Conductive Paint

so i had this genius idea

Instead of fighting with my z arm / servo / endstop switch to make sure my board is level how about.

1. Get a conductive paint for the top of the plate
2. Run a wire with heat casing from the hot tip to Z end stop
3. run wire from conductive bed to the end stop ( hell for that mattter just another wire that is longer then the hot end)
4. Side benifit i dont have to tape or glue stick my board anymore!

Anyway this sounds so perfectly easy that there has to be a reason its not an in wide use plan already. Anyone tried this yet ?

Lulzbot Mini, Taz 6, Zortrax does something similar, but instead of conductive paint they use conductive things on certain spots. It tends to fail over time because plastic on the nozzle isn't very conductive, if you know what I mean. This scheme works for CNC routers because usually the bit is pretty clean.

Conductive paint is a bit expensive (36$ per kg + shipping), if you need to keep reapplying it I don't think you'll see many benefits from using it.

Thought of this, and same thing. The nozzle spends its time extruding very non-conductive plastic, some of which ends up on the nozzle.

Using a steel or aluminum build plate, this would seem to be kind of a no-brainer otherwise. In this case, I would connect the sensor end to the hot-end, and ground the build plate. Pull-up resistor for the hot end, and contact to the grounded build plate would pull signal low.

Potential problems: Get a short from the heater wires to the hot end and say goodbye to your control board. you could probably deal with this by using a smaller control board, maybe charge the hot-end to VIN instead of 3.3/5V but that causes other problems with a short, including potential over-current.

if there is melted plastic on the hot end, you're going to get a crash. If there's plastic on the build plate, you'll get a crash. Way too much to go wrong.

Edit: Maybe with a brass brush for the nozzle it would be better.

Edited 1 time(s). Last edit at 12/20/2018 04:06PM by SupraGuy.

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

Conductive paint would work to make a force-sensitive resistor, or a few of them all over the print area. You'd use a MCU (like an attiny85) to measure the resistance and generate a low signal when it changed.

A force sensitive resitor would be triggered by a plastic blob on the nozzle, too. But the trigger-height would be wrong.

Conductive paint on the bed ? Indeed ! But ? Force sensitive resistor ? Why not but what about strain gauge or piezo or ... ? Yet, let's make it simpler and have just one sensor integrated in the printhead

Plastic blob on the nozzle ? No big deal, home when all is at working T°, eventually wipe before homing and make your sensor trigger around 1N.

Working like that for about 2 years.

Many ideas get reinvented regularly as they disappear then are forgotten, because they are not practical, unfit or too early (you got to be Da Vinci for that )

Sometimes you even end up with loops, like belts replaced by leadscrews replaced by wires then back to belts etc...

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

in theory this might sound like a good idea, but you want something that wont scrape away. these fdm machines are low impact, not zero impact machined.

look for a way to have reliability for homing purposes. such as a servo arm that lowers a leg with a reliable contact switch, or use a capacitive sensor that does not need to touch the bed but approximates its height.

if using manual adjustments for calibration calibrate for its running time state of temperatures. heated nozzle temp (less critical with stainless steal) and bed temp at whatever temp you use for the item being printed.

print 1st layer slower and over extruded, it is far easier to remove slag of first layer that to have a failed part from non adhesion.

my personal choice would be either an accelerometer sensor that senses stop force, and retracts head after it senses slow down from slow speed crash, or a capacitive sensor that goes near surface.

you would be better off in my opinion using a sensor that does not directly rely on the impedance of the nozzle, or the conductivity of the bed. especially when plastic that flows thru the nozzle is a good insulator.

Had the same idea, thought to try it on cr-10 aluminium bed... found that the aluminium bed, although it looks like bare metal, is treated and it is not conductive . Next step was to cover the glass sheet in aluminium adhesive tape(for testing purposes), modify marlin to invert the endstop type to be normally open (default is normally closed), connected a wire of the endstop to bed and another to the hotend. With no filament it worked beautiful. The problem is that as soon as you load the filament and heat the nozzle, the plastic is leaking from the nozzle and the hotned is pushed into the bed until the plastic is squeezed and the nozzle is touching the bed, so I abandoned the idea. Another problem was that the plastic won't adhere to aluminium...

Edited 1 time(s). Last edit at 12/21/2018 03:48PM by driver_x.

Quote
MKSA
Conductive paint on the bed ? Indeed ! But ? Force sensitive resistor ? Why not but what about strain gauge or piezo or ... ? Yet, let's make it simpler and have just one sensor integrated in the printhead

Plastic blob on the nozzle ? No big deal, home when all is at working T°, eventually wipe before homing and make your sensor trigger around 1N.

Working like that for about 2 years.

Many ideas get reinvented regularly as they disappear then are forgotten, because they are not practical, unfit or too early (you got to be Da Vinci for that )

Sometimes you even end up with loops, like belts replaced by leadscrews replaced by wires then back to belts etc...

Some dude did a bed touch sensor for an Anycubic Delta using FSR's and an arduino and it's so sensitive the tape on his build platform didn't even have any marks from the nozzle. I bought a piezo kit which was just an OPAMP and a couple of piezo discs and just couldn't get it to work reliably, plus it was really easy to destroy two of the disks.

Here's it in action:
[www.youtube.com]


And here's a kit much cheaper than the Precision Piezo and likely more reliable. It's just what I described: three FSR's and an Attiny85.

[www.ultibots.com]


Here's a dude doing it with just an opamp circuit (the kind that comes with arduino "soil moisture sensor"). He needs to adjust the opamp reference just for the temperature he wants. An Attiny85 could do this on the fly.

[www.youtube.com]

Now I really need to get me some FSR's

Edited 1 time(s). Last edit at 12/21/2018 10:19PM by ruyvieira.

Quote
ruyvieira

Quote
MKSA
Conductive paint on the bed ? Indeed ! But ? Force sensitive resistor ? Why not but what about strain gauge or piezo or ... ? Yet, let's make it simpler and have just one sensor integrated in the printhead

Plastic blob on the nozzle ? No big deal, home when all is at working T°, eventually wipe before homing and make your sensor trigger around 1N.

Working like that for about 2 years.

Many ideas get reinvented regularly as they disappear then are forgotten, because they are not practical, unfit or too early (you got to be Da Vinci for that )

Sometimes you even end up with loops, like belts replaced by leadscrews replaced by wires then back to belts etc...

Some dude did a bed touch sensor for an Anycubic Delta using FSR's and an arduino and it's so sensitive the tape on his build platform didn't even have any marks from the nozzle. I bought a piezo kit which was just an OPAMP and a couple of piezo discs and just couldn't get it to work reliably, plus it was really easy to destroy two of the disks.

Here's it in action:
[www.youtube.com]


And here's a kit much cheaper than the Precision Piezo and likely more reliable. It's just what I described: three FSR's and an Attiny85.

[www.ultibots.com]


Here's a dude doing it with just an opamp circuit (the kind that comes with arduino "soil moisture sensor"). He needs to adjust the opamp reference just for the temperature he wants. An Attiny85 could do this on the fly.

[www.youtube.com]

Now I really need to get me some FSR's

Why buy a FSR, make it. Many people have done it since 1870

Edited 1 time(s). Last edit at 12/22/2018 01:03AM by MKSA.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

You know that's actually a good idea? You can make one with two bits of copper clad and a sheet of conductive foam, both of which I just happen to have lying around

I've been playing with ideas. I'm happy with the Precision Piezo kit that I have, so I haven't done anything with it, but I have a kitchen scale that the LCD display died on, but so far as I can tell still works. I've taken the sensor from that, and wanted to play with it. I think that's an FSR that the scale works on. It seems like an idea. Considering that the kitchen scale is cheap, or in this case, costs nothing, other than not throwing it away immediately....

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MBot3D Printer
MakerBot clone Kit from Amazon
Added heated bed.

Leadscrew self-built printer (in progress)
Duet Wifi, Precision Piezo parts

Quote
ruyvieira
You know that's actually a good idea? You can make one with two bits of copper clad and a sheet of conductive foam, both of which I just happen to have lying around

You could wire it in a wheatstone bridge-fashion to amplify the difference.
Or use one on each side of the plate and use an OP-AMP to amplify the difference.

Quote
o_lampe

Quote
ruyvieira
You know that's actually a good idea? You can make one with two bits of copper clad and a sheet of conductive foam, both of which I just happen to have lying around

You could wire it in a wheatstone bridge-fashion to amplify the difference.
Or use one on each side of the plate and use an OP-AMP to amplify the difference.

Not could, MUST !
If you don't see these FSR given in ref, used for Z homing it is because people who can design the required mechanic, electronic concluded they are not the best choice for it.
BTW A strain gauge IS a FSR



.

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Quote
MKSA

Quote
o_lampe

Quote
ruyvieira
You know that's actually a good idea? You can make one with two bits of copper clad and a sheet of conductive foam, both of which I just happen to have lying around

You could wire it in a wheatstone bridge-fashion to amplify the difference.
Or use one on each side of the plate and use an OP-AMP to amplify the difference.

Not could, MUST !
If you don't see these FSR given in ref, used for Z homing it is because people who can design the required mechanic, electronic concluded they are not the best choice for it.
BTW A strain gauge IS a FSR

.

What is the best choice then? An RC servo raising and lowering a switch? Look at the videos I posted

Or even better, read what people using FSR's have to say about them. It still pains me that to this day companies who make "professional" 3d printers in Brazil are using the little chinese blue servo for bed probing.



Edited 1 time(s). Last edit at 12/25/2018 12:06PM by ruyvieira.

or you could level with your ears, no conductive paint needed.

Any progress with these under bad FSR ?

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"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)

Didn't receive them yet

Some people say they don't work at all for large beds, which is not my case