diy printer

Hi all, I am a complete newby and being retired I built a CNC router which I have built and mastered and so I progressed to building a 3D printer from scraps from my collection I used pictures of the everbot as a design and I built the sanguinololu board with the atmeg processor and I am using Pronterface to control it. I am of the opinion that I have configured the drivers correctly to the motors , The X axis is belt drive and the Y and Z are screw drive 8mm metric 1.25mm per rev. I can move all axis back and forth with pronterface without losing steps but when I load a program I am missing steps on the Y axis, I have come to the conclusion that my problem could be with the excellaration and or the jerk settings in the configuration.h file though I have spent days varying both and cannot find the soloution. Can anyone help please

Most repraps don't use lead screws for Y.

You will probably need to re-compile your firmware and change the max speed and acceleration for the Y axis.

Or set slicer to that all speeds are very very slow.

I think that your printer may be unusably slow using a lead screw for the Y axis. Can you replace it with belt and pulleys on Y ??

This is correct x/y lead screws will not allow for acceleration ramps with current firmware on repraps. For example if you try the same with a dated parallel port cnc controller and mach3, you would no longer loose steps. It has to do with the even timing of the steps with mach3, and the uneven step pulses of the reprap controllers. It is smoothed out by the belts system that can absorb and smooth out the steps.

Also it could be that the step pin may be an inverted input if your speeds are not that fast.


read up on Bresenham's line method which is what is used for reprap interpolated moves.

link is here: [en.wikipedia.org]
notice in the picture below that even though x step size is consistent that the y axis step size varies. this means the max speed of y is limited because of uneven stops and starts, unless a system is with some give such as belts.

this knowledge can be of advantage though. say you do infill at 45 deg then each step would evenly advance, and the distance covered would be 1.4 that of a single axis, so you could run it 1.4 times the speed as a single axis. (firmware would negate the speed to feedrate per second)




Edited 3 time(s). Last edit at 12/18/2013 10:26PM by jamesdanielv.

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I have come to the conclusion that my problem could be with the excellaration and or the jerk settings in the configuration.h file

Set jerk to zero (or turn off lookahead entirely) and acceleration to something very low, like 50 mm/s². This should give you a bot working without step losses. Then raise acceleration to find out the capabilities of your design. That done, start to raise jerk, too.

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This is correct x/y lead screws will not allow for acceleration ramps with current firmware on repraps.

Huh? Not sure what you mean with "current firmware", but Teacup Firmware definitely does proper acceleration ramps on all axes, lead screw driven or not. Note to those trying: lookahead works currently better with the code from the experimental branch.

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Generation 7 Electronics	Electrochemical Machining	RepRap DIY
Teacup Firmware	PCB Milling

Thanks all for your valid inputs, I have re-designed the Y axis to be belt driven and that fixed all my problems, thanks again