Precision Piezo Z-probe Now available.

My piezo arrived during the week , so I spent a little time today mounting it.

I've got to say, I'm very impressed with the quality... a nice piece of kit! Instructions are clear and complete. (Except for the Zesty Nimble ad, which was in such small font as to be unreadable to my aged eyes.)

Without thinking about it too much, I got the screw-mount version, but would possibly have been better off with the groove-mount... I could have clamped that into my effector where the hot-end heatsink had been clamped. But, not to worry, a couple of 3mm holes through my effector and I had everything in place, except the filament feed. The red LED lit up with power, and the blue one with pressure

Now to attach the bottom end of the Bowden cable and away.... But my Bowden connector screws directly into the top of my hot-end heatsink (cheap Chinese E3D "clone" (I assume) that came with the printer). The piezo module is above the heatsink, with only a 5mm hole in the "Upper Part". I disassembled everything with the intention of drilling a 15mm hole in the piezo "Upper Part" so the Bowden connector could get to the heatsink. But no, the piezo disk itself only has a 5mm? hole in it. I'm going to need something with the right thread attached to the top of the effector, or perhaps to the piezo "Upper Part".

I'm not even sure what the Bowden connector thread is... maybe 10mm diameter, but I'm pretty sure it's not M10. Some kind of pneumatic/gas-fitting thread? Maybe i should drill the "Upper Part" out to about 9mm and use the Bowden attachment to force-tap its thread into the part?

Any ideas/suggestions welcome!

Hi Frank,

Thanks for the feedback.

The piezo disc is only 20mm and if you drill any more out of it it won't work. We have experimented with a 35mm piezo disc with a huge hole cut out of the middle but this is an awkward way to solve the problem. The module would be massive!

Your best bet is to remove the bowden coupler from your hotend and relocate it above the module (or screw on into the top of the module or your effector). Then run a guide tube down into your hotend to keep your filament constrained.

I marketed these for genuine e3d as their bowden couplers fit into the unit. But I have clones too it just takes a bit of a different approach when using bowden. Direct 1.75mm with a guide tube through the module, or direct 3mm just works for clones as well as genuine.

There is a small bonus using the relocated bowden coupler idea and that is the bowden tube doesn't pull on the piezo at extreme effector/head positions meaning fewer false triggers, though the effect is marginal.

Edited 2 time(s). Last edit at 05/27/2017 03:41AM by DjDemonD.

---

Simon Khoury

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

Quote
frankvdh
I'm not even sure what the Bowden connector thread is... maybe 10mm diameter, but I'm pretty sure it's not M10.

Very often they are BSP threads. if it's about 10mm major diameter then it's probaly 1/8" BSP which is 9.7mm OD IIRC. Some of mine are tapered threads and some are straight.


I'm in the same situation as you, I need to mount the connector on the top of mine in order to try it out for real. Hopefully i'll have some time this weekend to develop a new top part of the mount to incorporate a thread. I'll share if/when i do.

I haven't yet produced a version with a bowden coupler thread on top (or included) as I presumed the module would be mounted below the effector but maybe there will always be a hotend sized hole in the effector anyway.

---

Simon Khoury

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

Thanks DjDemon & Slippyr4.

I wasn't intending to suggest that my problem was the fault of the Piezo or it's design or anything. Just documenting a surprise I got so that anyone else with an E3D clone is forewarned.

I'll try drilling and tapping the Piezo "Upper Part" for the Bowden connector. The "Upper Part" looks to be solid enough to be able to survive that.

[ Edit ] After overnight thinking, I'm not going to do this... the "Upper Part" is only 5mm thick, and the thread is maybe 8mm long. I don't want the bottom of the connector to be pressing on the piezo disk. So I'll add an 8mm or so thick piece to the top of my effector to screw the Bowden connector into.

My Bowden connector can slide further up the PTFE tube, so I can push that down through the Piezo onto the top of the hot-end.

Longer term, I'll design and print an "Upper Part" with some more depth for the Bowden connector to screw into.

BSP thread looks right, although only the British could come up with a system where 1/8" describes a 9.7mm fastener.

Edited 2 time(s). Last edit at 05/27/2017 05:23PM by frankvdh.

I received it yesterday and just wanted to say that I'm very happy with it. I did have to slightly change the Hotend clamp so that my J-Head would fit, but it's working without any issues now. I'm using it on a Duet 0.8.5 btw.



Edit:
My Probe settings in dc42 RRF 1.17e:

M558 P4 X0 Y0 Z0 H5 F120 T9000
G31 P600 X0 Y0 Z0

I had underbed FSRs on it before and didn't change anything.

Edited 1 time(s). Last edit at 05/27/2017 09:20AM by Ramon3D.

Awesome glad you like it. Any issues let me know.

Thanks for posting your config, I haven't tried settings like that but I will do.

Edited 3 time(s). Last edit at 05/27/2017 10:49AM by DjDemonD.

---

Simon Khoury

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

What size machine screws are recommended for assembly? I have an original board from M, but I'd like to try the simplicity of this mounting solution. Do assembly instructions exist?

Hi clearlynotstephan I've PM'd you.

An assembly guide is available by PM but whilst it's open source I'd like to limit cloning efforts for long enough to recover my costs so far so please don't publish it.

---

Simon Khoury

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

Quote
frankvdh
My piezo arrived during the week , so I spent a little time today mounting it.

I've got to say, I'm very impressed with the quality... a nice piece of kit! Instructions are clear and complete. (Except for the Zesty Nimble ad, which was in such small font as to be unreadable to my aged eyes.)

Without thinking about it too much, I got the screw-mount version, but would possibly have been better off with the groove-mount... I could have clamped that into my effector where the hot-end heatsink had been clamped. But, not to worry, a couple of 3mm holes through my effector and I had everything in place, except the filament feed. The red LED lit up with power, and the blue one with pressure

Now to attach the bottom end of the Bowden cable and away.... But my Bowden connector screws directly into the top of my hot-end heatsink (cheap Chinese E3D "clone" (I assume)

Any ideas/suggestions welcome!

I created a little thing for china clones to mount the coupler above the effector plate.
Take a look here: [www.thingiverse.com]

But you can not use the coupler that came with the hotend. Its too big. Use PC4-M5 or PC4-M6. I made one for each thread.

Quote
frankvdh
But you can not use the coupler that came with the hotend. Its too big. Use PC4-M5 or PC4-M6. I made one for each thread.

Looks good, but you can't push the Bowden tube thru, unless you drill them open. Which is a bit creepy with a HSS drill...

No but you can run a guide tube down from below the bowden adaptor. There is an advantage to this, it mechanically decouples the bowden tube from the piezo disc, but its only a problem occasionally, so drilling out the bowden coupler also works.

Edited 1 time(s). Last edit at 05/30/2017 09:59AM by DjDemonD.

---

Simon Khoury

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

Quote
o_lampe

Quote
frankvdh
But you can not use the coupler that came with the hotend. Its too big. Use PC4-M5 or PC4-M6. I made one for each thread.

Looks good, but you can't push the Bowden tube thru, unless you drill them open. Which is a bit creepy with a HSS drill...

With the PC4-M5 you are right, you can't push the PTFE through.

The PC4-M6 comes in two flavours and one is push through and you don't have to drill the coupler.

A bit more constructive criticism for the screw-attachment version:

1. I inadvertently found that touching one of the mounting screws with my finger (or a metal screwdriver blade touching my finger) caused the blue LED to come on. I suspect that this was because I didn't quite have the piezo disk centered, and that it was touching the screw or nut. Maybe leave another mm or so space between the disk and the screws? Or, better yet, have a more positive mechanism for positioning the disk correctly?
2. I haven't yet used the probe successfully. When I issue a G29 or G30, the head moves to Z=5.1mm, and an error message comes up on the LCD. I suspect that the problem is that the probe's output is the inverse of the (absolutely hopeless) endstop microswitch that my printer was originally fitted with. To test this, I guess I need to change the firmware -- something I have been avoiding. Maybe it's possible to have a 4-pin connector with 2 output signals, one the inverse of the other? Or at least mentioning this in the documentation?
3. When I first mounted the piezo, I did it with the PCB at the front to make the blue LED visible. That put the screws for the heatsink attachment at the back, out of sight, and made it awkward to attach the heatsink to the piezo mount. The two diagonal screws are a bit fiddly to position, especially when you can't see what you're doing. Subsequently, I've installed the piezo mount the other way round... the blue LED is still visible, indirectly.
4. With the Bowden tube going through the piezo mount down to the heatsink, it's awkward to remove the hot-end... the fairly-rigid Bowden tube stops the hot-end from sliding sideways out of the piezo mount.
   
   To address these last 2 points, I suggest something like this, with a hole through which the heatsink fits, and a single M3 screw which presses the heatsink against the far side of the opening, This worked very well mounting my hot-end to my effector, and is simpler than the current piezo mount design... no moving clamp part.
   
   
   

   Untitled.png

Hi Frank,

Thanks for providing such great and detailed feedback. Let me address your points in order:

1. Yes the capacitance of your finger will cause the PCB to "trigger" if you are touching the piezo disc or anything electrically connected to it, but under normal use this shouldn't be a problem. I take it you aren't seeing false triggers when you are not touching it? I chose to have the hole spacing as it is to ensure there is sufficient space between the edges of the part and the holes, it might be possible to tweak it slightly, I will look into that. One of the things I have already changed is to make the lip the piezo disc sits on slightly wider creating that more positive location. That part is available on thingiverse [www.thingiverse.com] if you wanted to try it instead of the one supplied.

2.Yes this probe operates in "normally open" logic i.e. goes High when triggered supplying 5v/3.3v (depending on supply voltage) to the signal pin. Most microswitches are configured as normally closed, and as such offer some fail-safe, which we are still working on. Inverting the logic in firmware is the least compromised solution. But It is also true that you can turn the Left/VR2 adjuster so that the LED is just illuminated instead of the point at which it just goes out. This reverses the logic, so that the PCB sends a LOW signal when triggered. The only issue with this is to make the unit light-up we had to specify a fairly powerful LED, which might not survive long term if it is constantly illuminated (only blinking off when triggered). So use this mode if you wish but I cannot guarantee the triggered LED.

The alternative is to get a small mechanical 5v relay, use the signal output from the piezo20 (green wire), to the coil of the relay. When it triggers it will open the NC contacts on the output of the relay. Feed 5v (or 3.3v if your controller uses it) to COM, then the NC output of the relay to your signal pin on your controller. This essentially inverts the signal. You can also do it with transistors.


3. Yes it was a difficult decision where to put the PCB, and I am the first to admit that this system might be less ideal if you frequently need to remove your hotend. You can relocate the PCB elsewhere by extending the piezo leads (carefully), but a very long wire can pick up interference. That being said I've yet to come across a hotend clamping system that allows for easy, quick change and yet holds the hotend firmly in place.

4.That is a possible clamp design worth looking into. Can you send me some files of that design, or point me in the direction of them, and I will have a look into it. I think what we tried to achieve was a very firm hotend clamp, partially to address the perpetual issue of groovemount being very unsatisfactory, so if this system can solidly clamp your hotend, and then screw mount to your printer you essentially are no longer relying on groovemount. But if it proves problematic then I will review it.

Hope this helps.
Simon.

Edited 2 time(s). Last edit at 06/01/2017 05:26AM by DjDemonD.

---

Simon Khoury

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

Surely a relay on the output isn't a great idea? There's a hard-to-quantify, possibly variable, and significant delay on the output which will serious reduce accuracy!

Simon, is the electronics open source? Where is the schematic?

Yes its open source, its on the website [www.precisionpiezo.co.uk]

A relay is just one possible way to do it, they switch faster and more reliably than they are given credit for. Changing the firmware is the answer, the firmware needs to be configured to use the right type of probe specifically in this case to use an active high output.

Edited 1 time(s). Last edit at 06/01/2017 06:10AM by DjDemonD.

---

Simon Khoury

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

If you must convert to an active low signal I can draw you a diagram of how to use a mosfet but really its best done in the firmware. Adding another circuit to the board would increase the part count and require larger connectors adding to the cost for a problem that I suspect affects only a very small number of people.

Re-tuning for an active low signal is guaranteed to damage the trigger LEDs if you're using 5v (ramps or smoothie). If you're using 3.3v it shouldn't be a problem, though I won't guarantee that.

Extending the piezo wires to re-mount the board provided the length is short, under 150mm will be fine, I don't know how long you can make those wires before problems start occurring.

The next batch of PCBs for PP20 modules has arrived. Unfortunately I'm tied up for a few days but they should be ready some time next week

Idris

---

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

The length of the leads I have experimented a bit with. I was using around 70cm leads on a delta and had the PCB situated on the frame, so that I could adjust it more easily. It worked fine until I added a second extruder to the machine. Then it became quite noisy. So longer leads can work but if you're getting flickering of the triggered LED, or the set point on Left/VR2 pot is a bit vague then your leads are possibly too close to sources of interference. Mounting the PCB somewhere on the effector is also a reasonable strategy.

---

Simon Khoury

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

For inverting the signal, there is no need to add more components to the board. It can be done on the connector to the controller with a small board there.

I'm interested in the DIY kit. Question: is it possible to mount the sensor somewhere on the hot end but not between the E3D v6 and the mount? I have a custom made hotend holder which holds two E3D v6 3mm hotends. Heated bed is also possible, although I have one that has 4 mounting points and no adjustment for extra stability. I'm guessing it needs to sense the force applied immediately, not the touching of the hot end on the bed.

Here's an image of the hotend holder. As you can see it's very compact, 66x46x41mm as a printed piece. It completely encapsulates the hotends with no room for the sensor.


Edited 1 time(s). Last edit at 06/01/2017 07:05PM by imqqmi.

---

--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Quote
DjDemonD
1. Yes the capacitance of your finger will cause the PCB to "trigger" if you are touching the piezo disc or anything electrically connected to it, but under normal use this shouldn't be a problem. I take it you aren't seeing false triggers when you are not touching it? I chose to have the hole spacing as it is to ensure there is sufficient space between the edges of the part and the holes, it might be possible to tweak it slightly, I will look into that. One of the things I have already changed is to make the lip the piezo disc sits on slightly wider creating that more positive location. That part is available on thingiverse [www.thingiverse.com] if you wanted to try it instead of the one supplied.

No false triggers. But I did wonder if the screw/nut touching the disk would affect the tuning? I did also wonder whether tightening the 4 screws down hard would damage the disk if it was out of place.

Quote


2.Yes this probe operates in "normally open" logic i.e. goes High when triggered supplying 5v/3.3v (depending on supply voltage) to the signal pin. Most microswitches are configured as normally closed, and as such offer some fail-safe, which we are still working on. Inverting the logic in firmware is the least compromised solution.

I'll go that route. Just thought that if there was a spare pin or room on the PCB for a transistor, this would be a nice option to offer.

Quote


3. Yes it was a difficult decision where to put the PCB, and I am the first to admit that this system might be less ideal if you frequently need to remove your hotend. You can relocate the PCB elsewhere by extending the piezo leads (carefully), but a very long wire can pick up interference. That being said I've yet to come across a hotend clamping system that allows for easy, quick change and yet holds the hotend firmly in place.

4.That is a possible clamp design worth looking into. Can you send me some files of that design, or point me in the direction of them, and I will have a look into it. I think what we tried to achieve was a very firm hotend clamp, partially to address the perpetual issue of groovemount being very unsatisfactory, so if this system can solidly clamp your hotend, and then screw mount to your printer you essentially are no longer relying on groovemount. But if it proves problematic then I will review it.

My effector design is at OnShape.com , but I've already changed it to match the screw-mount piezo. You would need to go back to V2 to see the clamp, I've extracted V2 in this design, but you may not be able to get enough detail from that. Feel free to copy whatever bits are relevant.

The "collar" part is designed to go in the groove and prevent any vertical motion of the hot-end, but I found there was enough friction that this wasn't an issue. And fitting the collar was fiddly I suggest you align the screw underneath the PCB if you can.

Edited 1 time(s). Last edit at 06/01/2017 07:54PM by frankvdh.

Hi Frank

I will take a look at the files.

As for tightening the unit down you want to tighten the four corner screws just enough that the upper and lower parts are firm. You can apply some preload to the disc, but don't tighten it down so tight you cracked the ceramic and bend the disc.

---

Simon Khoury

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

Imqqmi,

Yes you can place Piezos under the bed please see this thread [forums.reprap.org] for some ideas how to do it.

Other options include (for your setup) a piezo mounted somewhere in/on the carriage. As long as the piezo flexes (only slightly) or is compressed as your nozzle touches the bed then you can tune it to give a trigger. I've been experimenting with a piezo in a titan bracket which works this way.

I have found the hot end mounted system the most direct way to achieve this but it is only one of many ways to use these devices. They can be bonded to a surface that will flex and used to detect the flex. I have also got some piezo film to play with which does this even better.

The kit will be on the website www.precisionpiezo.co.uk as soon as I have piezo discs in decent numbers from the suppliers.

Edited 2 time(s). Last edit at 06/02/2017 03:54AM by DjDemonD.

---

Simon Khoury

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

Sounds promising, I'll have to think about a way to make it flex in my setup. Would it be possible to put the piezo disk between the x-carriage and the hot end holder?
Did you experiment with the sensor on a servo, just like the microswitch type? How does that affect accuracy? My problem with any modifications to the hotend or bed is that it adds another layer of flex/springiness to the system which results in more backlash etc. to the printing. The servo eliminates this but introduces inacuracies in probing the bed. I'll have to weigh the pros and cons, I haven't made up my mind about it yet. My accuracy so far is around 0.05-0.1mm which is just within the limits for a good first layer. If I can halve that it may improve the first layer, but I'm not sure if it really makes much difference.

---

--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

Hi the perpetual issue with nozzle contact sensing technology is the compliance introduced by adding a compliant element into the mechanism, such as a sensor. I feel we have solved that problem with something like the Piezo20 module as the hotend is firm, the sensor is permanently mounted. Piezos are perfect for this application as they are cheap, durable, and will generate large voltages for very little pressure/flex, can be preloaded (which is the secret to eliminating the compliance).

I do not like probes on the end of servo arms etc... the least bad version of this technology is something like Nebbian's z-bend sensor which uses the servo to deploy or stow the probe but the sensor is an optical endstop, so it achieves good repeatability between probings. Plus a sensor with an offset in x and y is anything from an inconvenience to a pain in rear end, especially on deltas where an element of tilt will occur even in the best machines. Piezo offers no offsets in x and y (perhaps 0.15mm in z but thats repeatable).

To give you an idea my delta with a 27mm piezo unit in the hotend, now calibrates across a 330mm bed to 0.006-0.01 deviation. At this point I have ceased to attempt to improve it (never thought I'd say that, but I cannot see how I could without spending ludicrous amounts of money and indeed what I would gain).

Edited 3 time(s). Last edit at 06/02/2017 05:28AM by DjDemonD.

---

Simon Khoury

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

Sounds good, but there's one thing that always bothers me when using the nozzle for bed probing: how do you deal with the bit of filament sticking to the end? Mine always seems to have some there, it's a bit springy. I think I've seen a Lulzbot cleaning its nozzle but that would loose some build area. I'd be interested to hear how you've handled this problem.

---

--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

We get asked this a lot. Probe with the bed fully heated. Set the nozzle temp to 130 deg C when starting a print. This is quick enough, and is below ooze temperature of any filaments & hotends I've used. Then clip the residual filament. (you are doing some element of this anyway right?)

Now probe. The temperature ensures no new plastic oozes out, that any residue is easy to squash and won't overly affect the first probing point and that you've closed the thermal expansion "gap", (calculated at 0.02mm for en e3d v6 going from 25 deg C to 250 deg C so it's marginal) before probing. Once probing is complete go to full hot end temp and print.

We recommend during initial commissioning to follow this procedure, then do a paper grab test to determine how much compliance is present in your sensor assembly or underbed mounts etc... it's usually between 0.1mm and 0.3mm. But it is a constant so you only do this once. Enter it as your probe z offset in firmware (it's a negative number as the trigger point is essentially below the bed). If you then want to add 0.01mm for thermal expansion you can (if you can be bothered). If using marlin 1.1 or RRF you can babystep z on the first layer, note the amount and add or subtract it from firmware probe z offset.

If you want to implement an auto nozzle clean (easier on some machines than others) that works too, clean the nozzle at 130 to remove residue but not allow any more to ooze out.

Hope this helps.

Edited 5 time(s). Last edit at 06/02/2017 09:19AM by DjDemonD.

---

Simon Khoury

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

Ok thanks for the info and time! As it works now, the hot end will heat up during bed level probing, during this time some of the filament oozes out and I remove it at that point. But I like the idea of heating it up to 130 first, then heating it up after leveling.

---

--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]

It would seem Slic3r doesn't allow to heat up the hotend after bed leveling as far as I can tell. I can do it manually of course but it would be nice if it's in the generated gcode.

---

--
Kind regards
Imqqmi

NFAN CoreXY printer:
[reprap.org]