Sourcing a high accuracy distance sensor - 3d Printer bed

Hi All,

I have recently decided to recommission my MendelMax 1.0, albeit with some slightly ure-designed plastic parts.

I’ve come to the point of bed leveling. The current manner for completing this, is every so often using the software to manually control the print head, moving it to certain locations on the bed, and lowering it to it’s 0 point, in order to just pinch and hold a single sheet of paper between the bed and print-head nozzle.

I figure it would be much easier with a high-accuracy, high-repeatability optical distance sensor.

I need it to repeat 0.1mm, although I’m having trouble sourcing one.

The plan is to set 8 locations on the bed, 4x corners, 4x sides, and just have the code move the head to each point, measure the distance, and if there is an issue, stay in that location, measuring again every 10 seconds, until I have adjusted the screws to within the predetermined tolerance.

Does anybody know of where to source a sensor or have another idea which would improve this process?

I figure the sensor should be mounted to the extruder, above the hot end, so it can be permanently attached, and not get in the way of the printer when in operation.

Thank you guys. - Once I source a better option I will generate a model and upload it to thingiverse so it’s free for all to use.

Wenglor has high performance distance sensors with 0,8 µm resolution. Part Number PNBC004.

https://www.wenglor.com/index.php?id=925.

Don’t know what it costs …

Many manufacturers offer precise optical devices for distance sensors.

If I understand your problem correctly, you are attempting to verify a plane parallel to the bed. If the plane is out of parallel, you make an adjustment to the bed.

If that’s correct, it sounds like you need a milling machine tool height presetter, but in reverse. A highly repeatable switch that triggers after 0.1" (or whatever you need) of motion attached to the print head would work. Is that correct?

I’m wondering if you could not achieve the same solution by using the nozzle as a capacitive distance sensor antenna to the bed. I don’t know how this matches to your particular 3d printer, but an Arduino should come a long way and more cheaply:

http://playground.arduino.cc/Main/Capac … n.CapSense

As distance to the bed goes down to zero, the capacitance should increase sharply (theoretically to infinity). The nozzle shape and remaining plastic on it might create some repeatability problems though. As the nozzle is stepping down in height (slowly) the changing capacitance is recorded and a distance-to-bed is predicted based on the slope/rate of change of the asymptote. As distance is inversely proportional to capacitance. Depending on the repeatability of your vertical positioning axis you may get the desired accuracy. Just a thought if you don’t mind getting creative.

I should have thought of capacitance! Last time I was discussing the issue of automated tool height setting, it was for a milling machine where capacitance obviously won’t work because everything is cast iron and steel.

Good idea.

And why would that not work with cast iron and steel? Anything conducting and having a surface would act like a capacitive plate.

Because there is a direct conductive path between the two things you need to know the distance between: cutting tool and table.

Ok, I wasn’t thinking fully with both hemispheres apparently. So the point was electrical isolation, not really the type of metal.