Z stall and cutting depth issue

[fwharris]

I am trying to get a local guys A machine (it has been upgraded with the A907 Z pack and CarveTight chuck) that he wants to sell. It was in storage for almost 2 years. As far as I know (not assuming anything with that statement! ;) it was working when he put it in storage.

After getting it all cleaned and lubed up and running all of the sensor and axis tests the first test carve ran without any issues. Since I have it set up in the shop of the maybe future owner I told him to go ahead and carve up some Christmas ornaments that he wanted. His next carve ran good including the cut out.

Problems for then on: A long winded one but wanted to get as much info in as possible.

Next carve ran good but when it stopped and was suppose to ask for the cutting bit it went to Z stall message instead. Modified MPC and ran the cut path with no issues.

He then ran 2 more and on these the carving depth stared changing. The depth started getting shallower as it got to the highest parts of the pattern and then leaving the top surface of the board as not carved for those areas and as the pattern goes lower back into carving the detail.

Today I went over and reset the FFC cable and double checked all of the other connections. FFC did seem a bit out at the back of the Z truck. Ran a small carve region test with a 2" x 2" region with a cut out of the center. All ran well. I then loaded up one of the prior carved pieces with the high spots and started it over. When it got to same area of the flat carve it was doing the same thing. I aborted and modified the pattern height to lower the highest spots. In designer it showed them to be 0.01 depth. I had to take the height down to 75. The re carve ran good and no Z stall when stopping for the cutting bit.

I ran the board thickness calibration and modified the rest of the MPC files to lower the height setting. All prior uploads were done as a "normal" carve quality and since he is carving these in walnut and cherry I selected optimal.

His next carve went the opposite way. As it got 1/3 of the way into the pattern it started going deeper and finally into the bottom of the jig.

Any insights for what to look at next? My thoughts would be the Z motor ( I did remove the back cover and it was clear of dust and the clear disc was in good shape) , head termination board and the z motor electronics board.


PS: It is Christmas time in Colorado Ya Know! ;)

[bergerud]

Sounds like a loose z encoder disc. Did you check that?

[fwharris]

I did check it when I took the cover off. It seemed tight on the shaft and rotated when I move the truck up and down.

[bergerud]

Well it sounds like the z position is slowly changing and that seems like an encoder thing. What else could it be? A broken wire connection in the FFC?

[fwharris]

I agree 100% on the changing Z position. I will probably swap out the FFC cable as the first test. I did give it a good inspection but you never know. After that the Z electronics board.

[Digitalwoodshop]

Move the Z up to the top pin.
Open Z Data and it should be 0000 as it is where ever the head is when you start sensor data.
Move the head down and up a dozen times and return to the top. It should be 0000 at the top pin if not....

Bad FFC or bad connection, loose in the plug.
disk spinning on the shaft
broken or missing z tooth


AL

[fwharris]

Move the Z up to the top pin.
Open Z Data and it should be 0000 as it is where ever the head is when you start sensor data.
Move the head down and up a dozen times and return to the top. It should be 0000 at the top pin if not....

Bad FFC or bad connection, loose in the plug.
disk spinning on the shaft
broken or missing z tooth


AL

Al,

Thanks for the added tips! I will let everyone know what I find out.

[SteveNelson46]

It could also be a controller. I've had similar problems and replacing the controller fixed it.

[fwharris]

It could also be a controller. I've had similar problems and replacing the controller fixed it.

Well lets hope not! They guy that I am trying to sell it for might not like to hear that bad news, his selling price would have to come down. I've already had to replace the cracked cut motor case.

[SteveNelson46]

Well lets hope not! They guy that I am trying to sell it for might not like to hear that bad news, his selling price would have to come down. I've already had to replace the cracked cut motor case.

What caused the cut motor case to crack? Over heating, a sudden obstruction of the spinning bit, etc? All the more reason to suspect the controller. In my case, a static discharge took out the controller and it was giving me the same intermittent symptoms you are having.

[fwharris]

I suspect the motor end was cracked from the constant movement of the flex core as it moved back and forth during the carve. CarveWright is now tie wrapping it down at the point it comes out of the machine. When I called the owner to let him know it was cracked he was not aware of it. The guy he had working for him appeared to try fix it with epoxy or JB Weld, but as we all know that does not work.

The guy who is thinking about buying the machine brought back to me tonight and I ran Al's Z reading test. All reading stayed constant top to bottom at several different locations on the Y axis. No change in reading while moving the FFC cable around either. I will set up another test carve and run it to see what happens and go from there.

He does have another machine at his shop so he took the memory card back with him to do a carve on it to verify/eliminate anything with the files on the card.

[Mike1]

I'm not sure it if this will help or not but it worked great on my hot tub pump that had a crack in the fitting. Pretty amazing stuff. https://www.plast-aid.com/pages/plast-aid-101

[Digitalwoodshop]

My take on cracked cut motor cases is packing up the machine with the flex installed and it stresses the cut motor to the point of cracking... Always remove the flex when boxing the machine. At least that is my opinion....

As for the Z Drift.... How about a loose bit...?

AL

[CarverJerry]

Mike, that Plast-aid looks like some real good stuff. I watched the 3 videos...impressed with that stuff..thanks for sharing that with us.

[Mike1]

Jerry, it really is amazing. It worked exactly like it said and no clean up, imagine that! You are very welcome.

[fwharris]

My take on cracked cut motor cases is packing up the machine with the flex installed and it stresses the cut motor to the point of cracking... Always remove the flex when boxing the machine. At least that is my opinion....

As for the Z Drift.... How about a loose bit...?

AL

I agree that the stress of the machine being in the box with the flex shaft still attached to the machine is one cause for the cracked motor case. I also think the long time effect of the shaft core moving back and forth has caused the as well.

I rolled out the bit slippage as it is a CarveTight bit set up. Have not had time to get back into working on it and probably will not until after Christmas. Thanks for the input and keep them ideas coming.

[fwharris]

The problem was the Z motor.

[bergerud]

Do you know what it was about the z motor? Bad encoder, gear slipping,...?

[fwharris]

My WAG would be the encoder even though it was tight on the shaft and looked in good shape. All of the gears looked good and matched up well with each other.

I swapped out the FFC cable first and the machine would not even go through the bit check routine without giving a Z stall error. Before I got into the part swapping I stated a test carve and it was very rough looking (a lot of bit marks) and when it got to the highest part of the pattern it was carving above the board so I stopped it. When I answered the abort prompt the Z truck went to the top and gave the Z stall message. I did a Z sensor reading check at that point and the reading was something like 0.05 or something similar.

After swapping out the Z motor and gear box assembly I restarted the carve and it was a big difference in carve quality. Very smooth with no sign of bit marks.

[bergerud]

Sounds like the electronics of the encoder was bad. I had a z motor with a bad encoder. Looked fine, just did not work. (I swapped it out and replaced it with a board tracking encoder.)

Good job on the fix. It was a tough one.

[fwharris]

It was the original motor for the A907 Z pack upgrade that I installed for him a long time ago and had I think over 600 hours on it so I think it must of been some internal failure. I need to check with the techs at CarveWright to see if they do some type of bench test on these.

So you swapped out the encoder? What all did the entail? I do have a couple of old Z motors that I think are still good. They were from the A907 upgrades I've done and from an old parts machine I picked up. Would they be okay to swap out for the bad one?

[bergerud]

The encoders on the motors are soldered on. The encoder in the tracking sensor is exactly the same except it is not soldered. It makes for a perfect replacement part.

One could certainly swap encoders between motors by desoldering and resoldering.

[fwharris]

Dan,

Thanks for the info, I will keep that in mind for future reference. I have a couple of motors from a display unit but the wires were cut off right where they come out of the motor body.

Another question, would you know what difference, if any, there is between the older style motors and what they are using now? Older style being the ones on the A series machine. With the A907 upgrade they send a new motor and I still have the one I replaced. I do know the newer ones have a shorter body style for better clearance in the back of the machine.

[bergerud]

I thought all the motors were the same. Look on the casing (under the heat sink) RS-555PH-24110. Could it be that it is just the cap on the end which is shorter? (The motor casing on mine are about 5.5 cm long.)

[fwharris]

I thought all the motors were the same. Look on the casing (under the heat sink) RS-555PH-24110. Could it be that it is just the cap on the end which is shorter? (The motor casing on mine are about 5.5 cm long.)

Thanks, that is what I am thinking but I will check out the numbers..

[fwharris]

Well after digging through my spare part boxes I came up with 4 motors and a couple of them even had the gear boxes. All of the numbers match what you posted and they all are the same length. They all have the old style heat sinks and end caps but I think I should be able to just swap out the motor into the new style heat sink with the clear plastic cover.

This should make the current and new owner happy that they will not have to invest $100 for a new one.

I will report back next year! ;)

[TerryT]

I know it is a long shot Floyd, but did you check the roller bearings on the Z truck. I had a similar issue and found the bearings were just loose enough to allow the bit to push up slightly and cant to one side when it contacted the board.

[fwharris]

I know it is a long shot Floyd, but did you check the roller bearings on the Z truck. I had a similar issue and found the bearings were just loose enough to allow the bit to push up slightly and cant to one side when it contacted the board.

Terry,

Thanks for the tip. Even though I did a complete clean and lube prior to testing the machine I did verify the bearing movement prior to digging into the other causes. I believe I have it narrowed down to the Z motor electronics.

Thanks again,

[fwharris]

Well the temperature in Colorado finally got out of the deep freeze the last couple of days so I swapped out the Z motor with one of the spares I had. I removed the heat sink and end cover from the bad one and put it on the spare motor. Very easy once I figured out that I had to loosen the screw on the heat sink so it would open up to get the motor out. :D

I reinstalled the ffc cable and Z termination board that was with the machine and the test carve ran without any issues or stalls.

It would be nice to know what the issue/problem is with the old motor. It must be something with the encoder system but I am not going to spend much time to worry about it.

[Digitalwoodshop]

As long as you install the 14 pin circuit board on the old motors you should be good.

I call it a 16 pin in one picture but it was 18 pin.

AL

[fwharris]

Al,

Yes it was the 14 pin board. I was the one who did the A907 Z pack upgrade for the guy when he first contacted me about helping him get the machine out of the box to start using it. He also had be do service on the machine as needed. They guy he had doing the carving for him was only good at loading up the pattern designs to be carved and it took me several hours of training to get him to that point. ;)

For removing the encoder circuit board from the motor Dan said it is two solder connections to undo. Is that about all there is to it? I might take the old one apart just to look at the back side.

[Digitalwoodshop]

Al,

Yes it was the 14 pin board. I was the one who did the A907 Z pack upgrade for the guy when he first contacted me about helping him get the machine out of the box to start using it. He also had be do service on the machine as needed. They guy he had doing the carving for him was only good at loading up the pattern designs to be carved and it took me several hours of training to get him to that point. ;)

For removing the encoder circuit board from the motor Dan said it is two solder connections to undo. Is that about all there is to it? I might take the old one apart just to look at the back side.

If a rotary encoder is giving you trouble it could be the disk lines worn off or the LED and Sensor box has dust in it.

To troubleshoot I would just plug it in and with a exposed encoder and use sensor data. It just counts lines from 0000 to 0001, 0002.....

Something else that can fail is the jack installed on the board. IF the plastic plug was not seated all the way down on the circuit board when it was wave soldered. Later pushing the wires on the board and vibration can cause the DONUTS on the under side of the board to break away from the bottom of the board leading to a open wire or trace on the board.

AL