Layer shift on one axis only

K8200 3D Printer K8200 - Issues while printing
1

Hello all.

Still very happy with my K8200. Have been quietly printing and upgrading/tweaking for the last couple of months, and having great fun.

I have just this week, completed this project thingiverse.com/thing:724999 I experimented printing parts in PLA, ABS, Taulman’s Alloy 910 and Tech-G, and just recently Eastman’s Amphora 3D Polymer, and Polymaker’s Poly Max. It’s really astonishing just how strong parts printed in some of the more exotic filaments can be!

But I digress. As per the title, I have a small and annoying problem that I cannot seem to figure out! I have layer shift/miss alignment, but only on one axis. I have tried may things to eliminate this, but so far I have had only managed to minimize it. Please see pictures below for better understanding.

https://drive.google.com/file/d/0B2nobe1HZXsEWF8wbnhmZVdDcjQ/view?usp=sharing
https://drive.google.com/file/d/0B2nobe1HZXsEckJvdUl3M3lGS00/view?usp=sharing

As you can see, great results in one axis, not so great the other.

Upgrades as follows. Z axis upgrade, TR12X3 trapezoidal lead screw with brass nut, gt2 belts, custom tensioner assemblies and 16 tooth pulleys on x and y axis, DV8825 stepper drivers with heat sinks and active cooling, 24v upgrade to heated bed and 24v E3D v6 hotend.

I have gone over the printer with a fine tooth comb and checked every bolt, screw, fastener, checked voltages for drivers, checked the linear slides and bearings, belts, wiring. Please can someone give me some sage like advise? I am running out of ideas.

The only thing I am yet to check, that is kinda weird, is one stepper (x axis) is virtually silent in operation, the other (y axis) is noticeably noisier. I have been thinking about swapping the steppers (x to y) to see if the miss alignment follows the stepper. Might do this soon.

I’m open to any suggestions, please help before my head explodes!

Kind regards.
J.

2

This looks like the mounting arm of the extruder is shifted sideways by the z axis drive.
Check if your z axis spindle is mounted concetrically with the motor axis and if it is absolutely straight.

Maybe make a little g-gode script to move the z axis up and down full length in high speed a few times
and watch if the extruder mount slightly moves sideways.

3

Quick update. I just printed a 25mm calibration cube. The shift is now isolated to one face of the cube only (the face that faces the z axis) the opposite side (facing the control board) is unaffected!

I an more confused now.

4

Can you post a pic of the cube please?

5

Have you checked the screws that hold the pulleys on the motors?
You may also want to look at the bearings the belts go over make sure they are turning freely.

6

Thanks for all the great advice guys.

I post the results of the z axis travel text and pics of the calibration cube later today. All also check everything else you’ve suggested.

Thanks heaps.
J.

7

Sorry for the lack of updates.

I does look like I have had a win though. Firstly I would like to say thankyou very much for all the advise. In a round about way, it helped me finally solve the issue.

On to the solution. I first did the check that ichbinsnur sugested. I could not see anything by eye, so I set up my dial gauge to monitor any movement at the nozzle (relative to the build plate. There was a very (less than 1 thou) small shift. But not enough to account for the layer shift I was experiencing.

Next I did some repeatability tests on the x and y axis movements (again with the dial gauge) and something strange occurred. Sometimes the test was perfect (within measurable limits) others it could shift up to several tenths of a millimetre, and only on the y axis? (left to right) sorry not sure how velleman label their axis.

Long story short (after much tightening, tweaking, adjusting belts, adjusting voltages, swapping steppers, generally banging my head against that wall) it turned out to be a crack in the spacer that spaces the hot end away from the extruder (the white tube thing on the stock velleman hotend) I can only assume I must have over tightened it the last time I installed the stock extruder assembly.

I never occurred to me to check this. Very early on, whilst initially learning and setting up my printed I had come across a post from a user that had the hotend work loose and cause some minor inaccuracies in his prints. Upon reading this I checked mine, and low and behold I was not quite tight. From that day on, whenever I had to remove the extruder/hotend I would make double sure that everything was nice and tight going back together. As I knew it was indeed tight (having only recently swapped back to the velleman extruder to do some rapid prototyping I never bothered to check.

This is what happens when you assume things. Back to my printed extruder and E3D hotend now, and everything is running smooth as silk. Prints are better than ever (I guess running a spanner/eye over everything was time well spent). But I do feel silly for having overlooked such a simple thing.

This white spacer thing. Is it available as a spare part? I really liked the stock velleman extruder and .5mm nozzle setup for fast prints.

Thanks again. And feel free to call me out for being a nong!

8

The part number is EXT8200FG
http://www.vellemanusa.com/products/view/?id=527513

9

Great. Thanks for the info.

10

No problem.

Enjoy your printer.