Slow Y-Axis Acceleration During Print: Layer shifting

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Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Thu-17-Mar

This is a heavily modified Printrbot 1405 Simple Maker's Edition.

Current Mods:
1.1405 X-Expanded Mod
2.Tri-rod Mod

Current issues: (only affects Y-axis stepper motor)
1. Fast acceleration during homing of y-axis, but slow accelerating during moves during print
2. Slow accelerating is causing layers to shift, major inaccuracies.

Troubleshooting I have already tried:
1. Factory reset M502
2. Reflashed stock firmware
3. Changed speed settings (in firmware, slic3r, and Repetier)
4. Changed acceleration settings
5. Changed jerk settings
6. Increased Stepper motor current (tried range from 30% to 80%, same issues)
7. Used Cura engine instead of Slic3r, same issues

You help is much appreciated.

Tim
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Slow Y-Axis Acceleration During Print: Layer shifting

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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Thu-17-Mar

Even as a newbie, you can post a picture (use the "Upload Attachment" tab), which would be helpful.

It's doubtful that a low acceleration value in EEPROM is causing print problems; usually the opposite is true: if the acceleration value is too high, then you can get artifacts.
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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: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Thu-17-Mar

Thanks for the input.

I do have a video of the problem, but I'm afraid I can't illustrate it well with just a picture
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Thu-19-Mar

You might be able to embed a YouTube video as a newbie; I don't know. But you can always type the link this way: YouTube(dot)com/myvideo
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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: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Thu-22-Mar

This forum has a good filter for urls. I can't even post the url with all the slashes taken out and replaced with words.

As for uploading the video, that wasn't allowed or possible.
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Thu-23-Mar

The magic formula for embedding a video looks like this (I put it inside a "code" box so it wouldn't be live). Note that you must use "http" and not "https".
Code: Select all
[youtube]http://youtube.com/myvideo[/youtube]

Again, I'm not sure this is available to newbies.

Another alternative: everyone knows the URL for youtube; just give us the stuff that follows youtube.com
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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: Slow Y-Axis Acceleration During Print: Layer shifting

Postby Mooselake » 2016-Mar-Fri-09-Mar

There's a sticky that describes the exact format, but if you give us the part of the youtube link after the q= one of us will edit it for you.

Videos are big, better to Les the googlian horde (who's sucked up YouTube) host them. Don't forget to make it public.

The no links for newbies is a pain, but we're waging a constant war against spam. Otherwise we'd be deluged with ads for inferior quality (room where we prepare food) cabinets and products not discussed in family friendly forums.

Kirk
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-11-Mar

Thanks. Here's the rest of the url: watch?v=eDqW-L13Y5U
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Sat-11-Mar

Heavily modded... I guess!!
But I don't see where the shift is taking place; it all looks normal. Are you sure your toothed pulley on the Y motor is firmly tightened onto the motor shaft, with one of the setscrews tightened onto the flat of the shaft?
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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: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-12-Mar

I'll scale up the print and give you another link to a video to better explain the issue.

The layer shift and position of the printhead are all secondary issues. The closest problem to the root cause seems to be the behavior of the Y-axis motor. Instead of executing tight, quick movements up to corners and along lines, as the X-axis does, it gradually accelerates up to speed and then slows down as it nears the next point. This is very unlike the behavior I have experienced, in hundreds of prints before I did this mechanical upgrade.

I will add that I did invert the plug for the Y-axis stepper motor to allow the Y-axis to home in the correct direction. As far as I know, however, inverting the connector shouldn't affect the performance of the motor.
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-12-Mar

Here's a longer video and larger print with the Y-axis issue:
watch?v=HcFUayaQjKQ

And another part of the print (in which the horizontal shell is being extruded) when the Y-axis seems to be moving properly. (Opposite direction diagonals)
watch?v=Y4mPNHrMNQA
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Sat-12-Mar

I could hear the slow acceleration you are talking about.

But if the Y motor were actually missing steps and accelerating more slowly than the firmware thinks it is, then diagonal lines would not be straight, they'd be curved. So in fact, your X and Y axes are staying in sync with each other and your motor is not missing steps in these videos.

Acceleration values are both in EEPROM and in Slic3r; whichever is lower will control - so you need to check in both places.

BTW, the way stepper motors work is they move in tiny increments called (wait for it...) steps. So the firmware sends individual commands for every single step. The firmware keeps track of where the printhead is by keeping track of the step count (it assumes that the motor executes every step successfully). Generally the sound of a motor that's missing steps is much more rough; your motor sounds normal. But if you ever hear a buzzing or clicking that's louder than normal, then maybe you are really missing steps. And that would definitely cause position shifts in your print.

So I have two more suggestions:

1) Make sure that your Y axis can move smoothly with very little friction. You have to disconnect the belt to check that. It should move with just the slightest finger pressure when the belt is disconnected, and there should not be any clicking or grinding sounds from the bearings.

2) If the Y axis does move smoothly but you still are having missing steps, then you can increase the power being sent to the motor. On a Rev D board, you do this by adjusting a manual potentiometer. On a Rev F board, you do it with G-code commands: M907 Ynn to set; M909 to read; and M910 to save the value in the digipot's EEPROM (which is separate from the other EEPROM). The value is in percent, so M907 Y100 sets the motor current to maximum (much more than you will need or want). If you go too high, the motor will run very hot.
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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: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-13-Mar

Well, I suppose it doesn't hurt to try changing those settings again.

enaqtim wrote:This is a heavily modified Printrbot 1405 Simple Maker's Edition.

Current Mods:
1.1405 X-Expanded Mod
2.Tri-rod Mod

Current issues: (only affects Y-axis stepper motor)
1. Fast acceleration during homing of y-axis, but slow accelerating during moves during print
2. Slow accelerating is causing layers to shift, major inaccuracies.

Troubleshooting I have already tried:
1. Factory reset M502
2. Reflashed stock firmware
3. Changed speed settings (in firmware, slic3r, and Repetier)
4. Changed acceleration settings
5. Changed jerk settings
6. Increased Stepper motor current (tried range from 30% to 80%, same issues)
7. Used Cura engine instead of Slic3r, same issues

You help is much appreciated.

Tim
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-13-Mar

By the way, here are my M501 and M909 settings:

Code: Select all
12:08:46.835 : echo:Stored settings retrieved
12:08:46.835 : echo:Steps per unit:
12:08:46.835 : echo:  M92 X160.67 Y160.65 Z400.55 E96.00
12:08:46.835 : echo:Maximum feedrates (mm/s):
12:08:46.835 : echo:  M203 X125.00 Y125.00 Z5.00 E14.00
12:08:46.835 : echo:Maximum Acceleration (mm/s2):
12:08:46.835 : echo:  M201 X2000 Y2000 Z30 E10000
12:08:46.835 : echo:Acceleration: S=acceleration, T=retract acceleration
12:08:46.835 : echo:  M204 S3000.00 T3000.00
12:08:46.835 : echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s),  Z=maximum Z jerk (mm/s),  E=maximum E jerk (mm/s)
12:08:46.835 : echo:  M205 S0.00 T0.00 B20000 X20.00 Z0.40 E5.00
12:08:46.835 : echo:Home offset (mm):
12:08:46.835 : echo:  M206 X0.00 Y0.00 Z0.00
12:08:46.835 : echo:PID settings:
12:08:46.835 : echo:   M301 P22.20 I1.08 D114.00
12:08:46.835 : echo:Min position (mm):
12:08:46.835 : echo:  M210 X0.00 Y0.00 Z0.00
12:08:46.835 : echo:Max position (mm):
12:08:46.835 : echo:  M211 X168.00 Y190.00 Z187.00
12:08:46.835 : echo:Bed probe offset (mm):
12:08:46.835 : echo:  M212 X25.00 Y0.00 Z-0.30
12:09:03.668 : echo:Stepper current values [%(raw)]:
12:09:03.668 : echo: X:50.00(1760) Y:70.00(2464) Z:50.00(1760) E:60.00(2112)
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-13-Mar

Looks like I managed to fix the problem, although I do have to sacrifice LCD support. After installing the 9-point bed leveling software, the Y-axis is functioning as expected. No other changes were made at all.

Video:watch?v=opyv_368jsU
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sat-19-Mar

Alright, here's my latest discovery:

When using the default 100x100x100 max position setting on M211, the print proceeds quickly without any slowdown during moves. When I change the M211 values to match my larger print space, even if the object is being printed at the same size in the same location, the Y-axis will exhibit the problem I have been describing. This is all on the exact same firmware.

Why would the firmware slow the Y-axis acceleration during moves when there is a larger print space set?
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby RetireeJay » 2016-Mar-Sat-20-Mar

enaqtim wrote:Why would the firmware slow the Y-axis acceleration during moves when there is a larger print space set?


I can't think of any reason why it would. My Plus uses bed dimensions similar to yours, and the actual acceleration that I see matches what I tell it to be with M201. (I've started printing with an E3D, and I find that lower acceleration helps the quality of the print; I'm at 400. See my post about acne on the print.)
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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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RetireeJay
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Re: Slow Y-Axis Acceleration During Print: Layer shifting

Postby enaqtim » 2016-Mar-Sun-14-Mar

I've tried identical prints at 100x100 with the heated bed on and off, and there was no issue with slowdown. I tried once again with the M211 at 168x190, and the problem returned. Nothing else was changed. The mechanical resistance of the Y-carriage on the Y-axis arm is consistent along its entire travel.

I'll continue testing prints to see if layer shifting becomes a problem. All my belts are reasonably tight.
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