Piezo20 probe and piezo kit now available
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Its weird. Both P1 and P5 do more a less the same thing for me but get slightly less crashed heads with P5. When I send the command to probe and it tap the nozzle it will register the tap .
It's like seems to be a delay between the trigger of the sensor and duet reading the probe point before it pushes though the bed. I don't think its a sensitivity problem because sometimes it will trigger from just the movement of the effector.
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Sounds like you've got everything there, its just a case of finding the sweet spot where it triggers well. I might do a few videos later showing how I have it setup. You might have the clamp/piezo assembly tightened too much, try loosening it off a tiny bit. There is a zone where you find the optimum between a tight assembly/less sensitivity/firm nozzle, and a loose assembly/high sensitivity/wobbly nozzle. I say this as there is no delay as I have it setup the lightest touch of the nozzle gives an above threshold trigger.
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A question. Why all this trouble and not use a simple conductive touch plate with an known thickness? Same like most DIY CNCs use? Hot end could be wired constantly , led could be implemented for visual check if working, prior to test. Costs absolutely nothing. Plate could be moved sequentially manually to predefined places on heat bed. Is this possible with the Duet board?
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Because the end of a hot end nozzle is not a good contact, it's frequently coated in a layer of gunky/charred plastic.
Moriquendi
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Boytan
It would be possible as it could be setup as a switch, and the firmware will accept any sort of trigger as an endstop. (The signal needs to be within the 3.3V range however that is manageable).
One issue is as Moriquendi described - inconsistant conductivity due to plastic buildup on the nozzle. The other issue is that many(most) bed surfaces are non conductive to you have to have the manual intervention of applying a conductive sheet to the bed.
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Yes I'd love to use a electrified nozzle and at one point I used to print onto aluminium and considered it. Plastic on the nozzle isn't really an issue if you probe hot. But now I print onto printbite which is super convenient and permanent and about as conductive as ceramic. I'd say most people are using glass or polymer surfaces of some sort.
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Updated the tuning guide (long post) above and included a video of how I have it setup which might make it easier to see what I'm on about. https://www.youtube.com/watch?v=F3vi6BOi6sA
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Awesome! I linked your post and the video from the Tutorials page:
https://duet3d.com/wiki/Tutorials#Experimental_FeaturesAlthough at the rate this is progressing it wont be experimental for much longer.
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Next iteration is to make the nozzle wobble disappear almost completely, I had in mind attaching the upper part of the piezo sensor module to the lower with small smooth rods (or delrin rods?) which would slide into the lower clamp part, and if metal, could be greased. This would result in a very firm nozzle constrained laterally but free to move upwards by a small amount to flex the piezo disc.
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DJ
PTFE rod is quite cheap and would probably be a better choice than Delrin or steel (Has self Lubricating properties IIRC).
a 500mm length of say 10mm Diam is about £2.50 from one of my local suppliers it is available in 4,5,6,8,10 mm diam plus a lot bigger as well.
https://www.directplastics.co.uk/ptfe-rodLook forward to seeing your design for it lol
Doug
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Well here's a preview:
I've modded Lykles version as he did his in proper CAD with all the holes geometrically correct etc..
Its pretty simple just 4 rods (in the only places they can go without redesigning the clamp (which is a bit beyond my cad skills TBH). Bonded at the top piece or interference fit, and then initially adapted to the clamp by manually filing the holes in the clamp lightly to achieve a fit that allows vertical movement but not lateral movement. Either that or drill the top holes to 4mm and the lower ones to 4.2mm or something like that. I'd grease them if it were steel but maybe won't need to with PTFE. My concern is maybe the PTFE will flex a little and reduce the stiffening effect I'm hoping for, which is why I was thinking delrin if not steel, which is also self-lubricating (although much more expensive and harder to get hold of).
What do you think? Very much open to ideas for a better way to do this.
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Hmm, would the wobble be decreased if we used a bigger peizo sensor?
In other words, have a wider base where the hot end is pressed into.Related, how big is the wobble and how does it show up in your printing quality?
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Problem with Delrin is getting anything smaller than 10 mm Diam.
a 500mm long piece of 10mm delrin is about £1.25 so is about half the price of PTFE but I can pop in and get it of the shelf so to speak
Would it help if I went and got a length of each and sent you say 100mm of each to try.
I would be tempted to drill the top at 10 but the bottom at 10.1.
Doug
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Doug. Thanks for the offer but 10mm is way too big for what I've got in mind. The whole assembly shown above is only 40mm in diameter and its convenient that it is, it fits inside an effector quite easily. It could be a little bigger but not to accommodate 10mm dia. rods. I'd also be concerned the friction would be quite high with that much surface area to try to slide on. I take your point about the drilling this is why I'd hand file it its easier to control the fit.
Lykle no the wobble would be less with a smaller piezo sensor, but then the sensor would flex less and be less sensitive. This might work with an FSR if there is one with a 4-5mm hole in the middle?
My first attempt at this version is going to be steel as Im sure I've got some thin rod lying around, doesn't need to be very stiff as they are only 15-20mm long.
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OK So would you like me to get some 4mm PTFE rod it could be stiffened with some bigger stuff round it maybe
Doug
Tell you what I need to print the parts so if you could send me the files (If you haven't put them on TV Yet) I will get some 4mm PTFE Rod and give it a try?
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I haven't put this one on TV yet as its totally untested. but here they are:
https://1drv.ms/u/s!Apv79JfGbPIwgu08dlMg3WjnTvCcQAI'll host them there for a while until they go on thingiverse.
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If you have some PTFE rod spare, I'd try it if you're having success with it. Just found some nice chromed steel 4mm rods lying around at work.
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I wonder whether you're over engineering this? The movement of the hot end is tiny, less than 0.5mm and probably less than 0.1mm. I would suggest that a compliant mechanism would allow the necessary movement with minimum weight while maximising lateral rigidity. I've got a pic but nowhere to host it, what's the best way round that?
Moriquendi
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Email sent Idris I will host it for you and give a link in this thread.
Doug
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Moriquendi's clamp
