Help me improve my prints!

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By Lars_A 14 February 2017 21:47

Member · 13 comments

Hello!

I´ve recently assembled my Kossel XL with robodigg corners and effector.
I´m using E3D Titan with V6 hotend and can't get my retraction setting right and I can't understand what can be wrong.

The test procedure I'm using is that I'm printing 4 retraction prints with 4 different processes at once so that I can compare the different settings after each print.
This is the particular print I'm having issues with: http://www.thingiverse.com/thing:607968
Printing stuff like benchys and such turns out fairly good but this one gets really messy

In the picture you can se 4 prints. Print 1 is by the white benchy hull and goes clockwise to print no 4.
The retraction settings are:
Print 1: 15mm/s, 2.5mm (lower right corner)
Print 2. 20mm/s 2,5mm
Print 3: 30mm/s 2,5mm
Print 4 40mm/s 2,5mm (top right corner)

The issues I'm experiencing is that the stepper motor seams to be skipping steps the faster I´m retracting. Actually It's not skipping steps when retracting, I'ts skipping steps when extruding after a retraction. I can replicate the sound of skipping steps by extruding for example 20mm @20mm/s or faster/longer. Only when I´m extruding 5mm slowly I'm not skipping any steps.

Is this a result a stepper that's not getting enough amps and if thats the case how do I change it on the DuetWifi?
The motor I'm using is a Nema17 1.8 deg 1.7

Picture of print https://www.dropbox.com/s/arqcs9vifun1p … o.jpg?dl=0

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By DjDemonD 15 February 2017 01:37

Member · 319 comments

Either the motor current is too low so look for M906 in your config. This sets motor current.
So it would looks like
M906 X1000 Y1000 Z1000 E1000 if you wanted them all to be at 1000mA. Set E value for extruder,  aim for 80% of your motor's rated current, maybe lower it if it gets too hot.

OR... Your idler is too lose. Tighten it.

The way I set max retract is to heat hot end then using web control or by sending gcode try to see what is the fastest you can retract. So try 2mm at 50mm/s see what happens. If motor stalls you won't see any movement in the gears. If so extrude 2mm, then lower speed to 45 and try retract again. When you know how fast you can retract use that setting in your slic3r.

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By Dougal1957 15 February 2017 10:09

Member · 218 comments

How long is your Bowden Tube I had this very issue when mine was long the Titan would just chew up the Filament since I went to Flying Extruder with short Tube the issue has disappeared It also sounds like you are trying to extrude to Quickly with the long Bowden I had to reduce print speed considerably to reduce the stripping issue.

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By Lars_A 15 February 2017 20:27

Member · 13 comments
Dougal1957 wrote

How long is your Bowden Tube I had this very issue when mine was long the Titan would just chew up the Filament since I went to Flying Extruder with short Tube the issue has disappeared It also sounds like you are trying to extrude to Quickly with the long Bowden I had to reduce print speed considerably to reduce the stripping issue.

Thanks for your advice! I Changed the currency to 1000mah and it works much better. No more skipping steps.
My bowden is 64cm long and I don't thin I can make it any shorter...

Although it's not skipping any steps the print quality looks terrible... Seams to be printing quite ok until it reaches some height. This print is made with 4mm retraction @40mm/s
Print speed 50mm/s
https://drive.google.com/file/d/0B88AB7 … sp=sharing

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By Dougal1957 15 February 2017 20:31

Member · 218 comments

Ok just to give you some insight My Original Bowden was around 80-85 cm  long and I had issues with it at that length however I also had something like 9-10 mm of retraction at that length of Bowden to get anything like good prints (This was with both the Titan and a Mini Mendel which never skipped a beat at all)

So you may have to up your retraction somewhat

Doug

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By Lars_A 16 February 2017 22:37

Member · 13 comments

I have now done a bunch of new prints without any improvements.
I bumped up the amps to 1000 and then 1200a
Tried retraction between 2,5-6,5mm (mm steps each print)
Tried retraction speeds between 20-70mm/s

If you look at the print (in the link) you can see that some layers come out just fine and then suddenly it over extruders massively...

Any idea?
https://drive.google.com/file/d/0B88AB7 … p=drivesdk

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By James 17 February 2017 00:41

Member · 22 comments

Does the extruder make a very audible "click click click" noise when skipping steps? I have a cartesian that makes this noise, and while it seems to print ok, I haven't been able to figure out why (or even for sure where the noise is coming from, but it does seem like the extruder) this is happening. It's strong enough that you can feel the clicks by touching various parts. I had not considered that it could be due to retraction -- maybe that's why it seemed random to me.

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By briangilbert 17 February 2017 02:32

Member · 70 comments

Before I switched over to the Nimble extruder I was using Bowden with 9mm retracts.. now with the Nimble I am using 0.9mm retracts.

Getting rid of Bowden if you can, makes a lot of sense.

Last edited by briangilbert (17 February 2017 02:33)


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By deckingman 17 February 2017 08:40

Member · 593 comments

@Lars_A,

This looks very much like an issue that I had with firmware retraction a little while back. The problem was caused by the default value for extra length on unretract being set to a non zero value. So, I was retracting 2mm but unretracting 3mm. Your comments back up this hypothesis.

So look for anything that could be causing the extruder to do extra length on unretract. I you are using firmware retraction, set the R parameter in M207 to 0 (zero). If you are using David's latest firmware, it should now default to 0 but set it anyway just to be sure. If you are using "normal" retraction, check your slicer settings for anything that does similar. e.g, in Slic3R there is a setting under "Extruder" called "Extra length on restart" Make sure this is set to 0. Also, disable any pressure advance settings, either in firmware by commenting out any M572 commands, or setting any slicer settings to 0. HTH
Ian


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By Lars_A 18 February 2017 17:03

Member · 13 comments
deckingman wrote

@Lars_A,

This looks very much like an issue that I had with firmware retraction a little while back. The problem was caused by the default value for extra length on unretract being set to a non zero value. So, I was retracting 2mm but unretracting 3mm. Your comments back up this hypothesis.

So look for anything that could be causing the extruder to do extra length on unretract. I you are using firmware retraction, set the R parameter in M207 to 0 (zero). If you are using David's latest firmware, it should now default to 0 but set it anyway just to be sure. If you are using "normal" retraction, check your slicer settings for anything that does similar. e.g, in Slic3R there is a setting under "Extruder" called "Extra length on restart" Make sure this is set to 0. Also, disable any pressure advance settings, either in firmware by commenting out any M572 commands, or setting any slicer settings to 0. HTH
Ian

Thank you for your input!
I´m no experimenting with flowrate and are down to 85% and I´m not getting the blobs anymore.
I have a theory that the flow was to high and eventually it gets to high and press out all the filament at once... I´m not used to bowden setups but my feeling is that this can happen with a bowden tube. What do you think?

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By Lars_A 18 February 2017 17:46

Member · 13 comments

Not perfect but waaay better than before!
I will try multiple prints and decrease flow with 5% at a time and see where I get the best result

https://goo.gl/photos/fsekpNx1NPaj3i5SA