Here are some notes on my build that may help:
1) put bearings in all the pieces first. 1 bearing in each piece for the bed, 2 in all the rest except for the piece that holds the extruder which gets 3 (two on top, one on bottom).
2) put the end stop screws and end stops onto the plastic pieces. pictures on the web site are adequate to see how that works.
3) put bearings in the plastic pieces. pictures are adequate again.
4) solder wires onto end stops
5) assemble the frame (corners and motor blocks and gantry) – check for square
6) put motor mounts and pulley for the bed on the frame.
7) put the plastic piece that holds the timing chain on the bed. * make sure that it aligns with the motor and pulley pieces. *
8) put the bearings on the bed.
9) put the end pieces on one end of the rods for the bed.
10) put the bed on the rods.
11) other end pieces on those same rods.
12) put on all the stepper motors
13) put the bed on the frame. – check for square
14) build the x axis. – this is the longest two rods into the plastic pieces and the carriage onto the rods. put the timing chain on at this point too. it will be easier. make sure the brass nuts are also put on at this point.
15) put the top of the y axis rods on the frame if you didn’t already.
16) put the x axis on the y axis rods. put the y axis rods into the mounts at the top of the gantry, slide them up and then down into the motor mounts at the bottom.
17) slide the threaded rods down through the brass nuts and lock them into the steppers. check for square.
18) bottom timing chain. – set the end stop screw lengths now. make sure that they touch at the appropriate points.
19) route wires
20) mount power supply and ramps
21) mount extruder (and wire it if necessary)
22) headed bed
23) plug in wires
24) power up and initial movement test. — home it.
25) wire cleanup.
for the thermistor in the bed I used a high temperature silicon gasket compound and let it dry overnight. do this in advance.
I also wired in a power switch for the whole unit. I recommend doing this as well.
since I have an MPCNC, I put two 8 pin DIN circular plugs on the extruder (one of the plugs for extruder power, the other plug for two fans and the thermistor) – this lets me move the extruder back and forth with minimal effort. I cut a wooden block and mounted the DIN’s into that and glued it to the frame next to where the ramps is mounted in order to facilitate easy transfer back and forth.
the mk3 bed uses #4 screws and not #6. – get one inch ones.
the wire bundle I have is pretty big. you MAY want to trim a long section of the stepper wires out if you don’t like large bundles. I don’t mind and I left them.
I recommend using shrink tube on all connections when you solder them.
I usually run mine through a raspberry pi using repetier server and if you do the same, you may need to flash the speed down to 128k baud from 250k.
still to do is print off a box to hold the display
and make a filament holder and a couple things to route it.
hope this helps.