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Mendel axes directions?

Posted by gkaindl 
Mendel axes directions?
April 01, 2010 07:42AM
Hello there,

I've basically finished building my Mendel (everything complete, extruder works well, but I have not done the final jigging/comissioning/calibration exercise yet), but there's one rather trivial thing I can't seem to find documentation for in the RepRap wiki:

Which direction are the axes supposed to move (e.g. which way is "towards lower values", which "towards higher value")?

I've wired up my steppers (the popular high-torque ZappAutomation ones) according to the datasheet - all of them wired the same way, but my x and y axes seem to be inverted (I'm using the Makerbot firmware though, so that might be the cause).

So, which way should the axes move? Looking at the Mendel from the front, my axes currently move like this:

X: lower -> towards right, higher -> towards left
Y: lower -> towards front, higher -> towards back
Z: lower -> downwards, higher -> upwards

Are my X/Y axes inverted or is it supposed to be like that? If so, is it a "known issue" with the electronic wiring or is it because of the makerbot firmware, e.g. should I rather hack the firmware (I already have a custom branch, since I'm using a Pololu board to drive my stepper-based extruder), or should I swap the positions of the coil wires for the x/y axes?
Re: Mendel axes directions?
April 01, 2010 08:57AM
They should all move towards their opto limit switch when going lower.

x opto is on the left, so the x-axis goes left to right.
y opto is at the back but that means lower y-values are the front of the bed, so y axis goes front to back of the bed.
x opto is at the bottom, so z-axis goes bottom to top.

I don't know how it relates to Makerbot, they move the bed for x which inverts it. And they move the table for z which also inverts it, but it also depends which way round the motors are mounted.

It's probably better to swap the motor wires than to hack the firmware unless you have your own version anyway.

Re: Mendel axes directions?
April 01, 2010 09:29AM
Ah, thanks, that makes perfect sense. I'm a bit embarrassed I didn't think of this myself :-)

I think I'll change it in my firmware branch then, since they already have proper methods to invert axes - My future goal is to improve the Makerbot firmware a bit, since it has nice features like printing from SD card and updating thermistor tables on-the-fly, but its stepper control is surprisingly unsophisticated, compared to other firmwares.
Re: Mendel axes directions?
October 20, 2010 03:35PM
Old topic, but i figured i'd ask here than make a new topic along the same lines:

How do I invert the min/max for each axis in the standard fiveD firmware? Every comment on this seems to say "yeah there's some flag in the firmware, i think."

Would it be INVERT_X_DIR in the configuration.h file, and I just flip 1>0 or vise versa?

(gotta load my own firmware anyway. I might just flip the wires but it would be nice to have this documented somewhere)
Re: Mendel axes directions?
October 21, 2010 12:43AM
Answered my own question. Yes, it does invert the axes. there's a define for each axis: INVERT_X_DIR, INVERT_Y_DIR, INVERT_Z_DIR

I haven't found similar for the extruder in the config.h file, but i'm sure it's somewhere (probably with a different verbiage)
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