Lines in print. Stepper resolution problem?

Electronics, Components etc
kleingeist
Posts: 25
Joined: Wed May 24, 2017 11:51 am

Re: Lines in print. Stepper resolution problem?

Post by kleingeist » Sun Aug 06, 2017 9:15 pm

Hmm looks good. The Igus bearings have a little more play afaik. That shouldn't have any effect here.

I will try a solid coupler on my fabrikator as well ,even if the leadscrew is supported above the stepper motor.

FranJans
Posts: 27
Joined: Wed Jul 19, 2017 10:35 am

Re: Lines in print. Stepper resolution problem?

Post by FranJans » Mon Aug 07, 2017 9:42 am

Solid coupler on the Z-axis? I bought some solid couplers from ebay. They where all eccentric as hell. That will create a lot of Z wobble :( I cannot use those :( I also doubt that the problem has anything to do with the flexible coupling.

Let me first try to finish the extruder assembly ;) I think it is possible that the lines are created by the tyrap assembly.
It will take some time for me to finish this.

kleingeist
Posts: 25
Joined: Wed May 24, 2017 11:51 am

Re: Lines in print. Stepper resolution problem?

Post by kleingeist » Mon Aug 07, 2017 10:28 am

I got some random solid couplers in my new printer that peforms well. The motion system there might be immune to influence by the leadscrews though.

Looking forward to the results. Hope the bracket does the trick :)

FranJans
Posts: 27
Joined: Wed Jul 19, 2017 10:35 am

Re: Lines in print. Stepper resolution problem?

Post by FranJans » Sun Aug 20, 2017 8:15 pm

Update!
I mounted the extruder. I'm fairly certain this thing isn't going anywhere :mrgreen:

Image

Image

With the extruder wheel mounted
Image

Image

There is a reason for this rather stiff bracket system. I could see the extruder push itself up and down before I designed the brackets. The little bowden tube with its connectors was stretching a little bit. I eliminated any stress on this system by designing stiff brackets. Therefore the length between the extruder and nozzle has as less stretch as possible.
I Also noticed the extrude axis was bent. This printer ways a ton and perhaps something happened during the many times I took it apart :oops: I got 6 extruders of this weird type so that was a easy fix.

Did it work? Partially yes. In the picture below you can see the difference between before and after fix. Left is before, right is after.
Picture

Sadly enough there are still lines in the print. But they are getting more repetitive. This is a good sign. :D I think I can see the Z axis wobble a little bit. I will need to film this to be sure. That one will be next. I also noticed some squeaking noise from one of the belts. Something is out of line.

It is amazing how much more problems you can find when the printers is back on your desk instead of placed somewhere in the attic :mrgreen:

I'm getting closer :D

kleingeist
Posts: 25
Joined: Wed May 24, 2017 11:51 am

Re: Lines in print. Stepper resolution problem?

Post by kleingeist » Sun Aug 20, 2017 9:56 pm

That printhead assembly looks sweet :)

I did a bit more research in the meantime and found that the heatbed can cause this either through emv (emc) issues in the electronics or thermo mechanical deformation. I tried letting the bed off during the print and only saw slight improvements. I also stiffened my extruder mount and modified the y axis coupler. Will see tomorrow if that had helped in any way.

I definetely want perfect walls. No way around that and I´m pretty close i think. :D

FranJans
Posts: 27
Joined: Wed Jul 19, 2017 10:35 am

Re: Lines in print. Stepper resolution problem?

Post by FranJans » Mon Aug 21, 2017 9:43 am

That's interesting. Never thought that the bed heater could create emv (emc) issues in the electronics. That is a badly designed electronics board. I'm fairly certain this isn't the problem with my printer. I have a 230V bed heater with a SSR. I even rerouted the nozzle heater in such way that the current stays outside the circuit board. There is a diode on the power connection of my electronics board. Originally everything had to pass through this diode. All 15 amps! :shock: That thing was insanely hot!

I have heard of thermo mechanical deformation of the bed. This is definitely not the case with my printer. My printer has a silicon heater attached to a aluminium plate with a glass plate on top of it. I even wait 10 minutes (PLA) after the temperatures hit there targets. This way the heat can fully penetrate the glass plate. That glass plate is a good insulator :(

Looking forward to your results!

kleingeist
Posts: 25
Joined: Wed May 24, 2017 11:51 am

Re: Lines in print. Stepper resolution problem?

Post by kleingeist » Thu Aug 24, 2017 2:45 pm

I haven't sorted out those possible causes yet. I also went the SSR silicone alu path with my diy but I'm a bit worried to move a 2 kg build plate in high frequencys (prusa style). It is a milled 6mm alu plate with matte glas on top. Wish me luck :D

Vibrations are in focus at the moment. I'm thinking about correct dampening of steppers instead of over "riggifying".

Investigating...

FranJans
Posts: 27
Joined: Wed Jul 19, 2017 10:35 am

Re: Lines in print. Stepper resolution problem?

Post by FranJans » Fri Aug 25, 2017 8:10 pm

That is going to be interesting indeed. May I suggest a rather strange solution to your possible resonance problems with your heavy bed? Add more driving belts. Not for stiffness but to create friction. This might reduce the resonance issues.

I have been working on my 3D printer as well. I tried to solve some possible Z wobble issues. The spindle does wobble. The wobble is created by the flexible coupling on the motor :shock:
Picture of the flexible coupling

This is annoying. I have 3 flexible couplings and all of them suck. Here is a video of the spindle just above the flexible coupling. I used the best flexible coupling I got.
Video of the flexcoupling. Watch video at full screen to see the wobble

I don't think there is anything I can do about this. :(

kleingeist
Posts: 25
Joined: Wed May 24, 2017 11:51 am

Re: Lines in print. Stepper resolution problem?

Post by kleingeist » Fri Aug 25, 2017 10:15 pm

Add more driving belts
I´m going to build it with the mechanics of the smaller bed first to have a reference. I´m probably just going for a wider belt. Will see, got three of those bed combinations here. This needs to work therefore :P

Hm, regarding your wobble, I doubt somehow that the coupler isn´t straight. You could try one of these elastomere https://www.dold-mechatronik.de/Spielfr ... -635-635mm couplings.

I suppose the leadscrew isn´t fully straight or your stepper motor might be offset a little sideways. There could also be another reason fot the remaining lines. I also got some line artifacts left and still investigating the cause.

https://www.dropbox.com/s/x32wzp9xdskhx ... W.jpg?dl=0

The blue is the subject of further investigation, on the right side a print of an earlier BCN3D Sigma.

FranJans
Posts: 27
Joined: Wed Jul 19, 2017 10:35 am

Re: Lines in print. Stepper resolution problem?

Post by FranJans » Sat Aug 26, 2017 9:41 am

I'm 100% sure the flexible coupling is the problem. Or at least, the biggest problem. The motor and spindle are in line. I think there is no other explanation for Z wobble just above the coupling than the coupling itself. You can clearly see the whole coupling wobbling.

One of the reasons for the alignment error in the coupling is the tolerance of the hole. You push the axis to to one side of the hole by means of 2 screws. This means you push the axis away form the midpoint of the coupling. The bigger the play between the axis hole, the bigger problem.
You have to remember that the industrial version cost somewhere around €50,- a piece. The one we use are a lot cheaper and are not industrial quality. The tolerances are horrible.
The challenge of these consumer 3D printers lies in designing a printer which is the least sensitive for horrible quality parts. My printer is sadly enough rather sensitive. I think the Prusa design is better design regarding sensitivity for horrible quality parts.

Those elastomer couplings are interesting. I like the clamping coupling design. However, what about torsional stiffness? Are these even stiff enough? How good is the alignment of these things?

Interesting print! Those lines are fairly similar to mine indeed. However, you printed a complex parts. Perhaps the geometry if the parts itself is causing these lines to occur. If that is the case than the problem lies with your X, Y or extruder axis.
I always start printing with extremely simple objects.

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