Delta frustration - ready to give up.
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!!!!! Weirder alert !!!!!
Started checking the Z movements of the carriages and whilst Z/Y moved 150mm when asked X was only moving 148.6 !!!
I thought "what's to loose" i'll adjust the steps/mm, calculated the difference and set X to step at 161.52.
Printed a 40mm hollow cube and whilst the first 9mm of height still has the tiniest bit of offset you really need to be looking for it with the first few layers the most affected at just under a 1mm…. you would maybe normally spot it. I didn't till i went looking.
Guess i have a faulty stepper, can't think of any other reason for the step/mm being "wrong"
Note: even with the corrected steps…. the offset happening after positive X movement was still measurable but had dropped closer to 1mm of offset.... visually sorry didn't physically measure.
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Phil
This might sound really silly BUT where is the Pb suspended from the effector ie centre or from one edge point?
If from an edge is it possible that the additional mass supported out there is causing some misalignment (or Effector Tilt) when moving in one direction. (If so it would suggest some play in the system somewhere probably in the opposite side to the suspension mount)
Can you try the same tests with the Pb suspended from the nozzle point (or as close to the centre as possible).
Hope this makes a little bit of sense not sure I even know what I am trying to get at?
Doug
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Phil, please can you explain the apparent contradiction between these two:
3. Multiple moves do not increase the error so it doesn't accumulate
4. Repeated 100mm moves accumulate the error.
Also, please can you run M114 and report the step counts at (0,0) with the plumb line showing both the original position and the positions after the shift occurs.
It seems unlikely to me that it is a firmware problem. OTOH you are running a larger delta than anyone else I know of, so I can't discount the possibility of an overflow error somewhere in the delta calcs. Please can you give me your M665 and M666 parameters, also your tower steps/mm, and I will plug them into the simulator.
Also please check that when the head jumps sideways a little after homing, the 5mm that it has moved down is far enough that the sideways jump does not cause any of the carriages to hit the endstop.
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PS - also, please wind back the acceleration and jerk settings to these values and test again:
M201 X1000 Y1000 Z1000 E800 ; Accelerations (mm/s^2)
M566 X600 Y600 Z600 E1200 ; Maximum instant speed changes mm/minute -
Phil, please can you explain the apparent contradiction between these two:
3. Multiple moves do not increase the error so it doesn't accumulate
4. Repeated 100mm moves accumulate the error.
Also, please can you run M114 and report the step counts at (0,0) with the plumb line showing both the original position and the positions after the shift occurs.
It seems unlikely to me that it is a firmware problem. OTOH you are running a larger delta than anyone else I know of, so I can't discount the possibility of an overflow error somewhere in the delta calcs. Please can you give me your M665 and M666 parameters, also your tower steps/mm, and I will plug them into the simulator.
Also please check that when the head jumps sideways a little after homing, the 5mm that it has moved down is far enough that the sideways jump does not cause any of the carriages to hit the endstop.
Just checking back in, had to not go near it yesterday….
David,
Explanation is that the first 200mm +X move seems to return to 0,0 with an offset of say 1mm but 10 repeated moves did not show any further observable changes.
However a single 100mm +X move didn't show any initial measureable/observable offset however repeated 10-20 moves started to show an observable offset occurring.As i have a mile of height i drop the head 10mm after homing so the reset to 0,0 doesn't cause an endstop to be triggered, but i'll triple check.
M665,666 listed a few posts back but your next post shows you seen them, i'll drop the numbers later today and retest.
Still concerned now about the stepper on the X tower needing a different steps/mm for correct travel.
Cheers and thanks for the continuing help.
Phil
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Still concerned now about the stepper on the X tower needing a different steps/mm for correct travel.
Cheers and thanks for the continuing help.
Phil
Phil
What are you Step/mm for each stepper it is not normal for them to be different and would suggest you have a oddball toothed pulley in there.
Looking at the Config.g you posted a while back they were all set to 160 which implies 20 tooth pulleys?
on my first printer (an I3) I was getting very strange distances until I counted the number of teeth on the pulleys? the steps/mm was set for 16 tooth pulleys but I had been supplied with 17's so there are odballs out there and is worth checking and this may well be the cause of your issues.
Sure David will pipe in soon
Doug
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I agree, if you need different steps/mm for the motors then something is wrong. How did you arrive at your steps/mm values?
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I agree, if you need different steps/mm for the motors then something is wrong. How did you arrive at your steps/mm values?
Arrived at the values by measuring the actual z movement of the carriage in relation to the end stop in both the up and down directions to ensure comparison readings and then dropping the numbers into a steps/mm calculation.
Measurements taken with 200mm digital calipers for z=150mm of movement…. Y and Z both travelled 150mm +-0.05mm... ie measurement variance.going to order a couple of motors today but looks like no stock locally in Oz
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Phil
Surely it is more likely to be a pulley that is off in some way have you physically counted the number of teeth on each one?
Know what your steps/mm are currently set to may give a clue as well?
Doug
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I agree that the pulley (or belt?) would be a much more likely culprit than the motors.
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Phil, I really think your X pulley is slipping on the motor shaft, even though I know you have already checked that. Try energising the motors, send M906 I100 to prevent idle motor current reduction, then see if you can move the X carriage up and down a few mm by hand
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I haven't yet counted the teeth….. but some work in a spreadsheet shows that it can't be.
every tooth variance with a gt2 belt = 2mm difference in travel per revolution.
at 150mm of travel I have 3.75 motor revolutions
I assume if it was a tooth count error travel would be out by 7mm+So some further number crunching reveals something interesting.....
Pulley 20T
Motor 0.9deg
mm/rev = 40mm
distance for each full step = 0.1mmfor 150mm of travel I measured 148.55 to 148.6mm actual.
If we round that to 148.5mm for a minute we have 1.5mm of error
Now 1.5/3.75 = 0.4mm per rev of error
mmmm..... this is exactly 4 full stepsthat seems far to coincidental for me.
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Phil, I really think your X pulley is slipping on the motor shaft, even though I know you have already checked that. Try energising the motors, send M906 I100 to prevent idle motor current reduction, then see if you can move the X carriage up and down a few mm by hand
Ok tried that,
it does not move, not even with a very heavy hand.
Cheers
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Maybe stepper motors run the other way around in 'stralia.
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How about if you try to move it out at the extents you were having trouble with? Like at x290 or y290
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PS - also, please wind back the acceleration and jerk settings to these values and test again:
M201 X1000 Y1000 Z1000 E800 ; Accelerations (mm/s^2)
M566 X600 Y600 Z600 E1200 ; Maximum instant speed changes mm/minuteFurther Update:
Done this no change…Next test: Swap the X and Y cabling and see if issue moves or stays with tower.
Result: (not fully tested, too cold outside) however initial tests shows the issue stays with the tower and this, for me, atm clears any firmware issue.
Further evidence that this is a partially failed/failing stepper is that with power off, moving the X carriage by hand reveals a very clear (hard to describe) rough then smooth movement. rough is what i feel moving the other two carriages at all times. whilst i haven't measured it the rough/smooth cycle looked like 40mm so 1/2 rev is "normal like the others the other 1/2 rev is smooth/less resistive.
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How about if you try to move it out at the extents you were having trouble with? Like at x290 or y290
The more i test/research/discuss and think about this and the more evidence i gather the more it becomes obvious the the moves to the extents enable the last issue of incorrect X movement to be clearly seen rather than a pure cause.
This machine has 674mm long effector arms to cover the print area which means the for the first 100mm of print radius the carriages really don't move a lot.
Think i'll end up parking this till I can replace the motor.
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Phil
What angle in relation to the bed do you get at full extent with those Arms?
Mine will be 750 long for a similar sized Delta with a slightly smaller bed than yours (around 550 mm dia)
just wonder if your getting close to or below the 20 degree angle that is the recommended lowest angle. if so maybe that is compounding the error's.
(Would be good to know as I haven't cut my rods yet so may be able to reduce them).
Doug
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Hi Doug,
I just went a did a quick check
Angle at around full extent is approx 30 to 32 degrees.I cheated a little for the long rods, i placed the effector at the outer edge, and measured to the carriage at a 30 deg angle to get the arm length, subtracted the end offsets to then get the cut length.
the final arm length will depend on the carriage design and the arm ends and you may be better to physically measure at your desired min angle.
