Printing ovals instead of circles!

Re: Printing ovals instead of circles!

SupraGuy — Fri, 02 Feb 2018 13:17:56 -0500

I had a problem that looked similar.

The problem wasn't loose belts. The belts were tight and seemed fine. I had a problem where the connection from the belt to the moving parts wasn't as secure as it should have been, allowing for some slop in the movement, which resulted in circles that looked much like yours.

In my case, the whole design of the printer was crap, and it needed a major rebuild. There was simply no way to get a good connection between the belt and the Y bed movement, or the X carriage movement at the point where it was at.

I would suggest that you look at the screws that connect the belt holder to the bed, and the ones that connect the belt to the print head carriage.

Re: Printing ovals instead of circles!

DeltaPsi — Thu, 01 Feb 2018 12:50:53 -0500

I discovered my printer was printing very distorted ovals holes towards the rear 2/3 of the bed and clean circles in the front 1/3 of the bed. I inspected and found the left guide rail was bent. Replaced it and now I am getting less distorted ovals in the front and rear. Yay and argh at the same time!

Re: Printing ovals instead of circles!

orictosh — Mon, 16 May 2016 11:04:25 -0400

I found when calibrating steps values it's better to use a longer distance say about 100mm rather than going smaller. Also check the measurements on the corners of squares as I had problems with circles being oval and I found that my X axis has too much roll as it moved up and down it's axis.

Re: Printing ovals instead of circles!

vladek7 — Fri, 13 May 2016 19:12:32 -0400

Quote
Carlcox89
I printed a 20x20 cube that came out with 20.50x20.48, a then tried a 40x40 cube that and this one came with something like 40.26x40.23. Weird isnt i ? Since in a 20x20 cube it gave me bigger dimensions, a 40x40 cube would make the error even bigger, and not smaller, right ?

Not necessarily. As I see it you could print cube 80 by 80 and you could find that this would be spot on target! Errors are not % of the dimensions you are printing. They are related to calculation errors when the motor steps needed to create X linear movement are calculated and also your mechanics specifically motors, pulleys and belts. There always will be errors due to the belts stretch, diameter tolerances on pulleys, motor steps accuracy etc. You will find that each machine has the 'golden range' where dimensions are very close to expected and they will be off by much more in smaller or much bigger elements but again I would hardly expect that smaller size will be more accurate...

Re: Printing ovals instead of circles!

Carlcox89 — Fri, 10 Apr 2015 21:18:12 -0400

Quote
supernielsen
Steps pr mm on the axis beside extruder is waste of time, yes you can hit a perfect square 20x20mm but as soon as you print something bigger you will have an even worse offset on your print and a 40x40 make came out way to big or way to small.

I've tried to put the default value of 80 for steps per mm X and Y axis and only calibrated extruder steps, measuring the extruded filament length, however I still cant get good values for parts.
I printed a 20x20 cube that came out with 20.50x20.48, a then tried a 40x40 cube that and this one came with something like 40.26x40.23. Weird isnt i ? Since in a 20x20 cube it gave me bigger dimensions, a 40x40 cube would make the error even bigger, and not smaller, right ?
Dont know what else I can do to get at least +- 0.1mm precision on X/Y axis, any hints ?

Re: Printing ovals instead of circles!

rich1812 — Thu, 09 Apr 2015 23:13:35 -0400

Quote
Carlcox89

Quote
rich1812

Quote
Carlcox89
Related to circles and squares
should we really change steps per mm? I mean, we take a 20x20 cube, print it and it comes with 20.5x20.48, we adjust the steps per mm for both X and Y, and print it again, it comes this time with something like 20.03x20.01, nice... but if we print something like 5x5 or 40x40 the steps per mm will be off. Changing the steps per mm might be exacerbating the error. Am I wrong?
at least this is whats happening with me

The print outs I have seem to be always slightly larger by 0.1 or so mm, I have adjusted my printer o the best I know how. My theory is that it has to do with the solidfying and the melting of the plastics. Perhaps I am wrong.
so you didn't change the steps per mm on X and Y to get that accuracy?

I did try that. I am still a some what newbie on 3D printer, but I experimented with it base on what I have learned on the net. I believe I did the best to my knowledge, It seems not making much difference. so in my 3D model design, I compansating. Perhaps I am not going about the right, If anyone knows a better, I would like to hear from you.

Re: Printing ovals instead of circles!

Carlcox89 — Thu, 09 Apr 2015 09:06:45 -0400

Quote
rich1812

Quote
Carlcox89
Related to circles and squares
should we really change steps per mm? I mean, we take a 20x20 cube, print it and it comes with 20.5x20.48, we adjust the steps per mm for both X and Y, and print it again, it comes this time with something like 20.03x20.01, nice... but if we print something like 5x5 or 40x40 the steps per mm will be off. Changing the steps per mm might be exacerbating the error. Am I wrong?
at least this is whats happening with me

The print outs I have seem to be always slightly larger by 0.1 or so mm, I have adjusted my printer o the best I know how. My theory is that it has to do with the solidfying and the melting of the plastics. Perhaps I am wrong.

so you didn't change the steps per mm on X and Y to get that accuracy?

Re: Printing ovals instead of circles!

rich1812 — Thu, 09 Apr 2015 08:30:42 -0400

Quote
Carlcox89
Related to circles and squares
should we really change steps per mm? I mean, we take a 20x20 cube, print it and it comes with 20.5x20.48, we adjust the steps per mm for both X and Y, and print it again, it comes this time with something like 20.03x20.01, nice... but if we print something like 5x5 or 40x40 the steps per mm will be off. Changing the steps per mm might be exacerbating the error. Am I wrong?
at least this is whats happening with me

The print outs I have seem to be always slightly larger by 0.1 or so mm, I have adjusted my printer o the best I know how. My theory is that it has to do with the solidfying and the melting of the plastics. Perhaps I am wrong.

Re: Printing ovals instead of circles!

supernielsen — Thu, 09 Apr 2015 03:39:12 -0400

Steps pr mm on the axis beside extruder is waste of time, yes you can hit a perfect square 20x20mm but as soon as you print something bigger you will have an even worse offset on your print and a 40x40 make came out way to big or way to small.

Re: Printing ovals instead of circles!

Carlcox89 — Thu, 09 Apr 2015 03:07:34 -0400

Related to circles and squares
should we really change steps per mm? I mean, we take a 20x20 cube, print it and it comes with 20.5x20.48, we adjust the steps per mm for both X and Y, and print it again, it comes this time with something like 20.03x20.01, nice... but if we print something like 5x5 or 40x40 the steps per mm will be off. Changing the steps per mm might be exacerbating the error. Am I wrong?
at least this is whats happening with me

Re: Printing ovals instead of circles!

rich1812 — Wed, 08 Apr 2015 20:31:12 -0400

Is the oval longer on the X or Y axis? This happened to me once before , As it turned out that the Y pulley was jammed in the U shape holder.

Re: Printing ovals instead of circles!

SupraGuy — Mon, 06 Apr 2015 11:17:25 -0400

I'm having almost exactly the same issue.

It happened before when one of the belts for one axis had a bit of slack in it. I'll be taking things apart to re-check belt tension and see if there is any drag on the belt's movements that I can remove this week.

When there is slack in the drive belt, you get compression of circles, because the print head doesn't reverse direction right away, it stays in place until the slack is taken up. this ends up being very much consistent over various layers. Check your belt tensions, and see if tightening things up fixes things.

Re: Printing ovals instead of circles!

papabur — Sun, 05 Apr 2015 15:24:06 -0400

I ended up having to do the same thing, recalibrate the steps in the firmware. Thanks for all the suggestions and help, much appreciated!

Re: Printing ovals instead of circles!

BelowYet — Wed, 29 Jan 2014 20:15:05 -0500

Since the diferance was the teeth from 8 to 18 teeth
It was for Fact my settings. The measurements of the travel between the X,Y,Z needed to be Recalculated and flashed from the arduino software to the bootloader holding sprinter in my sanguino 1.3a board. that sure made a difference in the printB)-

The steps are not to dificult for anybody to follow.

Example is at:

[www.youtube.com]

Also A Prusa Calculator at:

[calculator.josefprusa.cz]

Re: Printing ovals instead of circles!

cat.farmer — Wed, 29 Jan 2014 19:21:26 -0500

If the machanics are all ok, belts tight,pullys,good carriage movement, then it is in your steps per mm setting. Print a cube measure the x and y and that will tell you which is off.

Re: Printing ovals instead of circles!

BelowYet — Wed, 29 Jan 2014 18:06:05 -0500

Hello Everyone.

I'm having the same problem. I'm printing oval pulley gears unstead of circle pulley gears!

I never had this problem until I went from a 8tooth pulley to a 18tooth pulley for BOTH X and Y on my reprap

But, this only started right after I purchased the
"---->T2.5 Aluminum Timing Pulley 18T + Timing Belt 3m for RepRap<-----".

So, Originally I had ABS Plastic pulleys with less teeth now I have 18 teeth......Here is where the problem prints begun!!!;-(

Anyway My setup is

Sanguinololu 1.3a
Sprinter Software for the boot
with reprap setup
using the 1.8 steppers which are nema 17 stepper motors I believe

In the Sprinter (Config.h) File Page these are my settings BELOW

//// Calibration variables
// X, Y, Z, E steps per unit - Metric Prusa Mendel with Wade extruder:
#define _AXIS_STEP_PER_UNIT {80, 80, 3200/1.25,700} I Still need to change the {X,Y where it is {80,80
// Metric Prusa Mendel with Makergear geared stepper extruder:
//#define _AXIS_STEP_PER_UNIT {80,80,3200/1.25,1380}
// MakerGear Hybrid Prusa Mendel:
// Z axis value is for .9 stepper is 4545.4544(if you have 1.8 steppers for Z, you need to use 2272.7272)
//#define _AXIS_STEP_PER_UNIT {104.987, 104.987, 2272.7272, 1487}

I Figured the settings I would have to change would be the X and Y numbers which are (80) for both X and Y to some other setting.

That is where I needed HELP for the calculation and how it would be determend to correct the oval printing problem I have.

Any help would be greatly Thankful;-)

BelowYet

Re: Printing ovals instead of circles!

uncle_bob — Thu, 21 Nov 2013 20:01:48 -0500

Something slipping in the mechanics is always a possibility.

Motor skips are often driver drop outs. The driver overheats and it stops stepping. Once it cools down it starts stepping again. Since it's a gap in the steps it will give you an offset. You can only *loose* distance with a skip. You can't *gain" distance. To get the previous ovals you would need to "get back to" the correct points in order for the circle / oval to match up the way it does.

Re: Printing ovals instead of circles!

alecKarfonta — Thu, 21 Nov 2013 17:04:53 -0500

My printer seems to be experiencing a similar issue. My circles come out as ovals. I thought this was a skipping issue but it consistently shifts the same direction each print. I tried adjusting the pots and printing in different areas thinking it may be travel friction. But it always seems to shift in one direction. Any thoughts?

Re: Printing ovals instead of circles!

uncle_bob — Wed, 20 Nov 2013 12:42:42 -0500

Usually steppers missing steps gives you a random abrupt shift in the axis. It moves over (or up/down) and then stays there until the next shift. If the shift comes back in a highly repeatable fashion, it's unlikely to be missing steps.

Re: Printing ovals instead of circles!

papabur — Tue, 19 Nov 2013 21:24:32 -0500

hmmm...sounds like its time to do a thorough inspection then..

Re: Printing ovals instead of circles!

uncle_bob — Mon, 18 Nov 2013 17:51:43 -0500

First check that everything is lubed and free moving. Some stepper driver problems on previously working printers are actually dirty bearing issues.

If you adjust the stepper driver pots, use a voltmeter. Doing it by hand with no feedback is just going to drive you crazy.

Re: Printing ovals instead of circles!

papabur — Mon, 18 Nov 2013 16:47:55 -0500

jbernardis: Yes it has just started happening as I have just started printing again...unfortunately I have had to move and it has been moved around quiet a bit in the last 2-3 months..before the move though(in the picture i posted earlier) it was printing fine.

Re: Printing ovals instead of circles!

papabur — Mon, 18 Nov 2013 16:45:26 -0500

"It's possible that one of your motors is missing steps, check they get enough current from the stepper drivers"

Thanks for the suggestion, I will check the Nema motor and make sure its getting enough power and this is a new problem I am just noticing..I have posted pictures of prints from a couple months ago on imgur :

5JeCW0O.jpg

Also a update; the stepper driver started giving me issues yesterday...missing steps...so i think it may be the same driver causing the circle issue's...idk 100% though...the x axis is still moving and I do get some response when i mess with the tuning dial on the driver..but it does not seem to be able to find a "happy medium" and more...up to high and you can hear it whining and wont move, too low and the obvious happens...I will be ordering a new(probably a few for backups!!) pololu stepper driver this week and will update the status of how it prints after i get the new one put on, thanks!

-papabur

Re: Printing ovals instead of circles!

some_biker — Mon, 18 Nov 2013 16:25:39 -0500

the belts do stretch over time. I'd check the calibration then also tighten the little flush bolt on the motor gear drive just like Dirty Steve suggested.

Re: Printing ovals instead of circles!

Dirty Steve — Sun, 17 Nov 2013 09:50:49 -0500

looks like a loose set screw on a motor drive gear.

Re: Printing ovals instead of circles!

uncle_bob — Sun, 17 Nov 2013 09:07:51 -0500

Is something binding in your system? I'd go back to checking that everything is sliding easily. If you have adjusted or tightened something recently that could be the source of the binding.

Re: Printing ovals instead of circles!

jeffegg2 — Sun, 17 Nov 2013 01:35:04 -0500

Looks like the parts are not tight and your head is shifting?

Re: Printing ovals instead of circles!

sheck626 — Sat, 16 Nov 2013 20:03:37 -0500

Could it be the pulley sliping on the motor shaft?

Re: Printing ovals instead of circles!

jbernardis — Sat, 16 Nov 2013 16:11:47 -0500

I doesn't really appear to be missed steps to me because it is very consistent. Missed steps would occur at random and I see definite directions here.

How is this image aligned with the x and y axes? that would help to narrow it down to one particular axis (if it IS just one).

This looks like a bad steps/mm setting to me, but you say it has just started happening.

Re: Printing ovals instead of circles!

rogerclark — Sat, 16 Nov 2013 14:58:39 -0500

It's possible that one of your motors is missing steps, check they get enough current from the stepper drivers

BTW is this a new problem or just something you've only just noticed?
Print some calibration cubes etc and measure their dimensions with a micrometer and if necessary change the calibration settings (steps) in the firmware