Precision Piezo Z-probe Now available.

No worrys. I have something in mind that should work for me but I would like to come up with something every one could use

To increase sensitivity, try adding another layer or two of kapton under one of the piezo sides - that should put it under extra stress.

Hi Ian,
I just looked at the pictures with and without the bed adjusting nut and noticed that the pressure pad adjusting screw seems to have come clear when the bed adjusting nut was fitted. This would seem to point to the pressure never getting to the pad and would account for the lack of response.



Mike

Hi Mike
It has made no difference weather the nut was tight or not.
What I did to setup is
No bed a just nuts. Wind pressure pad down to touch the piezo then a 1/4 turn more, tested and no go. Put bed ajusting nuts on still no go.
I have even tryed putting bed ajustment nuts on 1st then winding pressure pad down followed by a 1/4 turn with same results. I know it's some thing to do with the bed setup but what ever I try I can net get it to work.
I have an item, what is I put a 1/2 mm ring under the the piezo and make the pressure pad domed dy 0.2mm. May be I will get a better trigger?

Ian

Yes, I did that (disc under edge) to check difference between direct pressure/flexing
edit: I found that the output with pressure change was 2.5 time more when the disk was allowed to flex but the compliance was much less with direct pressure

Mike

Edited 1 time(s). Last edit at 07/21/2017 04:36AM by leadinglights.

Thanks for the info, Will investigate on Monday when I get home.

Okay so beta version of delta bed mounts on thingiverse. Testing them now.

[www.thingiverse.com]

If you want to copy and edit [www.tinkercad.com]

They won't necessarily fit your printer but may adapt to it fairly easily, but use them as a guide to see the principle involved. The first run of these and the sensitivity is amazing.

Make sure to set z acceleration to 200mm/min or less.

EDIT - so these seem to work well. As long as the part that actually holds the bed is quite a tight fit into the middle part, the bed will be quite firm. Managed to use Rich Cattel's Marlin from a few years back to autocalibrate even my microdelta to 0.07 deviation which isn't too bad for a machine with 1.8 degree steppers and rods made from threaded aluminium. Thermally they seem to function fine, with the bed at 115 deg C there is not noticeable change in the piezo response.

Edited 4 time(s). Last edit at 07/22/2017 09:58AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Today I've printed a few parts to angle the x-carriage to a top down mount, then in turn back to the back to front mount for the hotend holder. Between these I've placed two piezo disks of 27mm, with one side the brass is cut without cutting the ceramic part. Cutting the disk with scissors is very easy. Just make sure the cutting side of the scissors is on the correct side as that part is getting bent.
This seems to work ok. No drilling is needed this way, and the filament doesn't need to go through the disk either.

Here's a scope plot of the nozzle touching a block of wood placed on the bed. With the prototype parts printed the nozzle couldn't reach the bed anymore but that's ok. I need to redesign it anyway for much better stiffness and rigidity. The blue trace is the PIC16F1827 output (which is now connected to the z endstop connector on the ramps board). the yellow trace is the piezo signal after filtering. I didn't use shielded cables, I'm going to buy some tomorrow to reduce the hum and noise. And if it's build on a pcb it will improve a lot I expect. The comparator threshold voltage is now set to 320mV.


Here are the two mounting plates I've designed to get the z direction forces onto the piezo disks:


The orange circles represent the piezo disks:


Here are the parts printed and mounted. I used kapton tape to secure the wires to the disks since the x axis motion moved the wire and gave big spikes in the signal. Fixing them to the hotend holder solved the problem. I think I'm going to design a part that'll encapsulate the disk including the wires.




I've filtered the output of the disks (in series) using a simple passive 1k and 33nF filter network. This seems to be the sweet spot between signal amplitude and x axis motion immunity. It's immune to velocities up to 133mm/s (8000mm/min). I haven't checked the acceleration, but I've set mine pretty low anyway to prevent ripples in my prints (1200mm/s^2 iirc).

I need to redesign the hot end holder and x carriage to be much more rigid. It's flexing a lot now and is held together with cable ties. I'm also working on building a cnc machine that is capable of machining aluminium. I may be able to make something with that to improve rigidity.

Once redesigned my hotend will be even more compact than before, I could get rid of the servo mount, and I'd be glad to see it go I could even make it so that I don't loose any z height.
I think this is going to work. Too bad it's not going to work for the cnc machine, I don't fancy hanging a 3.5kg spindle off a few piezo disks But I will think about how I could make this work for that as well. Maybe a separate sensor that can be placed in the collet or attached using neodymium magnets to probe the bed with a known offset if the bed/plate/stock isn't conductive.

The PIC and the handful of other components probably fit on a 20x30mm pcb when everything is done using smd components. It takes 12V, conditioned/smoothed it using ferrite bead and filtering capacitors, 5V is created using a 78L05.

Edited 3 time(s). Last edit at 07/23/2017 07:43PM by imqqmi.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Hi imqqmi,
I will look through you posting and reply on the other thread to keep this uncluttered for support of DjDemonD's Piezo Z Probe.

Mike

Ok, please let me know what thread it is in case I miss it.

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Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Quote
imqqmi
Ok, please let me know what thread it is in case I miss it.

It is on [forums.reprap.org]

Mike

Thanks guy its super interesting and I very much appreciate moving it over to the "research" thread.

Edited 1 time(s). Last edit at 07/25/2017 08:42AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Just to say the bed mounts I designed work very well. Its so sensitive I can blow on the bed and get a trigger!

Measured the force required to trigger, using scales on the bed, 4 grams is all it takes.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Quote
DjDemonD
Just to say the bed mounts I designed work very well. Its so sensitive I can blow on the bed and get a trigger!

Measured the force required to trigger, using scales on the bed, 4 grams is all it takes.

Can this be converted to go on a standard 3 point bed?

Yes, you would need to adapt the upper most part to hold the bed on in some way. What I envisaged was two sensor assemblies with corner shaped relief in them, and one with a flat sided relief, for the middle of the opposite side of the bed. Other than that I cannot see why not, but I'd consider using a 27mm version which would be these enlarged by 135%, as the 20mm version holds my circular 120mm bed nicely, but might not manage to hold a larger bed.

The way I'd approach this is copy my tinkercad design, model your printer's bed fixings on its carriage, and then the bed itself and then decide on what relief to but into the top parts, and whether to move the screw hole in the lower part to either suit your setup or as I have to ensure most of the sensor assembly sits under the bed, maximising pressure on the piezo itself.

See what you come up with.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Hey @SM3D, do you have ringing or stuff like that having a titan with a nema on your effector ?


additional note to DjDemond, still very satisfied with my piezo, works like a charm

Edited 2 time(s). Last edit at 07/25/2017 03:29PM by Hergonoway.

Quote
DjDemonD
Yes, you would need to adapt the upper most part to hold the bed on in some way. What I envisaged was two sensor assemblies with corner shaped relief in them, and one with a flat sided relief, for the middle of the opposite side of the bed. Other than that I cannot see why not, but I'd consider using a 27mm version which would be these enlarged by 135%, as the 20mm version holds my circular 120mm bed nicely, but might not manage to hold a larger bed.

The way I'd approach this is copy my tinkercad design, model your printer's bed fixings on its carriage, and then the bed itself and then decide on what relief to but into the top parts, and whether to move the screw hole in the lower part to either suit your setup or as I have to ensure most of the sensor assembly sits under the bed, maximising pressure on the piezo itself.

See what you come up with.

Ok thanks Simon, Will have a look when I get more time. Looks like laptop is coming away with me this weekend

Ian

Ian - sounds good.

Hergonoway - glad you're happy with it.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Simon
quick question if I may please?
Is it open or closed?
Think about the weight off a large print false triggering!

Not sure what you mean open or closed but a large print shouldn't make any difference as the piezo only generates voltage when it bends or is squeezed more than it already is.

And in any case you aren't probing when printing. And you get triggers when printing all the time, the controller ignores them as it's not looking for a z probe or z min endstop at that point. It's quite useful to watch the LED it gives an indication of how rough the previous layer is.

We talked about using this as a way to slow down or stop a printer in distress. Haven't got anywhere with that though.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Ok thanks Your mount with the top flattened out should work then!
I have spent the last 2 nights adding 4mm alli strips to the bottom of the bed support to take as much flex out off it as I can

Everything is hard to make rigid (and lightweight!).

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

NEW STOCK ANNOUNCED

So I have 8 Piezo kits and 5 modules available in the shop.
We also have the printed parts available to make modules or titan (and aero) piezo brackets.

[www.precisionpiezo.co.uk]

Edited 1 time(s). Last edit at 07/25/2017 05:05PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Have released a v1.11 module to thingiverse
[www.thingiverse.com]

And if you want to edit it, its here on tinkercad.
[www.tinkercad.com]

The changes are slightly improved groove in the lower part for less adjustment after printing, better layout for easier printing and offset mounts for the PCB to allow better alignment of the endstop cable.
These are minor changes so don't rush to upgrade.

EDIT - Tinkercad links expire after 1 hour! So if you want to copy it on tinkercad, create an account and login.

Then search for me DjDemonD or use [www.tinkercad.com] youll find all my public stuff there which if you have an account you can copy/fork and then adjust.

Edited 2 time(s). Last edit at 07/26/2017 10:31AM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Tinkercad links says "expired"

Regards

Yeah they've changed things recently, links have a 1 hour expiry. I'll try to sort something out. Maybe we can speak on Skype pm me and I'll help out.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Don't worry, I was just curious about the design

Cheers

Video overview of the underbed mounts is now available on youtube

[www.youtube.com]

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Hey Folks.. I've been trying to get the piezo working on my setup but I've been running into issues and would like some help figuring out what's going on with mine.

I first bought the piezo kit several weeks ago. While waiting for delivery, I remixed the top piezo mounting part into my existing X carriage so I wouldn't lose too much height. See pic. When I got the kit, I put it together and all I saw as the red power led. I contacted Simon and he walked me through some troubleshooting steps and it looked like the board wasn't responding to any triggers.. even tried shorting the piezo leads per Simon. Anyway, he graciously sent me a replacement board which I just got. I plugged it in to the existing setup and BAM, I was able to do auto leveling and print!

But then I'm not sure what happened next. The first print finished so I loaded up a 2nd print and I look over and the piezo's blue light is lit and it won't do the beginning homing step. I tried power cycling the printer and still the blue led stayed lit. So I turned the left potentiometer until the blue led turned off but now I can't get the piezo to trigger. I also tried touching the piezo leads and still no trigger. I checked the resistence on the right pot and it's set at .5 Mohms.

I'm not sure what to try next. I'm hoping this one isn't brokent like the first.

Just additional info - I have a MKS Gen 1.0 and I have the wires plugged into the Z Min connector correctly. The board's connector is ordered (V, G, S) so I swapped the wires for G and S to correlate to the piezo's wires (V, S, G).
Also, I noticed during the first successful print that the piezo was lighting up blue when retractions were occurring. I'm assuming this is ok but just throwing it out there.

Any help is appreciated.

Check the piezo polarity is right by just flipping it, tuning and trying again.

Also make sure the piezo leads haven't become desolderd, they might be making a connection on retract.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions