Axis missing steps inconsistently

Hi all, I have been searching the internet near and far for someone that may have this similar issue but everything I found has one matching piece but not the other and the solutions have yet to work so here's my issue, any suggestions would be appreciated.

When printing mostly taller items, though not exclusive to them, I had the issue where my prints where shifting on the X-Axis on random layers (most of the time it was either unrepeatable or the layers it shifted on were different for every attempt). I started searching for shifting X-axis and as most suggest that it may be missing steps I tightened the belt and ran it at high acceleration going side to side and couldn't detect any slipping. So I started to print another and the same thing still happened, I then restarted that print and painstakingly watched the whole print...I noticed the layers were getting thinner and thinner until the hotend eventually hit the layer and possibly caused the shift. So I did a search for z-axis not moving enough and that came up with try tuning the axis steps per mm so I went ahead and checked that, I moved the z-axis 100mm and it moved exactly 100mm...And here is where I am stuck...

I have searched for z-axis not moving enough on prints but is tuned correctly and came up with nothing...so now I come to you for assistance. Has anyone had this issue and found a solution or know of what this could be?

Thanks

Edited 1 time(s). Last edit at 08/06/2014 08:15AM by Dinkleburg238.

I can't think of what may cause the Z axis to be off if the step per mm are correct, however, you may want to check your extruder steps settings as it may be pushing out too much material, causing layer heights to be off. That is my guess, do you have any pictures of the print?

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Here are some pictures of just two failed prints, as you can see by the side by side it really doesn't have a specific layer where it goes wrong. Also I had checked the extruder steps per mm by trying to extrude 100mm of filament and it extruded exactly that, I'm not sure if there is some other way to check this but that's what I've seen to do. I also retried that gear after the first failed attempt and it came out perfect with great precision, this is the other part that is baffling me about this is the basically perfect parts I get otherwise...

You definitely have skipped steps; have you tried upping the voltage from the pololu to the skipping motor? That could help even if there is some sort of problem with the Z axis.

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I will try going up more, I'm afraid of burning out the motors because they already get too hot to touch and I've got the current as far down as it'll go and still move...could it also be the pololu's overheating for a split second shutting down and causing the missed steps? I have a fan on the drivers I just don't have it plugged in as I didn't really think it was necessary since they have heatsinks, but now I'm second guessing that...

I'll bet having no heatsinks is the problem. After burning out two of them myself, I think that you really should have some heatsinks on your pololu drivers, as it will cause them to overheat and shut down for a second to cool (as you mentioned), causing the exact problem that you are having. Also, having heatsinks will also allow to send more (and perhaps even less?) voltage to the motor, which can come in handy. I've got a couple of extra pololu heasinks should you want to buy them...

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Sorry I must have mistyped, I have heatsinks on them I was just saying I have a fan that I can put on them if that would help as well. I'm running a print right now with higher current and fan on to see how that fares.

I think I misread, actually!
But I use a fan on my pololus as well as heatsinks, to keep everything cool. Good luck on your print!

Edited 1 time(s). Last edit at 08/05/2014 08:45PM by 3D-ME.

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I tried the fan on the steppers as well as turning up the current last night and the print came out perfect. I will keep an eye on it but look like that solved my issue. Thanks for your help, glad to finally have this figured out.

Awesome! I'm glad to be of help.

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