prusa i3 MK2 - my way ...  

prusa i3 MK2 - my way (2) ...

as you can see from the pictures, i've build my printer esd-proof and highly shielded (to avoid radio interferences and electronic smog).
the cable trunks for the extruder-carriage, the heatbed and the x-motor are all electromagnetic shielded. and they all contain a 3mm nylon filament as enforcement and a similar cable harness as the black one delivered by prusa.

the nylon filaments are fixed at the frame underneath the enclosure for the electronics.

prusa i3 MK2 - my way (3)...

now about the electronics.
as stated above, i use a mega 2560 board in combination with a ramps1.4 shield.

but i've altered a lot and added some required circuits.

first the polyfuse crap has been replaced by car fuses (yellow).
then i added a driver for the little endstop "traffic-light" (pink).
instead of the shield for the 2nd extruder motor, i fittet a small pcb with a n-channel mosfet to drive the coldend fan (blue) and the electronics fan that mainly cools the n-channel mosfet (with the black cooler) that drives the heatbed (with 15.0 amps).
the little pcb under the green cirlce contains the rc-filters for the pwm current control of the x&y, z and extruder stepper motors (because i still want to be able to use the "high-power" and "silent" mode option as intended by prusa).

yeah, and now about the red circle !
at this little pcb i've assembled an additional 5V power supply to provide the current for the lcd display, because i've noticed that the lm1117 at the mega 2560 was to weak. as i used a toshiba flashair sd-card the voltage dropped by about 0.1V.

and there is another circuit at this board: a high precision voltage supply, where i can adjust the voltage for the p.i.n.d.a. probe with high accuracy.
why is this nescessary ? because the sensitivity of the probe is directly influenced by its supply voltage.
and, as the things get better: the lower the voltage, the higher the sensitivity.
my probe started to work above 3.30 V, where the sensitivy allowed me to detect the calibration points of the heatbed at approximately 2.25mm above the surface. but in this state of operation, the probe wasn't completely reliable.

the p.i.n.d.a. i got from prusa as spare part was very "deaf". at 5.0 V supply voltage it only triggered 0.7mm above the surface.... which doesn't leave much space for a decent distance to the tip of the nozzle.

actually i operate the probe at 3.80 V, where the distance between tip of the probe and the surface is about 1.4mm to trigger above the calibration points.
this gives me a reliable behaviour of the probe and enough space to get the thickness of a credit card as distance between the probe and the tip of the nozzle.

so as a matter of fact: i'm able to adjust the sensitivity of the probe while adjusting it's supply voltage !
this might be very useful to know, if you are planning to remove the thin pei sheet and use a printbite or filaprint surface, which are much thicker !

💡 so furthermore: if you got problems with an inconsistent sensitivity of your p.i.n.d.a. probe (which leads to different live z-adjustment levels) during operation of your printer: check the supply voltage for the probe ! if it varies only 0.05V (which is way inbetween the spec of the voltage regulator), your live z-adjustment level may vary about 100µm. this may be a problem especially when you "steal" some power of the 5V circuit (maybe to feed a raspberry...) or use an sd-card that requires significant more power than a standard one (as my mentioned toshiba flashair card).

not much to say about this picture, just the rear, where you can see the (shielded) cable for the heated bed. btw. to extend the cable length: use 2.5mm^2 cable... nothing less !

and last, but not least: the enclosure for the power supply. with attached usb-power outlet (e.g. to feed a hungry octopi).
at the top end you can see the "grounding" of the aluminium profiles that has been done at every corner.

prusa i3 MK2 - my way (4)...

💡
a few things to add:
as bearings for the y-carriage 4 cheap lm8luu were used (for the x-axis and the z-rods i used inexpensive lm8uu ones).
as y-carriage i used a standard trespa one from a company in the netherlands... but its accuracy was disappointing. the holes didn't fit exactly to the printbed (neither the genuine mk42, nor standard mk2B heatbeds).
it took me a while to figure out that the inaccuracy of the y-carriage was the reason why i wasn't able to get a perfect perpendicular alignment (which should be achieved at first attempt with the rebelix frame design !). the mounted heatbed simply was a little bit rotated at the carriage (about 5mm), which was not visible at first sight but always ended up in a "XYZ callibration all right. Skew will be corrected automatically." after the x/y/z calibration routine instead of the desired "XYZ calibration ok. X/Y axes are perpendicular. Congratulations!" message (which was finally achieved after fixing the problem with the y-carriage).

trying to assemble the printer with 8 DryLin® Igus RJ4JP-01-08 & DriveLin rods instead of the 4 lm8luu at the y-carriage ended up in an inappropriate hard resistance when moving the y-carriage, so i went back to the good old stainless steel smooth-rods and the ball bearings.

by the way: the printer is more quite than the genuine mk2, which you can't call very loud.

extruder, x-carriage, y-motor holder, y-idler parts have been printed with biofila platech filament. the orange parts are printed with petg from herz (even the trapezoid nuts).
the black end-covers for the aluminium profiles are made of pla as well as the drum of the spool-holder and the usb-b extension holder (red).

software used for for modelling all the customized parts (psu enclosure, electronics enclosure, endstop traffic-light, cable holders, corner brackets, end-covers) was designsparks mechanical 2.0 (a free 3d design software).

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oops, nearly forgot to mention:
the standard power connector of the ramps 1.4 board (a green "plugable" one) was replaced by high power terminals with screws*.
and all the "high power cables" (power supply, heatbed, hotend) were fitted with wire end ferrules.

*) this was necessary because the heatbed draws 15 amps and the standard ramps 1.4 connector only was allowed up to 12 amps.... so at the first attempt to heat up the bed at 100°, the connector simply melted...

Re: prusa i3 MK2 - my way ...

Hi.

Amazing work, I especially like the function over form ideology.

Deepest respect for your work and the amount of knowledge involved.

Best Regards.

Re: prusa i3 MK2 - my way ...

...
Amazing work, I especially like the function over form ideology...
old bauhaus school

Re: prusa i3 MK2 - my way ...

This is an Prusa I3 MK2X 😉

Good job !

I see, you print the some parts in PC ? Why ?

I also think about to build the y-frame with aluminum profiles.

Thomas

Re: prusa i3 MK2 - my way ...

...
I see, you print the some parts in PC ? Why ?
hi thomas 😛
no, i didn't use poly carbonate stuff. i guess you think about the orange parts with the translucent petg.

the choice of used filament was primarily influenced by the vicat temperatures and the mechanical properties. so i used the expensive biotech stuff for the extruder and all the mechanical loaded parts, and the herz (translucent) petg filament for the larger, visible parts.

and by the way, even if this is a form follows function design: black & orange is always a nice, fashionable combination

Re: prusa i3 MK2 - my way ...

...
I see, you print the some parts in PC ? Why ?
hi thomas 😛
no, i didn't use poly carbonate stuff. i guess you think about the orange parts with the translucent petg.

the choice of used filament was primarily influenced by the vicat temperatures and the mechanical properties. so i used the expensive biotech stuff for the extruder and all the mechanical loaded parts, and the herz (translucent) petg filament for the larger, visible parts.

Re: prusa i3 MK2 - my way ...

Hi Jeff,

Great stuff. I'm about to build an MK2 clone myself.

Looking at the Z axis, I wonder how you attached the T8 spindles to the stepper motors and how the X axis is connected to the Z axis.

And by the way... thanks for the calibration squares - helped me a lot when calibration my Original Prusa MK2.

Jan

Re: prusa i3 MK2 - my way ...

...
Looking at the Z axis, I wonder how you attached the T8 spindles to the stepper motors and how the X axis is connected to the Z axis...
➡ i simply ordered a complete set of steppers, two of them already assembled with 300mm spindles (which is just enough because the stepper itself is assembled a little bit higher than at the original frame design).

if i had used steppers without spindle, i would have to attach the spindles with (flexible) couplers. but then i would have to fix the spindles with ball bearings at the top of the frame (as in david.t2's rebelix mk2x design) and lift the whole heatbed up a few millimeters (so that the x-idler & x-motor parts wouldn't interfere with the couplers)...

❓ what do you mean with the x-axis / z-axis connection ?
i use the genuine mk2(s) x-motor and x-idler parts, fitted with two lm8uu bearings at each side and self printed trapezoid nuts (which fit the spindle).

Re: prusa i3 MK2 - my way ...

...
❓ what do you mean with the x-axis / z-axis connection ?
i use the genuine mk2(s) x-motor and x-idler parts, fitted with two lm8uu bearings at each side and self printed trapezoid nuts (which fit the spindle).

Exaclty - I meant the trapezoid nuts: Do they have a printed thread?

Re: prusa i3 MK2 - my way ...

...Exaclty - I meant the trapezoid nuts: Do they have a printed thread?

yes, of course. you can find the files (even the open-scad source file) here at thingiverse.
the printable trapezoid nuts are designed by our forum user david.t2, who mentioned his rebelix design here as well.

Re: prusa i3 MK2 - my way ...

Hi Jeff,

Maybe just one more question since I'm looking for a replacement PSU since my cheapo AliExpress PSU blew up: What PSU did you choose for your interpretation of the MK2?

Jan

Re: prusa i3 MK2 - my way ...

Maybe just one more question since I'm looking for a replacement PSU since my cheapo AliExpress PSU blew up: What PSU did you choose for your interpretation of the MK2?

I'm not sure where you are located but I have used this MeanWell purchased from Amazon in a printer I have built. Much better quality than the generic ones found in most places.

https://www.amazon.com/NES-350-12-Switching-Power-Supply-110-240/dp/B007K2H0GI/ref=sr_1_1?ie=UTF8&qid=1492695808&sr=8-1&keywords=meanwell+12v+power+supply

Re: prusa i3 MK2 - my way ...

... What PSU did you choose for your interpretation of the MK2?...
my choice was this one* in the 240W version (20 amps). but it won't hurt to choose a few amps more (as i ordered, the 25 amps version just was out of stock).

*) just noticed that the seller is no longer active... but this one looks identical to the one i ordered previously.

the one that richard.I has choosen seems to be a good choice as well (but approximately twice the price).

anyway: both, the mean-well (got a 12.5 amps here) and the cheap one are fitted with 105°C capacitors.... so quality seems to be reasonable.

Re: prusa i3 MK2 - my way ...

Excellent work, piece of art jeff
waiting for a y-carriage to finish my Prusa i3 MK2S-X

Re: prusa i3 MK2 - my way ...

Great job, thanks for sharing!

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?

Do you know which cables would be most resistant to breakage from repeated bending? I'm about to rebuild the extruder cables one way or another.

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:

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.

Re: prusa i3 MK2 - my way ...

Hey Jeffjordan,

You say you used a cheap e3d clone, did you have to modify the extruder body to fit that?

I have an extra cheap one laying around but the diameter of the heatsink is bigger than the e3d so I might need a modified mount....

Or which clone has the same dimensions as the e3d?