two 685ZZ Bearings inside the Y Gear box.

Cut Motor brushes too every 250 cut hours....

AL

It is not easy to break the 1/16" carving bit. Something is wrong.

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Originally Posted by wpickrel

The y rails are extremely clean

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I assume you took off the roller scrapers and checked the rollers also. Does the carriage feel right when you manually move it from side to side?

Maybe, as Al says, you need to look into the y motor. Check the gears, bearings, and encoder disk.

Can you post a picture of the carving that broke the bit?

Did you change the version of acrylic you are using now as the hardness can be very different.

Cast Acrylic Carves but Extruded Acrylic does not carve or rotary engrave. This is from the Engraver side of my business, lots posted on the engraving forums about engraving Acrylic.

Cast is more expensive than Extruded.

AL

Thanks for all the help on the post, Still not sure what has caused the issue. I have about 400 hours on the carvewright had some issues about 2 weeks ago with the y motor so I changed it solved the issue the cut motor brushes have been changed twice. Just recleaned the entire machine, checked all connections and double cleaned the y rails, inspected the belt can't find any issues calling Carvewright tech support tomorrow. The 1/32 bit was brand new as I suspected the bits were getting dull from the amount of extra sanding and detail issues on the wood projects

Can you post a picture of the actual carving that broke the bit?

Here's a picture of now 3 broken bits. Only on lithos do I get the issues of clean y rails. No issues at all on wood projects. Have not changed the material supplier and its still the first pieces I have gotten. Getting expensiveAttachment 79369

What exactly is the material you are carving? Did the bits plug up?

Have you checked the spindle for play? Does the bit seem to be held firmly by the machine? Does the bit wobble at all?

Posting a picture of the litho might help us see what happened.

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Originally Posted by wpickrel

Here's a picture of now 3 broken bits. Only on lithos do I get the issues of clean y rails. No issues at all on wood projects. Have not changed the material supplier and its still the first pieces I have gotten. Getting expensive

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WAG.... Ask your supplier if the Acrylic is CAST OR EXTRUDED? Cast CAN be Engraved or Litho... Extruded can be harder and is not recommended to be carved or engraved as it will damage your equipment... ANY chance a BLOB of Acrylic MELTED on the Tip and FROZE to the SHEET, HENCE SNAPPING THE BIT.... Inquiring Minds want to know....

AL

So here is a picture of one of the lithos the bit broke on, I included a whole shot then one close up with the bit tip still in the material. As far as the answer to the questions. To the best of my knowledge everything is correct nothing loose no wobbles fits tight. Again no issues with wood projects, I have included a picture of the latest wood project done after the litho issue started. A gift to my brother who retired from the air force. Also ran off two wood clocks today with no issues. Attachment 79371 Attachment 79370Attachment 79372

It also looks like the path went askew?? I presume you have that in a sled. Is the fit tight? Looks like there was movement of either the sled or the corian itself.

Nice thought, didn't think about the sled, tight fit and taped but only on two sides not all four.

It looks to me like the bit was not cutting right just before it broke. Maybe plugged or somehow dulled. A mystery.

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Originally Posted by bergerud

It looks to me like the bit was not cutting right just before it broke. Maybe plugged or somehow dulled. A mystery.

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Or melted... Is that the broken tip of the bit still inside the plastic?

AL

yes that's the tip of the 1/32 bit

Did any of these happen right after you stopped the carving to do some cleaning?

Yes the machine stopped and told me to clean the y rails, I cleaned them half hearted on the first one. after that I cleaned up the entire machine really good. On the 2nd one I cleaned as good as I could. All 3 breaks happened after the clean y rail came on. The breaks occurred within 10 seconds after I restarted the carves

Any chance that you moved the Y/Z truck while cleaning? Is so the machine probably lost it's location.

The clean Y rails message is do to the machine seeing the Y not moving as expected. With Corian it is a harder material so more force is needed to carve. You might try tightening up the Y belt tension just a little bit.

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Originally Posted by fwharris

Any chance that you moved the Y/Z truck while cleaning? Is so the machine probably lost it's location.

The clean Y rails message is do to the machine seeing the Y not moving as expected. With Corian it is a harder material so more force is needed to carve. You might try tightening up the Y belt tension just a little bit.

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Since the Carvewright is a servo motor style CNC machine with encoders providing feedback I doubt it lost location because of manually moving any of the axis. That's the nice thing about encoder systems. With the encoders being on the back of the motor it's not a true indicator of machine position but it's close enough. Stepper systems running without feed back encoders on the other hand can and do lose position when manually jarred or moved beyond any position not commanded by the software. While a chip could prevent an axis from moving to the position designated by the software; the encoder would notice this discrepancy and either adjust or abort machine movement with most modern day cnc systems.

I think a "clean Y rails" message is reported if the current being drawn by the y motor becomes relatively excessive. I agree, it is not a slip, but, an indication that it is having to work harder than it should to move.

That is why I was thinking that the litho material may have been clogging the bit. It could get pretty hard to push a clogged bit.

Hi
This is Dian's other half, Butch. I was looking at the picture that shows the broken bit. By the look of the fresh cut edge to the right of the broken bit it looks like it was not cutting clean for a little while prior to the breakage. The way the plastic appears to be "smeared" along the edge before the break leads me to believe that the bit was over heating and starting to smear the plastic vice cutting. I would read the cause as the bit started to get hot and smear the plastic which plugged the flutes with plastic up to even with the cutting edge. This would cause it get hotter as a metal bit will do when it stops cutting.

My guess as one possible cause would be the long length of the edge it was cutting (as shown in the picture). My observation (based on watching Dian's work) is that most carving seems to be in short bursts that allow time for the bit to cool a little between cuts. A long cut in plastic does not allow the time for the bit to cool, which for wood ends up as burnt marks but in plastic would start to melt the media. I would recommend trying a carve on the highest resolution, optimal, as it would take smaller bites out of the plastic and should cause less heat in the bit/plastic. Sorry if I seem to ramble on.
Butch

So yesterday I tried a small litho 4x4 taped the entire piece . Had no issues. Am wondering if the correct answer is bit getting hot and melting the piece instead of cutting it. I am going to try and slow it down, the cuts on the 8 x10's have been about 1 hour long on best so I will see if stopping the machine helps or optimal. Again thanks for all the help