Delta frustration - ready to give up.

Aussiephil

David just went back and looked really closely at the 30mm hollow cubes i had printed last with 0.85 board and it shows the first couple layers shift the worst then by Z=9mm we start going straight up. Nearly like whatever calc error stops accumulating.

Toddimus

Just a few ideas if you haven't already thought of these…

If you are doing a bed calibration at the beginning and using calibration points out near the extents of the printable area:

is there something out near those outer extents that binds up in the slides/carriages/effector (leading to missed steps or even skipping of a belt tooth??)
or are one or more of the belts damaged out at the extreme positions (this could lead to some hysteresis of position)
or is your suspended extruder cold end/Bowden tube somehow pulling on the effector when you calibrate out at the extremes
or is there a "booger" or burr in your ball ends out near the furthest extent of calibration or movement that could cause an error in position (less likely, but had to include it in the list)
or is the current supplied by the steppers just not quite enough to pull the carriages out of those extreme positions (missed steps)
Last but not least… is the plumb bob heavy enough to cause missed steps or even "sag" of the carriages between movement commands (you had the idle current set to 40%, which might not be enough to hold things in place??)

So to test out the motor current being the issue…
Instead of this line in your config.g:

[[language]]
M906 X1600 Y1600 Z1600 E1200 I40        ; Set motor currents (mA) and increase idle current to 40%

```try this instead:

[[language]]
M906 X2000 Y2000 Z2000 E1200 I60 ; Increase motor currents (mA) and increase idle current to 60%


I know when I was first trying to get my bed calibration parameters dialed in, I had a few hard crashes into the bed with the nozzle. Nothing seems to be damaged, but it sure didn't sound good. I haven't taken things apart to inspect but I'm hoping I didn't damage the belts.

I just can't imagine it being a software bug that is only affecting your setup this way. Granted, you probably have one of the bigger delta machines out there so you are in uncharted territory with this board. My bet is that it's either something mechanical or some settings of parameters in the config.g or somehow bed.g file.

Aussiephil

Hi Todd,

Good thoughts but only the motor current is not yet tested.

The bed.g file used for actual calibration is currently set to a 250mm radius, well inside my reach of over 300mm.

The carriages move freely and have no apparent binding and i here no strange noises.

The belts are all literally brand new as part of the rebuild.

No evidence that the flying setup pulls the effector out of spot.

The ball ends are all smooth and i've rechecked

I haven't got any spring scales handy but the pb is 150gm and it takes a lot more than that to displace the motors even at 40% idle.

yeah I too don't believe it is truly software but I'm running out of ideas.

Aussiephil

!!!!! 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.

Dougal1957

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

dc42

Phil, please can you explain the apparent contradiction between these two:

@Aussiephil:

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.

dc42

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

Aussiephil

@dc42:

Phil, please can you explain the apparent contradiction between these two:

@Aussiephil:

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

Dougal1957

@Aussiephil:

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

dc42

I agree, if you need different steps/mm for the motors then something is wrong. How did you arrive at your steps/mm values?

Aussiephil

@dc42:

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

Dougal1957

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

bot

I agree that the pulley (or belt?) would be a much more likely culprit than the motors.

dc42

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

Aussiephil

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 = 0.1mm

for 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 steps

that seems far to coincidental for me.

Aussiephil

@dc42:

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

bot

Maybe stepper motors run the other way around in 'stralia.

Toddimus

How about if you try to move it out at the extents you were having trouble with? Like at x290 or y290

Aussiephil

@dc42:

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

Further 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.

Aussiephil

@bot:

Maybe stepper motors run the other way around in 'stralia.

LOL - needed a smile