Automatic Belt Tensioner and Mechanical Low Pass Filter

thingiverse

While printing on the Predator, I often gently feel the effector plate and the drive belts to assess the condition of the printer. There is always a high frequency component of the stepper drive signal, which is detectable by touch. Any belt drive system has one side of the belt under tension, and on a 3D printer, the side of the belt under tension reverses each time the stepper reverses direction. It occurred to me that letting the two side of the belt "talk" to each other would cancel out the high frequency "noise", while allowing the low frequency motion do its thing. Kind of a mechanical absorptive low pass filter. I think the results speak for themselves. These are the glassiest, smoothest, most consistent objects I've ever printed. The tensioner in the photo was, of course, printed without a tensioner. You can see, and feel, the difference in surface quality. I designed this in FreeCAD, sliced it in the latest Cura, and they take no time to install. Printed in PLA at 0.2mm layer height. You need one for each belt (3 total), and they pop onto the belt under the vertical traveler. They don't work as well on top of the traveler. They automatically seek their own lowest energy location, and are fascinating to see in action. It remains to be seen how much belt wear they cause, but it doesn't appear to be much at all.