fluctuating print speed issue

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fluctuating print speed issue

Postby dwill207 » 2016-Nov-Tue-19-Nov

Strange problem here... After updating to a new version of Simplify3D, I noticed my Simple Metal print speed slows down and speeds up but only near a certain area of the build plate. The general area of x210 y-70. I don't have this issue when printing rafts or support material. It's only when actually printing the model. To me, it sounds like the voltage of one or two of the motors is fluctuating. I tested it with Cura and I have the same problem there. I've also re-flashed the firmware and the problem still persists. I have no idea, but I'm thinking the board may be bad...? But, probably not since I'm able to print rafts and support alright. It's a rev F6, by the way.
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fluctuating print speed issue

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Re: fluctuating print speed issue

Postby RetireeJay » 2016-Nov-Tue-21-Nov

You've eliminated all the software explanations for the behavior, so what remains is hardware. It's very possible that you have fatigue failure of the wires going to some of your motors. This would correlate with the position dependency: when a copper wire fatigues and breaks inside the wire's insulation, it doesn't pull very far away. So in some positions it makes contact and in other positions it doesn't. Wires that get bent back and forth repeatedly at a point will break. Period. So look at how your wires are arranged and find the points where the wires are getting tightly focused bending. It's possible to splice around these breaks, but you need to know how to do it correctly so you don't create a new breaking point. It's best to use something like "cable chain" to spread out the bending and avoid this problem. (Use Search in this forum for Cable Chain).
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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
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Re: fluctuating print speed issue

Postby frankv » 2016-Nov-Tue-22-Nov

My first guess is exactly what RJ said.

Possibly the difference between rafts/support and the model is the speed at which the head is moving. It may be that at higher speeds the wire is only "broken" for a short time, and then reconnects. Or maybe when your're printing rafts and supports in that area, the head is only moving positively in X and/or Y, so the wire break doesn't open.

To confirm the diagnosis... is the motor just slowing down when it goes through the "bad" area? Or is it skipping steps?

If you move the head to (say) x210 y0, then x210 y90 (i.e. through the bad area), then move to x0 y90, x0 y0, x210 y0 (i.e. back to the starting point, avoiding the bad area), do you actually arrive back at the starting point? How about if you repeat the process, but go in the opposite direction? Now do another triangle, using only the Y motor to move through the "bad" area... does that cause the problem? And if you go in the opposite direction?

Maybe try printing some triangular columns that cross the bad area to see if the walls are vertical?
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Re: fluctuating print speed issue

Postby dwill207 » 2016-Nov-Wed-07-Nov

It's slowing down and speeding up like the software is telling it to do so. When it speeds up, it seems like it's faster than it is when printing normally. I'll have to try your troubleshooting suggestions when I get home from work later today.
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Re: fluctuating print speed issue

Postby dwill207 » 2016-Nov-Mon-13-Nov

Sorry... I had some things going on and wasn't able to troubleshoot for several days. It turns-out I may have found the problem. I had the max for the x axis in my slicer set at 250mm, (because I have the x-axis upgrade), and the max in the M501 settings was 220mm. I realized that after using frankv's suggestion to print several triangles in the area in question. I noticed it was only printing half of the triangle and the motors were speeding up and slowing down near the area where the other half of the triangle was missing. I changed the max setting in my slicer to 220mm and now the problem is gone. I'm glad there isn't anything wrong with the printer. The downside is I lose 30mm of print space.
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Re: fluctuating print speed issue

Postby RetireeJay » 2016-Nov-Mon-14-Nov

dwill207 wrote:I changed the max setting in my slicer to 220mm and now the problem is gone. I'm glad there isn't anything wrong with the printer. The downside is I lose 30mm of print space.


Why not just change the max setting in the printer? The M501 output shows you exactly how to do it. Just type in the same line (I think it's M211 or M212?) with the correct value for X. The bed size settings for your slicer, your printer, and in your UI (Cura or Repetier...) all need to agree.
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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
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RetireeJay
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Re: fluctuating print speed issue

Postby dwill207 » 2016-Nov-Tue-13-Nov

I thought about that but then I was worried the hot end might impale the build plate when the printer auto-levels with the z probe. There is a 1 1/2 gap at either end of my build plate and the z probe won't sense the plate at the actual physical x-axis max position. I'm also not sure if the auto-level function is able to check user-designated positions, or if it just automatically checks the perimeter of the max settings.
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Re: fluctuating print speed issue

Postby RetireeJay » 2016-Nov-Tue-14-Nov

I don't use a probe, but I am pretty sure that you can actually tell it exactly where you want it to probe at all three points. This will probably be visible to you when you do an M503 readout of all your settings. Change the appropriate setting and save it back to EEPROM with M500.
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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
User avatar
RetireeJay
My next printer is...
 
Posts: 4598
Joined: 2013-Jan-Wed-13-Jan
Location: Greenville, SC
Reputation: 474


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