Friday, February 20, 2015

Prusa i3 Rework: Build Log Part #9- Extruder Assembly

Now that we've finished the rest of the printer, we can start building the extruder. Here are all of the parts needed, laid out on my work table.


I also used needlenose pliers, a small file, and a rubber mallet in this step. I needed the pliers to remove the support parts from the printed body pieces, the file to clean them up, and the mallet to get parts together.


The very first thing that I did was tear off the support pieces on the outside lip of the Wade Extruder Body. By gripping the support pieces with pliers, I was able to rip them off easily.


And here is the part without the supports. I filed the lip down so that it would fit the other mating part, the Extruder Idler.


Next, I fit two of the M4 nuts into the gaps in the bottom of the Wade Extruder Body. Contrary to the directions, I didn't need to use a lighter or other source of heat to get them to stay. In fact, they wiggle a little bit in their holes.


Here the bearing and grub screw are together, and the two parts are put into the Extruder Idler printed part. I got the screw and bearing in all of the way by lightly tapping them with the mallet.


Now the Extruder Idler assembly is attached to the Wade Extruder Body with one of the M3x30 screws.


The Extruder Idler assembly should fit on the attachment part from the Wade Extruder Body loosely enough that it can be pushed in and out without much force. If it is too tight, file down the attachment lip on the Wade Extruder Body.


Here is another of the support pieces. It is located inside one of the bearing holes on the Wade Extruder Body, and it can be pulled out carefully with needlenose pliers.


This is what the part looks like without the support piece.


Now the bearing has been pressed into place. I had to use the mallet to jam it in tightly.


At this point, I had put the hardware and the Wade Big Gear on the hobbed bolt. I then pushed the hobbed bolt through the bearing hole from the image above. By putting a crescent wrench on the end of the screw with the gear on it and a socket on the end with the Nyloc nut (upper middle), I was able to tighten the nut on the screw until it became close to the bearing. Mine was not tightened fully- the nut was about an eighth of an inch away from the bearing.


Another shot of the part with the hobbed bolt installed.


I put M3 nuts into the attachment holes on the Wade Extruder body, then added the 60mm screws with springs and washers to the part. This keeps the Extruder Idler bearing pressed up against the filament, which is pressed against the hobbed bolt.


I then inserted the hotend into the bottom of the part and lined it up so the wires pointed to the right side. After that, I added the screws at the top to secure the hotend in.


Next, I attached the fan to the fan duct. Most small fans have arrows on the outside that point towards the direction that air is blown. For the Prusa i3 Rework, the air should be blown into the Fan Duct part.


I then attached the whole assembly to the Y-axis carriage with the four M4 screws and the nuts in the Wade Extruder Body.


A shot of the back of the carriage, with the mounting screws in.


I then added the fan assembly to the Wade Extruder Body. It is attached with a short screw and a nut that tightens it in place. For me, the fan worked best at cooling the extruder when the assembly was tilted all of the way downwards.



Here is a closeup of one of the NEMA 17 motors that is used on the printer. This one was used to drive the extruder.


This gear is tightened with a set screw. It's set up by putting a nut into a trap on the gear, and then threading a set screw into it to press against the motor shaft. I also twisted a 5mm drill bit between my fingertips in the inside of the gear to make it fit on the shaft properly.



Here is the extruder motor, before the gear was tightened down on it. The set screw lines up against the flat of the shaft on the motor.


And here is the extruder motor, installed. It should line up easily with the larger gear. Also, the long holes on the Wade Extruder Body part can be used to tighten the motor closer or farther from the large gear to minimize backlash. Backlash is something that you want to avoid- it's the gap where the extruder will not move when the motor drives one direction and then immediately switches the other direction.


Here is the printer so far! It's nearly done- the only thing left is setting up the electronics.

This post is the ninth of ten that goes over my Prusa i3 Rework build. These posts are in the order given on RepRap's wiki page for the Prusa i3 ReworkAll of the images from the build are in this Flickr photo album.

My build log: