I believe the current and original design of the Prusa i3 3D printer has a lot of areas that need improvement. It seems the printer serves a great purpose of teaching you about Fluid Deposition Modelling (FDM) printers, but as a printer in itself, it leaves a lot to be desired. They should have called it “The Trial and Error Printer.”
If you make the mistake, as I did, of building your printer out of lexan or acrylic, you’re going to have a lot of problems. Additionally, if you buy some random set of printed parts off ebay for your printer’s structural members, you’re going to have even more problems.
All in all, it is a wonderful stepping stone to the next printer project, but in itself, I would not call it a production class machine that you can rely on day in and day out. No, sadly, those cost a few more bennies.
Here are some pictures of what I have done to harden my machine so it prints more precisely. Note, I’m not calling it reliable, or precise, but “more precise” than a vanilla kit machine.
My first priority was to stabilize the platform and frame. I made a bad choice in using the 6mm acrylic frame. But I’m stuck with it for now. So I am doing the best I can with it.
I dug out a piece of 18×24 MDF for the base. I set the printer about in the middle and marked the places where the frame had zip tie holes and drilled through the board. I ended up using zip ties for the time being, but reality is, a screw and nut will be a more permanent solution.
Next on my list was the X axis carriage. I reduced the bearing count from four to three, and re-arranged it so the two bearings are oriented on the top where the two belt ends connect to the carriage. Though not scientific at all, my theory was that this was a better arrangement to control wobble on the X axis carriage.
The next big area of improvement, especially when using printed bushings, is to constrain the bearing sleeves on the X axis. The combination of ABS and HIPS here causes too much slip. So I used M3x6 screws as a set screw. I drilled a hole in the side of the X Motor carriage bearing sleeve using a 2.78 mm (7/64) drill bit.I then followed suit on the right side X Axis Idler. Additionally, pictured above and below you can see a set screw that holds the Z axis nuts in place. These are important because these nuts come unseated easily.
Next thing I wanted to do, but didn’t get around to it until now, is to get rid of the silly zip ties on the bed that hold the bearings in place. I finally got these half printed before something happened and oh well I used them anyway. These greatly minimize the wobble of the bed that is caused by the zip bearings rotating in their seat. The zip ties do not constrain it enough.
Lastly, I used dry lube that you can get at a quality bike shop. This is the lube we use on chains to keep dust from collecting on the chain. Apply a thin coat with a foam brush to all your rods and move your axis all the way from one end to the other several times.