Printable Linear Bearing For 8mm Rods
Description
The first step was to get the basic BB function working. I designed a "racetrack" so the bearings could make a loop and only contact the bar in a straight line. My original idea was to have three racetracks arranged so that the BBs contacted the bar in an equilateral triangle configuration. This proved very difficult to adjust.
After failing with the three racetracks, I decided to try a flat version with four racetracks. This would be nice and compact in one direction (typically vertically) and be easy to adjust. It would also only require two parts because each part could have two racetracks built-in.
The racetrack is designed so the groove gets larger when the BBs are away from the rod. No reason to constrain them as tightly until they are contacting the rod.
Pictures to come!
Instructions
Anyhow, you only need to print two of these per bearing. The time consuming part (for me) is cleaning up the prints. I clean up the racetrack as best I can then I use a little acetone to smooth the racetrack out even more. I ended up with two great pieces in my first try! Yay!
I recommend putting one BB into the track to make sure it can roll around easily. Ideally you want the BB to roll around the entire track just by tilting the part. If it catches on anything, you have more cleaning to do.
If the parts are made correctly, you can turn them upside down and the BBs will pretty much stay in the racetrack. I've had a few fall out here and there. Get a couple 4mm bolts and clamp the two pieces together around an 8mm rod. Optionally add grease.
Oh, each racetrack takes 13 BBs for a grand total of 52. Cost of about $0.08.
Enjoy!
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Oh, I forgot to mention, this design can easily be stretched to be longer, or even shrunk to be shorter. I would suggest stretching or shrinking it in increments of 2.25mm (which would add one BB to the racetrack.)
I'm not sure which would be better, making one bearing about twice as long, or using two bearings spaced apart.
Could you post a video of this Printable Linear Bearing in action! Amazing stuff!
If you make a silicone mold of this you could cast them in a metal reinforced resin for penny's each and they would last almost forever. (iron fillings and polyester resin)
To rapid cure normal household silicone in large amounts for mold making just mix a few drops of acrylic paint with the contents of a tube of silicone (mix well) and the entire thing will cure in under ten minutes.
Nice work! This is a great start :)
To remove the ooze factor and some durability issues - make a blind slot for a steel insert (just a flat bit of plate, maybe with the edges filed so the balls don't get trapped or dinged) - then the balls with be riding between steel rail and steel - the printed part is only a holder ;)
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Maybe the bearings can be shrunk by using even smaller ball bearings. For example, the balls in ball point pens can apparently get down to 0.4mm, and they're produced and shipped in bulk. http://www.tungstenspheres.com...