Coordinate system

I am having an interesting discussion bout repetier host software here [forums.reprap.org]
The problem is the orientation of the coordinate system on my kit mendel90.
It all comes down to one question : what are the coordinates of the front left corner of the bed?

The centre of the bed is 0,0 and with a 200mm square platform, this gives...
100, -100
100,100
-100, 100
-100,-100

for each of the four corners.

Which you define as front left always confuses me as it depends on which way you view the machine. If you think of the back being the side nearest to you when the MELZI is to your right, (and where the bed comes to when at home), then front left will be 100,100 (I think!).

Alan

Edited 4 time(s). Last edit at 08/25/2013 07:44AM by Alzibiff.

I think the corner on the front left is the one furthest from the melzi. I thought it was needed to orient the 3d view on some programs and indeed my repetier host has it backwards and shows me the platform and the object as if I was looking the machine from the back. Trying to change it, however, does not do anything as the values are constantly overwritten by the "sanity check" to -100,-100.
It's not a big deal but it's annoying.

@andrea.rimo
I like repetier a lot. Up 'til now, I've just accepted everything is printed 180 degrees, but have recently had stupid problems with the fan casing hitting the foldback clips because I forgot when I was plating up. I'll follow the repetier thread as it's definitely worth getting this sorted.

@Alzibiff
> then front left will be 100,100 (I think!).
Certainly is for my M90!

Which you define as front left always confuses me...
So glad I'm not alone. Worst is bed levelling with Pronterface, press the left arrow and the carriage moves right ...!

I'm sure nophead wrote something about this somewhere, darned if I can find it now.

Remove the top handles from the clips and fan should clear them. The print area is then symmetrical.

Yes the front of the bed is actually at the back of the machine. If you want it the other way round make the X and Y limit switches into MAX switches instead of MIN and invert the direction of the X and Y axes and the homing direction. I.e. make X and Y the same as Z.

For bed levelling use the buttons provided in the pronterface config provided.

I must admit I find it irrelevant which way the arrows in pronterface are because it depends which way round your PC is relative to the machine. Also the Y axis moves the opposite direction to the nozzle so you can never have both X and Y moving as the arrows in pronterface or you will print mirror image objects on a machine with a moving table Y axis. Similarly Z will move the opposite way to the arrow on machines where the table goes up and down. I just look at the plus or minus legend as those are the logical directions it goes in.

I am used to running my machines without any GUI so it never occurred to me that it would cause such confusion.

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