homing postion

Hello Guys
I have built and run the traditional A frame style Reprap for awhile now but wanted to build something different.
I built a machine based on a post here [www.thingiverse.com] which is just a Ultimaker 2 knock off.
Instead of buying Ultimaker controls/motherboard; I used the Ramps1.4/mega2560 and Latest Marlin Software to control the machine.
My Question is this:
I want to move the print bed up to the hotend when printing "Z probe at top" but park the bed at it's max position "all the way down" when printing is complete.
What would the settings be in Marlin for endstops and do I need to add a max endstop for Z position?

Any help would be appreciated.
Thanks

Two options.

set Z0 (min end stop) to be at the hot end, z+ must move the bed down, home direction -1

Then add a G1 Z(height of z travel) to your gcode.end or equivalent file in your slicer program to lower the print to the bottom on finish.

Or you could do the reverse

Put a max end stop at the Z bottom position, set home direction 1, and make sure the #define Z_MAX_POS 200 is equal to your max movement in Z
z+ still moves the bed down Then you can just home at the end of a print also via gcode.end

The issue with the latter is that homing Z will go all the way to the bottom then all the way to the top again, and z axis is normally quite slow (unless you use decent lead screws)

Edited 1 time(s). Last edit at 03/28/2016 02:50AM by Dust.

Dust
First off thank you for responding!

{set Z0 (min end stop) to be at the hot end, z+ must move the bed down, home direction -1}
{Then add a G1 Z(height of z travel) to your gcode.end or equivalent file in your slicer program to lower the print to the bottom on finish.}

I figured it was probably like this but thought there might be away to set this into firmware so the slicer didn't need special commands to move this machine.
Sounds like the best solution though!
One last question: Can the max endstops be enabled but only use the Z max endstop?
I've never used the max endstops and don't know there actual role when enabled. I've always assumed they were just a means to stop an over shoot and crash.
Which actually could have helped a time or two.


Once again thanks for responding.

Yes you can enable and use 1 max endstop (for some reason a lot of people have started using X max endstop)

The machine actually has software endstops for the endstops your missing, but hardly anyone sets their travel limits correctly so they hardly ever kick in.

Dust
LoL ok well you brought up one last question. I swear
I just recently upgraded Arduino to the latest version and of course had to do the same with Marlin Firmware. To give you an Idea, the Arduino version was 1.0.5. "Yeah its been awhile since I checked for new updates"
Anyways needless to say there were many updates and features I had to reset and discover. The one that's giving me trouble is the Auto leveling feature with probe.
I know how it works but my question is; there used to be a way to set the raised height before the homing of Z.
I'm not speaking of the three settings of Auto leveling but a height setting when homing the Z probe. As in a G28 command just before the probe/servo is enabled.
Do you know where that setting is now or if it even exist?
Crashed the bed twice now because it does not lift high enough before a Z probe. Have to remember to raise the bed if the last job does not finish high enough.
Thanks again

It's right below where you set the offsets for the probe.

This is the one you want. My z probe offset is -2.1, so 5 works fine.
#define Z_RAISE_BEFORE_PROBING 5 // How much the Z axis will be raised before traveling to the first probing point.

Stephenrc

Thanks for responding.

Thats what I thought; but if so something has changed since the older version and new.
I transferred these setting from older to new version. You would think this would work the same as before " nothing changed in my setup" but it has crashed twice by not lifting high enough after restarting a bad print job. "nozzle at its lowest point when restarted and probe can't swing all the way down"
Well I'm sure your right so I will play with that setting till it's not possible to crash.
Thank you for verifying Stephenrc
I will give that a shot.

#define X_PROBE_OFFSET_FROM_EXTRUDER -25 // X offset: -left [of the nozzle] +right
#define Y_PROBE_OFFSET_FROM_EXTRUDER -10 // Y offset: -front [of the nozzle] +behind
#define Z_PROBE_OFFSET_FROM_EXTRUDER -14.95 // Z offset: -below [the nozzle] (always negative!)

#define XY_TRAVEL_SPEED 8000 // X and Y axis travel speed between probes, in mm/min.

#define Z_RAISE_BEFORE_PROBING 25 // How much the Z axis will be raised before traveling to the first probing point.
#define Z_RAISE_BETWEEN_PROBINGS 10 // How much the Z axis will be raised when traveling from between next probing points.
#define Z_RAISE_AFTER_PROBING 7 // How much the Z axis will be raised after the last probing point.

I noticed a new setting in RC4 that could be the fix, it's right after where you can invert the motor direction. It's commented out by default.

#define MIN_Z_HEIGHT_FOR_HOMING 4 // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...

Yup
Thats it. I guess I missed it among all the other new settings.
Thanks !