sage12
Posts: 2
Joined: Wed Sep 12, 2018 10:03 pm

Z-Axis G-Code Offset

Wed Sep 12, 2018 10:05 pm

Hello,

I was wondering what the Z-Axis G-Code Offset in S3D actually does? Will the software make the the gap between the bed and the extruder nozzle "smaller" and ignore the Z stop limit switch? Using the JPEG as an example, from my understanding it will add 0.5mm to all the z-axis measurements in the G-code, therefore will it raise the bed closer to the extruder nozzle and go beyond the z stop limit switch.

This would be helpful as I would just have to be fairly close to the gap I want between the extruder nozzle and fine tune the final distance in the software.
I would worry that I might damage the switch if I would have it compressed more than it was designed for.

Mike
Image

S3D-Chris
Posts: 38
Joined: Wed Jun 20, 2018 11:52 am

Re: Z-Axis G-Code Offset

Fri Sep 14, 2018 10:47 am

G-Code Offsets are used if your prints are off-centered or too high off your build-plate. The G-Code offsets are a great way to fix that. For instance, if your prints are 2 mm too high off your build plate, apply -2 mm in the Z-axis. If your prints are 10 mm to the right, place -10 mm in the X-axis.

greybeard
Posts: 114
Joined: Mon Mar 02, 2015 1:23 pm

Re: Z-Axis G-Code Offset

Fri Sep 14, 2018 5:51 pm

Offsets are used to primarily to address Hardware setup. Not generally used for centering or adjusting Z.

On most machines, Z is adjusted via adjusting the Z-axis limit switch.

When you Home the machine, the nozzle should barely touch a piece of paper on the bed - a slight dragging is the 'sweet spot' for getting an excellent bottom layer on the bed (glass) side. Adjust the limit switch for this.

If needing to Center a part on the bed, ensure you have the correct bed/machine dimensions setup. The Centering of a 'part' is based on the machine dimensions as well as Offsets. But, Offsets are primarily used for machines where the extruder Homes off the bed area (such as to a Wiper and Debris bin).

As an Example: I installed V6 hot-ends that put the nozzle 14mm to left of the bed when Homed. So, I set the Offset to 14. The attached shows the Home (14mm to left of bed) and the Center of the bed where prints get centered.

Additional considerations for setting ToolHead Offsets and which Offset panel (the Process or Preferences) input fields to use require some homework and playing around to fully understand...
Attachments
Screen Shot 2018-09-14 at 3.46.09 PM.png
Screen Shot 2018-09-14 at 3.41.03 PM.png
3D Print Parts
https://www.thingiverse.com/Still_Breathing/designs

SWCNT
Posts: 27
Joined: Mon Jul 16, 2018 8:51 am

Re: Z-Axis G-Code Offset

Sun Sep 16, 2018 3:31 pm

Hi Mike,
Here's how it works
1) When you home the z-axis, the limit switch will engage twice then the printer will stop on the switch, that marks the HOME, or zero position. Any z-offset you have is ignored here.
2) The printer moves to print the first layer. The head moves up based on the layer height (e.g. 0.2 mm) but there's an additional height because of the gap between the bed and the nozzle when you used the business card for leveling. So the actual nozzle height is 0.4 mm (assuming the card was 0.2 mm thick) above the bed. If you have any z-offset, it will be added, so if you had +0.1 mm z-offset, you'd end up 0.5 mm above the bed. Same with a negative offset, except you will hit the limit switch and/or bed, so that's the practical limit for the negative. Yes, you can plow into the limit switch.
The z-offset is useful because you may find that with different materials and different bed adhesion methods, you'll need to make some fine adjustments. It would be a pain to adjust the bed for that every time or the actual position of the limit switch--cannot reliably move in <1 mm increments anyways. For example, you may find that sometimes the first layer segments aren't connecting. Small negative z-offsets can help that. You can accomplish similar results by using extrusion multipler and first layer width, but I'd argue that's not best practice. It's also handy on laser cutters, where you may want to finely adjust the position of a material with respective to the beam waist.

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