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Z axis issues?

Posted by callumburns 
Z axis issues?
March 08, 2015 11:18PM
I have a strange issue with my printer! I have a Wilson with e3d V6 hotend and the issue I am having is that all my parts are off with the height! If I print say a 10mm high Cube its 3mm off. I printed a 10mm stepped cube and each step was 3mm off. How ever I jog the axis 100mm I moved 100mm exactly! Thats the strange thing about this issue. Im using M5 rod on the Z axis, and the frame is sold as could be very little wobble, no play in anything. Im totally stumped! Steps per MM check out too.
Re: Z axis issues?
March 09, 2015 06:24AM
Is this a 3mm of in just the z direction or all? If all this could be a scaling issue in your slicing program.
If in just the z direction, your z-movement is probably set faster than the motors can keep up. Try to slow down your "non-print moves" in your slicing program of choice.
Re: Z axis issues?
March 09, 2015 06:34AM
I had a similar problem with the Prusa i3, it seems your printer is based on that design if my image search on google is correct.

Here's how I tackled it:
Try marking the the z rod, z nut and couplers and see after a print if there's any slipping. If so, tighten all grub screws. If you use tubes instead of couplers, replace them with couplers, they are known to be slipping often, especially if lubricant works its way down the z rod.

Also make sure that the z stepper motors have enough power.

Check the threads on the rod, it can have a small deviation which can translate in one or two mm difference over a longer distance traveled. Usually the threaded rods are within 0.05mm accuracy but sometimes it can be more. You can use two nuts, mark them then count the number of turns of one nut and measure the distance between the two. Try to get the distance as big as possible. M5 threads have a travel distance of 0.8mm per turn. Any deviation bigger than 0.1mm per 10 turns needs to be accounted for in the z-steps. This may cause some banding in the print so keep an eye out for this problem and possibly replace the rods if they are off too much.

Make sure the maximum velocity of the Z axis is not too high. For prusa i3 like printers with a 5mm z-rod the default is often 5mm/s while 3mm/s is more reliable.

Edited 1 time(s). Last edit at 03/09/2015 06:35AM by imqqmi.
Re: Z axis issues?
March 09, 2015 10:42PM
Found out my issue! Sli3r or PrintRun was causing issue! Printed something with Cura and perfect... Although theres now an issue with gaps in the solid top and bottom infill but can soon sort that. (I hope..).
Re: Z axis issues?
March 13, 2015 10:58AM
And I was wrong! Not sure what this phantom issue is! It only ever shows during a print. Never any other time. Everything checks out to be fine so I'm really confused. I have went through everything I can think of and been told. Although it seem that if it has infill then thats wast causes the issue. If its just something like a vase then its fine. OR that could be due to the fact I used the Z spiral feature to make the vase..
Re: Z axis issues?
March 13, 2015 02:41PM
Regarding the gaps in the infill, that is caused by the extrusion width. The offset in Z might be cause by an unsupported layer height by the rod. Can you tell me your nozzle size, extrusion width and layer height?

If you are trying to print a 10 mm cube with a 0.3 layer height it will never be 10mm but 10.2, if you have a 0.5 nozzle with a .60 extrusion width and the wall is 1.3 it will have a gap.

Now 3mm is way off unless you set a weird layer height that add up to that. Most likely the problem is with the slicer scale. Did you downloaded the test cube or made it yourself? Was the original drawings in inches or millimeters?
Re: Z axis issues?
March 13, 2015 06:56PM
Sorted the infill issue that was the exact reason. smiling smiley

These are what I have tried to print: [www.thingiverse.com] and [www.thingiverse.com] Printing this: [www.thingiverse.com] came out 25mm smaller! Should of been 50mm high Layer height: 0.2mm.
Re: Z axis issues?
March 14, 2015 02:19PM
I don't use slic3r or Cura, but all should indicate the number of layers generated (I know Cura does) have you checked that the number match the actual number? For a 50 mm piece at 0.2 should generate 250 layers, if it only indicates 125 then your problem is in the scale factor on the slicer.

Now the funny thing is that 250 layers at 0.1 will produce a 25 mm piece, slicers should adjust accordingly with layer height, but if for some weird reason is not doing it that could be the problem too? Have you checked the G code to find what kind of values are been generated?

Edited 1 time(s). Last edit at 03/14/2015 02:22PM by ggherbaz.
Re: Z axis issues?
March 14, 2015 02:25PM
Can you attach here your G code so I can take a look at it?
Re: Z axis issues?
March 14, 2015 03:18PM
Gcode link: [www.dropbox.com] Made in Cura, 252 layers. The 10mm steps on this come out 3mm smaller so 7mm high! [www.dropbox.com]
Re: Z axis issues?
March 14, 2015 10:45PM
Your G code is fine, part should come out at 50.4

Now like I said, I don't use slic3r or Cura, but most likely they should have something like the settings you can see in the picture I attached? if they do, check for the right steps per mm. the issue might be there.
open | download - sample4.jpg (261.8 KB)
Re: Z axis issues?
March 15, 2015 04:30PM
Nothing like that in Cura or Sli3er. Stumped! M5 rod Steps per mm 4000 so its bang on there.
Re: Z axis issues?
March 16, 2015 12:22AM
I will check if my slicer have your printer in the list, if so I will slice one of the parts you posted and we would be able to find if the problem is with your slicer or the printer.
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