# Corexy steps per MM for Z axis

have read that X&Y for steps per mm is x2 so calculated 200 =400mm for the X and Y Check (belt driven 2mm)
1st question
Do you also multiple steps per MM for the Z axis ?
Using leadscrews x3 motors no belts if 1/16 with 0.9 is 5120 and 1/32 is 10240 steps per mm (calculator) for a 8mm leadscrew direct drive
you don't double steps for z -axis do you (belt or Leadscrew)  (assume not)

2nd quetion
how do you define the Z area travel for the motors ?

My 3D printer is rather big X=550mm y=550mm and z =815mm
when i set the home and start positions for the motors  is there a way to calculate the position or is that up to the home an end stops and bed sensor? at this time when i home it moves about 12 inch and stops

best guess is the travel area for the z axis is about 28 inch (about 712mm) of my 800mm length
finally got every thing moving once i manually entered M92 z 10240.00 then entered software and saved in eprom using repetier host and repetier on my ramps 1.4 so a step at a time. :>)
thanks in advance for any and all help

• 1. No Z axis in not affected by this.

2. Not sure what you mean. You home and then you are at home position. We do not know position before that, which is why we home at all.
• How do i determine the position in Repetier? Based on the end stops, a calculation?

Assuming home is X and Y all the way left @ zero (value unknown) and  Z is 28"  down (100mm) (assumed we home at end of print) If we say the start position (center)  is at say X and Y =180x180 (unknown value =center of baseplate) and Z is UP 28" (700mm) Sensor is at 0.01 (unknown value)  ready to print (assumed I will stage the baseplate midway since that is a long way to travel)

Maybe calculate 400mm step @*25.4 = value for X and Y 180x180 and 10240 steps @25.4= for Z height (guess overthinking this?)

at this time I am only moving in manual (testing), with none of my end stops in place as yet and the z-sensor is not wired yet (have to cut and fit the baseplate) Moving only the Z Axis mounts at this time,.

Further enlightenment Setup: 800mm leadscrew TR2@8 coupled to stepper using 3 steppers /0.9degree 17HM19 1.6A @59 oz my mounting system with 12mm linear rod at 5” between motor and rail 12mm linear rod is also 800mm

Ramps 1.4 with drv8825 and the Arduino 2560   COREXY setup (home brew 80/20 frame 24”x24”x36”) roughly an 800mm lift and 600mm print area) Call it Baby!  More of a medium frame.

I am certain I am over thinking all of this :>)

Any help in getting my mindset wrapped around this is appreciated.

• If you home to min that position is 0 and from there on you know how much you moved, so positions afterwards are known. All you need is set steps per mm correct and set xyz length to what is possible. You can start with higher value and and test when you reach the opposite end and then set dimension again in eeprom. You set all positions in mm so no need to get confused with steps per mm in that aspect. You only need to multiply them with sqrt(2) or 2 not so sure since I do not have a corexy I always forget.

As I said you do not know start position and each axis needs to be homed, no quick tricks. If you have z min homing (if you have z probe you must use z probe also as z min pin and better use dev version) you can spare the way completely up and down.
• Think i understand, seems to be very close in the mm vs move how ever seems to be getting off a little more with each subsequent move.

also in manual mode when i move 300mm moves 300 then stops but it wont let me move another 300mm even after entering G0 OR G1 Z 300 ? seems like  I missed something even without the home and end sensors?

would their be an adjustment to fine tune for Z axis, or is that only for z probe calibration ( cant do that until i cut base plate)
at this point every thing is measured to each z axis bracket
• G1 Z300 in absolute mode will not move on second call as you are already at Z300. Use Z500 or Z600 (lower then z length as it would otherwise ignore move). Z steps per mm are used for all z moves. These van be computed e.g. with the leadscrew calculator in repetier-host.
• OK, duho that makes sense :>)
Thanks