New user here, and new to machines, though reasonably hands on.
I’ve recently bought a secondhand Chinese 1060 (basically a larger k40. Same setup, boards, motors, etc). During the course of aligning the mirrors after transport, and our first dozen cuts or so, we’ve gone from having a machine whose y axis seemed to be perfectly fine, to a machine where as the gantry travels the depth of the machine (from front to back, vice-versa), where the gantry very quickly becomes uneven. Example, travels 30cm from the back towards the user. The left hand side travels 40cm and the right hand side travels 36cm.
So, I have questions:
How critical is belt tension? I’ve tried loosening and tensioning both belts using the belts tensioners at the rear. This seems to make no difference.
The Y axis stepper motor is the type where the coupler is on one side and the belt gear is on the other. Is there something in the stepper that can go wrong to cause the shafts on opposite sides of the stepper to turn at slightly different speeds?
I’ve tightened up the grub screws on the coupler (drive shaft at front of machine) - they were all very tight already, so basically no movement when trying to tighten.
The frame is measured as best I can in the machine to be square, with all screws tight.
This is my first cutter, so I’m struggling a bit to get the machine back to operational. Any suggestions on what to look for would be amazing.
A stepper shaft goes straight through from one end to the other, so the stepper shaft won’t turn differently at each end. But I’ve had pulleys on steppers slip even with a tight grub screw when the shaft doesn’t have a flat on it for a grub screw to engage.
I’m not sure I understand about your Y axis stepper; can you upload a picture of it?
I don’t see how it is mathematically possible for any part of the X axis rail to move less than the 2 ends of the X axis rail. Both ends are stated to move more than 30cm yet you state “travels 30cmd from the back towards the user”.
That really implies something starting to slip, then the slippage getting progressively worse. I know you have double-checked the grub-screws but they would still be my prime suspect. Dismantling the mechanism and looking for signs of slippage on the shaft under the pulley could be a good idea.
I think I’m not alone in despising grub-screws after having had them fail me repeatedly.
Thank you very much. I guess the answer at this stage is pulling the running gear and frame out of the machine entirely. The pulleys look to be a nightmare to get in to.
The left side is moving at a faster rate than the right, causing the gantry to progressively become out of square until the bearings bind and allow no further movement.
You should already have a pair of mm/in calipers so I would make a measurement on the teeth of each belt to see if they have the same spacing. Someone might have replaced one belt with the wrong size and that’s causing the belt to ride up on top of the pulley gear therefore creating a larger diameter and hence the results you are seeing.
Given that it worked right for a dozen cuts, I’d be surprised if it’s a wrong-pitch belt. Also the most common pitch substitution is off by only about 2% IIRC.
looking for anything since this should be an obvious issue to pinpoint but seems not to be. Who knows, maybe those initial cuts were only small and something caused the OP to observe the much larger deviation.
I sharpie marking the gears at their shaft(both sides of the machine), motor shafts at couplers(both sides of the motor) would show if any of those are slipping. 4 cm is a huge amount to be off by.
Ive got time set aside tomorrow morning to begin pulling the machine down and get in to the more inaccessible spots - eg the pulley driving the side of the gantry which seems to move less (and possibly the side thay is slipping). In its current form i cannot reach a couple of bits, so this will be an adventure for the newbie.
when I removed my motion frame of my K40 to cut down the exhaust duct I marked the edges of the frame on the mounting plates so that I could put it back exactly where it came from. Could mean no or very little mirror adjustments once returned to the case.
Thanks everyone. Ive just had the frame mostly out of the case: didnt want to remove mirror assembly to take it all the way out as the mirror would not pass the case edges whilt mounted to the frame.
What i discovered was the pulley on the left hand side at the front, which i was not able to see and it was difficult to feel and discern, had the belt mounted up over the lip of the pulley. So the synptoms maych the cause in this case. It in effe t made a larger wheel which the left belt was rotating around, thus the left hand side of the gantry was moving faster from the same drive shaft rotation. This seems like it is a problem that could reoccur in the future if i allow the gantry to come within about 2-3 inches of the front of the machine. Not entirely sure why yet, but at least im back up and learning.
Ive just gone through basic mirror alignment again. Its a pain in the butt and certainly not mm perfect, but its cutting reasonably round dots.
Ill try a cut tomorrow and see how everything goes.
Is there some kind of mis-alignment between the 2 pulley gears and the attachment point on the X axis which is pulling the belt out of the center of the pulley? Maybe a drive pulley can be loosened and moved on the drive shaft so that the belt stays between front and back pulleys.
Possibly. Thats something I’ll look into at a later date, i think.
Im already diving down the rabbit hole of looking at controller andnoptics upgrades, so for now ill use the 90% usable area on the cutting table to learn more about the machine and things we can do, and then at another point in time if i do something that requires pulling the optics, bed, or other bits again ill remove the entire frame since ill be in that deep anyway.