What am i doing wrong w/ the ir probe??

mikebridge

I'm using DC42's ir probe w/ a duet wifi board, on a modified tronxy x5s corexy machine, and this is what a mesh grid scan looks like:

but when i slap a level across the bed and just look for a gap along the bottom, if anything, the middle of the bed is sagging by ~.2mm (i can slip a narrow strip of paper under it, but i feel a light drag)

peirof

try to put a flat surface over your bed, and try compensation, like a glass…

mikebridge

@peirof:

try to put a flat surface over your bed, and try compensation, like a glass…

I've tried it with multiple flat materials over the aluminum mk3 bed, and get similar results each time, what i'm finding confusing is the mesh grid compensation shows the bed curving 'upwards' in the middle, but when i use the edge of a level, its actually sagging in the middle (or am i misunderstanding what the compensation is doing? is it showing me how much its going to compensate in various locations?)

Dougal1957

what colour is the surface that the probe is looking at?

mikebridge

@Dougal1957:

what colour is the surface that the probe is looking at?

i've tried semi-matte aluminum (the mk3 heated bed), a buildtak knock off, and the weird fiberglass/circuitboard sheet the tronxy comes with, all surfaces show a similar result.

Dougal1957

try a piece of Black paper/card under a piece of glass
the IR sensor doesn't always like some surfaces

mikebridge

@Dougal1957:

try a piece of Black paper/card under a piece of glass
the IR sensor doesn't always like some surfaces

i picked up some float glass & high temp spray paint today, and the weather here should be above freezing tomorrow, so i'll try to get the glass cut down to the bed size & one side spray coated, then report back in a few days what the result is.

dc42

Your height map shows 2 characteristics:

1. Consistent low values at low Y. I suspect that the sensor is probing very close to the edge of the bed at these points, or there is some feature of the bed along that edge that is affecting the trigger height. It could also mean that you have a Y axis mechanical problem at low Y.

2. A "random" variation This is probably caused by variations in the bed surface causing the IR sensor trigger height to change; although it's also possible that is it caused by excessive friction on the Z axis.