Z Home Question

Hi all,

Still a noob, so just a heads up.

I've got the Z homing sorted, I hit home in pface and it homes nicely (maybe a bit close but that's easy fixed)

However, when I start a print X, Y then Z all home, but when Z homes it drops down gets close the bed as expected, then comes back up, then back down but maybe 0.1 or 0.2 higher than where home should be, then prints from there?
SO nothing really stick to the bed properly because it's to high, but when I test home it looks good?

Any ideas? I'm thinking I might just start over with a new config.

Cheers, Craig.

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xxilim
However, when I start a print X, Y then Z all home, but when Z homes it drops down gets close the bed as expected, then comes back up, then back down but maybe 0.1 or 0.2 higher than where home should be, then prints from there?

That is what is supposed to happen. The nozzle should be 1 layer height above the bed when extrusion starts.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Oh... I though it started at Z0 thanks DC42

Is there any way to reduce how high it lifts on the first layer? I feel like it's to high and that's causing the first layer to release?

I've been using UHU glue stick on a glass buildplate and no Kapton tape.

Cheers, Craig.

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xxilim
...Is there any way to reduce how high it lifts on the first layer? I feel like it's to high and that's causing the first layer to release?...

You could set your zero lower than bed surface in the config.g but would not be right - when I start a print I keep an eye on the first perimeters of the shirt, if it look too high I manually lower the nozzle by turning the z-treaded rod counter clockwise a couple of clicks, one full turn is 0,8mm = 50 feel-able clicks from the stepper, 0,8mm/50 = 0.016mm per click

I mounted a 8 arm star nut on top of the z-treaded rod for easier access



Erik

Quote
xxilim
Oh... I though it started at Z0 thanks DC42

Is there any way to reduce how high it lifts on the first layer? I feel like it's to high and that's causing the first layer to release?

After homing the Z axis, you could use a G92 command to tell it that the head is a little higher than it actually is. For example, if your Z homing sequence leaves the head at Z=0, you could send G92 Z0.1 after homing to make it think the head is still 0.1mm above the bed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The problem is likely to be that the Z home position that you think is at 0 is really a bit too high. Set your zero position 0.1mm or so lower and it should be OK. The infill on the first layer should be solid with no ridges or gaps. If the zero was too high the infill will have gaps between the lines, if too low it will overlap giving ridges. If way too low the nozzle is effectively blocked and the extruder will start missing steps (skipping). Having the zero slightly too low can help with bed adhesion, but the print will have a slight lip at the bottom that needs to be files off.

Dave

Edited 1 time(s). Last edit at 05/25/2015 09:03AM by dmould.