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Auto retracting z-probe

by nophead, published

Auto retracting z-probe by nophead Apr 4, 2011

Description

A probe that can make Z measurements and then retract itself out of the way. It was designed for HydraRaptor but can probably be adapted for other wooden machines like Makerbot.

See http://hydraraptor.blogspot.com/2011/04/auto-z-probe.html

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Any suggestions on mounting this to a printer with a moving x-head (e.g. a Prusa Mendel)?
That solves a different problem, i.e. the bed being not flat, whereas I assume it is flat and compensate for it being inclined. The former leads to a distorted object, but the incline can be completely compensated for.

The best solution would be a combination of the two. I.e. fit a best compromise inclined plane through the points to incline the object and then modulate the Z coordinates with bilinear interpolation.

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Instructions

Print the parts, ream the 4mm holes in the guides so the rod slides freely. Drill the 4mm hole in the hat so that it is a tight fit on the rod. You could glue it but I haven't found that necessary. Press fit the two magnets oriented so they attract! Use a low force (e.g. 15gf) microswitch.

Mount as close to the axis of the nozzle as you can get and arrange the rod to be about 5mm above the nozzle tip in the raised position.

Attach a weight sufficient to operate the switch reliably.

Any suggestions on mounting this to a printer with a moving x-head (e.g. a Prusa Mendel)?
That solves a different problem, i.e. the bed being not flat, whereas I assume it is flat and compensate for it being inclined. The former leads to a distorted object, but the incline can be completely compensated for.

The best solution would be a combination of the two. I.e. fit a best compromise inclined plane through the points to incline the object and then modulate the Z coordinates with bilinear interpolation.
This is a very cool design. Simple. Practical. Not over-automated.
So this is a tool head with a micro-switch?

Was it an issue if the flat disc touched an object with it's border and thus applied levered force to the disc or was the micro-switch always sensitive enough?

Could be very useful in combination with an automatic change of tool heads.
It could be used as a stand alone tool but then it wouldn't need to retract.

I have only used it to measure the distance to the bed, so the shape of the probe doesn't matter. If I wanted to probe an object then I would sharpen the end of the rod to a rounded point. Then perhaps I could use it digitise one of those Makerbot printed vinyl disks :)
The probe sits next to the toolhead. You can see it in the last picture, but it's a lot clearer in the video (which is in the blog post).

This is very slick!
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