Posts: 12
Joined: Sat Jun 07, 2014 2:26 pm

What am I missing? Auto bed-leveling

Sat Jun 28, 2014 9:51 am

I have a new Printrbot Simple Metal which uses an inductive proximity switch for the Z axis position. The prox. works fine as the software will allow me to home z in multiple locations on the bed when I do so through the manual controls.
While I am completely familiar with cnc controls this is my first 3d printer.

When I go into bed leveling it homes xyz as it should, just as it does when I press "home all" in jog mode, but when the machine moves to the the y stops where it should and the z axis comes down until it crashes into the bed even though the switch was made way before it did so.

I'm sure I am missing some parameter but I was up until 1am reading and I can't find it.

Thanks in advance!


Posts: 1
Joined: Thu Aug 28, 2014 9:20 pm

Re: What am I missing? Auto bed-leveling

Thu Aug 28, 2014 9:22 pm

Did you get any help? I am getting started and have the same question.

Posts: 183
Joined: Fri Aug 29, 2014 9:59 am

Re: What am I missing? Auto bed-leveling

Fri Aug 29, 2014 10:07 am

With the PrintrBot Simple's that have an autobed leveling probe, the Z-end stop mechanical switch is replaced with the magnet proximity sensor.

When "homing all", a G28 command is sent in which requests the printer to home the X Y and Z axis'. Since there is no end stop trigger on the z probe, the z-axis will indefinitely jog downward, and crash into the bed. In your starting G-Code you have to specify that you only want the printer to home in the X and Y axis. This can be done by changing the conventional "G28" command to "G28 X0 Y0". Afterwards, you will want the printer to get Z offsets by probing, this is done by issuing a "G29" command.

So, your starting G-Code should look like this for printrbot simple:

Code: Select all

G28 X0 Y0; home only X and Y
G29; probe for z offsets

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