IR Probe Setup - some questions and Results during setup

[McAdam]

So I spent the best part of 3 hours yesterday converting my manual adjustment bed to use the IR Probe instead.
Firstly, there's a lot of documentation that's in lots of different places, so every time I came across an issue I would have to Google and try to find a solution. David (DC42) Maybe I'll write up a list of what would be good to change in the wiki and your blog post.

The Repeatability Test
I decided to run a repeatability test, to see why my mesh seemed very odd, and have come up with results that vary a bit - but might be within tolerances - that's where I need your help

This is all done on a PEI Sheet that has been used heavily over the last few months and sanded to a dull matt finish (Its supplied by Lulzbot).

Probing Script added as a Macro:

[[Gcode]]
;Probe 1
G1 Z30
G30 S-1
 
;Probe 2
G1 Z30
G30 S-1
 
;Probe 3
G1 Z30
G30 S-1
 
Etc....
 
;Probe 15
G1 Z30
G30 S-1
 

Results

Just Bed:
Average: 0.609
High: 0.620
Low: 0.600
Difference 0.020

Bed with Tape on top:
Average: 2.193
High: 2.197
Low: 2.188
Difference 0.009

Is a Difference of 0.020 acceptable?

Results of Auto 4 Point Bed Compensation

Homing z Axis then adjusting "Fixed" adjustment screws

Re-homing then checking again

Setting home point to same as one of the 4 probe points

What I can tell by doing these tests is that my Z Home point was significantly higher that any of the other points… Which shows in the:

Mesh Bed Compensation results
So after all the really fine tuning to get the 4 point compensation as level as possible, here are the results of the Mesh Bed Compensation

So…

Is this all acceptable?
Is this within "reasonable" tollerances?
I haven't managed to print anything with the mesh on, because during testing I snagged my Extruder Motor Wires, so need to do some soldering to repair it.

When I look at the images above a part of me feels that its time to replace the PEI Sheet… But what do you guys think??

Thanks for all the help!

Edit: Fixed image links

[dc42]

Please can you supply the complete URL to your images.

The large difference in trigger height with the tape on/off suggests to me that the PEI isn't painted black on the underside.

[McAdam]

Ok, So I made an assumption that my PEI sheet was working ok with the IR Probe
You are correct, the underside of the PEI is not painted - but the surface is very dull and matt looking as opposed to the usual transparent PEI.
You are correct again, The tape measures only 0.15mm thick so the difference should not be that big. So I guess the IR probe is somehow going through the PEI Sheet (which is about 1.3mm thick)….

Damn - I read that there was a chance sanded PEI would work with the IR Probe - I guess not in my case.
The issue is these PEI sheets come with the 3m Adhesive already attached - and none of the other PEI sheets I have tried have worked well for me.

I guess its time to look for another probe then