Can i change the shape of a circle but keep the same circumference

john_mcnicholl

I am trying to print some tyres for my bandsaw they have a 300mm dia. My printer bed is 250mm x 250mm .
i am printing in TPU95 so for my application i dont need to print it as a circle as it is effectively a rubber band 
i know there is a simple salutation to this issue thanks

S1mon

I would question the durability of any 3D printed elastomer. However, I'm also assuming you're not planning to roll your saw around too much, and that the tires aren't under load when not being used to transport the saw. Elastomers tend to creep over time when under load.

In theory, it would be possible to create a wavy shape which would have the same path length as a true circle and fit in the bed. I suspect they might be kinda weird once you stretch them to be round again. You could also split the tire into two half circles with some tabs that interlock on each end. 

robert_scott_jr_

I believe the 'tires' John refers to are the rubber bands (mine are somewhere between 1/16-1/8" thick) that fit on the outer surfaces of the 'wheels' upon which the band saw blade rides. I question if TPU (especially printed) would have the properties required to safely hold up for very long. - Scotty

S1mon

@robert_scott_jr_

Yep, now that I think about the size, you're most likely correct. And yes, I would be even less likely to try to 3D print such a part. When (not if) that disintegrates, a band saw blade rapidly coming off the wheel doesn't seem like a safe thing. Just buy the proper replacement part. It's likely a specific durometer and material that's gone through a lot of testing and development to get to where it is today.

john_lopez363

@john_mcnicholas

First off, I tend to agree with the previous comments.  This may not perform as you expect.

That said, I do not know of a feature that will take a circle and fold it while maintaining the circumference dimension.  You can "hack" this by creating a closed spline and then using the measure tool to determine the length of that spline.   Adjust the spline until the length is what you need. The circumference of a 300mm circle is 942.47mm.  Here's an example.

Once you have this then do an Extrude Thin to the final size you want.

rick_randall

Don't forget to add draft to create the crown that band saw tires require. But I'm with S1mon on this one - I think service life would be a problem.

john_mcnicholl

I have all ready  printed one for the 250mm idler and it work great as for longevity I will have to wait and see thanks for all your help I will print the next one with a crown I've cut aprox10 linear meters of wet log of cherry no signs of ward so all good I don't use the bandsaw every day so if I havev to print them every so often that's OK as I can't buy them.
There is a place in the states that will make them to order but the cost is prohibitive once again thanks for all your help