I recently bought a molded reprap prusa mendel kit from Metrix create space. They are a hacker space in Seattle, Wa. The molded kits cost anywhere from a third to half of what a set of printed parts cost because they take far less time to produce. One downside of the printing method is that parts will end up sloppier and require some more post processing.
Here is what the base looked like as it arrived.
Here is the other three parts, unprocessed.
The next picture is where you can start to see the disadvantages of this method. There is a lot of plastic on the bearing holder (purple) that needs to be cut away, and you can see the way that the miniscus on the big gear has made the entire gear cupped. I want to clearly state: none of those are deal breakers. This is a great deal, and even the RP parts require a fair bit of processing. I was surprised when these parts came in, but after thinking about it I don’t think I should be. They appear to be functional, and that’s all that really matters to me. As long as they last long enough to print their replacements, I’ll be happy!
Tools
sandpaper
xacto knife
emery board (optional but very useful)
circular rasp (optional but very useful)
3mm, 4mm, 8mm drill bit ( i used 1/8, 5/32, and 5/16 if using inch sizes)
7/8″ spade bit
4mm tap
I found this partial set of instructions on the metrix createspace wiki. It is incomplete, and I’m sure mine will be missing something as well. Hopefully the two will combine for slightly more detail than either provides.
Main motor mount block:
Clean up all of the edges and obviously unneeded blobs with an xacto knife and sandpaper.
Clean out the motor mounting slots. These are on the big piece and are the 4 slots that the motor bolts will slide in. I also used an emery board to sand the slots large enough to allow the motor bolts to slide in the channel.
Drill out the 4, 4mm holes with the 5/32 bit. I used a 2×4 in order to support the piece on the drill press table.
Use the same bit to drill out the bottom 3 holes, then flip and drill out the small hole on the top block. That will be the hole that the filament feeds into.
Switch to the 1/8 bit and drill out the two small holes on the bottom side of the mount.
This next sequence needs to be done in this order, but it is easy to follow. Use the spade bit to drill out 3mm or so into the marked side with the 8mm dimple on it. These will hold the bearings in place. Then switch to one of the other smaller bits and drill through the piece. Flip it over, go back to the spade bit and drill 3 mm into that side using the hole you just drilled to center it. Now go to the 5/16 bit and drill straight through.
Use the 4mm tap to tap the 4 holes by the bearing indentation.
Bearing holder:
Cut through bearing holder back to allow bearing to slide in. Sand slot until bearing can easily slide in.
Cut the side walls out of the bearing axle slot. Use the rasp to sand the slot until it is big enough to fit your bearing axle.
Use the 4mm or 5/32″ drill bit to drill out the 4 holes on the bearing holder. If your holes don’t line up, then drill this out one bit larger.
Big Gear:
Use the 5/16 bit to drill out the center. Be careful to center it as much as possible.
Little Gear:
Use the 5/32 bit to drill out the center. Be careful again. My molded piece seems to have the hole off center. I hope that isn’t as bad as it seems like it would be… Even if it isn’t then this is still going to be my first test print!
Use the appropriate size drill and tap to tap out the hole for your set screw. Most hardware kits will not come with this, so pick your own. I’m looking at a 3mm set screw right now.
Right now you should be able to start putting it together. Go and make (or buy) your hobbed bolt and get to printing! I’ve gotten this far and now I need to figure out how to run a 4th stepper with my electronics. I’m sure I’ll post on it!
This is where mine is right now. That box of springs was only $4 at home depot! Pretty good for trying out different lengths and stiffnesses. I now have 2 new heater cores coming from makergear, so hopefully I will be back to printing fairly soon. I also have some extra thermistors and I’m planning on trying to build a heated build platform. Check back for more details.