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Ir probe for Fisher

Posted by Aledt 
Ir probe for Fisher
June 18, 2019 07:08PM
I'm thinking of adding one of dc42's ir probe boards to my (modified) fisher beta, however mounting it under the effector will be a problem as the Z distance from the base of the effector to the tip of the nozzle is only 17mm and the board is ~18mm high and needs an extra 1mm of clearance.

As I see it I have 3 options to mount it-
1, mount it to the side of the effector
2, shim the hot end mount to bring the nozzle 2mm lower.
3, redesign the effector with a recess in the base to mount the board higher.

I've already designed the mount to attach it to the side but it will put the ir sensor 31mm horizontally away from the nozzle, is this going to be to far for the leveling to compensate for?

Number 2 I thought might work by putting an extra nut or spacer on the bolts that secure the heatsink, would need slightly longer bolts, might make it wobbly and it feels a bit like a bodge.

The right way is probably number 3 but it's a lot more involved so I'm leaning towards trying out the mounting it to the side of the effector as long as it's not going to be pointless due to the large offset from the nozzle.

Any thoughts before I pull the trigger on buying the board?
Re: Ir probe for Fisher
June 19, 2019 01:48AM
The problem with using any type of offset Z probe on a delta is that any slight geometric inaccuracy in the construction of the printer will cause the tilt of the effector to vary slightly as it moves in the XY plane. That will cause the relative heights of the nozzle and the probe to change, causing and apparent change in trigger height. The greater the distance between the probe and the nozzle, the greater this effect will be.

What bed surface are you using? The IR sensor works very will with a bed surface of blue tape, but not so well with transparent bed surfaces such as glass and PEI.

Edited 1 time(s). Last edit at 06/19/2019 01:50AM by dc42.

Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Ir probe for Fisher
June 19, 2019 02:46AM
I'm using the standard buildtak sheets (black).

Won't any tilt be constant each time and compensated for once the initial setup is done?
My problem with the fishers original bed probe design is the force needed to push the bed off the stops is never consistent, remove and replace the bed and it throws the calibration out the window.
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