RepRapPro Huxley heatbed assembly
Contents
Goal
By the end of this stage, your heatbed will look like this (Viewing Bottom / Heat-bed is shown upside-down)
Assembled heatbed
Tools
- Wire strippers
- Pliers
- Scissors
- Pan head screwdriver
Step 1: Assemble the thermistor
Follow these instructions to prepare your thermistor.
Step 2: Assemble the heat element
nichrome and thermistor wiring To connect the Nichrome wire to the PTFE insulated wire, cut the insulation from a ferrule and slide the Nichrome and PTFE insulated wire in from each end, then crimp the two wires together. Cover the join in black heatshrink to electrically insulate the join.
Before laying out the Nichrome wire, it is advisable to cover the underside of the Aluminium bed in Kapton
The side with holes beveled is the top; heater wires go on side without beveled holes.
This will reduce the risk of shorting the heater (and potentially other circuits) in the event that the Nichrome insulation fails. (The following images were taken without this extra insulation layer. The bed has subsequently been modified to include this).
Nichrome wire temporarily taped
Note the Nichrome wire path. This is designed to give even heating of the build platform. The nichrome wire should not protrude outside the area of the Aluminium bed plate, and should not be closer than 5mm to any edge.
Nichrome and thermistor fitted
Step 3: Insulate the heatbed
Nichrome and thermistor fitted
Heat shield fitted Tape around the perimeter of the heatbed to secure the heat shield.
Step 4: Heatbed wiring loom
The heater connecting wires should be high temperature, high current capacity wires (the thick red silicone insulated wire), cut to a length of 200mm. For the thermistor input wires, use some spare from the motor wires.
The Molex connectors are keyed to only allow connection in one orientation. The male crimp pins fit into the female connector only. The pins are also keyed in the connector; the grooved side of the pin matches the key inside the pin hole. They lock into place when you have inserted them far enough; give them a tug after you insert them to make sure they locked. Don't try to fit the male pins into the male connector.
It is possible to remove a Molex pin from a connector after installation. The easy way is to use a removal tool; its a tube just a little bigger than the pin. You slide it over the pin to make the latches retract, then pull the pin out. You can probably make the tool out of brass tubing from the harware store.
In case you get in trouble, these Molex connectors are the 0.165" pitch Mini-Fit Jr. connector series. The female pins are 39-01-0039-C and the male ones 39-01-0041-C.
Step 5: Mounting the heatbed
RP parts Quantity 1 1 Hardware Quantity Bed mounting plate 2
- 6x3/8" self tapping screw 4
M3x30mm cap head screw 3 M3 nut 10 M3x16mm screw 4 M3 washer 10 Bed spring 3 Insert an M3 nut into the hexagonal recesses, two on the double spring anchor, and one on the single spring anchor. Screw the spring anchors to the frog using the M3x16mm screws, and an M3 nut on each screw. The pressed-in nuts go on the BOTTOM of the spring anchors! Use a little superglue on them if they are loose.
The Aluminium bed plate is to be screwed to the laser cut bed mounting plates using four #6x3/8" self tapping screws.
(note from TheCase: had to re-drill the holes in the aluminum bed with a 9/64" bit to allow the #6 screws to pass through) (note from Rob: Same situation with mine (Huxley #20), used a 3.5mm drill bit to enlarge the holes. My 4 screws were in bag #13, not #2 as indicated by the packing list)
Now insert one M3x30mm screw through the centre hole of one of the bed mounting plates, with a washer either side of the laser cut part. Slide a bed spring onto the screw then secure with an M3 nut, screwing the latter on such that at least 5mm of thread protrude beyond it. Repeat this process with two screws on the other side.
NOTE: Ensure the number of springs you have on each side matches the position of the spring anchors. The bed heater and thermistor wires should protrude from the end nearest the Y axis motor.
Finally, attach your heatbed to the machine by screwing the M3x30mm screws into the captive M3 nuts in the spring anchors. The heatbed needs to clear the Y axis end brackets as it goes right over them during normal operation.
