First triangle is easy
Make two of them
Ensure all sides are equal length (a scrap piece of rod used as a jig would be more accurate)
This is how the triangles are connected at the top
This is how they are connected at the front
This is how they are connected at the back
The bottom threaded rod goes over the bottom of the triangles
Use another scrap piece of rod as a measuring jig
(I measured equal distance between the threaded rods from triangles, not the distance between the plastic parts)
My jig was 258 mm long
Other places to measure
Finally, measuring at the top
This is how I ensured the Y smooth rod was parallel to the bottom rod of the right triangle
57mm worked for me
It's only parallel if the distance is equal on both sides :-)
Clamp the plates together and then drill four holes in the corners of the 140x225mm plate.
This is how it should look like
(I didn't actually drill through my table ;-) )
Then use the 140mm of the bottom plate to ensure the left smooth rod is parallel to the right smooth rod. Also use a level to ensure your work table is not crooked, and that the smooth rods are level. Initially, mine weren't.
Use some leftover 8mm threaded rod to enlarge the bushings, until they slide easily on the smooth rods
You can use the same trick to enlarge holes in other places
Drill the holes for the belt clamps
Glue the PLA bushings to the bottom plate
This is the pulley for the Y motor, push in an M3 nut
Push the pulley onto the motor shaft, aligning it with the bearing
Then fix the pulley in place with an M3 grub screw
Attach the motor - note how I had to move things to the right to clear the clamp that holds the left smooth rod
Resulting in re-drilling the belt clamp holes :-)
Attach the print plate. I used M4x40 fasteners, and springs. The springs allow you to level the print plate easily.
This is how the print plate looks
Before installing the Z smooth rods, do some leveling (at the top of the assembly, and the print plate itself). Check that your work table is level, too ;-)
I used a plumb (well, an M8 nut attached to some thread) to ensure the Z axis smooth rods were upright and parallel to each other
Attach the X smooth rods to the x-end-motor. Don't forget the M3 nuts and the M3 fasteners that hold the X smooth rods in place from below. Glue the PLA bushings while the X smooth rods rest on the leveled print platform - I did x-end-motor first and let the glue harden, then did x-end-idler.
Glue the PLA bushings to the x-end-idler. Note how the smooth rod sticks out quite a bit on the x-end-idler side (right side). This was necessary because the motor wouldn't fit in x-end-motor with the rods under it.
I decided to add more fender washers where the bolt with the bearing is attached to the x-end-idler.
Looking at the x-end-motor from below, you can see the M3 fasteners that push the smooth rods up
Glue the X platform to the PLA bushings on the X rods.
Adjust the bearing on the x-end-idler side on its M8 bolt with nuts and washers so that it aligns with the pulley on the X motor.
Not sure if I did this right.. I didn't have belt clamps that fit the holes on the X platform and had to improvise.
Attach the Z motors - one on each side.
Before attaching the Z motors, I had pushed the rod-clamp onto the motor shafts, and attached the Z threaded bolt.
View from the rear
View from the front
This is the RAMPS board from ultimachine.com on an Arduino Mega 2650. Make sure you turn the potentiometers on the pololu stepper drivers to approx. 25% - this will limit the current. You can always increase the current later. (There are other options for the electronics, you don't have to use the RAMPS board - see the Mendel Prusa wiki page.)
This is my power supply. It was on sale, otherwise I would have gone for cheaper-looking stuff - 600W might be overkill :-)
RAMPS with X and Z stepper motors connected. The yellow wire coming from the power supply is +12V, black is GND.
Mount Wade's extruder on the X carriage. I got the hot end from makergear.com
The back of the extruder
You want at least the min end stops - this is y-min. You can use microswitches instead of the optos.
This is the z-min end stop.
This is the x-min end stop. I need to find a more permanent way of mounting it.
This is the PLA I am printing with - 5lb of 4043D with 3mm diameter.
Finished Prusa Mendel! The print bed is lined with blue painter's tape and calibrated so that the nozzle has <1mm distance to the print bed when at z==0.
Finished Prusa Mendel, front view.