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Printing Issues | Nozzle Dragging

Posted by jininjin 
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jininjin
Printing Issues | Nozzle Dragging
September 17, 2012 08:24AM
I am having issues with prints. The prints stick the bed fine now but I still have the nozzle dragging through the plastic. What should I change to solve this? The print bed is level and the nozzle is paper height away from the bed.

Prusa Mendal V2 Sanguinololu 1.3a w Marlin 1.0 Pronterface Slic3r

The wall is the 0.5mm-thin-wall.stl which the walls print out as 3mm high by 3mm wide

Edited 1 time(s). Last edit at 09/17/2012 08:26AM by jininjin.
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rhmorrison
Re: Printing Issues | Nozzle Dragging
September 17, 2012 08:52AM
Either you are extruding too much plastic OR you are loosing steps on the Z-axis.
Have you verified that when you tell the z-axis to move 100mm at the speed set in your slicer program that it really moves 100mm? If NOT do that first! You may need to increase the current on the z stepper controller or reduce the speed that you are running the z-axis.

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
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brnrd
Re: Printing Issues | Nozzle Dragging
September 17, 2012 12:43PM
Did you calibrate your extruder steps per mm and enter the measured diameter of your feed?
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jcabrer
Re: Printing Issues | Nozzle Dragging
September 18, 2012 02:17AM
If you are printing in pla, you need to blow a fan on the print, or the heat buildup will cause the layers to rise.
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rhmorrison
Re: Printing Issues | Nozzle Dragging
September 18, 2012 03:00AM
@jcabrer: I have been printing exclusively in PLA for the last two years and have never used (nor needed) a fan. For doing bridges it would help for sure but other than that - NOT NEEDED.

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse
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glyn
Re: Printing Issues | Nozzle Dragging
September 18, 2012 04:11PM
I had this problem and now use the slic3r lift option which although not ideal (slightly blobby prints) does solve the drag. I usually put in a lift of half the layer height.
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brnrd
Re: Printing Issues | Nozzle Dragging
September 18, 2012 04:52PM
From the photos of the part, the lift option won't make a difference. I actually don't use the lift option at all since I'm more concerned about lag in the z lead screw or threaded rod.
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Chris_NZL
Re: Printing Issues | Nozzle Dragging
September 20, 2012 06:48AM
@glyn I had the same problem and used the same solution, not idea but worked to a point. I found a better solution is to solve the under lying problem (often easier said than done) and not have to use that feature at all. It was worth the effort and would encourage anyone to keep trying.
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jininjin
Re: Printing Issues | Nozzle Dragging
September 22, 2012 08:29PM
sorry for the delayed response.... I've been a little busy. In pronterface I clicked the 10 for Z axis which I assume it means 10mm. I measured 2.21mm movement in the z axis. So how do I increase the current of the stepper motor. Do you mean the pot on the polulu driver? or is this in the software? How do I calibrate the extruder steps per mm? I apologize if this is all written down in wiki somewhere but I'm out of my comfort zone at the moment.... haha

@brnrd I did put the correct average diameter of the pla into slicer.
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brnrd
Re: Printing Issues | Nozzle Dragging
September 22, 2012 10:09PM
How fast is the z speed? Did you try lowering it to see if you're missing steps? Depending on how your z axis is, it might not be able to keep up with the default setting of 200 mm/sec. You can often hear the motor skip steps if you play close attention. Also, did you set the correct z steps per mm based on your threaded rod?
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Idolcrasher
Re: Printing Issues | Nozzle Dragging
September 23, 2012 05:19AM
Are you using Slic3r 9.2? It does not lift the nozzle to the correct height on the first layer .
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jininjin
Re: Printing Issues | Nozzle Dragging
September 23, 2012 01:43PM
@BRND The speed is set to 200mm/s. The motors all sound smooth. I will check again. Pots are at .4v. I have not set the steps per mm though.... how do I calculate this? Also what does steps per mm actually mean? I'm a learning at the moment so bare with me.

@Idolcrasher I am now using slic3r 0.9.2 now but I had the same issues with 0.7.2. This could have compounded the problem though. How should I check this?

Thanks

Edit 2:

I calculated the steps using Josef Prusa's calculator x,y,z,e = 80,80,??,625.77

Not sure how to determine the Z axis yet. what does the default 200x8/3 stand for? 8 is for the threaded rod size I presume.

The e-steps were calculated based on these values
1.8 degree step angle
1/16 pololu
M8 Leadscrew
45:11 ratio mentioned here [www.thingiverse.com]

Edited 2 time(s). Last edit at 09/23/2012 03:49PM by jininjin.
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brnrd
Re: Printing Issues | Nozzle Dragging
September 23, 2012 05:06PM
If your z threaded rods are M8, then it probably has a pitch of 1.25 mm. It's also possible that it's 1.00 mm, but this is not common. At 1/16 microstepping, each revolution takes 3200 steps. The z steps per mm would be 3200/1.25=2560 for 1.25 mm pitch and 3200 for 1 mm pitch.
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jininjin
Re: Printing Issues | Nozzle Dragging
September 23, 2012 06:51PM
Thanks,I am understanding now. All the calculations seem to be working now. I measured the movement with a caliper. I will need to do some test prints now.... I had a small hitch with my z axis coupler which pulled off the motor again.... I need to get a better coupler design. Ill update when I get back on this. Thanks for the help!
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brnrd
Re: Printing Issues | Nozzle Dragging
September 23, 2012 08:35PM
The z coupler designed by Nophead that comes with iteration 2 works quite well. The trick is to get the right size tubing on the threaded rod so that it's firmly clamped in but can still flex. I used polyethylene tubing but I placed my z motors in the bottom (upside down) in my Prusa i2 to minimize downward play on the threaded rod.
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jininjin
Re: Printing Issues | Nozzle Dragging
September 23, 2012 10:00PM
I am using this one it is derived from Nopheads. I bought it as vitamin kit online. I am also using aquarium tubing but it is falling off the motor peg since its a small smooth surface. That looks much more logical to have the motors on the bottom. Any drawbacks?

Edited 1 time(s). Last edit at 09/23/2012 10:07PM by jininjin.
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brnrd
Re: Printing Issues | Nozzle Dragging
September 23, 2012 10:51PM
It requires an extra threaded rod, nuts, washers, and printed rod clamps to support the motor mount.

A number of newer dual z motor printer designs like Mendel90, Prism, Bukobot, and Prusa i3 have the motor in the bottom.
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nophead
Re: Printing Issues | Nozzle Dragging
October 22, 2012 04:45PM
The PVC tube should grip the motor shaft. However, if there is any grease on it then it will slowly slide down, no matter how tight it is. I de-grease the shaft with denatured alcohol.

[www.hydraraptor.blogspot.com]
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jamesdanielv
Re: Printing Issues | Nozzle Dragging
October 23, 2012 11:10AM
i also add a dab of super glue or lock tight. it does not grip that much but it helps prevent slip. place it in the tubing, and then slide on motor shaft. be careful not to over apply because excess will leak out and damage the motor shaft.
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jininjin
Re: Printing Issues | Nozzle Dragging
October 24, 2012 12:35AM
Thanks, I am trying the rubbing alcohol trick plus I have gouged the tubing to add some friction hope this works for now.

Here is my latest print. Looks a lot better then before. Its supposed to be .5mm thin wall test but it appears to be 1mm thin wall... I will try some cubes next to test the calibration.

Another issue that just started to occur is after a certain length of time the filament gets stuck somehow in the nozzle and the none melted plastic folds up in the hobbed bolt area. Any idea why this might happen. I will try to figure it out shortly.
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Chris_NZL
Re: Printing Issues | Nozzle Dragging
October 24, 2012 01:34AM
There may be a blockage in the hot end. Once I found the smallest piece of PTFE in the nozzle. It didn't always block completely, but sometimes enough to get the filament to kink up as you describe. Also, the temp maybe too low, perhaps you have changed colours? If your close to the minimum temp already, changing the colour might be enough to stop it melting quick enough. Try measuring the nozzle with a temp probe, the reported temperature in the software may be different from what it actually is. Also, try skien-forge. I have only ever been able to get a thin (single) wall print of reasonable quality using skien-forge. It will at least give you a comparison. All of these suggestions from from my own trial and error so your mileage might vary.

Edited 1 time(s). Last edit at 10/24/2012 01:57AM by Chris_NZL.
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jakub.sturc
Re: Printing Issues | Nozzle Dragging
October 24, 2012 06:20AM
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jininjin
How do I calibrate the extruder steps per mm?
There is a great tutorial to Slicer. See step 1
[richrap.blogspot.cz]
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