First Probe

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felich
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First Probe

Postby felich » Wed Jan 17, 2018 6:24 pm

I have moved on to the First Probe.
After calibration I did a GoZo with a piece of printer paper on the bed.
The tip comes down slowly and then there is a "tink" as it stops.
The paper is held so tightly that it tears when moved.
So I ran another First Probe and then another.
The tip still pins the paper to the bed.
The Configuration Guide says "If it's too loose, run the following GCode: "G31 P500 X0 Y0 Z-0.25", then run "G32" to recalibrate, then "M500" To save all your current calibrations and settings."
What to do if it is too tight?

wepollock
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Re: First Probe

Postby wepollock » Wed Jan 17, 2018 6:59 pm

I have a macro script in my build notes that addresses that concern.

Here is a repeat of the posts that apply;


I was having a concern whereby after I did G32 the hot end was pressing exactly into the bed after G0 Z0, with zero room for paper or a gauge. So my offset from the bed was not correct. To correct the problem I did a rinse and repeat flowchart. To fix a problem like this I used the following flowchart.

FLOWCHART

HOME
G31 <parameters go here, see notes below>
G32
M500
G0 Z0
Repeat

Understanding G31 Towards and Away

This is conceptually a bit difficult to gleam, in terms of offset.

The minus sign (negative increments) is going away from the bed
The plus sign (positive increments) is going towards the bed

So a command G31 P500 X0 Y0 Z-1 goes one millimeter away from the bed
Therefore a command G31 P500 X0 Y0 Z1 goes one millimeter into the bed.
The adjustments in the G31 command are not cumulative.

Progression

I am too close to the bed without an offset - so I need to offset away from the bed in the negative direction.

Iteration One

Home
G31 P500 X0 Y0 Z-.55 ; so i started here and worked my way down to -.40
G32 ; now that we have a trial offset lets autohome
M500; now lock this test case
G0 Z0; now lets see if the offset is good or not

Iteration Two
Home ; Repeat the process, take it from the top
G31 P500 X0 Y0 Z-.50 ; a little bit closer to the bed from Bed-.55
M500
G0 Z0

....

Final Iteration
G31 P500 X0 Y0 Z-.40 ; so i started here and worked my way down to -.40 with seven iterations
G32
M500
G0 Z0

Here is a macro you can use.



G28
G31 P500 X0 Y0 Z-.48 ; edit this line between each interation
G32
M500
G0 Z0
M117 "Measure Gap From Extruder to Bed - waiting for 30 seconds"
G4 S30
G28

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felich
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Re: First Probe

Postby felich » Wed Jan 17, 2018 8:14 pm

wepollock,

Most Excellent, Thanks.
Your macro was a big help.
I got down to -.35.

Now my G0Z0 comes out perfect!

So in the Configuration Guide Step Five where is says "If it's too loose, run the following GCode: "G31 P500 X0 Y0 Z-0.25""
I believe it should say "If it is too tight, run G31 P500 X0 Y0 Z-0.25"

wepollock
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Posts: 180
Joined: Wed Apr 19, 2017 7:18 pm

Re: First Probe

Postby wepollock » Wed Jan 17, 2018 9:31 pm

Felich... I had the same perception. That why I suggested - move away and towards the bed.

After home G28, you are finding zero by going negative towards the bed
In this case when you go negative in the G31 command you are going up.


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