So since the auto-leveling on our new Delta Go printer uses the nozzle itself

3D Printing
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@Shai_Schechter , I haven’t had the time to play with the idea, but remember http://airtripper.com/1338/airtripper-extruder-filament-force-sensor-introduction/ ??

If you put the strain sensor at the other end, you could measure both filament force, and head deflection. Would make for an awesome touch probe that used the nozzle, and also as an indicator of nozzle diving, filament skipping, etc.

I need a different amplification circuit for it though, the amplifier I had drifted a lot over just a small amount of time.

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@ThantiK not sure how that works. I didn’t read the article, just looked at the images.

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@Whosa_whatsis Good point on the X/Y offset… completely forgot about that. The distance between the nozzle and screw is less than 10mm if I remember. So an offset might not even be needed because it’s such a short distance and our bed doesn’t deviate more than 0.15mm for sure I would say.

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@ThantiK ​ you should build a prototype.

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@Stephanie_A I already have – I need a new amplification circuit, and to be much better with software than I am now.

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Why not perform leveling after the effector is hot? It would then squish the plastic to a negligible thickness.

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@Shai_Schechter That depends on what you’re actually compensating for. If you have a flat bed that’s just slightly out of square with your Z axis, and everything else is correct, it’s probably close enough. If it’s something else, such as a slightly bowed platform or something higher up misaligned (which you have no other obvious way to test for), the offset makes a much bigger difference.

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@ThantiK I’ve got a microswitch setup on my Cerberus delta. The hot end is on a plate with a pivot on one side of the effector, and a microswitch opposite. Tip movement is maybe 0.1mm max to trip the switch, which is easily corrected for. https://lh6.googleusercontent.com/-MWM4rIJsiH8/Uu_avR31dMI/AAAAAAAAWDA/kC-LwlVeIGA/w269-h478-no/0203141020.jpg
Some day I’ll do a sensor based on what’s inside CMM touch probes. It’ll make it more crash resistant as a plus.
Search “Diy CNC touch probe” in the usual places for ideas. More good ideas over at http://cnczone.com.
Modern touch probes use the same kinematic setup for crash protection mostly, fine sensing uses strain gages.

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this thing works great for autolevel, a lil pricey but worth it

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@Mark_Fuller ​ idea is what I was thinking of. It’s an easy way to get accurate detection. You can fine tune it with springs, etc. The hotend doesn’t need to move a lot, and it can also provide a little protection in case of a head crash.

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@Mark_Fuller that’s the method that I use for my own personal delta. I love it, but boss doesn’t. We have to take lots of things into account that don’t really have to be taken into consideration on a hackers machine.

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On the same method, you replace the switch with a load cell like @ThantiK ​ said. We should really be looking into it. Repraps need to close the loop.