V-slot, the Ox CNC Machine and the Everman Belt Drive System,

Everman belt drive system

The Everman belt drive system (aka “Positioner utilizing engaged toothed gear belts, one static and one dynamic”) is a simple modification that reduces the stretch or flex of a timing belt over long drive systems.

When used with V-slot it simply involves securing by glue or tape a length of timing belt inside slot with the teeth up. This lines the slot with a grooved track (similar to a rack and pinion drive) that the drive timing belt fits into.

As you can see above the top timing belt loops around the drive pulley and then goes under the idler and engages with the fixed timing belt. This means that instead of the “loose” length of belt being equal to the distance from the drive pulley to the end of the timing belt (usually the end of the length of V-slot), only the length from the pulley to under the idler is free to stretch. So for a 1500mm length, effectively the length of belt that can be stretched is reduced from up to the max length of approx 1500mm to the much smaller length of a 20-30mm!

There are a couple of downsides to using this. Firstly, the alignment is a lot trickier to get exact – especially with two gantries, two steppers and two pulleys of a y-axis. Secondly, there tends to be greater wear of the belts as the contact area is not just the drive pulley, but also the idlers.

Overall the Everman belt drive system is a great, low cost, way to both improve accuracy and reduce backlash.

V-Slot and the Ox CNC Machine

The Maker Store GT3 timing belt is 2.45mm thick and when fitted together (as above) is 3.65mm thick.

The gap between the timing belt and the slid V-Wheel is 0.65mm, given the GT3 belt tooth depth is around 1.20mm there is plenty of grip to enable the Everman drive.

Some images of this set-up: