1 Topic by dave (edited by dave 2012-12-05 16:26:15)

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Topic: Skew/Slant Issue On Larger Prints

I received my Solidoodle last week, and have since been playing around with smaller items, most of which were downloads from Thingiverse. No problems.

This week I needed to make a "real" part for an item we're prototyping, using a solid model which was done in Autodesk Inventor. Part is L-shaped and measures roughly 5" by 4" by about 1/2" tall. No matter what I try or how I rotate it, I cannot get it to print properly without it skewing the print with each successive layer toward the X-axis limit switch.

I did an experiment by making a test part in various sizes, again using Inventor. The largest of these (about 5") did the same thing, but the smaller ones (under 4") all printed fine.

Any ideas?

Do I have a stepper drive current issue perhaps (I assume on the X)? If so, how do I adjust?

2 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

Can you post a picture of the failed print so we can be sure we're all talking about the same thing.

3 Reply by elmoret (edited by elmoret 2012-12-05 17:09:25)

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Re: Skew/Slant Issue On Larger Prints

Sounds like either:

Print carriage is sticking/not sliding freely
Stepper motor current is too low/high (look on solidoodle's website under troubleshooting)

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4 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

Here's a pic.

The current thing is my guess, but why only on larger parts?

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5 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

That is so consistent, and you say that under 4" it works fine with a very similar stl?  I'm going let the experts take over.

I do see a space puck on the desk (3dconnexion)  I've been using spaceball for ages, hate to live without it.  What's your line of work?

6 Reply by IanJohnson

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Re: Skew/Slant Issue On Larger Prints

Maybe there is a sticking point along the X axis that you only run into when you print a large part that reaches it.  Try something smaller, but at different points on the bed.

7 Reply by dave (edited by dave 2012-12-05 18:08:13)

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Re: Skew/Slant Issue On Larger Prints

Yes, small STLs work fine, no issues.

No sticky spots on the X travel that I can find. I ran the same file rotated on the bed and it consistently prints skewed in the same direction. If I scale it down, it's fine.

I'm a mechanical engineer, usually doing machine and automation systems design.

8 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

X-axis voltage checks out at .455V, the adjustment on the pot is too fine to get any closer to the specified .443V.

After trying to adjust this, I tried to reprint the file in question at full size. Now the stepover is even worse. Went back to another smaller item file I printed before and it's perfect.

I'm stumped......

9 Reply by IanJohnson

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Re: Skew/Slant Issue On Larger Prints

Try cutting the speed in half.  Maybe there is trouble with changing direction, and the larger print gives more time for the extruder to reach the max speed.  With smaller objects, there is more time speeding up and slowing down.  That one's a long shot though.  Have you tried putting the small objects at different places along the X axis, rather than centered?

10 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

I've done half-scale prints of the part all over the table and they look fine.

I'll try the speed thing next.

11 Reply by dave (edited by dave 2012-12-05 20:43:38)

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Re: Skew/Slant Issue On Larger Prints

No luck, tried printing a 3/4-scale version at speeds of 2000, 1000, and 500.

All are skewed identically on the X-axis.

12 Reply by elmoret

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Re: Skew/Slant Issue On Larger Prints

Are you cooling the electronics?

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13 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

It's too consistent to be a mechanical issue, it's got to be something in the settings or with the electronics.

14 Reply by Cwalster

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Re: Skew/Slant Issue On Larger Prints

Are those speeds listed in mm/s?

15 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

No cooling on the electronics.

Speeds are mm/s.

16 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

I tried running the file through Meshlab also (on Solidoodle's recommendation), and tried to print it full-sized again. It seemed to make it worse - when the second layer began to print, it skewed in both the X and Y axes by about 1/4" or so.

The part looks as it should in Meshlab or ReplicatorG, by the way.

On a whim, I scaled up a part from Thingiverse to fill most of the platform, and it printed without any problems.....

17 Reply by IronMan

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Re: Skew/Slant Issue On Larger Prints

This is perplexing...you mentioned you tried completely different parts over 4" and they were fine.  Perhaps it's something within the CAD model.  You may want to try to export to an IGES or Parasolid and then re-import as a "dumb" solid to create an STL.

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18 Reply by Cwalster

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Re: Skew/Slant Issue On Larger Prints

Those speeds are way too high. I feel like im pushing the boundary at 350 mm/s for travels. Chances are firmware is kicking in and reducing those speeds, I believe to 500. Try bringing it down to 250.

19 Reply by IanJohnson

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Re: Skew/Slant Issue On Larger Prints

Are you sure you aren't adding extra 0's?  My extruder won't keep up at anything over 200 and skips or strips the filament.   Set all of your speeds to 50 to start with and see what happens.  Or use the official Solidoodle slic3r profile.

There is no way you are actually reaching those speeds before having to slow down for a direction change, but your large model is providing enough room to too fast for the Y to reverse.   That motor my not have as much torque as Y so you only skip on that axis.

20 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

FYI, default speed was 3000 on the printer interface.....

I rotated the part slightly via ReplicatorG and tried again. You can see the results, the fill isn't even completing within the outline now. Speed was set at 50 on this trial.

I also tried doubling the size of a known good file (with a square base) and the print was shifting from side to side along the X axis.

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21 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

Now that looks more like a mechanical binding.  Do you hear any stepper grinding while this is happening?  I should think not but mine arrived out of square and I had to remove the belt and square everything up to get it to run right.  Smaller prints are fine, try printing a small 1x1 box in each corner and see if it's only on one side.  Just a process of elimination technique at this point.

22 Reply by dave

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Re: Skew/Slant Issue On Larger Prints

No, all motors run nearly silently at all times. No stepper buzz whatsoever.

Really the only thing I had to do out of the box is tighten the Y belts a bit, as they would skip. Other than that it runs very freely.

I just tried running this part again, which I had run previously with no problem. Each layer shifts to the right as it prints.

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23 Reply by IronMan

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Re: Skew/Slant Issue On Larger Prints

Have you checked the set screws on the belt drive pulleys to make sure they are tight?

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24 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

rdavidian28 wrote:

Have you checked the set screws on the belt drive pulleys to make sure they are tight?

That's a good idea, they could slip and you wouldn't hear it. 

The only other thing I could think of to eliminate another step is to slice a box and look at the gcode to make sure it's not something weird being done by the slicer.  Hopefully you've tried files sliced by both skeinforge and slic3r though so that should already be eliminated as a possible culprit.

25 Reply by cmetzel

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Re: Skew/Slant Issue On Larger Prints

Even the belt pulleys shouldn't be it though.  They wouldn't only slip on the furthest directional change, they should slip every time there is a reversal in X after reaching a certain speed.  Maybe the prints speeds are all fine but the travel speed is jacked up when it's moving back to the first part of the next layer and that's what causes the potential slip?