prusa i3 MK2 - my way ...  

Re: prusa i3 MK2 - my way ...

...You say you used a cheap e3d clone, did you have to modify the extruder body to fit that?...
yes, of course. my cheap e3d v6 hotend has had a bowden fitting at the top and came with a piece of ptfe tube. i altered the *.stl with designsparks mechanical 2.0 (-> you need to convert the *.stl into a solid before you can alter it), so that the fitting with the ptfe tube has enough room and sits a few mm under the extruder pulleye, exactly where it should be.

i just did it twice, with the MK2 and the MK2S extruder body, that's why i can show you a picture about how it looks like (the other one is inside my printer now).
finally i decided to assemble the MK2 version at my printer, because the p.i.n.d.a. mount works quite well for me and i can still use a protector for the probe.

Re: prusa i3 MK2 - my way ...

...Do you think the PINDA probe accuracy could also be increased by inserting a resistor in series in the correct cable, to drop the voltage ever so slightly?...

💡 no, a simple resistor won't do the task. but this little circuit should do:
pinda_sensitivity_adjustment.jpg

and just to remind you: it doesn't increase the accuracy, only the sensitivity. and i don't know if it works well for all probes... but it does at least at my two.

➡ about the cables: every single cable might be affected.
just make sure that none of the cables is going to be bend continiously at an sharp angle. the wider the radius, the better.
for me the 50cm nylon filament (as at the genuine kit) wasn't enough. the nylon enforcement inside my cable trunks is about 80cm long.

Thanks for that, I think I have a vague understanding how the diagram works. R1 is a trimpot and serves to fine-adjust the circuit I suppose?
Accuracy vs sensitivity....hmmmm......it's probably less accurate when it's more sensitive, because the accuracy error would be a certain fraction of the detection distance.

You are right about the cable length / radius of the cable arch between attachment points. When I came up with the idea to 'Nail it' I made a mistake by cutting the 3mm filament shorter. I should have left it unchanged and released as much of the bunched up cables from the RAMBo as possible. The stiffened section due to the nail has effectively shortened the radius of the cable and causes increased bending at the RAMBO end and increased bending everywhere except for where the nail is. http://shop.prusa3d.com/forum/prusa-i3-kit-building-calibrating-first-print-main-f6/self-test-error-t2724-s10.html#p21624

Re: prusa i3 MK2 - my way ...

...You say you used a cheap e3d clone, did you have to modify the extruder body to fit that?...
yes, of course. my cheap e3d v6 hotend has had a bowden fitting at the top and came with a piece of ptfe tube. i altered the *.stl with designsparks mechanical 2.0 (-> you need to convert the *.stl into a solid before you can alter it), so that the fitting with the ptfe tube has enough room and sits a few mm under the extruder pulleye, exactly where it should be.

extruder_modified.jpg

i just did it twice, with the MK2 and the MK2S extruder body, that's why i can show you a picture about how it looks like (the other one is inside my printer now).
finally i decided to assemble the MK2 version at my printer, because the p.i.n.d.a. mount works quite well for me and i can still use a protector for the probe.

20170421_233914.jpg

Looks Great! What is the plastic for the mount? is that plATech?
I don't think I have the same clone, mine has a heatshrink about 1.5x the diameter of the e3d. But I have seen these clones with the bowden fittings on amazon for cheap.
Think I will invest in one and print a back up mount in plATech.

Re: prusa i3 MK2 - my way ...

...Looks Great! What is the plastic for the mount? is that plATech? ...
➡ yes, biofila platec. be careful when you print it: it sticks like 😈 to the pei sheet. it's a good idea to add "mouse-ears" somewhere, so that you have a chance to lift the print with a spatula.

...Thanks for that, I think I have a vague understanding how the diagram works. R1 is a trimpot and serves to fine-adjust the circuit I suppose?
Accuracy vs sensitivity....hmmmm......it's probably less accurate when it's more sensitive, because the accuracy error would be a certain fraction of the detection distance. ...

💡 yes, it's a very simple standard circuit called "emitter follower". with the little pot you adjust the voltage at the base of the transistor and at it's emitter you get the same voltage minus UBE, which will then feed the p.i.n.d.a. probe with a lower, but accurate voltage (assuming the input voltage from the rambo board is stable).
➡ as i already stated, my "deaf" probe started to work at about 3.30V and was very sensitive then, but i got miss readings twice (out of approximately 20 calibration sequences).
so i decided to adjust the voltage 0.5V higer, which now delivers quite stable and reliable readings.
😕 the miss readings might have also been forced by the fact that i live only a few wavelengths away from the DCF77 long-wave transmitter, which delivers the time signal for the radio controlled clocks in main europe. and the p.i.n.d.a. probe operates at a similar frequency...

Re: prusa i3 MK2 - my way ...

Seriously... WOW!!! Don't even know what else to say.

Amazing job, no wonder you know so much about these printers!

Re: prusa i3 MK2 - my way ...

Hi Jeff,

Vey nice build! Would you like to share the files you changed to get the Prusa firmware (3.0.10) working with a Ramps board?

Karl

Re: prusa i3 MK2 - my way ...

Hi Jeff,

Vey nice build! Would you like to share the files you changed to get the Prusa firmware (3.0.10) working with a Ramps board?

Karl
sorry Karl, but i don't intended to do so. there are several reasons for this. but here i described the things you need to consider and alter.

Re: prusa i3 MK2 - my way ...

Hi Jeff,

No problem and thanks for the link.

Karl

Re: prusa i3 MK2 - my way ...

I thought you can't get a genuine MK42 heat bed. How?

Re: prusa i3 MK2 - my way ...

https://www.indiegogo.com/projects/mk42-heated-bed-ultimate-3d-printer-build-plate #/

Re: prusa i3 MK2 - my way ...

I thought you can't get a genuine MK42 heat bed. How?
you can get it from the prusa shop as a spare part, if you've bought an mk2 and asked the sales team to grant you access to the prusa spare-parts section.
i don't think this section will be unlocked for you if you aren't a known mk2 customer.
but take a seat before you look at the price for the genuine heatbed !

@david.t2:
thanks for that link ! even so it's not a genuine mk42 bed, it looks very promising (really curious about the quality now).
by the way, i already asked a pcb company here in germany how much it would cost to produce an mk42, based on the open available sources.... but it was far to expensive if produced in low numbers.

Re: prusa i3 MK2 - my way ...

i already asked a pcb company here in germany how much it would cost to produce an mk42, based on the open available sources....

jeffjordan,

Would you be willing to post a link to "...open available sources..."? I can't seem to find anything very detailed. I would like to see if it is feasible to build a larger version of this bed.

Thanks,
Joe

Re: prusa i3 MK2 - my way ...

PR's github is quite well known. 😉
https://github.com/prusa3d/Original-Prusa-i3/tree/MK2/Heatbed%20MK42

Re: prusa i3 MK2 - my way ...

David,

Okay, so I have a little egg on my face. Sorry for the rookie mistake.

I never thought to look at github. I don't know why. Perhaps age is catching up with me?

Anyhow, after I posted the above question, I took another shot at google and I did find the stuff on github.

Now I just need to figure out what software was used for the layout and schematic files. Of course, I have made exactly zero effort on this so far. So don't feel you need to help me on this. At least not yet.

But if you happen to know and aren't too busy... 😀

Thanks for the quick reply,
Joe

UPDATE: I think I figured it out. It was created using Eagle, right?

Joe

Re: prusa i3 MK2 - my way ...

It was created using Eagle, right?
Bingo. 😆

Re: prusa i3 MK2 - my way ...

I thought you can't get a genuine MK42 heat bed. How?
you can get it from the prusa shop as a spare part, if you've bought an mk2 and asked the sales team to grant you access to the prusa spare-parts section.
i don't think this section will be unlocked for you if you aren't a known mk2 customer.
but take a seat before you look at the price for the genuine heatbed !

@david.t2:
thanks for that link ! even so it's not a genuine mk42 bed, it looks very promising (really curious about the quality now).
by the way, i already asked a pcb company here in germany how much it would cost to produce an mk42, based on the open available sources.... but it was far to expensive if produced in low numbers.

JEEEZZUZZ!! whats so freaking expensive! i cant BELIVE how expensive the genuine heatbed is! By the way dude... you built that printer EXACT how i Dream of building mine
amazing work!

Re: prusa i3 MK2 - my way ...

...
JEEEZZUZZ!! whats so freaking expensive!
price is mainly a function of supply and demand, the role of labour, material and production costs is often overrated.... and because actually the run on i3 mk2(s) is very big, the price will stay high as long as it remains an exclusive source (won't say monopol). furthermore it is the good right of prusa to protect their shares.

my infrared pictures of the MK42 (1)

just had the chance to borrough a testo 875-2 from work and made some pictures of the mk42 at the printer.

first the unheated mk42 heatbed. you can see that the z-steppers are still "under current" and produce a little bit of temperature (picture was taken about 1/2h after powering up the printer):

now the printbed heating up to 40°C:

and here @60°C:

my infrared pictures of the MK42 (2)

now @100°C:

and here the max. temperature that i can reach without enclosure (131°C):
by the way: the heatbed at my genuine kit can't get beyond 119°C.

the cooler of the mosfet, that drives the heatbed with 15A, remains at a decent temperature:

my infrared pictures of the MK42 (2)

and here pictures from the heatbed at the genuine i3 mk2 kit.

heatbed idle, you can see that the steppers get a little bit warmer as at my clone.

no real differences in heating up the printbed:

or when it reaches 60°C.