Piezo20 probe and piezo kit now available
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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
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Thank you. I;d love to get printing this new version but I've a whole heap of parts to print for a customer. Maybe Ill print it on the microdelta.
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DJ Rods are in the post mate u shud get them tomorrow
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Thanks mate, I did slightly rework that top sensor holder for 5.5mm rods which I scavenged from work but they are too big the piezo wont fit. The version I sent to you was Lykles original top plate for his effector but I modded it with an extra recess to improve piezo sensitivity. Ive hosted my version here: https://1drv.ms/u/s!Apv79JfGbPIwgu1TAuVGDSUBP5ecuA you need to add holes for the new rods.
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I will wait till you have tried it out I think you will find 2 pieces in the package one PTFE good to 260 degrees and acetal which is good to 100 the acetal is the stiffer of the 2but I think if you can make the max exposed part of the rods to be about 1-2mm both will be plenty stiff enough. The PTFE also absorbs moisture much better at 0.03% acetal can by 0.3 IIRC.
Let me/us know how you get on
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DJ
This looks interesting wonder if same idea could be utilised with Piezo's
http://www.robotdigg.com/product/885/Auto-leveling-force-sensitive-resistor-sensor
A fitting that will fit on the nozzle temporarily whilst the Cal/bed mesh is done then remove and the Z Hight set manually would mean not doing it for each print tho?
Hope the rods arrived ok
Doug
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Hi Doug,
That looks interesting, not sure how it handles a hot bed, and certainly won't handle a hot nozzle, plus the sensing area is a big pad on the end however as an idea a clip on piezo module for probing would certainly eliminate the nozzle wobble issue and the need to change effectors etc…
I will try it, its not that difficult to do is it? The only thing I can't immediately visualise is how it attaches. That being said if we were going to develop a clip-on sensor is piezo the way forward or might FSR be better? Or maybe even a very precise microswitch or optosensor with spring loaded trigger flag a bit like Nebbians deployable touch probe http://www.thingiverse.com/thing:1517363
Haven't got the rods yet but the post in Bristol is notoriously slow.
Lol no pressure but David mentioned that he's developing a PCB/glass/epoxy effector and carriages and has a piezo version in mind but is waiting on the prototype… better get on with it then
Should get them tomorrow I am sure.
