My RevE Z-height learnings

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zemlin
Posts: 467
Joined: Thu Feb 04, 2016 9:32 pm
Location: Indianapolis, Indiana

My RevE Z-height learnings

Post by zemlin » Sat Apr 23, 2016 2:06 pm

I just started working with a Rev E machine. I have a few build platforms of different thicknesses and so I've been working out how to account for the different heights and how to confirm those settings. I run my printer through OctoPrint, so running the quick start with each change isn't a viable option, and it would also be rather slow going.

It's still a work in progress, but I thought I'd share what I've learned so far here. Much of this info has been shared by Scott @Makergear, so thanks for the great support.

When you run the QuickStart app, it finds and offset value for the bed and saves that in the EEPROM settings.

When I change build platforms I can manually enter a new offset and save the new value EEPROM using a few simple G-Code commands.

M503 will display the print settings currently stored.
The offsets for X Y and Z axes are displayed following M206.
My printer is currently setup with a 1/4" MIC6 plate wearing 1/16" PEI.
Here's what my M503 response looks like on the OctoPrint terminal window:

Send: M503
Recv: echo:Steps per unit:
Recv: echo: M92 X88.88 Y88.88 Z1007.70 E471.50
Recv: echo:Maximum feedrates (mm/s):
Recv: echo: M203 X200.00 Y200.00 Z25.00 E25.00
Recv: echo:Maximum Acceleration (mm/s2):
Recv: echo: M201 X2000 Y2000 Z30 E2000
Recv: echo:Acceleration: S=acceleration, T=retract acceleration
Recv: echo: M204 S2000.00 T3000.00
Recv: echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
Recv: echo: M205 S0.00 T0.00 B20000 X10.00 Z0.40 E1.00
Recv: echo:Home offset (mm):
Recv: echo: M206 X0.00 Y0.00 Z2.77
Recv: echo:PID settings:
Recv: echo: M301 P25.89 I1.94 D86.53
Recv: ok

M206 is the line that shows the current Z offset value.
I got M206 Z8.86 after running Quick Start with the glass+Kapton.

I have a piece of 3/16" G10/FR4 that I use with glue stick for Nylon. That needs a Z offset of 7.36. It is 1.5mm thicker than the glass. A smaller value in the Z-Offset moves the starting point AWAY from the extruder nozzle. Thicker plates will have smaller Z-Offset numbers.

To reset my printer back for the glass plate I would send
M206 Z8.86
M500

The M206 command sends the new offset value.
M500 stores that value to the EEPROM.
It does not appear that this has an immediate impact. I have to HOME the Z-Axis after the M500 in order for the new offset to take effect. I do that with the HOME button on the OctoPrint control tab, but it could be done from the terminal with the following commands:

G91 ; absolute mode
G28 Z0 ; home
G90 ; relative mode

<Still working out the finer details of this part, so there may be a revision as I learn more>
Now if I want to confirm the Z-Offset setting with the blue shim stock I send

G1 Z0.13

That will move the Z-Axis within .005" or .13mm of the nozzle. If there is too little or too much drag on the shim, you can send G1 commands with more or less clearance to determine the adjustment needed to your Z-Axis offset.

When you send a new M206 offset and save it with M500, you will need to HOME again before the new offset takes effect.

I always send an M503 after the M500 to confirm that the setting was saved as intended.

Scott suggested making custom control buttons in OctoPrint to store settings for different build platforms. I haven't gone there yet, but it sounds like a great idea.

wbp
Posts: 13
Joined: Sat Oct 22, 2016 8:44 pm

Re: My RevE Z-height learnings

Post by wbp » Wed Nov 02, 2016 12:06 am

This is a great article, thanks!
One question though, don't you have G90 and G91 reversed? I thought G90 was Absolute and G91 Relative positioning.
William

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Jules
Posts: 3144
Joined: Wed Jan 21, 2015 1:36 am

Re: My RevE Z-height learnings

Post by Jules » Thu Nov 03, 2016 3:47 pm

Excellent process writeup! (So we can find it again in a few months to direct other folks to, would you consider editing the title to contain the words "How To".....something like "How To Adjust the Z-Height for the Rev.E machines with G-Code". :D

It's the only way to find them with the search engine. (Or maybe insta could sticky it.)

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