Strange issues - Jig or Machine?

[karossii]

Okay, so I carved my first rotary litho yesterday, and despite only having it set to .18" deep in the .25" walls of the litho, it actually carved one small hole in a light area, and several other light areas came dangerously close to breaking through. Plus, and more concerning to me, even though I made the carve region 11" wide on the 10.992" width (for a 3.5" diameter pvc pipe), and made sure there was no feather, no floor feather checked, etc, it left a 3/8" or so gap of uncarved pipe - it carved the full width of the image, but it just didn't touch where the seam should have been. Is the software incorrectly judging the flat width of a 3.5" pipe (triple checked the actual outer diameter with my calipers...it is exactly 3.5" at the widest), or was there some slippage in the machine, or...?

That aside, the more pressing issues are taking place NOW, in trying to set up a second carve. Assuming maybe it was slippage of the pipe (I was following Michael Tyler's suggestion of the end caps from Home Depot, and as he and a few others said they were tight enough with nothing sealing them to the pipe, I tried it that way for my first carve...), I drove a 3/4" #6 screw into the pipe and end cap and block of wood inside the cap (between the jig and the 1/2" mark where it will 'part off' the piece...). The pipe rotates freely when spun by hand outside of the machine. It requires a bit of pressure - it can't just free spin, but there is next to no resistance when moving it by hand. Other than that, everything is the same as yesterday's setup.

However, I am unable to calibrate the rotary jig. I thought the screw itself would be an ideal touch point, since it is so visible. But when I am jogging, it will only jog a little distance and then stop. As in, I can no longer jog left or right, back or forth, and I can't even hit enter to start the calibration...it just freezes. I noticed the X belt is moving very slowly at that point, not engaging the jig; but both belts moving the 'board' from right to left (facing the keyboard side) very slowly. I looked at the belts and jig where they should contact, and the jig's belt seems to be touching the X belt in the machine, but the machine is moving and the jig is not. The wheels on the far (non drive) side of the jig are spinning with the machine's belt.

I did this multiple times, and have had this issue every time, sometimes within a second, sometimes within 5-10 seconds of jogging the bit as I start the calibration process. If I stop/cancel the calibration, the X belt continues to move slowly. If I turn off the machine, it briefly flashes an X drive error before the power kills the LCD.

So is this an issue with the jig somehow? Or the machine? Or both? I will be trying some troubleshooting steps here in a moment, just thought I would post for input now, before I get too caught up in that process. Will follow up as (if) I figure out anything more.

[karossii]

Okay, first I caught the error message this time... X Axis Stall E05-314

Second, I removed the jig, and measured a board. Fliped it front to back, side to side, and front to back again, and all four measurements were as accurate as this machine ever is (which is to say somewhere within 1/4") on measuring the length of boards. Not sure why my machine is so poor at measuring the length of a board, but it always has been, so I don't think that relates to the current rotary issue.

Then I took that screw out, the 3/4" #6 screw I used to keep the pipe from slipping on the end cap. It seemed to make no difference at all in turning the pipe by hand. I put the jig in the machine, and started the rotary calibration process - this time as soon as I hit enter (0,6,7,enter) the X belt starts spinning. Now before, it moved the pipe about 1/2" or so, moved it back to where it started, and then let me jog. This time, it just kept running the X belt. the LCD panel said 'jog to position' and had the coordinates, etc.; but the X drive belt was spinning, and the arrows on the keypad did nothing. I hit stop to cancel, did it a second time, and got the same result. I turned off the power as it was still running (and that is where I got the error message above), powered back up and tried again - and it is still just running the belts non stop instead of letting me jog to a starting point.

[karossii]

Okay, I formatted and re-flashed the card, and it seemed to work perfectly for a moment or three... then the jig stopped turning again. I played with a dozen different things, and I *think* I have found the second half of the issue (obviously, reformatting and flashing made a huge difference) - the JIG's drive belt keeps slipping away from the jig and toward the workpiece, and then binding against the workpiece.I have pushed it back into place three times, and gotten it as straight as possible across both gears and both bearings; but as soon as I start spinning it by hand, it will start working its way back towards the workpiece, getting harder and harder to turn. Not sure how I can fix this...

[karossii]

Took me forever, but the jig's belt is in the right alignment now. Then I get it back in the machine, and everything seemed to be working right - until it spun about halfway around and the jig stopped while the carvewright kept going. and the jig's belt slowly started creeping in to the workpiece, out of alignment again. I stopped it, fixed the belt, and started trying to spin it by hand out of the machine. It had a small, but not significant, catch as it turned past two points, about 180 degrees apart from one another. When the two screws are 90 degrees off of the hole you put them through. I pulled out the screws, and rotated it by hand again, and it was fine. So the screw heads were catching ever so slightly, but somehow that was enough to keep the jig from spinning as the carvewright moved, and throw the belt out of alignment.

Now I need to figure out what is going on with the screws. They are the recommended screws, except 2" in length instead of 1.25" (the 1.25" wasn't reaching through the PVC end cap and into the block of wood inside it - and since the carve was not even going through the PVC much less that wood block, I figured it would be fine).

This is a NIGHTMARE!

[fwharris]

Ken,

Well it looks like your deep into trouble shooting your problem with not much help from any of us. Good job on narrowing it down to the screw heads. Are they rounded, flat or oval heads? I would say you should be using a countersunk flat or rounded head.

[SteveNelson46]

I am having exactly the same problem. The belt on the Rotary jig seems to creep its way off of the large gear. That causes the belt to creep off of the small idler pulleys also. However, it could be the other way around. The misalignment of the idler pulleys may be causing the belt to creep off of the large gear. I was also having a problem with drag. It seemed as though something between the large gear and the end plate was rubbing so I disassemble the entire mechanism. I found that there were some burrs on the screw holes between the end plate and the large gear so I filed them off and reassembled the jig. However, I continue to have alignment issues with the belt. As best as I can tell, there is no way to adjust the tracking. I even tried placing some washers between the pulleys and the end plate but, to no avail. Then I tried flipping the belt over so it turned the opposite direction. That seemed to help a little but is still slowly creeped off of the gear and pulleys. The only way I am able to make it workable is to take a smooth object like a screwdriver handle and push the belt to the left during the calibration to keep the belt on the pulleys. I still have to make several attempts at calibration by adjusting the position of the jig and making sure the head pressure is pushing down on the jig enough before it calibrates correctly. After that it only has to make one revolution during the cutting phase so most of the time it seems to do okay. I intended to call technical support to see if there was a way to align the tracking of the belt but, I have not done so yet.

You are absolutely right in labeling this a nightmare. It seems like it takes an inordinate amount of time to finally get the jig to work correctly.

Edit: I might add that it is absolutely imperative that you get the screws that secure the wood to the jig below the surface of the large gear. If they rub, even slightly, the jig will not calibrate correctly.

[cestout]

Is your jig square in the machine. With the 1/16" carving bit in, does it touch the center marks at each end of the jig. Being canted could pull the belt off.
Clint

[SteveNelson46]

Is your jig square in the machine. With the 1/16" carving bit in, does it touch the center marks at each end of the jig. Being canted could pull the belt off.
Clint

I adjusted it once when I first got the jig but I have not checked it again. In fact, it could be a way of adjusting the tracking on the belt by adjusting the angle of the jig. Thank you Clint for the idea.

[karossii]

Okay, thanks for the replies and help. To answer the questions/advice...

I was using flat head screws, and I was as positive as I could be that they were below the surface with no rubbing. I was using the exact same coarse thread wood screws as used in the video here http://youtu.be/nzWZWYkcRMc?t=2m26s - except, as mentioned, 2" instead of 1 1/4". I switched to a fine thread 2" #6 screw which has a flat head about half that size (and is stainless steel instead of black) - and that seems to have fixed the issue of it catching at 90 degrees.

And yes, the first thing I have done every time I place the jig in the machine is to check it is still square, with the bit hitting the center of each of those marks in the sides of the jig. It has, thus far, stayed square since my first 2 hour adventure in aligning that.

I think I finally have it carving properly, though I just started and only watched 3 lines of optimal setting creep by before returning to my computer - I will go back to check it shortly and verify it is functioning properly. Only 8 hours later in the day than I intended to start, about the same time it would have taken to carve 2 and a half more of the PVC lithophanes I hope to have on display at a craft show tomorrow... with the first one mis carved, and this delay, I will be lucky to get 2 carved for the show; had hoped to have between 4 and 7 of them based on the carve times.