[Nava]

I am looking at the idea of making some improvements to my belt drive setup for the x z and z of my mill. So far I have a pretty standard setup and it functions well with about .05/.07mm backlash with ball screws. I have seen a few users using additional tension adjusters with ball bearings to take up any slack and would like to start a discussion as to if this helps and the pros and cons of doing such a modification.

For example here is one image I found of a belt drive tension design, I would consider using one each side.

[PaulRowntree]

That is the std way to go about tensioning, but watch that the idler has a radius that is at least as large as the minimum back-bending radius of your belt. T5 belt needs ~35 mm diameter. It can also increase the number of engaged teeth on the small pulley if it is close enough.

[Nava]

Thanks Paul for educating me, I wasn't even aware that they are referred to as idlers. Is one side enough or would I gain a more even tension by placing them either side?

[PaulRowntree]

My pleasure! One should be enough, unless you have a large excess. Sometimes folks use 2 in an S config that folds the belt back on itself. One idler then slides parallel to the belt, and an almost infinite amount of slack can be taken out. But if your system works well now, I guess you are just trying to tweak it a bit.

How have you adjusted it so far to get such a low backlash?

[Nava]

I used the SPI calculator to make the distance calculations, But I noticed that there is a few steps before the ball screw engages. Also my ball screw has a little backlash but not much I think .02mm

[PaulRowntree]

I like the SPI site for that, and the beta calculator is even better. Trouble is that every time I ask to see the pulleys that are spec'ed, it almost invariably says out of stock. Maybe they don't carry many T5 components.