Precision Piezo Z-probe Now available.

That's working really well. There is definitely something in this noise cancelling setup that has some merit, where achieving a good range of operation in a mechanically noisy machine is concerned. I must find the time to revise my corexy underbed setup and see if it improves it.

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Simon Khoury

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

I found a counter-intuitive setting, which might be worth mentioning.
I had a deaf area on my bed ( underbed sensors ) where PP didn't trigger reliable. That caused the effector to bend and, cautious person I am, made me reduce probing speed ( works well with proximity sensors ). But it got worse. You have to raise probe speed ( 1000mm/s IIRC ) until you hear a nice tap.

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o_lampe
I found a counter-intuitive setting, which might be worth mentioning.
I had a deaf area on my bed ( underbed sensors ) where PP didn't trigger reliable. That caused the effector to bend and, cautious person I am, made me reduce probing speed ( works well with proximity sensors ). But it got worse. You have to raise probe speed ( 1000mm/s IIRC ) until you hear a nice tap.

Yes, faster probing is generally better with piezos, and now with the multitap feature on the Duet, it is better to have the odd false trigger than no trigger at all.

I think you can raise the probing speed and get more reliable triggering, but its very dependant on the setup/mounts and how the piezo is actuated. You don't always get more accuracy, but the multitouch probing is indeed a big improvement for accuracy and reliability.

My microdelta underbed setup is so sensitive I think I could probe at 1 mm/s reliably (if I have time Ill try very slow probing).

In testing (we tested a range of probing speeds with the piezo20 unit - so this is most specific to that implementation) going much above 700mm/min (11.6mm/s) did not improve accuracy but in fact reduced it, this is the basis for recommending 4-7mm/s (240-420mm/min). But your mileage may vary as each setup is different.

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Simon Khoury

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

If you use a piezo disc as a microphone you will need to have enough speed to give a distinctive tap for it to detect- my guess is that as long as it is audible, even if very quiet, that is fast enough.

I use piezo discs as pressure sensors in which mode they are very responsive even at very low speeds. Most of my tests have been at 1mm per second at which speed I typically get 8 volts of output from my rigs but there is (almost) no lower limit of speed.

I am guessing that o_lampe meant 1000mm/min (not 1000mm/sec) earlier which is about the speed used by accelerometer probes which use only the high frequency part of the contact signal - i.e., as a microphone.


Mike

The only difference is the top disk is 1.1 mm taller.

My two cents here

With my Prusa clone, using a PP20 kit and the Duet, I'm probing at 150mm/min (so 2'5mm/s), as I've found the most reliable results. However, I don't know if it's because the way I tight the screws of the groovemount, my Z offset is bigger than before, I'm using now 0'23 as Offset (for a cold probing, so I'm assuming 0'15 for the piezo bending, taking 0'07 for the nozzle heat expansion).

I did a lot of tests, adjusting the sensibility, and what I got with that is problems due to mechanical noise, that are almost reduced to zero since I moved to 256 microsteps in Z, and reduced the probing speed, but no change in the Z offset.

The main drawback I find with the piezo is that is so sensitive that now, when I see the image Duet presents for the bed, I'm really ashamed of how it comes xD (not flat at all!).

BTW, I've also find important to mention that I usually do the Z homing right after X/Y homing (both includes a Z movement in my case), before the motors goes to Idle, as when the motors are powered back from idle, they usually do a strong mechanical noise that triggers the piezo (just the very first movement).

Regards

I took my hotend and PP20 apart today as I was having problems extruding. This was after trying to load some PETG. I have a Titan and use 3mm filament, direct extrusion in a D-Bot printer. This is what had happened



I think the filament must have struck the reverse side of the piezo causing distortion of the metal and flaking of the piezo material. Good job I bought a couple of spares.

I think thats the first damaged piezo disc which wasn't the result of bad drilling. Thankfully with this tech the sensor itself is cheap. Let us know if you need any assitance with it.

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Simon Khoury

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

No problem. I should be back up & running soon. I'm also thankful I printed spare plastic parts as I managed to snap the piece that secures the heatsink during reassembly. That was my fault - overtightened the screws.
I think I'll print another spare asap just in case

All working again now. I had to fit a new nozzle though - the fragments from the piezo disc had blocked it
I think I need to tighten up the 4 corner screws a bit - the hotend is a tad more wobbly than before and the readings a bit variable. Before today they were very consistent.

Tighten the 4 corner (or your equivalent) screws down a bit.

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Simon Khoury

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

Yeah, I had come to that conclusion. Not so easy with the Titan as you have to remove the groovemount to get at the 2 rear screws which means taking the front cover off. I might have a go at designing the piezo module into the mount at some point.

Have you seen our titan mount bracket?

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

Yes, I have. My printer is a D-Bot. This is my Titan mount
I modified it further for the PP20 to fit under. It can be modified further to allow the piezo to be in the mount similar to this one.

Sorry, you've probably told me that before

Idris

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{Precision Piezo} Accurate, repeatable, versatile z-probe plus piezo discs, endstop cables, pt100, 50w heaters.

Tekkydave, just put the piezo between the mount and xcarriage, this results in a more sturdy setup (and you gain some z-height in the process)

Thingiverse link

There is no gap at the moment as it is all one piece. Only gap is between mount and Titan.

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whosrdaddy
Tekkydave, just put the piezo between the mount and xcarriage, this results in a more sturdy setup (and you gain some z-height in the process)

Thingiverse link

I will give it a try in the CoreXY I'm rebuilding, but probably with a Bondtech instead of a Titan, although that should make no difference.

Are you getting good results with that setup? What Z Offset you've configured? Is the Xcarriage standard or you made modifications to put something that "press" more the disk?

Cheers!

okercho - not sure who your question is to, but I'm just using a standard PP20 groovemount at the moment in my D-Bot corexy.
The only mod I have made to the electronics is to replace the VR2 pot with a 10-turn one. It's much easier to calibrate now. I wouldn't rcommend this mod unless your soldering skills are up to it. It would be very easy to damage the tracks if you're not very careful.

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DjDemonD
Tighten the 4 corner (or your equivalent) screws down a bit.

I have tightened the screws about a turn each. It's more rigid now

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tekkydave
okercho - not sure who your question is to, but I'm just using a standard PP20 groovemount at the moment in my D-Bot corexy.
The only mod I have made to the electronics is to replace the VR2 pot with a 10-turn one. It's much easier to calibrate now. I wouldn't rcommend this mod unless your soldering skills are up to it. It would be very easy to damage the tracks if you're not very careful.

[attachment 103456 PP20.jpg]

Hi Tekkydave, sorry, the question was for whosrdaddy and his bracket

Cheers

Idris..

So the new thingy is working GREAT =)

I have been printing and probing all week. it seems less prone of interference than my own contraption( vibrating or inducing from the hotend fan)

I almost always gets 0.00000 in standard deviation, SO I'M SUPER PLEASED..

Keep in mind that I have reprinted the upper part in PETg with 3 perimiters 3 bottom layer and 4 upper layers and I used my own .STL

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okercho

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whosrdaddy
Tekkydave, just put the piezo between the mount and xcarriage, this results in a more sturdy setup (and you gain some z-height in the process)

Thingiverse link

I will give it a try in the CoreXY I'm rebuilding, but probably with a Bondtech instead of a Titan, although that should make no difference.

Are you getting good results with that setup? What Z Offset you've configured? Is the Xcarriage standard or you made modifications to put something that "press" more the disk?

Cheers!

Yes, is working like a charm. Z offset is -0.14 for my setup.
The back of the bracket houses a bit space for the piezo, the carriage itself is standard.

Edited 1 time(s). Last edit at 03/16/2018 08:57AM by whosrdaddy.

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whosrdaddy
Yes, is working like a charm. Z offset is -0.14 for my setup.
The back of the bracket houses a bit space for the piezo.

Cool, that's more or less what I've in my "traditional groovemount" setup, so the accuracy/pressure needed seems to be quite similar . Just curious, are you doing the probing with the nozzle cold or hot? I know is better (and recommended by the PrecisionPiezo guys) to do it hot, but in my setup I've found that the E3D fan is putting a lot of mechanical noise, so I've to turn it off, as even with 130C, PLA melted a bit, and sometimes (not always) caused clogs, so I always check my nozzle before probing (usually I go to 160C, clean the nozzle, cool it down to room temp and then make the levelling), and then just calibrate taking into account the expansion. Results are usually quite consistent.

Regarding the carriage, I saw in thingiverse the housing you mention in the bracket, but the carriage (the piece that has the bushings, sorry if it's not the correct word) is a "standard" unmodified one, right?

Regards

I have started doing a bit more probing when cold. I think it does lower noise and perhaps improve accuracy, but it's harder to clean the nozzle and of more benefit if you can switch off your fans, which on more basic controller boards isn't usually an option. If your bed deforms when heated and you're probing a grid then heat it.

Consider a noise cancelling piezo. I just bonded 3 under my corexy bed and suddenly it's working much better.



They are the opposite facing to the sensors in the bed mounts so are wired in parallel. It now probes reliably, but I need to tweak it a bit to get really good accuracy.

Edited 1 time(s). Last edit at 03/16/2018 10:24AM by DjDemonD.

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Simon Khoury

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

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okercho

Quote
whosrdaddy
Yes, is working like a charm. Z offset is -0.14 for my setup.
The back of the bracket houses a bit space for the piezo.

Cool, that's more or less what I've in my "traditional groovemount" setup, so the accuracy/pressure needed seems to be quite similar . Just curious, are you doing the probing with the nozzle cold or hot? I know is better (and recommended by the PrecisionPiezo guys) to do it hot, but in my setup I've found that the E3D fan is putting a lot of mechanical noise, so I've to turn it off, as even with 130C, PLA melted a bit, and sometimes (not always) caused clogs, so I always check my nozzle before probing (usually I go to 160C, clean the nozzle, cool it down to room temp and then make the levelling), and then just calibrate taking into account the expansion. Results are usually quite consistent.

Regarding the carriage, I saw in thingiverse the housing you mention in the bracket, but the carriage (the piece that has the bushings, sorry if it's not the correct word) is a "standard" unmodified one, right?

Regards

Yes it standard
I prefer to probe hot because my bed deforms a bit when heated up.

Edited 2 time(s). Last edit at 03/16/2018 10:03AM by whosrdaddy.

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DjDemonD
I have started doing a bit more probing when cold. I think it does lower noise and perhaps improve accuracy, but it's harder to clean the nozzle and of more benefit if you can switch off your fans, which on more basic controller boards isn't usually an option.

Consider a noise cancelling piezo. I just bonded 3 under my corexy bed and suddenly it's working much better.

[attachment 103463 20180315_23325501.jpg]

They are the opposite facing to the sensors in the bed mounts so are wired in parallel. It now probes reliably, but I need to tweak it a bit to get really good accuracy.

I found that when using many piezos (6 in total) in my underbed setup accuracy degraded.
My 2 + 2 noise canceling setup works fine though.

Where do you position your two?

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Simon Khoury

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

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DjDemonD
Where do you position your two?

See my photo on page 40?