Z AXIS PROBLEM

I recently built a Prusa i3. When I first started printing a calibration cube it started off fine for about 5 layers then it looks like the nozzle does not lift properly and eventually pushes down on the print. Any advice on this.

Hi,

IMHO, you have some over-extrusion.
Try to calibrate your extruder first.
Then maybe your coldend turns too hot in a while.

++JM

Check the Z axis screws and bearings to make sure they aren't binding. Check the Z axis motor current.

In the future, post photos of the problems so people can have more info on which to base their diagnoses..

Edited 1 time(s). Last edit at 09/10/2015 08:51AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

The extruder is calibrated. The first layers come out perfectly then it's as if the z axis does not go up the full steps.

have you calibrated the z-axis steps per mm?

[prusaprinters.org]

heres a link to a calculator for just that

I did. I double checked again. Still the same. I just don't uderstand

Just saw something interesting. Below the calculator u linked me to there is something about the z axis. It seems like it should be on full stepping and not micro stepping. I think I might just pull the jumpers and see what happens. What do you think?

from what I have just read this does not seem to be the issue, unless your z-axis motors are set to turn off between steps though I am not 100% sure. It cant hurt to try though, just take care not to short anything while switching jumpers, unplug =]

[www.buildlog.net]

[forums.reprap.org]

bit of reading as far as micro vs full step

If you're using slicer, check the 'infill/perimeters overlap' setting ( Print Settings > Advanced ).

Default is 15%

Change to -10% ( yes, Minus )

I found it calculates the overlap based on the centerline of the line of plastic, so anything greater than about -10% causes the infill to be deposited on top of the perimeter line, so it can't get down to the height it should be, and next layer your nozzle is crashing onto or scraping on the edges of the previous layer's infill.

Tried to set it to full step. The motors started whining. I eventually blew the stepper motor. Going to try the next post. It seems less invasive.

It could be a problem with the gcode file you're trying to print. Have you checked the gcode? You should see the Z axis coordinates increasing at each layer change. You can plug the file into gcode.ws in a web browser and get a visual indication of what the gcode is doing.

Assuming the gcode is OK, and it probably is, if it prints a few layers just fine then the Z axis stops going up, it is most likely a mechanical problem with the screws binding or the bearings binding on the guide rails, or a coupler slipping on a motor shaft(s). Without a photo of the prints or the machine it is hard to say for sure. If there's a little binding, you may be able to muscle through it by turning up the Z axis motor current.

Switching off microstepping won't fix a mechanical problem. It also won't cause the motor to "blow". You may have burned up the driver for the motor, but it is very unlikely that you ruined the motor.

Post photos and more detailed descriptions of what you have done to try to fix the problem. You can take pictures with your phone and post them to google drive or any other hosting site, then posts links to the pictures here.

You are going to need a lot of help getting your printer working, and it will be easier for others to help you if you help them by posting photos and being more descriptive.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

These are top and bottom pics of a 24mmx24mm calibration cube. I hope this helps.

A picture of the side of the cube would help.

It looks like you're over extruding, but that may just be due to the Z axis stopping. Have you checked the mechanism for binding? If you jog the Z axis up and down does it do what it's supposed to or does it get stuck? Jog the Z axis over the full length of the screws.

Have you checked the gcode? How did you check it?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I did check the z axis for binding. It moves where I tell it to move. I really don't think it's binding. I opened the geode in note pad. The only reference I get to the z axis is "G1 z5000 and then Go 0.400 the rest of the code Co ordinates are X y and e

Could it be an extruder problem? The top layer or is it bottom layer of the second image looks like dotted lines instead of straight lines. Check if the extruder motor runs smoothly without speed changes/rhythmic motion on straight extrusion lines. Check if the current is set correctly, the hobbed bolt is clean and catching the filament properly, the tension on the filament is not too much or too loose either. It's best to start out with a loose setting then tighten it until it doesn't slip anymore. If you start out too tight and think it's slipping it may be too tight and the motor will start skipping.
If this is the case, when the motor starts running smoothly recalibrate the extrusion length.

You should see commands like G1 Z0.2 Fxxxx.000 where xxxx is the feed rate in mm/minute. You should see these commands for each layer, so if, for example, you're using 0.2 mm layers, you should see a G1 Z0.2..etc, G1 Z0.4...etc., G1 Z0.6 ...etc.

Those commands will have a bunch of G1 or G0 commands with X, Y, and E values between them because those are the XY plane extruder paths for each layer.

You said the Z stops moving at 5 mm. Does the gcode file contain and G1 commands that go beyond G1 Z5.0?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Here are some more pics. It's a 20mm X 20mm block. I let the print go half way this time. You will clearly see how the nozzle digs into the print.

The extruder I am using is a mk7 moulded block style. There is absolutely no way to adjust. Things I have tried and checked. Z axes screws and bearings run smoothly. Z motors current is fine. Extruder calibrated. Z axis steps per mm are perfect. If I want it to move 20mm it goes 20mm. They same for all axis. Slic3r infill perimeter overlap set to -10%. Changed pvc to home made steel couplers. Set extruder down to 200 steps per mm just as an experiment and it did nothing. Extruder motor runs hot, but I think it's the heater block. The g code is a bit of a mystery. I don't see any co ordinates telling the z axis to keep going up. It does go up from visualy checking (at least partially). That is were I am so far.

This is my machine. Loosely based on the Makerfarm i3

A very short video.

Post the gcode of the cube that you're having problems printing.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Just want to thank everyone for their assistance with my printer. It turned out to be the extruder stepper motor that was shot. I will post some pics tomorrow.