z axis starts carve too high

[rflournoy]

Three projects previously carved correctly now won't carve. When CW finds bit during configuration routing all is well, next bit if fine, but when it asks for first bit, it doesn't go down far enough. The project begins to carve 1.75" above the board and tries to carve the project as if the board were 1.75" thicker than is specified in the file. I tried the calibration menu, and the x, y, and z, axis tests, but it seemed fine to the untrained home technician.
What could be going on?

[bergerud]

The first question is: does the bit touch the bit plate?

[rflournoy]

When the carving bit was first loaded it touched the bit plate and then moved across to the other side and touched the board. the next bit did the same, but when the carving bit was loaded to begin carving it didn't touch the bit plate at all...it tried three times vice two, but began carving anyway.

[SteveNelson46]

When the carving bit was first loaded it touched the bit plate and then moved across to the other side and touched the board. the next bit did the same, but when the carving bit was loaded to begin carving it didn't touch the bit plate at all...it tried three times vice two, but began carving anyway.

Which chuck are you using? Is it possible that the bit has slipped in the sleeve? I had that happen once with the 3/16" carving bit for the CT chuck.

[bergerud]

When the carving bit was first loaded it touched the bit plate and then moved across to the other side and touched the board. the next bit did the same, but when the carving bit was loaded to begin carving it didn't touch the bit plate at all...it tried three times vice two, but began carving anyway.

Did it ask you to refind, reload, or continue? If it did not, it seems like a software problem and I would say reformat-reflash the the card and try again.

[Digitalwoodshop]

It is a good thing to get into a habbit of watching the bit process. Watch every touch. It is likely that that 3rd bit did not touch the proper places... likely a dirty Z Rail or Rail Roller or even the Cog Belt is dirty. During bit checks at some point the motor current sensing is turned on and the computer looks for a increase in the load on the motor or increase in electrical current as the bit touches the bit plate or board surface. This is why it touches LIGHTLY then reverses... Finding the bit TIP... What can happen especially if you use a bit like a SHORT V60 Bit that is SHORTER than the other bits that have been used in the project... With a V60 the SHORT bit must travel into RAIL AREA that may now be DIRTY especially the KEYPAD side lower z Rail that gets the Bit SPLATTER. The Dirty Rails act like SPEED BUMPS and the Computer is FOOLED into thinking it touched the Bit plate of Wood... Stopping SHORT and creating what we call a "AIR Carve" That is WHY getting in a habbit of watching EVERY BIT TOUCH.... LOOK for a problem...

Now... Other possibibilities..

The FFC Cable can be BAD.... Intermittant BAD...

The Z Encoder is DIRTY

The Z Encoder clear plastic disk is allowed to SPIN FREE of the Servo Motor Shaft.... Saw one of them this WEEK posted... a Drop of glue fixes it...

Good Luck,

AL

Picture 5 and 6 show Carbon Dust inside the Encoder from what I think is from the servo motor?? But it prevents the light and dark areas of the disk as seen in picture 1 from making proper pulses you can see on the LCD in the Encoder Data test. This can cause "Air Carves"....

[rflournoy]

Did it ask you to refind, reload, or continue? If it did not, it seems like a software problem and I would say reformat-reflash the the card and try again. It didn't ask to refind, reload or continue. I'll try the reformat and then reflash and see what happens. Thanks.

[Digitalwoodshop]

Clean the Z Rails too.

[dltccf]

I always have to clean the z rails after carving pvc or I have that on the next carve.

Dave

[rflournoy]

I reformatted, reflashed and cleaned the z rails. Still getting "air carve." Any other suggestions?

[bergerud]

I think I misunderstood your first post. I thought you meant that the bit failed to touch the bit plate the second time it was measured. Sorry.

Move the z truck up and down by hand a check for any "lumps". Check also that the flex is not hitting the top cover when the truck goes down over at the bit plate.

If all that is well, the problem may be something more serious, as others have said, like a loose or dirty z encoder .

[rflournoy]

I'm getting different results every time I try something. First time, the bit would touch the bit plate, then I changed bits when it asked for the next one. Then back to the first bit and it touched the bit plate and began to air carve. Next time none of the bits would touch the bit plate and the message was something like "Board too thick to carve" or close to that wording. I'll go check for "lumps" and hope nothing new is broken. I had to replace flexshafts, controller, and broken bits in the last 45 days and have less than 200 total hours on the machine. It's a little frustrating.

[rflournoy]

UPDATE: I changed absolutely nothing, but moved the z truck up and down (something I had already done earlier this morning) and the darn thing worked! I wish I knew what made the difference, but it works and right now that's all that matters.

[bergerud]

Maybe you just had a piece of plastic in the belt.

[Digitalwoodshop]

If you don't have a spare FFC Cable you might be needing it soon... Other than a wood chip in the belt or stuck to the rails.... A FFC Cable going bad will do this.

AL

[rflournoy]

After one simple project carved properly in draft mode, I changed it to "best" and started over. It took three tries for it to accept the bits properly, but when it started carving the machine had scaled the project to fit a 9" width board instead of the 11.2" board it was programmed to use and the 11.19" board in the machine. The is the first time it scaled a project back so much. Could this also be the FFC cable?
BTW, I can't find any wood or plastic chips anywhere.