Piezo20 probe and piezo kit now available

fma · 31 Jul 2017, 06:53

Hi!

As cheap piezo discs are mostly made to build buzzers, why not using them this way?

The idea is to use 2 piezos: one on the head, and one somewhere on the heatbed. One of them is used to generate a vibration, and the other one to detect this vibration, which will be transmitted when the hotend is in contact with the bed.

It should be possible to find a resonant frequency to optimize transmission (far from motor vibrations and other noise…).

In fact, any kind of transducer can be used on the bed, to generate the frequency, to have more power than a simple piezo, so it can be easily detect by the head.

A friend in our hackerspace wrote, a few months ago, an Arduino routine to detect a single frequency, which can help to analyse the signal: https://gist.github.com/edgar-bonet/0b03735d70366bc05fc6

Just an idea. Let me know if it has already been discussed.

DjDemonD · 31 Jul 2017, 10:46

Thanks, it has been discussed more so on reprap in the general piezo thread http://forums.reprap.org/read.php?1,635075. I've never tried it, but whilst its an alternative approach is it potentially a solution looking for a problem, as the current method works so well adding a second piezo, and possibly adjusting/changing the PCB to search for the frequency outputted by it, would only be worthwhile if we were going to gain some sensitivity or better discrimination between a trigger and a false trigger (with current firmware settings this isn't particularly a big problem). I'm down to 4g of force to trigger on my microdelta with underbed piezos.

fma · 31 Jul 2017, 13:21

Well, I was trying to find a solution which doesn't need specific mount for the hotend nor the bed…

I will read the reprap thread. Thanks.

DjDemonD · 8 Jan 2017, 11:51

The gold standard (unless you want to calibrate/level manually) is electrical contact, but we don't have conductive printing surfaces, on the whole, so it isn't practical. You can get conductive PEI at eye-watering prices.

Whitewolf · 8 Feb 2017, 05:36

@DjDemonD:

If it's one that I made the disc fitted when I made and tested it. But sure you can print a new one if you want. Might be worth watching my YouTube video series on assembling it. It looks simple but won't work if done wrong.

How to Guides: https://www.youtube.com/playlist?list=PL9g_2J-RjkRCy5Sr5gIVwMYGhI9DrJewq

Sorry for being a while getting back to you I don't check here so often our official support thread is at reprap forum:

http://forums.reprap.org/read.php?1,767998,page=13

It was how it arrived look at the photo, bought one of your drop in units. I only dissasembled to see why it was so lop sided (have not even installed the thing because i dont want a hotend that sits at an angle. the disc does not fit in the outer recess, i will print another and follow the video. or i might just wait and install the bed sensors that you are shipping to me

just giving you a heads up for QA

DjDemonD · 8 Feb 2017, 07:04

That's just very odd, is it installed already? I'm tempted to send you another one and pay you the shipping to return it by regular airmail. I'd like to see what happened.

If it's installed and working then leave it if you're happy to.

Whitewolf · 2 Aug 2017, 17:29

Its not installed, it arrived, i took it out of the package made my post here then left on a fishing trip. Came home to an overheated and fried computer from this heatwave we are having hopefully ill have my computer up and running by the time your bed piezo sensors arrive.

fma · 4 Sept 2017, 06:01

Does anyone has a working design for a Diamond hotend? Ian, did you make progress on yours?

DjDemonD · 4 Sept 2017, 09:30

Your best bet here, and quite practical on a delta, for example, is to use underbed piezo sensors. There are designs for mounts, and with a stationary bed it works very well.

Here are some exmaple bed mounts
https://www.thingiverse.com/thing:2446460

You add to that the piezo kit:
https://www.precisionpiezo.co.uk/product-page/precision-piezo-z-probe-kit

After a bit of tuning you should be probing away with high sensitivity and with whatever hotend/nozzle you want.

fma · 4 Sept 2017, 10:14

Ok, thanks.

fma · 9 May 2017, 07:31

Mmm, I may have another idea… What about having the hotend (any hotend, in fact) mounted on a support which is anchored on one side, but free on the other side. On this free side, it is supported on a piezo disc. In order to have a good sensitivity, a spring put the right force on the piezo (just to maintain the head in its position). Then, once the bed calibration is done, an additional force can be applied (to increase the spring one) to firmly maintain the hotend (it can be a simple servo eccentric)...

In fact, it can be the opposite: a very strong spring firmly maintains the hotend, and the servo releases a little bit the force so the piezo is less strained, and more sensitive. Could work with a FSR too.

franzelka · 7 Nov 2017, 17:51

I ordered an assembled kit (screwmount version) and I‘m very curious how it will perform compared to the IR sensor (tilt problems etc.)

I didn’t find a dedicated effector design for my Kossel Mini (Think3DPrint3D). What will be the best way to mount the piezo20, just screw underneath the original effector?

DjDemonD · 8 Nov 2017, 15:53

Thanks for the order.

Compared to the IR sensor (unless you have an evenly reflective (to IR) bed surface, which remains evenly reflective at all times, and no tilt), it will be like breathing fresh air. Tilt isn't a problem in the same way. There is no x or y offset so the nozzle determines the height at any given probing point, whether the entire effector and attached nozzle are tilted or not. In theory, if your tilt is quite minimal this should generate little/no issue with calibration/first layer thickness.

However, if you have a very precise machine (or large one) then tilt is still going to feed into your calibration and reduce its accuracy to some extent, as instead of the trigger height being different relative to the nozzle at different probing points because of tilting that you see when using an offset sensor, its the nozzle height that changes if the effector tilts. So try to get rid of tilt if you can.

As for mounting start off by using the supplied drilling guide (also a natty keyfob) to drill 2 3mm (3.5mm) holes equidistant from your central hole for your filament path, then screw the unit under your effector using m3 screws. This works but absorbs around 18mm of your z printing height.

Once you've determined you are satisfied with the performance of it, consider designing an effector with the upper part of the unit integrated into it (even better if this is raised above the effector, so that just your heater block hangs beneath, this really reduces the effect of any tilt you might still have, but makes cooling the heatsink a little more challenging), to regain the z height you lost.

zendesigner · 26 Mar 2018, 10:20

HI Simon,

I just ordered your Orion module yesterday , with the intention to use it with a duet Wifi on a Kossel Metal delta printer.

Nice to find your thread here. looking forward to reading it and combining it with the DUet.

Bart

DjDemonD · 26 Mar 2018, 15:15

Thanks Bart. I think it will provide a great addition to your printer and its duet board. Accurate probes on a delta reduce the workload considerably.

deckingman · 26 Mar 2018, 15:29

@fma:

Does anyone has a working design for a Diamond hotend? Ian, did you make progress on yours?

No. I went for a different arrangement. My Diamond hot end assemblies (3 of them) have steel dowel pins which mate with oil filled bronze bushes in the X carriage. This allows an amount of Z movement whilst constraining any XY movement. Actually I reamed out one of the bushes and use a couple of springs on the other bushes which allows the hot end assembly to tilt when pushed from below. Then I went for a simple precision switch which has a repeatability of 0.005mm. So basically the hot end is the probe like the Piezo but I'm using a simple switch instead. When the nozzle comes into contact with the bed, the side of the assembly nearest the switch tilts upwards. I've got it set so that it only takes 0.3mm of movement to trigger the switch. It works like a charm and has been running for about a year. The mechanics are a bit involved but there is no calibrating - it's just a simple (but quite expensive) switch.

I wrote a bit about it on my blog, about half way down this page https://somei3deas.wordpress.com/my-corexy-printer-build/

There is a bit more on this YouTube video https://www.youtube.com/watch?v=0lW0EgNX0iQ&t=50s from about 2:24 and again at 3:42.

zendesigner · 30 Mar 2018, 16:15

HI Simon or maybe DC42

I'm currently testing the orion module you send me on my Duet wifi. Duet is configured with wifi and i'm testing the zprobe and end stops to see if it works.

So now i have this upside down behaviour.

The orion reacts to taps and switches from a red led to the blue one. I calibrated the sensitivity and thats ok. Now when i just push on my hotend it only triggers when i release it. I looked at your tuning video and you mention if this happens that you have soldered the piezo wrong. so don't think this is the case here as i installed exactly the same as your latest video.
Now in the webinterface of duet the Z probe is seen + the voltage is ok. But it stands constanly at a value 667 and when i tap the orion it returns quickly to zero.

*reversing the connector on orion makes the red led on all the time and creates the correct behaviour that it triggers on push down. But that then put's the value on 880+ in the duet and it almost doesn't change when tapped.

So what am i doing wrong and what needs to be reversed somewhere to get the correct 0 - 600+ value when triggered in dueton push down of the nozzle, not on release?

these are my Zprobe settings in config.g

; Z-Probe
M558 P1 H5 F120 T12000 ; Set Z probe type to unmodulated and the dive height + speeds
G31 P500 X0 Y0 Z0 ; Set Z probe trigger value, offset and trigger height
M557 R125 S20 ; Define mesh grid

Thanks for your help.

Bart

DjDemonD · 30 Mar 2018, 18:24

Okay hi. So best bet would be to use P5 mode in M558. Also use switch I1 which means an active low sensor.

Set G31 P100.

Please do not reverse the connector it might have very undesirable effects on either the Orion PCB or (more expensively) your Duet board.

Let me know if this helps.

zendesigner · 31 Mar 2018, 13:01

HI sImon,

Thanks for your excellent help. I tried the low setting before but it hought it was L1 instead of I1. So kinda misread the font

Now the value is 0 and goes to 1000 is being tapped.

Cheers

Bart

zendesigner · 31 Mar 2018, 17:38

Hi Simon,

I'm afraid it still doesn't work. the indication in duet wifi is ok now but, the piezo still reacts only when you let go, not when you put pressure on it. So the nozzle keeps pushing into the bed. and doesn't trigger the duet.

The piezo is mounted with the connector towards the nozzle tip. just like your video. Do i need to turn it around ?
Or could it be that the piezo's are not soldered correctly as you say that in one of your video for the old model also ?

Let me know what to do.

Bart