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I am building a dolly and I am confused as to which proximity sensor to use.

Should I go for M8 or M12 and 5 V or 6-36 V?

What should be the best detecting distance? Should it be 2/4/8 mm. Which one should I select?

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  • $\begingroup$ I'm using LJ18A3 - 8-Z / BX DC6-36V to 12V works great! $\endgroup$ – Fernando Baltazar Mar 22 '18 at 2:29
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Tomas Sanladerer has produced a nice video on this topic: https://www.youtube.com/watch?v=il9bNWn66BY

@ 7:31 you see an overview of the precision of various sensors, including the ones you mention. It appears that the M12-4 and M18-8 sensors are more accurate than the M8-8.

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  • $\begingroup$ I saw it, that is what made me more confused and i asked this question. $\endgroup$ – Jose Ben Mar 21 '18 at 13:22
  • $\begingroup$ It depends on your surface. Inductive works for Aluminium heat beds, but not when covered with glass. Capacitive sensors are inaccurate and should be avoided. The touch sensor types work with all surfaces. $\endgroup$ – 0scar Mar 21 '18 at 14:02
  • $\begingroup$ 5v or 6v-36v which one should I use??? $\endgroup$ – Jose Ben Mar 21 '18 at 15:34
  • $\begingroup$ I'm using the LJ18A3 - 8-Z / BX DC6-36V 8 mm Inductive Proximity Sensor NPN @ 12V using an OptoCoupler module. $\endgroup$ – 0scar Mar 21 '18 at 18:56
  • $\begingroup$ What is the surface of your heat bed? Glass or aluminium with tape? $\endgroup$ – 0scar Mar 21 '18 at 19:57
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As always cost will be a factor. I found the M4 sensors to be be just not good enough, they have to be too close, and eventually it's going to catch on your print and damage sensor mounting and/or the hot-end assembly.

The 8mm range sensors seem like a good distance, but you'll need to decide between a wider, heavier but cheaper model or the think, lighter more expensive model.

If your goal is to optimise for speed, go the lighter version.

In terms of sensing accuracy, if your layer height is typically 0.2mm then I don't think there's much point paying for more accuracy.

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Duet3D has a very nice overview. It totally depends on your demands. e.g., accuracy, different build surfaces, tolerance. Personly I realy like the piezo. It actually uses your nozzle to 'touch' the bed. So 0 height is absoluty 0. This eliminates the need for Z-offset.

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  • $\begingroup$ You still need to set up z-offset for the piezo. docs.wixstatic.com/ugd/… Whilst there is no x or y probe offset as the probe is the nozzle, and this is one of the most advantageous features of this system, there does need to be a slight Z offset as the assembly bends slightly on probing. $\endgroup$ – Makotosan May 15 '19 at 21:05

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