Printable Linear Bearing For 8mm Rods by TheRooster

Quick, how many bearings are on Thingiverse?  I was able to count at least 9 different examples.  You have your choice of over-sized bearings, pure printed bearings, and even linear bearings.

• Tri Linear Bearing For 8mm Rods by Sublime
• Printable Linear Bearing For 8mm Rods by TheRooster
• Sarrus Linkage Linear Bearing by fdavies
• Printable 608 Ball Bearing using BB’s by TheRooster
• Ball Bearing by RayRaywasHere
• Bearing by PP3DP
• Turntable (lazy susan) bearing by ferret7
• [experimental] 3d Printable Rotary Rolamite Bearing by Gene_Hacker
• Printed bearings using beads instead of metallic spheres by MakerBlock

If you’re looking to build a robot, invent something, or create a toy you now can print off a custom bearing for your project!

Printed 608 bearing using BB's by TheRooster

Some days, such as today, I love being wrong. 

The other day I suggested printing a 608 bearing using 4.5mm BB’s would be impractical given the dimensions of a standard bearing.  There were a number of very well thought out responses from Tre3 and TheRooster to my wild¹² accusations.³

Among other excellent points, Tre3 pointed out that with careful purchasing you can find ball bearings as low as $0.05 per bearing. ⁴ That’s pretty dang low.  TheRooster said he was able to pick up 2500 zinc plated steel BB’s for $4 from his local big-box store.  That’s about $1.70 for all 53 bearings required for a RepRap.  Cheap BB’s are all well and good – but you’d still need to find a way to shoe-horn them into a printed 608 sized shell.

And that’s exactly what TheRooster did – he designed, printed, and assembled a 608 sized bearing utilizing those 4.5mm BB’s as the ball bearings.  I cannot wait to try this design out.  I realize the labor costs involved in creating your own ball bearings is probably prohibitive.

I think this misses the central questions:

• Just how far can you push a 3D printer?
• When you can make nearly any arbitrary shape out of plastic, just what are the limits?
• What is possible once your biggest cost is the time required to assemble the parts in front of you?

Tre3: I was going to take you up on your offer to test my plastic bead bearings, but they are officially garbage now that I’ve seen TheRooster’s improvement.  However, I would love to see how TheRooster’s printed ball bearings using BB’s match up to your tests.  Are you guys up for the challenge?

1. Drunken?  Intoxicated? [↩]
2. BUI – blogging under the influence! [↩]
3. If I were really smart, I would claim that this was a bit of slight-of-hand reverse-psychology on my part.  Alas, I am just not so clever.  Or devious.  [↩]
4. Given that each bearing requires roughly 15-20 balls and there are 53 bearings in a RepRap, this comes to $39.75 for the lot. [↩]

Printed bearing, nearly 608 size

This weekend I tried printing Rayraywashere’s ball bearing with mixed success.  The plastic spheres inside we pretty well fused to the sides of the bearing, which made for a difficult cleanup.  Although it got better with time, it was a laborious process.  Ultimately, printed bearings that rely on printed balls may not be the way to go for everyone.  Even if you can print it without fusing the balls to the bearing, there’s no guarantee the balls would be sufficiently spherical to work properly.

That ball bearing design got me thinking – if I could find a reasonably ubiquitous and cheap alternative to small printed spheres, I could make the entire design much smaller and probably significantly more reliable.  The photo above is rough draft/proof of concept for a printed bearing only slightly larger than a traditional 608 bearing.  Rather than printed spheres, it uses plastic pellets of the sort typically used as stuffing in craft projects.  I sorted through a lot of these and used only the most nearly spherical ones.  However, there was still a lot of variation that lead to the bearing getting jammed.

Later I emptied the plastic pellets and tried out small spherical 3mm plastic beads.  These have worked really well in this printed design.  To improve upon this design I intend to move the “bead filling gap” to the interior ring or change the ring system so that two rings will snap together and cover the filling gap.  Overall, I am very happy with this result.  I’m looking forward to actually installing a slightly smaller version into my Cupcake 3D printer in place of a 608 bearing to see how well it works.

I spent $4.00 for 1700 identical plastic beads, silver in color, 3mm in diameter.  It takes about a dozen of these beads to fill the bearing.  The potential savings are pretty self-evident.  The per-unit cost for each bearing is probably only about $0.05 or so in plastic and beads.  That’s pretty good compared to $2+ for commercial bearings.  The real test will be how smoothly they work, how well they work at high speed, how quickly they might wear out.  However, I think I may be on the right track here.

Any suggestions?