Z Axis movement not well caliberated?

Hello Everyone,

I've had the chance to get back to my Prusa, and started printing test pieces. Seems my z axis is not moving the proper amount. For example when I hit the '+10' button in Mac Pronterface, it only moves up 2 mm!

It is supposed to move up 10 mm right?

Of course, when I try to print it just lays all the layers one into the other because it is only moving up a fraction of what it needs to.

Any clues as what I should do or check to track this problem down?

You either:
1. Have the wrong # of steps per mm configured for Z, or
2. The stepper motor driver (Polulu) current is set too low (not enough current), or too high (shutdown due to overheating), or
3. You are trying to move it too quickly - Try 30 mm/m! If that works then you can try to find the maximum speed where no steps are lost. Try 60 mm/m, 120 mm/m and etcetera.

I would recommend checking in this order although the cause is probably the SPEED.

Edited 1 time(s). Last edit at 04/18/2013 03:30AM by rhmorrison.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Thanks for the suggestions Bob!

I have to stop for now, so I will try #1 and 2 tomorrow. Where would the number of steps for Z be configured?

When you say speed, do you mean as seen in Pronterface up above the Z axis buttons? It was at 200, I have lowered it to 30, no change...?

Shutdown due to overheating sounds unlikely, I can pulse the Z +10 rapidly, and it doesn't hesitate. It only moves 2 mm per pulse.

Yes the Z speed you can set in Pronterface but it effects only the +Z/-Z buttons and not the gcode.

In your firmware usually in a file configuration.h but it depends on what firmware you are using where it is located and what it is called.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

There are detailed instructions located all over the place for calibrating steps/mm, and it is one of the first things you have to do before you can even think about printing anything. When I first installed Marlin firmware, the default Z steps/mm were WAY off and if I'd tried printing anything it would've just made a mess. When you tell it to move 10mm, it should move 10mm.

Bob, okay, I was suspecting something at the firmware level. My wife did that part a while ago, and we have been too busy to both sit down and test/tweek the printer! I have found the configuration.h file(not to be confused with preparation.h) in Marlin.

Sheck, I mentioned this to my wife and she found the lines in the configuration file. I found some instructions that seem to cover what we need. Next I have to check all the axis for accuracy.

I am hoping to start printing up a new Prusa to upgrade the creaky Techzone very soon.

Okay, looks like it is all sorted out. All axis are much more accurate thanks to tweaked firmware.

I printed out a small test piece and it turned out well. The only issue is that the hot end is of my own design, and at some thin internal corners the ABS turned a bit brown. I suspect it might be because the aluminium heater block is so close to the nozzle tip there is too much heat right above the work piece. There is also no cooling fan.

Maybe I could try lowering the hot end temp down a bit from 230°C.

Thanks for the help!