608 Bearing Smooth & Fast Spin

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While designing a new fidget spinner, I searched for the bearings I needed here at Makerworld, but I couldn't find bearings that spun really smoothly and fast.

There were three main problems with other bearings.

1. Balls that don't actually roll. This is a problem that most of the cool-looking ones have. They look cool, but in reality, the balls don't roll and just slide... so they can't spin smoothly.

2. Things that often fail to print. This happens when there's too small a part in the first layer.

3. When the balls don't move as planned. The balls in 3D printed bearings aren't all truly spherical due to printing reasons, and when they get misaligned, they interfere with the rotation.

So I ended up having to design a new bearing myself.

The goal was to make one that spins smoothly and fast like a ceramic bearing, but doesn't break easily, such as the balls coming off. Of course, it had to be easy to print.

The image below is the bearing I designed.

In order for the bearing to roll well, friction must be reduced in the end, and there are two main ways to do so.
1. Make the built-in balls roll well.
2. Reduce the area of the friction surface.

The picture below is a cross-section of an actual 608 bearing. The part highlighted in red here is the friction part. Basically, I thought that if the friction surface is wider than this, it would be difficult to rotate smoothly.

Since the balls are not iron balls, there are some limitations to how they roll. So my main focus was to reduce the area where friction occurs.

The concept is to create protrusions on the inside like the cross-section in the picture to minimize the areas where parts come into contact with each other.

The theory is that this will minimize tolerance while increasing the non-contact area, allowing for a smoother and faster rotation.

The result is very successful.. as shown in the gif below.

Unlike other printed bearings, this bearing actually rotates with the balls inside rolling, and they rotate smoothly and quickly. The oddly shaped balls were chosen to increase the success rate of printing.

I tested them all with layer heights of 0.08, 0.16, and 0.2 millimeters, and the lower layer heights were slightly smoother, but the bearings printed with 0.2 millimeter layer heights rotated sufficiently smoothly. 

There are some parts with a tolerance of 0.1 mm, so they may partially stick right after printing, but they fall off easily.

Now I'm thinking of making a new fidget spinner with this.

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And here is what I created using this bearing.

https://makerworld.com/en/models/1275564-transformable-fidget-spinner#profileId-1303335

Hope you Enjoy this model.

As always, I welcome your feedback.

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