(Right after I finished this mod, I looked online and discovered that Colin at Makerfarm is actually selling a kit to do exactly what I have done. You may have all the necessary parts lying around your shop – I did!)
One thing that has always bugged me about the Prusa i3 design is the lack of a good way to level the bed along the Y-axis. Leveling the X-axis is easy, if somewhat tiresome: Just home the Z-axis at the side of the bed nearest the endstop, adjust until your sheet of paper or your feeler gauge just slips under the hotend, then move the hotend to the opposite side of the bed. Home the Z-axis again, and twist the threaded rod until the feeler gauge again just fits. Repeat until both sides are equal, and you’re done.
Trouble is, if your bed slopes in the fore-aft direction, there’s nothing you can really do. I would assume that on the aluminum-frame version of the i3, once you get it set up, there’s not a lot to disturb it, since aluminum is generally stable. On the wood version, though, there seems to be some seasonal variation. Like all wood products, the Makerfarm frame will swell and shrink according to the temperature and humidity in the environment. As a result, I recently discovered that my print bed was out of alignment along the Y-axis 🙁
Not to be deterred, I reached into my hardware box and immediately found what I needed:
- 3 m3 bolts, 20mm in length
- 6 m3 washers
- 3 sections of spring about 10mm long(these were left over from the Z-axis endstop holder that was one of my first prints)
- 3 m3 nylon lock nuts
Assembly was a breeze, and the whole conversion took about five minutes, including looking around for parts.
Here are the parts you need, in the order you’re going to use them:
Basically, you’re going to just be replacing the nylon standoff that is already between the wood base and the heated bed with the spring and two washers.
Assembled and installed, it looks like this:
I left the nylon insert in place at the corner where the X and Y axes both home. It gives a single, static reference point, and establishes a “standard” height, so I don’t end up raising or lowering the entire bed over the course of several adjustments.
I now have a manually adjustable Prusa i3 bed!
As I mentioned earlier, Colin at Makerfarm now has a version of this mod available as a parts kit. He’s a good guy, and has done a lot for our community. If you don’t have these parts handy, please consider ordering from him. Here’s the URL:
On the other hand, if you’re stopping by the hardware store already, this represents probably about $2-3.00 us.