XYZ Directions

Hi, i have almost finished my Ultimaker clone. Im not shure if the XYZ axis going the right way.
If Z is zero, the lifting bed is on the top or on the bottom of the router, i assume Z=0 menans zero height of the model so it should be at the level of the nozle and Z+ in this sense should move the bed down... is that true? so the min Z endstop switch is at the nozle.
What about XY what are the directions of that?
Cheerz

Yes that's true for Z. You can use a Z min homing switch at nozzle height, or a Z max switch at the bottom of the printer, or neither and use a Z probe for Z homing.

Regarding XY the important thing is to use a right hand coordinate system so that looking from the top, the +Y direction is rotated 90 degrees anticlockwise from the +X direction. Most printers have X0 Y0 at the front left of the printer, with +X being to the right and +Y being towards the rear.

Edited 1 time(s). Last edit at 07/06/2017 07:04AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks

You can also think of it like this:

3d printers are cnc machines, with the hot end as the tool. Now, all cnc machines assume the tool is moving, even if stationary. So, say you have the bed moving on xy, when the bed moves left, its like the tool moved right.
Its good practice to view it like this, because g-code also assumes a tool moving in a cartesian coordonate space.
Also extending that, you know that the point of origin is where all axis meet at the minimal distance, making it the lower left corner with the tool at its closest distance to the build platform