Mini Kossel can't do circles
Posted by Focussys
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Mini Kossel can't do circles February 14, 2016 08:32AM |
Registered: 10 years ago Posts: 28 |
I have a Chinese Micromake Kossel Mini that has been working well since build 6 months ago. Recently it has started skipping over circles and the extruder judders badly. Straight lines are no problem and print fine. I have checked stepper current, changed stepper to a bigger more powerful version thinking it was not coping with my 0.4mm nozzle. Checked 12v supply, changed driver board from A4988 to DRV8825 and uploaded a fresh copy of firmware. I have now run out of ideas.
Any advice gratefully received.
Steve
Hardware:
Micromake Mini Kossel Delta
0.4mm Nozle.
Direct drive Bowden.
Heated bed.
Any advice gratefully received.
Steve
Hardware:
Micromake Mini Kossel Delta
0.4mm Nozle.
Direct drive Bowden.
Heated bed.
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Re: Mini Kossel can't do circles February 14, 2016 11:07PM |
Registered: 9 years ago Posts: 75 |
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Re: Mini Kossel can't do circles February 15, 2016 02:34AM |
Registered: 10 years ago Posts: 28 |
Hi rollingdice
Thanks for coming back.
I have checked the drive gear and all is clean. The stepper is jumping back all the time as if there is too much pressure. I have hand pushed the filament through and there is little resistance. As the straght parts print OK, as in the photos, I have tried different slicers to see if it is software related. Still no joy.
Thanks for coming back.
I have checked the drive gear and all is clean. The stepper is jumping back all the time as if there is too much pressure. I have hand pushed the filament through and there is little resistance. As the straght parts print OK, as in the photos, I have tried different slicers to see if it is software related. Still no joy.
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Re: Mini Kossel can't do circles February 15, 2016 02:44AM |
Registered: 9 years ago Posts: 916 |
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Re: Mini Kossel can't do circles February 15, 2016 03:07AM |
Registered: 9 years ago Posts: 5,232 |
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Re: Mini Kossel can't do circles February 15, 2016 06:53AM |
Registered: 10 years ago Posts: 28 |
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Anonymous User
Re: Mini Kossel can't do circles February 15, 2016 09:46AM |
Quote
Focussys
Thanks everyone for you ideas. I will try them all. I noticed a 5Mtr USB lead caused the print to stop occasionally and I have moved the printer closer to be able to use a 2mtr lead. I am using a Mega board and Ramps 1.4 so thanks for that one as well. I will report back with outcomes.
As the Controller boards are not electrically shielded, it is always a good idea to have usb as short as possible, or better use SD-Card.
For your main-Problem: Maybe your nozzle is clogged.
Get some 0.4mm wire (for example many wire-brushes have 0.35)
Heat up your nozzle to about 160-170°C NOT higher!!!
Pull out Filament and remove dirty part
Put Wire in and out of hot nozzle.
put Filament back in all the way
let it melt 30 seconds
repeat the last 4 steps until Filament can be pushed (relatively easy) through the nozzle, and no dirt is beeing pulled out.
EDIT: Just another Idea: Do you print PLA? - If yes, check hotend temperature - I had PLA to be printed at 185°C and now have one to be printed at 215°C!
Edited 2 time(s). Last edit at 02/15/2016 09:49AM by Sir_Death.
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Re: Mini Kossel can't do circles February 15, 2016 02:13PM |
Registered: 10 years ago Posts: 28 |
Well, for all of you who were placing side bets on which was the best solution, print from the SD card produced a near perfect print. The USB must be affecting the print quality, but the gattling gun sound from the extruder stepper persists and may be the cause of the gaps in the near perfect straight parts in the side walls.
So I am half way to a best print. Thank you all.
My idea to solve the juddering effect is to either fit a planetary geared stepper or switch to a wade extruder to gain more torque without the stepper kicking back.
Any comments?
So I am half way to a best print. Thank you all.
My idea to solve the juddering effect is to either fit a planetary geared stepper or switch to a wade extruder to gain more torque without the stepper kicking back.
Any comments?
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Re: Mini Kossel can't do circles February 15, 2016 06:27PM |
Registered: 9 years ago Posts: 916 |
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Re: Mini Kossel can't do circles February 16, 2016 02:17AM |
Registered: 10 years ago Posts: 28 |
Hi nebbian
I have adjusted the ref voltage to 0.5v then either side to see if the stepper quietens down. No setting seems to solve it. I have turned off retraction to see if that has an effect and used Cura matterslice and slic3r in case that is involved.
I thought it was going to be something silly I had missed!
Looks like plan B and change the extruder is next.
I have adjusted the ref voltage to 0.5v then either side to see if the stepper quietens down. No setting seems to solve it. I have turned off retraction to see if that has an effect and used Cura matterslice and slic3r in case that is involved.
I thought it was going to be something silly I had missed!
Looks like plan B and change the extruder is next.
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Re: Mini Kossel can't do circles February 16, 2016 02:59AM |
Registered: 11 years ago Posts: 14,686 |
If you have an ungeared extruder then you will need to run the motor at 80% or so of its maximum current to get enough torque. With most drivers, a Vref of 0.5V will only give you 0.4A current, which is much too low for typical stepper motors. So you may need to turn the current up a lot more. I suggest you find the label on the extruder stepper motor, read off the part number and look up its rated current. Then look at the markings on the sense resistors on your driver to see whether they are 0.1 ohm (the most common value) or 0.05 ohm. With that information you can adjust Vref to get the correct current.
Edited 1 time(s). Last edit at 02/16/2016 03:01AM by dc42.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Edited 1 time(s). Last edit at 02/16/2016 03:01AM by dc42.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: Mini Kossel can't do circles February 16, 2016 03:02AM |
Registered: 9 years ago Posts: 916 |
Hmmm well if you've adjusted the current and you're still getting juddering then it's one of the following:
You're going to have to do some faultfinding on this one, because it's "almost working"...
With the hotend hot, try pushing the filament through by hand, not by using the extruder itself. If you get a good flow out the nozzle, then the problem is the extruder motor. If it doesn't seem to flow freely, then the problem is a restriction.
btw my ungeared direct drive motor only ever judders just before it grinds the cr@p out of the filament, and I think my voltage is set to 0.35 or so. The juddering has only happened once or twice. It's got plenty of torque, more than enough for printing.
Edited 2 time(s). Last edit at 02/16/2016 03:06AM by nebbian.
- Bad connection to one extruder wire
- Restriction in the hot end / bowden cable
You're going to have to do some faultfinding on this one, because it's "almost working"...
With the hotend hot, try pushing the filament through by hand, not by using the extruder itself. If you get a good flow out the nozzle, then the problem is the extruder motor. If it doesn't seem to flow freely, then the problem is a restriction.
btw my ungeared direct drive motor only ever judders just before it grinds the cr@p out of the filament, and I think my voltage is set to 0.35 or so. The juddering has only happened once or twice. It's got plenty of torque, more than enough for printing.
Edited 2 time(s). Last edit at 02/16/2016 03:06AM by nebbian.
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Anonymous User
Re: Mini Kossel can't do circles February 16, 2016 07:01AM |
Sorry
I do not think the Extruder alone is your Problem.
I think you still have clogged nozzle, or printing too cold - I did the sam mistakes - see my post above...
For Extruder I'd recommend this - works perfectly: MK8-Extruder
I do not think the Extruder alone is your Problem.
I think you still have clogged nozzle, or printing too cold - I did the sam mistakes - see my post above...
For Extruder I'd recommend this - works perfectly: MK8-Extruder
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Re: Mini Kossel can't do circles February 16, 2016 02:40PM |
Registered: 10 years ago Posts: 28 |
Hi Guys
I have manually fed filament through with no heavy force required. The filament exits straight down with no curls.
The spec of the stepper is:
Step Angle: 1.8
Motor Length: 60mm
Rated Current: 1.5A
Phase Resistance: 2.5Ohm
Phase inductance: 4.5mH
Holding Torque: 67.3N.cm
Flying Lead Count: 4
Dc42, I cannot see the resistors on the DRV8825 they are too small for one so old!
I have read an article on setting the driver for 1.5A and it suggests 0.7v ref so I have set this for now.
The test print attached was using a 2Mtr USB cable and the noise was worse than ever.
Sadly I cannot upload a video due to size contraints.
I have manually fed filament through with no heavy force required. The filament exits straight down with no curls.
The spec of the stepper is:
Step Angle: 1.8
Motor Length: 60mm
Rated Current: 1.5A
Phase Resistance: 2.5Ohm
Phase inductance: 4.5mH
Holding Torque: 67.3N.cm
Flying Lead Count: 4
Dc42, I cannot see the resistors on the DRV8825 they are too small for one so old!
I have read an article on setting the driver for 1.5A and it suggests 0.7v ref so I have set this for now.
The test print attached was using a 2Mtr USB cable and the noise was worse than ever.
Sadly I cannot upload a video due to size contraints.
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Re: Mini Kossel can't do circles February 17, 2016 03:00AM |
Registered: 10 years ago Posts: 28 |
Hi Sir_Death
I have ordered an extruder as you suggest. I am getting desperate so will try anything to solve this. I am not sure how to solve the USB problem. I have shortened the 5Mtr cable to 2Mtrs but little has changed. Running from SD card did improve the output significantly. If I haven't mentioned it before I am printing ABS at 235 C.
I have ordered an extruder as you suggest. I am getting desperate so will try anything to solve this. I am not sure how to solve the USB problem. I have shortened the 5Mtr cable to 2Mtrs but little has changed. Running from SD card did improve the output significantly. If I haven't mentioned it before I am printing ABS at 235 C.
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Re: Mini Kossel can't do circles February 18, 2016 01:51AM |
Registered: 10 years ago Posts: 32 |
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Re: Mini Kossel can't do circles February 18, 2016 02:11AM |
Registered: 10 years ago Posts: 28 |
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Re: Mini Kossel can't do circles February 18, 2016 03:22AM |
Registered: 11 years ago Posts: 14,686 |
Quote
Focussys
Dc42, I cannot see the resistors on the DRV8825 they are too small for one so old!
I know the problem well. Do what I do, use a pair of very strong reading glasses and/or a magnifying glass.
Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod
Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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Re: Mini Kossel can't do circles February 19, 2016 02:17PM |
Registered: 10 years ago Posts: 28 |
Hi everyone
I have sort of cured the problem in a drastic way. I have swapped out the extruder and stepper and installed a planetary geared 5:1 stepper and aluminium direct drive extruder. The clicking noise has reduced to once every few seconds as against 10 times a second.
It seems like cheating as I am no closer to a fix of the original hardware.
Still, thanks to all who contributed
I have sort of cured the problem in a drastic way. I have swapped out the extruder and stepper and installed a planetary geared 5:1 stepper and aluminium direct drive extruder. The clicking noise has reduced to once every few seconds as against 10 times a second.
It seems like cheating as I am no closer to a fix of the original hardware.
Still, thanks to all who contributed
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Re: Mini Kossel can't do circles April 18, 2016 09:19PM |
Registered: 9 years ago Posts: 31 |
Hi,
I have that problem, I heard roumer it was cause current was to high!
Overall , i found that pushing up more on the extruder release (helping the spring) worked for it , so i printed a quarter of a ring about 1 cm high (it was pickey to what was perfect hight , so build tall and shave down!)
, that i jam in there and hold in with hair elastic, i still havnt gotten around to turning power down
prolly not the best solution , but enough for me!
I have that problem, I heard roumer it was cause current was to high!
Overall , i found that pushing up more on the extruder release (helping the spring) worked for it , so i printed a quarter of a ring about 1 cm high (it was pickey to what was perfect hight , so build tall and shave down!)
, that i jam in there and hold in with hair elastic, i still havnt gotten around to turning power down
prolly not the best solution , but enough for me!
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