I recently made some improvements to my Geeetech Prusa i3 3D Printer. These quick and easy upgrades provide a massive improvement in build ease and quality.
PEI Plastic Build Platform
By far, the biggest, single ~$20 improvement you can make to your machine is switching from the included aluminum print bed to a PEI sheet.
Since the aluminum plate deforms as it heats, to get that perfectly flat print surface, you'll also want to get a glass plate as well.
If your PEI sheet didn't come with adhesive, be sure to get a piece of 3m sheet adhesive as well.
Stick the PEI sheet to your glass plate and attach both to the aluminum bed using a couple binder clips. That's it! I didn't need to use any tricks to get the sheet to stick. I just put the adhesive on the back of the PEI sheet, then pushed both onto the glass.
As long as your bed is level and the proper distance from the new print bed, ABS and PLA will stick perfectly. I use a 95 degree heated bed when printing ABS.
Fix the Z Axis Constraints
Do you get a wavy lines on the walls of your 3D prints?
If so, your Prusa i3 is over constrained on the Z-axis. So how does one fix this? Remove the excess constraints! I used my trusty WEN 2305 Rotary Tool Kit with Flex Shaft to remove the constraint. Basically, cut away the holes for the threaded rod and just let them float there.
Here's how it looks when complete:
I know, this "fix" sounds crazy, but it really works. After doing this I'm getting amazingly accurate walls with very little variation.
Printing ABS? Put it in a box
Seriously, just find a cardboard box big enough and set it in there. Close the doors when printing.
Sometimes, if it's a really cold day, I heat up the inside of the cardboard box with a heat gun or hair dryer.
This works because ABS shrinks as it cools. By keeping the whole part warmer as it prints, it is much less likely to shrink while printing, which would cause the whole print to pop off the bed.
Build a wooden box.
After a while my cardboard box was badly worn, so I bought some thin plywood and built a real box, out of wood.
A little paint and we're done! I'll put some plexiglass in the holes. I've moved the electronics to the outside.