Z min for Mendel90

Is it possible to put the Z Endstop the minimum position of the Z axis?
In 2012, on the Nophead site I saw a mount with Z min.
How have STL files and how to modify Marlin?
Thank you for your help

The Mendel90 is designed to use a top Z end-stop and nophead has strong views that this is the correct way to implement the Z reference. Why do you wish to change it?

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

I do not use the full height of Z. I print very flat pieces. it is not necessary to move the Z up, every time.
"Merci"
Gérard

People keep requesting this but there is no time lost while the Z axis is moving because the bed is warming while it descends and the bed and parts cooling while it ascends.

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[www.hydraraptor.blogspot.com]

Yeah, homing to the z max can take a while. At first I moved my z limit switch to the min and glued a stick to the x-end-motor to trip it. I put a screw through the stick that was adjustable. Later I made a printed part for it.

You would update marlin to have
#define Z_HOME_DIR -1
instead of
#define Z_HOME_DIR 1

Otherwise, to avoid long z home max times, you can type g92 z1000 and then manually bring the nozzle down to the bed and when you have it at just the right spot type g92 z0 to zero it.

I've since moved to auto bed leveling, which I'm loving so far. That too removed z max and using min instead, but the switch is on a servo that pops down to measure where the bed is.

Also, comparing a fixed max switch to a variable min switch, I did enjoy the fixed max much more. It was much more reliable.

Instead of fine tuning with a set screw, I tuned using z offsets in slic3r. I'm using Cura now though and I don't see a z offset option and have to fine tune by uploading new marlin config.

Quote

Yeah, homing to the z max can take a while.

My builds all end with Z = 200 so it takes a second or so to home at the start of the next build. There is never any Z travel that wastes time in my builds because it all takes place during heating and cooling.

Edited 1 time(s). Last edit at 06/18/2014 12:20PM by nophead.

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[www.hydraraptor.blogspot.com]

If your prints are all very flat then couldn't you just print a part to hold the Z stop fixed to the smooth rod at the max height of your prints?

Fixing the switch to the smooth rod I think would result in tiny nudging of the switch higher and higher throwing off the starting point of prints over time.

The bottom limit switch is still part of the design. You can enable it by setting

bottom_limit_switch = true; 

in your machine config. However it doesn't work because the nozzle can't get to zero when there is any ooze on it.



You might be able to set it a bit high and then correct it in your start gcode.

Edited 1 time(s). Last edit at 06/18/2014 08:59PM by nophead.

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[www.hydraraptor.blogspot.com]

Thank's. For your help
CAN you email me STL files ?

Best regards

Gérard

You can git clone the Mendel90 repository from git hub then do the scad change that nophead suggests above and then rebuild the stls. There is a good README in the git repo.

I have just added it to the list of accessories so you can find the bom here: [github.com] and the stl file here: [github.com].

I still don't understand why anybody would use it though? For me it has no advantages, only disadvantages. For example you need to move one of the bed clips so the nozzle misses it when homing.

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[www.hydraraptor.blogspot.com]

Quote
ejbantz
Fixing the switch to the smooth rod I think would result in tiny nudging of the switch higher and higher throwing off the starting point of prints over time.

It could be fixed to the dibond aswell. i.e. make a copy of the printed part holding the top of the smooth rod and the z stop switch and mount it further down.