Prusa i3 z axis problem (drives into a bed)

Hi,

I have prusa i3 though I have not used it for long time and since then reinstalled my system and lost all the configuration etc. I got back to use it recently and have one problem. When I home the printer everything works fine, endstops etc. and printer homes as it should. But when I start a print after the bed heats printer drives the extruder past the end stop and into a bed. Any sugetions/ideas how to solve it? It is quite strange for me, I don't know what I missed but last time I used it few moths ago I did not have this problem..

Greg

Make sure the end stop is triggered properly. Use M119 and see if it triggers when the end stop is triggered manually. Also make sure the homing direction is setup properly and the axis is not inverted. When you home and move the axis, does it move as expected?

Yes axes move as expected and home as they should, end stop works perfectly then but when I start the print thats when it does not stop on the end stop (I will use M119 later when I'm home, but I expect it to work.). I find it all strange to be honest, I might miss something obvious?

May it be caused by something that Slicer does with Gcode? Would anyone care to look at my config.h? I would apreciate.

Please post config and gcode (as downloads/attachments please, not directly in the post).

Hi, attached, thanks in advance.. Regards!

So, anyone have any ideas?

The gcode looks fine. Except that the extrusion width is set to 0.4 and the nozzle is the same as the extrusion width, better to use 0.5mm.

You have the z offzet set to -10.88mm. Check if the probe really is offset that much from the nozzle:

#define Z_PROBE_OFFSET_FROM_EXTRUDER -10.88

Try manually homing and levelling:
G28
G29

Then move the Z axis down by 1mm increments until it hits the bed. Use a sheet of A4 80g paper, it should just fit under the nozzle with a bit of light friction. Read the z position, this should be used as the new Z offset. Either use the display if you own one or the gcode
M114

Edited 1 time(s). Last edit at 10/13/2015 04:09PM by imqqmi.

Hi, thank You for help. When I follow your steps after M114 I get:

SENDING:M114
X:58.00 Y:58.00 Z:0.00 E:0.00 Count X: 58.00 Y:58.00 Z:0.00

But if I set it as new offset (0,00 that is) in Marlin, then instead of driving into a bed during print it hovers over the bed few millimetres, so I guess that is it but how should I tweak it? My Z endstop is at the bottom. G28 and G29 works as it should (whatever offset I set for Z) does not drive into bed or hover over, just when I start print things happen..

What position does m114 give you just after g29? Make sure you're within the time out after which the auto bed leveling is invalidated.

Try this with z offset at 0
G28
G29
G1 X100 Y100 Z0

Now move the nozzle down manually and note by how much, use thisas your new z offset.

Quote
imqqmi

#define Z_PROBE_OFFSET_FROM_EXTRUDER -10.88...


...Then move the Z axis down by 1mm increments until it hits the bed. Use a sheet of A4 80g paper, it should just fit under the nozzle with a bit of light friction. Read the z position, this should be used as the new Z offset. Either use the display if you own one or the gcode
M114

sorry Im going to butt in here with my own problem, so im having problems with it printing too far above the build plate. Are you saying that to fix this i need to simply move the nozzle to just above the build-plate, then replace the value in my "Z_PROBE_OFFSET_FROM_EXTRUDER" variable with the distence that i had to move the nozzle? I've been trying to manually move the posistion of the end-stop. this sounds like a much better option.

I'm not sure this will work without auto bed leveling but you can certainly try. The problem is that you need to go beyond the end stop location for it to work. A probe with servo can move the probe out of the way, or in case of an inductive probe it'll trigger before the nozzle hits the bed. You can make it work with an optical endstop if you set it up right. But it won't level the bed of course.

Do you have anything in the custom Gcode section?