Mid-print head lifts up too far for next layer

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Mid-print head lifts up too far for next layer

Postby NeilIde » 2016-Dec-Tue-20-Dec

I've been banging my head against my Simple Metal for 2 weeks now.

I will start a print and everything looks gorgeous. Printing 0.2mm layer height and everything is gravy, starting about 10 days ago the machine started randomly failing mid-print.

The nature of the failure seems that the head raises up several mm to start the next layer and the large gap left means everything goes drip city afterwards.

It doesn't matter what I'm printing past successful prints are now utter failures. The location of the giant head lift seems to be random as well most failures occur between 10-100mm and after 30 minutes or several hours. I'ts completely random.

I'm slicing with Cura and running my machine in a heated enclosure. The control board (F6) is outside the enclosure so it doesn't overheat.

Has anyone experienced this before? I'm completely out of ideas.
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Mid-print head lifts up too far for next layer

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Re: Mid-print head lifts up too far for next layer

Postby RetireeJay » 2016-Dec-Wed-07-Dec

Generally, I'm in agreement with Mooselake that re-flashing the firmware is a solution of last resort. But in this case, maybe we are at the last resort; I think I would try re-flashing if it were my printer.

(I had thought about a poor connection between the board and the motor, e.g. due to wire fatigue, causing full steps when there were none -- but then I realized that there is no motion of the Z motor relative to the board, thus no opportunity for wire fatigue. And that whole idea is pretty shaky anyway!)
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
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Re: Mid-print head lifts up too far for next layer

Postby Mooselake » 2016-Dec-Wed-09-Dec

On the off chance that there's a sticky spot on the rods or screw that causes a problem moving down manually run the Z all the way up (not off) to the top of the screw. Wipe the moving parts off with your favorite solvent (dry thoroughly if water based), then lubricate them. Light machine oil (3 in 1, gun, sewing machine, etc) will work if you don't have a favorite.

Run the Z up and down a few times to distribute it, then see what happens. Worst case you'll have smoother movement, best it'll fix the problem. You should lube your rods regularly anyway, especially in that heated box

Kirk
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Modified KickStarter Classic Plus 7/2012
KS Thingybot Delta Pro 10/31/16
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Re: Mid-print head lifts up too far for next layer

Postby NeilIde » 2016-Dec-Wed-16-Dec

Kirk/Jay thanks for the quick response.

I switched to a spare F6 controller I had in my shop and the problem persists. I also checked the z screw for travel and everything glides smooth there. I used engine oil as the lube on the screw since it can take the heat.

At this point I think the next step is to replace the Z-Stepper and see what happens. It wouldn't surprise me if the motor is having issues given the temperature I'm running the enclosure at. Though it seems odd that it would only be the one stepper and not all.

Any other thoughts?
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Re: Mid-print head lifts up too far for next layer

Postby RetireeJay » 2016-Dec-Wed-18-Dec

Stepper motors are extremely simple inside: just magnetically-permeable iron or steel and insulated copper wire wound into coils. They can take a lot of heat without damage - as in too hot to hold your finger on them. However, if they should become extremely hot then thermal expansion of bearings and internal parts might cause them to jam. I can't imagine how a motor could fail in a mode of moving more than it was commanded. It's just magnetic fields that move the motors around. But then again, strange things can happen.

So if replacing the motor fixes the problem, be sure to post that result here!
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Printrbot Plus operational January 2013
Brass threaded rods (5/16" X 18) & nuts for Z axis
GT2 belts & pulleys
Cable chain to reduce probability of fatigue failure in wires
E3D V5 Hot End, 0.4mm nozzle, also 0.8 and 0.25 in use occasionally
PB fan mount + 40mm fan -- using printed mount adapter, not the E3D supplied fan
Injection molded extruder gears
Optical Z "endstop" (custom designed and built)
Have used many pounds of T-Glase filament. Now also doing some work with Ninjaflex SemiFlex
Print on glass with Scotch Craft Stick or other glue stick
"My next printer is..." Prusa i3 MK3
User avatar
RetireeJay
My next printer is...
 
Posts: 4915
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
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Re: Mid-print head lifts up too far for next layer

Postby NeilIde » 2016-Dec-Wed-18-Dec

For sure, steppers are simple. Unfortunately for a lack of a better option I'm trying this out. Going to get one from Lin since they can take more heat. I'm running my enclosure around 70°-80°C which is beyond the temperature rating for the stock motors.

If any other ideas come to mind please shout them out!
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Re: Mid-print head lifts up too far for next layer

Postby NeilIde » 2016-Dec-Sun-16-Dec

Now I'm thoroughly boggled, I switched the X/Z steppers and everything started printing great. My expectation was to see layer shifing on X and normal function on Z but it appears that X & Z are now functioning normally.

Weird.
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