Piezo20 probe and piezo kit now available
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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
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This is a rough representation of the lower part (Blue and Red) of DjDemonDs effector and would bolt to the upper part at the four corners with standoffs.
Moriquendi
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How would it clamp the E3D Heatsink firmly?
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It would need to be split into two parts like DjDemonDs, I just knocked it together to demonstrate that you don't need dedicated bearings and shafts, you can achieve the same thing by arranging for flex in specific areas. I've been using a similar mechanism to support my bed with piezo sensors for months with no issues.
Moriquendi
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I am quite certain that the design for this can be simplified and improved, and it will be, its been a very engaging collaboration so far.
But this is where I'm coming from: my printer was never better in terms of precision than when my hotend was clamped rigidly in a metal clamp, in a metal effector (with magnet arms and metal carriages on linear rails) and had literally zero play whatsoever. Now I know I am not going to get to that level of precision as I am now using a printed effector and carriages, and my hotend is attached to a compliant mechanism. But I do want to limit that compliance to 0.15mm of vertical movement, enough to trigger the piezo, and no lateral movement at all. If this would work with the piezo clamped firmly between two flat parts I would go down that route but it doesn't bend enough to have high sensitivity in this configuration.
I have noticed the nozzle move laterally as it slides over a slightly squashed down first layer, I don't like that at all.
All I'm talking about are 4 short rods pushed through some holes, I wouldn't consider that over engineering it, I'm just pushing to see if I can achieve the aims above. I'll leave the wobblier version available for anyone who wants to settle for that, it works.
I used to be very much a "that's good enough" pragmatist, but since building this large kossel and striving for a lot more precision I'm very much bitten by the bug. I'm only developing this way of using the sensor, as I was not happy with the precision I got from the IR sensor, which is to be fair fairly precise.
BTW the easiest way to image share for this forum is https://postimage.io just upload image and you get all types of links, and they host in perpetuity.
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I use Photobucket but it is the same Idea
I'll drop into my Plastics place tomorrow for the rods I will get a length of PTFE and a Length of Acetal (Which is a form of Delrin) total cost for 500mm of each is £0.51.
DJ Drop my a Mail with your Address and ill get some of each of to you tomorrow if I get chance (If I can find a PO Open)
Doug
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BTW the easiest way to image share for this forum is https://postimage.io just upload image and you get all types of links, and they host in perpetuity.
Much obliged.
Moriquendi
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DJ no prbs mate you have done much to help least I can do to send you some bits of Plastic
