Auto Z Stop using all metal hotends

So i was thinking last night that all metal hotends would make it very easy to make a auto Z stop.

had a play the weekend using a E3D V4 hotend.

Crocodile Clip to the top of the hotend which runs to 1 wire of the Z min on ramps

Then some copper tape on the glass bed with a wire attached to the copper and then running again to the Z Min on ramps.

tried it and it seems to work

i thought humm oozing plastc might cause a problem. it seems to not.

heres a video http://youtu.be/PhacRCle_UE

Would be interested if other people try this and how they get on.

Dont blame me if it doesnt work and it breaks your glass!!

Doesn't work. I have kapton tape on my bed. Oh, and I use the already sufficient adjustable endstop on the side of the machine. And, how will you ever be able to level your heatbed with the correct height? If you calibrate it well, the hotend doesn't touch your heatbed, but floats right above it You should be able to slide a piece of paper underneath it.

Also, it's kind of making a simple thing more complicated, thus probably creating much more variables that you haven't thought about yet that you add and actually make it more prone to failure.

Nice idea though, I like out of the box thinking, I also had a similar idea, but using a Z-endstop mounted on a retractable arm on the extruder but I ditched the idea because I wanted a lighter extruder.

Shouldn't matter what tape you have on your bed.

as long as you use a small bit of conductive tape to finish the circuit it should work.

and in terms of leveling the bed the Z should hit in the top left corner so leveling your X and Y comes after that.

in therms of you should be able to slide a paper under it. You are causing it to be a paper high by the height raised by the copper tape. (the copper tape would go into top of your kapton so is then 1x copper tape higher then the kapton).

Did you take this idea from CNC mill Z height probe systems? Cause after reading about how some mills can automatically detect tool length with pretty much exactly the same system as you are using, I also thought about using the hot end (or a metal spike on the X carriage) as circuit closing element for the Z endstop. The only problem would be homing Z in a different position, which ultimately kept me from using this system. But it is nice to see that it indeed works.

not seen the cnc mill.

iv always wanted to do this but was a problem connecting to the hotend heater block. but with all metal hotends you have conductivity all the way up so you can connect to a cool area.

im hoping to get a prusa nozzel start of next month (as long as there are some left) this i think will offer a better option instead of a crocodile clip as the hotend goes into a large mount plate which will also conduct the electricity.

just had a look the cnc mill video i think your refering too. its another idea which would work nice. you could have a sensor wich homes at a might higher hight by pressing a button. then have start gcode which comes down depening how hight your button device was.

i also had ideas of using a presure sensor under the glass to sense when the glass was touched but didnt go down that route as it would lift the glass in one corner.

i think having a small bit of copper tape seems to work nice. and if you want your nozzel higher you can just add copper tape onto to give it another 100 microns (depending how thick your copper tape is)

uGen Wrote:
>The only
> problem would be homing Z in a different position,
> which ultimately kept me from using this system.
> But it is nice to see that it indeed works.

Not a problem, home Z and use G92 to adjust the current Z coordinate to give whatever offset you want.

Enlightx, i noticed the glass plate on your board is cracked. is this from trial and error?


the concept is nice, is there a failsafe you can add to make sure it does not go past a certain distance?

for example, if i home and the limit switch fails, what damage would i end up with. the ideal answer is hopefully none.

hehe no i broke the glass the day before.

quite funny really.

a hand made clay/resin model (by tom lewis) fell from a shelf above my printer and cracked the glass.

i think it was an attack on 3D printers taking over hand made art LMAO

should be getting new glass today so i can try and get this setup a lot neater.

i plan to solder a wire to the copper tape but hide the wire connection under the heated bed. (folder copper tape around glass and bed)

will post better pics / video on my twitter when its sorted

Not a bad idea,

Not to hard to to wire up either.

But I'd be worried that a bit of extrusion stuck to the nozzle would prevent the tip from making electrical contact, and drive the head into the copper plate.

Quote
Andrew Smith
Not a problem, home Z and use G92 to adjust the current Z coordinate to give whatever offset you want.

Yes, you can set the Z height this way, but what I actually meant was that you cannot home Z on an arbitrary X/Y position. Sometimes, this is necessary, like after running into problems mid-print, so that you will crash the hot end into the unfinished object if you homed on the usual position.

Putting a homing switch on Z max like Nophead did on the Mendel90 kits and using the bed/hot end switch as a secondary referencing point (for example if you use hot ends of different dimensions, calibrating Z or whatever) might be very useful, though. After all, you don't have to calibrate the Z offset every time or after a mid-print problem.

Found this thread after finding your youtube video. I had been planning on setting this up myself so I decide to use Google to see if anyone else had tried it. I have the same hotend and I have a prusa nozzle. Being able to switch them out and not having to mess with my stinking endstop will be great. I was thinking if it works I would solder a short wire to each hotend with a plug so I can swap easily. I assume you need to make sure you get to temp on the nozzle an wipe the ooze before homing. I do that anyway because more than once I've had let a cool hotend with a little plastic sticking out keep it from hitting my endstop and then screwing up and leveling when the nuts screw out from under the carriage. Great I idea and I'll let you know how it works for me.

I finally got around to setting it up. I hadn't gotten any conductive tape so I just used square of aluminum foil that I taped down with some Kapton. It works great. I did find that I had to set my Z offset to .2 but once I did that I got the best first layers I've had so far. It working very consistently. Of course getting solder to stick to tab of aluminum foil and the aluminum sink on the hotend was almost impossible. My solution is temporary, but definately am hoping to use the setup as my go forward. The two concerns I've had were 1. getting consistent results and only time will tell on that, but I ran several pieces over the weekend and it was much more consistent than my mechanical hotend and 2. being able to home the z axis from any position in xy space, but so far I haven't needed to do that or found a reason that I couldn't take the x and y axis to home before homing the z axis.