Calibrate Z probe offset

Written By: Filip Goc (and one other contributor)

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Difficulty

Moderate

Steps

Time Required

Suggest a time??

Introduction

ALERT (optional): NEW PROCEDURE that is simpler and does not require computer at http://bit.ly/Jellybox-OneNote-Guides. (It's unpolished, but correct.)

Step 1 Position the printhead

Remove any filament from the nozzle.
Put a sheet of a common office paper on the bed and keep lowering the nozzle until you can just barely move the paper.
This puts the nozzle just shy of touching the printbed. That's our goal.
PRO TIP: you can simply rotate the Z leadscrew with your hand to lower the printhead. No need to turn on the printer yet.

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Step 2 Position the z probe

We want to position the probe so that it is about 2.5mm away from the bed if you're using a steel bed or about 1mm away if you're using an aluminum bed.

First, loosen up the z probe mount with your M3 hex key (2.5 mm)

Then, use a small IMADE3D zip tie as a spacer to get the right gap with ease. The width of the zip tie is ~2.5 mm, and the thickness is ~1mm!

We want to position the probe so that it is about 2.5mm away from the bed if you're using a steel bed or about 1mm away if you're using an aluminum bed.
First, loosen up the z probe mount with your M3 hex key (2.5 mm)
Then, use a small IMADE3D zip tie as a spacer to get the right gap with ease. The width of the zip tie is ~2.5 mm, and the thickness is ~1mm!

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Step 3 ALERT: NEW PROCEDURE

While this guide can be used as-is, there is a simpler procedure that does not involve using computer at all.

While this guide can be used as-is, there is a simpler procedure that does not involve using computer at all.
You can find draft of instructions (unpolished but correct) at http://bit.ly/Jellybox-OneNote-Guides

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Step 4 Connect the Jellybox to the computer

Use a USB cable to connect the Jellybox and the Computer.

Use a USB cable to connect the Jellybox and the Computer.
Turn the printer on.
Open Printrun application and connect the printer.
Our Connect to a computer with Printrun via USB shows step by step how to acquire Printrun and connect your Jellybox.

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Step 5 Find the offset part I

Follow the video walkthrough to find and save the correct z probe offset. Gcodes used in the video follow:
M851 Z0; Set Z probe offset to 0 (this is missing in the video; sorry)
G28; home the axes
G29; level (tram) the bed
G1 X50 Y30 F5000; position nozzle for easy access
G1 Z0.0; drive nozzle to Z origin
G92 Z10; make printer think it's 10mm above origin
M114 Z; read the value a and computer the offset = 10 - a + 0.1

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Step 6 Find the offset part II

move the nozzle towards bed until a sheet of paper just barely slides underneath
M114 Z; read the value a and computer the offset = 10 - a + 0.1
M851 Z-offset; set the offset as a negative value (!) of the result of previous step
M500; save to EEPROM so as the value is not wiped out on power cycle
DONE!
This process only gets you into the right neighborhood. There is variance in thickness of paper you're using and in the subjective feel of the paper sliding. You may need to further tweak the z probe offset with M851 while you watch the printer print until you get the perfect first layer.