In this video I show how I ended up mounting all the electronics for the Prusa i3 MK2 clone. As the frame wasn’t as solid as the original’s aluminium one I decided that it needed a brace, which provided the perfect location to mount the Arduino, RAMPS, Raspberry Pi and all supporting parts.
I also added a brace to the other side – which gives me room for electrical expansion!!!!
I mounted the whole thing to an office desk, I picked up for free, and even though all four corners of the Y axis are square and sit on the desk, there is a slight amount of hammering when printing.
To silence that I drew up and printed out some little securing clamps which just make sure they cannot move. You can click the image below to download the STL for these clamps. They should work on any printer using the same Y Axis design and the Prusa i3 MK2.
I power on the printer for the first time and set up the Limit Switches, Axis Movement, End Stops, Bed Extents, Bed Levelling, Z Probe/Bed Sensor and do the Extruder Calibration!
I spent quite some time going through the Marlin documentation to see what each possible configuration instruction could do. I had already done a very basic run through of the Configuration.h file in this video/post but now it was time to get it spot on.
One side benefit of the exercise is that I can see I will need to change the way I mount the heated bed. Most importantly the nyloc nuts sitting on top reduce the Y axis extents by nearly 25%!!!!. But secondly the ply wood under the bed allows the nuts to squash the edges down too much, resulting in the opposite bed bend to that I had before! Still, good enough for a first print 😉
Aside of being careful to keep everything lined up, parallel & square the build of the Z Axis, mounting the Y Axis and putting all the extruder and hotend parts on was pretty simple and in line with the official Prusa Manual.
Really the only thing I had to find a solution for was mounting my lead screw nuts. Toms version uses 5mm threaded rod and he provides STLs for parts to hold a M5 nut for that. The original MK2 looks like they use their own lead screw nuts. The ones that came with my lead screws had their mounting holes too close together and there was no way to centralise the nut in the Z carriers. I customised Toms Z nut holdahs to do the job – which it seems to do fine.
I will say this though, after building it all I examined the extruder to “sanity check” it and it turns out that it was very tricky to feed filament through the extruder and into the telfon tube running to the hotend. I will do an extra post discussing that as I think it is a mis-match between the extruder body design and the commonly available MK8 hobbed gear. I think if this was left unchanged, apart from having to use tools to get it to feed in, it would put a lot of load on the extruder stepper just to overcome this tightness.
I would also recommend that if you can squeeze an extra £20/$30 to get a Z axis frame laser cut – do that. It will save you a lot of time and insecurities about the Z axis being parallel and square. My wood will probably work fine, but it’s just a lot harder to make sure it is correct.
In the last video I noted I could’t work out how the Y limit switches fitted. In the course of investigating I noticed a bigger issue – the 3D Printed parts on all four corners of the Y Axis should have cutouts in the top to let the linear bearings partly slide “into” the corners….. mine didn’t.
Turns out that there is extra material in the prints that needs to be removed – revealing these cutouts!!! If you know you know – and I didn’t 🙂
I’d like to think this is an easy mistake to make – so worth mentioning here and in the video.
Sadly it means that the Y corners were also the wrong way around, so will have to take the Y Axis apart and make the corrections. Doh!
The good news is that it should fix the issue with the limit switch. Every cloud and all.