cant print proper circles

I have a Solidoodle 4 and have this issue. Might be a problem not specific to this printer other users here might recognise and know the solution to.


The extruder makes sharp turns at 5 oclock and 11 oclock. Red dots in this illustration,


The printer prints this circle counterclockwise. Red dot 1 in this image is when the Y motor has slowed down and started rotating the opposite direction (to go up), Red dot 2 is when the Y motor has slowed down and started rotating the opposite direction again (to go down). I say this after dozens of experiments with printing circles and checking the motion of the X and Y motors when these sharp turns/dents/bulges happen. So the sharp edges on the circles happen when the Y motor has slowly stopped rotating on one direction and starts rotating the opposite direction. This might give you a hint on what is wrong.
If the same issue was with the X motor, the areas in green circle (point where X motor starts rotation in the opposite direction) I think would be deformed instead and they are not.

Looks like your Y belt is loose and you have backlash from that. The part where it's travelling in X only (before the red dot) is where the motor is taking up the belt slack without actually moving the print head, then it all moves at once with a jerk.

That's a very good explanation, and something I was thinking about myself before.
However, I've made the belts as tight as possible (more causes binding) and as loose as possible. Results are the same.

I also don't notice any slack on the belts while printing those parts.

I've also printed the same circles at 50% and 150% speeds with the same results, if this helps.

Could it be a power supply issue? The stock power supply has problems running the fans and lights at full speed and brightness respectively when printing and when I turn on print bed heating and hotend heating to prepare for printing, the fans slow down and lights dim. Don't know if the motors get enough power and what happens in practice when they don't.

One last thing I havent tested and adjusted are the stepper chip voltages on the motherboard. Could that affect this? I don't know electronics and so i don't know what setting more or less voltage to the y stepper can result in.

Edited 4 time(s). Last edit at 10/27/2014 12:57PM by jaques.

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jaques
That's a very good explanation, and something I was thinking about myself before.
However, I've made the belts as tight as possible (more causes binding) and as loose as possible. Results are the same.

I also don't notice any slack on the belts while printing those parts.

I've also printed the same circles at 50% and 150% speeds with the same results, if this helps.

Could it be a power supply issue? The stock power supply has problems running the fans and lights at full speed and brightness respectively when printing and when I turn on print bed heating and hotend heating to prepare for printing, the fans slow down and lights dim. Don't know if the motors get enough power and what happens in practice when they don't.

One last thing I havent tested and adjusted are the stepper chip voltages on the motherboard. Could that affect this? I don't know electronics and so i don't know what setting more or less voltage to the y stepper can result in.

No, it is clearly x axis backlash. It could either be in the belts (but you say those are tight) or flex in the attachment point of the belt to the x carriage, or a loose gear on your stepper that walks back and forth slightly on the shaft when changing directions, or gear/belt slip (are they printed gears or machined gears?) or mechanical slop in your carriage that lets it rock, or a loose hot end that is rocking slightly. Those are the main issues with backlash (I've had them all at one time or another).

-Rob A>

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RobA
No, it is clearly x axis backlash.

Im asking this because Im a newbie: if its an x axis backlash it means the problem is with the x belt or motor?

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or flex in the attachment point of the belt to the x carriage

Those holders seem to be as tight as I can get them too.

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or a loose gear on your stepper that walks back and forth slightly on the shaft when changing directions

You mean inside the X motor? Sure hope not.

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gear/belt slip (are they printed gears or machined gears?)

gears (pulleys) are not 3d printed.

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or mechanical slop in your carriage that lets it rock

I dont think I understand this.

If a video of something will help, let me know what I should record and I'll upload a video.

Edited 1 time(s). Last edit at 10/28/2014 02:18PM by jaques.

Sorry - I messed that up - I was too quick glancing at your diagram. It is Y backlash. So all the same things but on the Y axis.

See the attached diagram I generated from a spreadsheet model of backlash. This was for a backlash of 5% of the radius. (i.e. a 20mm dia circle would look like this with 0.5mm of backlash in the system).

If anyone wants to play with it I've uploaded the spreadsheet to my website: [silent9.com]

-Rob A>

Edited 1 time(s). Last edit at 10/28/2014 03:26PM by RobA.

Thanks. How should I use the data from the spreadsheet to help me?
To me the extruder head also seems to go a bit higher than it should before the "peak" and a bit lower when drawing the circle from top to bottom respectively. Or maybe its lower than it should be in the middle.

Edited 2 time(s). Last edit at 10/28/2014 03:53PM by jaques.

EDIT: Here are photos of a circles. This is after I adjusted the stepper chips. And did the belt calibrations again. Looks same to me.



here's a video showing the extruder printing circle and a close up of the y motor at the same time.
[www.youtube.com]

Edited 1 time(s). Last edit at 10/29/2014 06:17AM by jaques.

Hi there, I have a Solidoodle 4 and I ran into this issue before. Since you said you tightened all your belts, have you also made sure that the Y motor pulley is aligned straight with the pulley right on top of it? Also, make sure that your "Y smooth rod" (the thinner one that sits horizontally on the back of the printer) is properly aligned. If you take off your side panels, and slide your Y axis back and forth while looking at the sides where that bar sits, that bar should stay in place and should not stick out of the bearing holder to the left nor right. If it does, you have alignment issues.

Let me know if you still have this issue and I will try to walk you through it the best I can. Take care.

Romel

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romels33
Since you said you tightened all your belts, have you also made sure that the Y motor pulley is aligned straight with the pulley right on top of it?

Yes, I have. I will try it again though.

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Also, make sure that your "Y smooth rod" (the thinner one that sits horizontally on the back of the printer) is properly aligned. If you take off your side panels, and slide your Y axis back and forth while looking at the sides where that bar sits, that bar should stay in place and should not stick out of the bearing holder to the left nor right. If it does, you have alignment issues.

I have checked this too. The rod sticks out equally from both sides and doesn't change its offset as the x carriage moves.

My belts are as tight as I can get them, so I'm not sure what the problem is anymore. Tried everything Solidoodle suggested as well.
Last thing that keeps me suspicious is this thing marked with red arrow.

Maybe it is bending the rod slightly, or something.

The belts shouldn't be too tight, and they should have a little slack on them. This is the same for the belt on the Y Motor's pulley. Im not really sure what that other bearing is doing there (the one marked with the red arrow). I don't have that on mine. Also, it doesn't look like it is attached to anything, except for the rod itself. Probably wouldn't hurt to try and take it off, and see what happens.

When you said:

"I have checked this too. The rod sticks out equally from both sides and doesn't change its offset as the x carriage moves."

You are referring to the Y axis right? =) So you grabbed both carriages and slid it back and forth and saw that the y rod was equal on both sides as you slid it? The x axis has no effect on this rod.... =) Just making sure.... =)

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romels33
Im not really sure what that other bearing is doing there (the one marked with the red arrow). I don't have that on mine. Also, it doesn't look like it is attached to anything, except for the rod itself. Probably wouldn't hurt to try and take it off, and see what happens.

I took it off and it didn't affect the print.
I noticed that without it, the back rod got a little bend on the left part. Maybe was added to protect the back rod and keep it straight.

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When you said:
"I have checked this too. The rod sticks out equally from both sides and doesn't change its offset as the x carriage moves."

You are referring to the Y axis right? =) So you grabbed both carriages and slid it back and forth and saw that the y rod was equal on both sides as you slid it? The x axis has no effect on this rod.... =) Just making sure.... =)

yes

Edited 1 time(s). Last edit at 10/31/2014 01:50AM by jaques.

Hmmmm, this is really strange. Is there a "CLUNKING" or "GRINDING" noise when you move the Y axis via Repetier? My hunch is that although you verified that the back rod is equally positioned and doesn't stick out to one side more than the other when sliding the y axis back and forth, you still have an alignment issue somewhere.

I'm almost certained that you have already loosened all the pulleys attached to the back rod and then slid the y axis back and forth, causing all the pulleys to "fall in place" to their natural alignment with the rod right? Then re-tightened them all back up? Then verified again that the back rod doesn't stick out? =) I'm thinking that there's a possibility that one of the pulleys from the y axis, either the one from the left y carriage or right y carriage is not alligned straight with the pulleys attached to the back rod.

Romel

Are the pulley's properly fixed to the axle? You can test this by pulling the belt a bit when the motors are powered (but not moving).

Seems like more SD4 owners are having this problem: [www.soliforum.com]

At this point these are the problems I can think of:

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Mechanical problems

1) Problem with the motors (unlikely to be 1. underpowered for what it is intended for, unless everyone else owning a SD4 hasnt noticed this, 2. all 4 of us having faulty motor(s), odds of that are also extremely low)

2) problem with the rods (still bending?) or problem with the bushing setup

3) problem with pulleys and belts and all of us fail to calibrate them properly (unlikely)

Software problems

4) Problem with this version of Repetier Host and Slic3r? (unlikely, jagowilson tried with Simplify3D as well)

5) Firmware (still)

6) Driver? (at this point, who knows?)

Electronics problems

7) PSU (at this point unlikely, jagowilson uses a very poweful PSU, Ive tried running with a car battery)

8) wires?

9) motherboard (unlikely, jaqowilson tried with Rumba board)

If you can think of something else, please let me know.

And yes Romel, we've all done that already.
k.p., what axle?

Romel and everyon else owning a Solidoodle 4, please print this 1 layer circles STL, it is very simple and prints in few seconds. And then make a top-down photo of the result and post it here.That would help us very much to know other SD4 owners do not have this problem.

Edited 5 time(s). Last edit at 11/03/2014 02:52AM by jaques.

You could check if there is noticeable play at your hot end by moving it by hand (when the motors are powered).

After talking wit someone else with this problem, we noticed the X carriage wasn't glued properly.

The left side had little glue/epoxy that didn't hold it at all.

Here I have removed the extruder, hotend, motors and belt from it.

top view:


bottom view:


left side:


right side:


Again, the left side wasn't glued properly, so it just came off.


Left part of the carriage:



(Horrible quality, btw)

This is how much the rods were sticking out when I noticed it wasnt glued in place:


I think this kind of made the Y rods bend a little and made calibrating such a pain.
So the thing is I'm not sure how to glue it, if the rods should be sticking out as much, or not at all ("how much should the length be?"). And what glue to use. I've contacted Solidoodle about this problem and about getting a replacement.

I don't even know if this will solve my circlular problem. Thoughts?