Manual Z Probing

The IR Z-Probe doesn't work for me - in the morning it will measure different values to the evening, depending on the lighting in the room / florescents / shadows etc. I can't even use it to calculate the axis compensation because it gives different results at different places on the board.
I've taken to using one of those spark-plug gap testers to manually moving the head.

What I wanted to mention is that I saw a printer where the hot-end is sprung and has a switch behind the spring, so when the head is driven into the bed it lifts and presses the switch. Then a simple calculation gives the height above the bed. Thought that was a fairly clever idea - anyone have similar ideas that could work with the Ormerod?

I think that is essentially the same as Kim Brown's probeless technique as described here . The Ormerod head is not sprung but does have a bit of rotational give and combined with gravity gives the equivalent of a spring. The switch then detects a bit of rotational displacement. Dc42 mentioned he was checking the same idea but with a force sensitive resistor rather than a micro-switch to detect the displacement.

Both have the advantage that the hot end tip is used effectively as the reference but this means it must be used hot to avoid any remaining plastic disturbing the result.

The sensitivity of the supplied IR probe to light has been covered many times in this forum. It's fine with fluorescent light AFAIK and with LED light, but not with direct sunlight or incandescent light (especially halogen).

I have been selling a modulated IR sensor board that is about 100 times less sensitive to light than the supplied IR probe. See this thread [forums.reprap.org]. I still have a few boards that I can populate as kit 2 or kit 3. RRP also has a modulated IR sensor under development. More recently I have been looking at capacitive sensors, inductive sensors, solenoid-activated probes, and differential modulated IR. See this thread [forums.reprap.org].

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes I'm very happy with the MicroSwitch. Having nothing other than the HotEnd hanging down has been a particular advantage, as there's nothing to tangle with the Skirt of a print, and drag it into the nozzle. Since fitting, it's been 100% reliable. Do bare in mind that you need to do the transition from probe to probeless in a couple of stages.
1) Fit an X-axis MicroSwitch (I have an adapter arm on ThingVerse that helps re-locate the MicroSwitch to pickup the X-carriage).
2) Then you can do away with the Probe, and sortout a mounting for the Z-axis MicroSwitch depending on your type of Fan-Duct.

I intend to add the mounting holes to Big Blue, and a Bracket to suit soon. In my tests I've used a MicroSwitch with roller that is always in contact with the X-axis.
It works very well, but I am now thinking that a better way might be to have a button type MicroSwitch that only makes contact when Probing.
I did think of using a servo with an arm and Switch on, but it seemed more of a gimick to achieve the same thing, and I believe in keeping things simple.
If it's simple, it's less likely to go wrong, and be more accurate..

Kim

PS In the Bracket I made to fit to my Big Blue, The mounting holes are slots... This allows adjustment for setting up, and aren't used after that.
Big Blue has to stiffeners either side of the HeatSink Chamber. I just drilled holes in mine and use two M2.5 cap head screws to fit it.

Edited 1 time(s). Last edit at 05/11/2014 06:47AM by KimBrown.

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Please send me a PM if you have suggestions, or problems with Big Blue 360.
I won't see comments in threads, as I move around to much.
Working Link to Big Blue 360 Complete

Quote
KimBrown
...It works very well, but I am now thinking that a better way might be to have a button type MicroSwitch that only makes contact when Probing...

my thoughts exactly, to take out the wear factor, should be enough free play to do that, could be made even more accurate with more leverage, as in if was able to detect on the top of x-axis, but there's too much stuff in the way (think you said that already), could be done from the other side of the x-axis, would require the extruder moved to another place, the bearing could do with a bit more leverage too, esp. on the acrylic rib, as it is now it's close to 1:1, same as you switch - but would not make sense to better the precision of the switch without doing the same with the runner bearing

Your switch is tracing the path of the bearing that sets the high of the nozzle beautifully, the only possible variable I see is the thickness of the acrylic part, and that is very small, 0.06mm on mine (from 4.61 to 4.67mm)

Nice and simple, well done!

Erik

I must remember to do more research before typing! I read those threads you mentioned dc42, and some of those ideas are great.
I will abandon this thread and comment in the others if necessary! :blush:

Hi Erik,..... sleep.sleep...I need sleep....

yes I wanted to move the switch higher, but there is to much clutter, what with the feeder clip... Cables, etc... Also I thought that moving it further away from the linear bearing, isn't a good thing thou, because it would increase the leverage moment on the HotEnd (put more pressure on it, I know it wouldn't be much, but it's a bit). Maybe a redesign of the X-carriage, where the switch was mounted near the 9mm bearing on the back of the X-axis might be better. But then I'm thinking it's adding complications. I think the simple solution is the best.


Kim

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Please send me a PM if you have suggestions, or problems with Big Blue 360.
I won't see comments in threads, as I move around to much.
Working Link to Big Blue 360 Complete

Quote
KimBrown
... I think the simple solution is the best...

Me too, let's mount a small grinder at the exact same hight and position of the nozzle and square the bed of before printing :-)

Erik