Piezo20 probe and piezo kit now available
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A hinge could be tricky guys. I'm thinking of the fact that I have 3 Bowden tubes sticking out at 28 degrees, 120 degrees apart. The extruders are suspended above the centre of the bed in a sort of counter balanced "flying" arrangement but there are cords attached between the extruder mount and the X carriage to keep the Bowden tubes in compression all the time. The Bowden tubes are only about 250mm long but the bed is 400mm square so there is some twisting force being applied at extreme corners of the bed which might dislodge a hinged mount.
However, perhaps I could do something with magnets or springs. Ideally, I'd like to have a "bolt less" mounting arrangement because I have a couple of Diamond assemblies made up complete with heat sinks, fans, heaters pt100s etc but with different nozzle diameters so it'd be good if I can swap between them easily. I quite fancy the idea of magnetic mounts.
Edit. Just read the bit about 0.2mm of movement. So a kind of restricted hinge or some method of arranging for there to be 0.2mm of flex should be doable. The weight of assembled Diamond is 250gms (nozzle, HeatSinks, cooling shield, fan, heater cartridge & thermistor). What sort of forces are we looking at for the Piezo sensor?
Cheers
Ian
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Minuscule forces to trigger it so long as the piezo element bends by that 0.2mm (0.15 is enough) when the nozzle contacts the bed. In my MkIII design you will see that the top of the clamp, which is the part that pushes up into the piezo is a certain diameter, the piezo is then supported by the top piece with a small recess to allow it to flex. This combination seems to apply the right amount of pressure to get a signal above the noise, and they're noisy things (basically they're guitar pickups). So whatever suits your printer, if the piezo is between two components with approximately these dimensions it should work. It doesn't matter if there's some preload either so you can eliminate almost all wobble that way.
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It would be relatively easy to arrange the pivot of the hinge to reduce movement of the nozzle to a minimum while providing a longer lever to actuate the piezo element at the top of the carriage. If you made the pivot removable you could switch hot ends with ease without affecting the piezo element.
Moriquendi
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So I've had a chance to play my minimal bodge job setup today got it working really well. Repeatably across my warped bed is far better than my FSR. I think I can do better, maybe something more sophisticated than a nut but I'm happy with it as I have no play in the nozzle at all for the moment. I'll upload pictures later but here is my mount for the Moriquendi PCB board for now.
https://drive.google.com/open?id=0Bxtr4ocyxEMsdVFFdHhQalR6TDg
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Glad you've got it working, they're a bit of a pain to setup but very sweet when they're running. I like the mount for the piezo board, currently mine are stuck with bluetac onto some rejected top pieces from my sensor design. It wouldn't load in slic3r but I ran it through 3dbuilder engine and it repaired okay. Would you mind if I added the mounting to the thingiverse listing with attribution to you?
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Be interested to see how you set yours up?
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Sure, feel free
was a bit lazy with the modelling so a few unwelded edges etc. 5 min jobby. Sliced fine in kissslicer though so I left it as is.Couple of pictures mine.
So principle is the same but the mount is a little different. Couple of badly taken photos, my wiring needs tidying up I know!
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Looks great nice neat lightweight way to do it.
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Need to solve now how to stop the bowden tube leaning onto the sensor at certain angles probe points giving it false trigger.
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I had not really thought about that. The piezo might be tolerant of another 0.5-1mm drilled out of it (or a new one) or put a top on that top part that holds the piezo, which is how I've done it, that could even have a guide projecting out of the top of it and the bowden could be almost interference fit with the hole (not quite or the piezo won't bend) to prevent it moving sideways and hitting the piezo.
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I had not really thought about that. The piezo might be tolerant of another 0.5-1mm drilled out of it (or a new one) or put a top on that top part that holds the piezo, which is how I've done it, that could even have a guide projecting out of the top of it and the bowden could be almost interference fit with the hole (not quite or the piezo won't bend) to prevent it moving sideways and hitting the piezo.
Hi everybody,
I follow your upgrade about piezo sensor for z probe mesh auto Bed leveling my prusa mk2 and you are in the final way i think!!! I would like to give my advise to finish the design and solve the problem of the bowden tube that cause false sensor respond…
Fix between the center of the Piezo and you top part this:
http://m.ebay.com/itm/191261810475?_mwBanner=1
First you Will have better result in the precision of your extrusion due to constant pressure of the filament (use 2 of it, one At the output of the filament box and the other between the Piezo sensor and the top of the heatsink of your HEAD E3d v6 Or diamond) like in the vertex K8400 3D printer.
second you Will increase précision of the Piezo sensor because it Will be fixe in 2 points ( center and on it's end of the diameter)…
I wait you feedback by testing this solution that cost 2€ more maximum ?If you prefer in full plastic mode you can download this very clever idea:
http://www.thingiverse.com/thing:1854549
Best regards,
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HI tesla_power (do you drive one?) and welcome, I think what you're suggesting is to mount the bowden coupler on the top part of the sensor assembly, this opens it up to those using non-e3d hotends, that's a great idea on the face of it, I will do that tonight its an easy thing to do.
Something like this:
Then I would envisage a PTFE guide tube dropping down from the coupler into the hotend? This will result in 0.2mm vertical movement on retraction as retractions will pull the hot end up. It doesn't matter from the point of view of triggering the piezo, as you aren't extruding or retracting when probing anyway. But it will introduce an tiny amount of poor filament control around retracts/unretracts. There is not space to put two bowden couplers, one on the top part and one on the hotend as yet, and also this means that the hotend would perhaps not move vertically enough up into the piezo. The other option would be to just push the tube through the coupler and all the way into the hotend, this migth work, the tube should have enough compliance to allow the 0.2mm of movement up into the piezo.
I will try all three of these options.
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I wonder whether you could use the extruder to actuate the piezo element as a way of checking the zprobe is working? A small extrude/retract of the filament, without heating the hot end, might move the hot end enough to actuate the element and confirm that the probe is working before probing the bed and risking a crash.
Idris
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That's a good idea Idris. I'm just going to try that now, it will definitely work if the hotend is cold and it just gives it a tiny tug.
Doesn't seem to pull hard enough to really see any rise on the probe value.
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That's a good idea Idris. I'm just going to try that now, it will definitely work if the hotend is cold and it just gives it a tiny tug.
Doesn't seem to pull hard enough to really see any rise on the probe value.
Hi,
Yes very good idea!
If you want look at this company about accelerometer (it's in FACT very small piezo) kit very easy to integrate in Any hotend and duet wifi board…https://learn.mikroe.com/mems-sensors-conversion-physical-world-digital-world/
Best regards,
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That's a good idea Idris. I'm just going to try that now, it will definitely work if the hotend is cold and it just gives it a tiny tug.
Doesn't seem to pull hard enough to really see any rise on the probe value.
Hmm, that's a shame, what's your retract speed? It should work in either direction, maybe you can apply more force by extruding, or build up pressure in the bowden tube then release it quickly. It's be great if it would work as it wouldn't require any hardware changes.
Just had a thought, you could prove the principal by manually pushing the filament at the extruder but with the extruder disengaged. Of course this wont probably work if your bowden tube coupling is in the hot end itself as there's nothing for the force to act against. I think this will only work if the bowden tube terminates on the end effector.
Idris
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Have you tried a short fast downward head move that is rapidly reversed?
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Moriquendi - I tried with cold extrusion allowed, 0.5mm at 80 mm/s, I can do this through the web interface console by manually ntering the commands, but if I write a macro
M302 P1
G1 E-0.5 F5000
G1 E0.5 F5000
M302 P0The console states, "unable to perform move due to heater fault" or something similar. So not sure why that is?
David - Not yet but I will.
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The firmware probably has cold extrusion protection, I think marlin had something similar when I was using a RAMPS, you may be able to turn it off somewhere.
A sharp Z movement of the head would work for delta printers but it wouldn't work for printers that don't move the head on the z-axis, or that can't move the z-axis rapidly.
Idris
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I tried turning cold extrusion protection off, which I can do from console, and then the extruder will move, but with a macro it ignores the cold extrusion enable and gets an error.
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I will try the head up/down see if that helps. It would work on Duet as you can see the sensor value but on Ramps or other firmwares, how do we detect a trigger if we're not probing, agreed this is not useful if the head is not moving in Z.
