Piezo20 probe and piezo kit now available
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This is quite interesting and I would like to find what is giving rise to the differences that we getting. The setup arrangement that I use and the sort of outputs I get are shown in the original article of the RepRap forum thread http://forums.reprap.org/read.php?1,635075,page=1
I have not documented my studies of bending but the setup was a 27mm piezoelectric disk epoxied to a 70mm by 30mm piece of 1.6mm FR4. One end was secured and a point load applied at the other end. Once I saw how much output I was getting I tried tapping with an admittedly uncalibrated finger on both the new "flexing mode" setup and the old compression mode setup. The difference was 2.7V from the compression rig and 7.4V from the flexing rig.
I use "no-name" piezo disks as I have found that the sample to sample spread is less than the Murata devices - which also have the opposite polarity of output. The Murata disks are less temperature sensitive.Mike
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Made a few slight mods to the design, added a small lip above the lower sections to avoid the bowden coupler being squeezed (and disconnecting) when assembling the unit. This should also decrease the contact area onto the piezo for a stronger signal. Made a slight cutout in the upper section to allow the piezo to bend slightly more. On thingiverse.
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the piezo method is well beyond my capability I think to be fair I may try to get rid of the tilt completely instead lol. I wouldn't know where to start or what to wire to where so unless doug makes it for me and tells me I'm screwed lol
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I like the one company that's using an accelerometer to detect the impact, Congrats on your work however, hope it all works out well.
Jeff
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Rommie, its not very tricky really, you need a board which Moriquendi can make for you for a donation to his charity, and a sensor the total cost is about £10. Print the (3) parts and assemble it, then adjust the board to get a trigger when pressing up on the hotend, but not when just moving around (I actually don't mind if it triggers a bit when moving as I set slow speeds for bed probing and normal speeds for printing and I am not using the probe when printing so it doesn't matter), instructions are provided. Then setup your z probe (I can provide details for this for duetwifi, I will plug it into a ramps board too and work out the config required).
After that you're away. Super accurate, nozzle based probing! I am still improving the design to find the optimum between sensitivity (which is very high with piezo's - so plenty of headroom here) and nozzle firmness. The latest revision is very sensitive and works but my nozzle is too wobbly for my liking.
Jeff thanks for the thumbs up, I've seen the SeeMeCNC accelerometer z probe but then also read comments suggesting it would be difficult/impossible to make it work - thats beyond me I am not an electronics native.
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My sensor board arrived this morning (Only ordered it on Sunday)
Doug
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ok so need a sensor board then, Moriquendi have you got any boards left buddy?
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Sean
You need to PM him he is not normally on here he did have 5 on Sunday?
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I've got two left, PM me if you're interested.
Moriquendi
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I've got two left, PM me if you're interested.
Moriquendi
Just to let you know mine arrived safe and sound yesterday
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So latest version mk 2 draft 5,on thingiverse http://www.thingiverse.com/thing:2034152 so far very firm nozzle if done up tight when assembling, plenty of sensitivity for probing. Hitting 0.011 deviation when probing so very pleased.
Plus Lykle has made an effector version for Haydn's setup which will be Nimble extruder compatible too.
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Yes and I can add a base plate you can use if you are not going to use a Nimble.
Simple little modification.It integrates DjDemonD's system with the new effector by Haydn.
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Yes and I can add a base plate you can use if you are not going to use a Nimble.
Simple little modification.It integrates DjDemonD's system with the new effector by Haydn.
Lykle
Have you published it anywhere yet?
How's the Nimble coming along?
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I've got two left, PM me if you're interested.
Moriquendi
Just to let you know mine arrived safe and sound yesterday
Have sent a message buddy
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The design will be on Thingiverse. I was kinda waiting for DjDemonD to print it first to see if it would work, before publishing it, but I will do it as a work in progress. So be aware it is untested as yet.
edit: Here is the thing: http://www.thingiverse.com/thing:2047422
The Nimble, is ready to go, we are chomping at the bits to go. Wait is for the legal stuff. We now have a registered company so it is a matter of days rather than weeks before we can open the web shop. Need to get the bank account and register it with Paypal, that sort of stuff.
It is amazingly difficult to find a bank that will accept 2 business partners that live on separate continents. They all insisted Brian to come into the office and sign in person. A 27 hour one way trip. Not going to happen. But we have it sorted now. (sorry, going off topic here) Rant over, I will post the designs now on Thingiverse. -
The design will be on Thingiverse. I was kinda waiting for DjDemonD to print it first to see if it would work, before publishing it, but I will do it as a work in progress. So be aware it is untested as yet.
edit: Here is the thing: http://www.thingiverse.com/thing:2047422
The Nimble, is ready to go, we are chomping at the bits to go. Wait is for the legal stuff. We now have a registered company so it is a matter of days rather than weeks before we can open the web shop. Need to get the bank account and register it with Paypal, that sort of stuff.
It is amazingly difficult to find a bank that will accept 2 business partners that live on separate continents. They all insisted Brian to come into the office and sign in person. A 27 hour one way trip. Not going to happen. But we have it sorted now. (sorry, going off topic here) Rant over, I will post the designs now on Thingiverse.Good news?
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Sorry didn't get chance to print it but I suspect others may have done already by now. Looks great.
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I'm glad everybodies boards have arrived, if you have feedback I'd like to hear it. I know that the trimmers are too small, it's hard to visualise how tiny something is by the footprint in the PCB software.
I'm currently debating getting some V1.1 boards made with:
Individual connectors for three Piezo elements
Onboard series resistors for each element
6mm trimmer pots (standard size)
Footprint to replace VR2 with fixed resistors (VR2 seems to be a fairly fixed value)I also have a board design for replacing endstops with piezo elements, three separate channels with three outputs.
Thoughts welcome.Moriquendi
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well sent my donation to Moriquendi last night and bought my piezo today so just need to print the parts and then get it all together and fitted I guess, have you got any config changes that is required DJ and wiring diagram to the duetwifi board if you could, thanks in advance
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I intend to edit this as it develops. This now refers to the Mk III version (http://www.thingiverse.com/thing:2069480)
Edited 29-01-17
Edited 22-01-17
Edited 21-01-17
Edited 20-01-17So when assembling ensure the top circular part is attached to the lower clamp parts fairly firmly, doesn't matter if it bends a bit, get the torque around equal on each side. Then firmly attach it to the effector. Make sure the clamp is sliding on the rods. There will be almost no nozzle wobble if the clamp slides on the rods but doesn;t rock laterally.
Okay so I have these two gcodes, about 10 lines up from the bottom in my config.g
M558 P1 F500 I1 X0 Y0 Z0 ;analogue piezo sensor output falls on contact, probing speed 500 mm/min
G31 X0 Y0 Z0 P600 ;sensor is nozzle, offsets for probe (nozzle) and trigger value.M558 sets an analogue sensor using the z-probe connector with an inverted output i.e. drops as it contacts the surface. It does not home any of the axes. I have selected probing speed 500 mm/min which gives the bed a firm tap, this increases the gap between signal and noise from the piezo sensor.
The G31 offsets are 0,0,0 although depending on how compliant the assembly is it might need a tiny offset for z. So Z could read 0.05 to 0.015. You are likely to need a slight positive offset to counteract the fact that the assembly squashes down slightly into the bed to trigger (like with FSR's). You can add this offset in your slicer if you prefer. I think David is implementing babystepping soon which will be great. P600 is the trigger value from 0 to 1000. I chose this value by connecting it up, setting the signal board (see below) then moving around a bit and seeing what value is displayed under z-probe on the web interface during travel moves and sudden jerks etc… I chose a value above this, to prevent false triggers.
Wiring. On Moriquendi's board the piezo has a two pin connector. I believe + and - need to go the right way around, the piezos come with red and black wires. It seems initially as though the series resistor is not required - but watch this space.
The other side has +, -, sig which go to the Duetwifi z-probe port. You need a 3 pin connector at Moriquendi's board and a 4 pin connector on the duetwifi.
On the duetwifi the z probe connector has 4 pins looking from the front of the board (the side with the LED's and USB port), the closest pin is signal, the next is -, the 3rd is unused and the 4th is +.
On the signal board there are two trim pots. Adjust them cautiously if the power is on, as you might with a step stick, I momentarily made contact with something with my screwdriver bit and it triggered a reboot on the duetwifi - no damage done but take care! As I have mine configured (which is slightly different to Moriquendi's instructions) I turn VR2 until the led just comes on, then around a quarter turn more. Then try a few upward presses on the hot end, if it flashes off/on convincingly you are probably there, if not try VR1 in a variety of positions and try a few more head moves and nozzle pushes. You're looking to minimise triggers under normal movement but get a solid off/on on the LED when you push up on the hotend. If you see a few slight flickers during head movement that's okay, as long as when you press up on the hotend you get a much more obvious off-on on the LED. Don't be tempted to set it up so that only a really hard push gives a change in the LED this won't be sensitive enough. Mark the trim pots when you have a good position, they are very sensitive.
Alternatively you can set VR2 so the LED just turns off, which is Moriquendi's method, then adjust the sensitivity on VR1, it seems to reverse the logic so that the signal rises as the piezo is bent/triggered. If you prefer this mode then change I1 to I0 in M558. I have not found this mode to work as well but let me know if you do.
I have these lines in bed.g before probing, please modify to suit your machine, basically its low motor current, low jerk and low acceleration.
;slow down movement to improve accuracy, improve probing and lmit damage in case of head crash
M906 X500 Y500 Z500 E800 I60 ; Set low motor currents (mA) and increase idle current to 60%
M201 X250 Y250 Z250 E1000 ; Accelerations (mm/s^2)
M203 X15000 Y15000 Z15000 E3600 ; Maximum speeds (mm/min)
M566 X100 Y100 Z100 E1200 ; Maximum instant speed changes mm/minuteand these after
;restore speed settings to normal printing speeds
M906 X1100 Y1100 Z1100 E800 I60 ; Set normal motor currents (mA) and increase idle current to 60%
M201 X3000 Y3000 Z3000 E1000 ; Accelerations (mm/s^2)
M203 X15000 Y15000 Z15000 E3600 ; Maximum speeds (mm/min)
M566 X1200 Y1200 Z1200 E1200 ; Maximum instant speed changes mm/minuteSo that the machine accelerates/decelerates and jerks much less for probing, improving accuracy and eliminating false triggers.
Make sure you delete your config_override.g file and set the approximate height in m665 in config.g by jogging down and measuring the distance travelled. This assembly lowers your nozzle by around 15mm (Lykle's effector does not so ignore this bit) if you don't do this (or forget to delete config_override.g) you will crash your nozzle on the first run.
Calibrate with the bed hot, but with the nozzle, depending on the toughness of your printing surface, either stone cold - in which case you will need a z offset when printing as the hotend will expand when heated. Do the paper grip test after calibration to determine how much z offset. Or with the nozzle at your full first layer temp - I don't use this as a head crash onto printbite with nozzle at 250 deg C melts a hole in it, perhaps brief contact doesn't but I don't want any more holes, so I use 160 deg C (below ooze temp for ABS) and have a +0.2mm z-offset which I set in slic3r. I set the nozzle to come up to 160 in start gcode before autocalibration at start of each print, then to first layer temp after probing. It's better to have the nozzle hot (at least above glass transition temp) in case there's a bit of filament on the end from the last print, which will just squash down to nothing.
A video of how I have it setup, and it working is now on youtube, apologies for the low production value.
https://www.youtube.com/watch?v=F3vi6BOi6sAAll feedback and any grammatical/spelling errors let me know I will try to incorporate this into the thingiverse listing along with some idiots-guide assembly pics, and make a wiki page here/wherever needed.
