So I'm getting into a CNC router build with a 4x8 capacity and right now my plan is to utilize OpenBuilds NEMA 23 Belt & Pinion Actuator assembly for the Y axis (one on each side). I spoke with customer service and they confirmed that I can purchase the assemblies with the 20x80 V-slot increased to 3000mm and the belt lengths being increased as well. Obviously I've read about quite a bit of stretch issues with the belts being too long, but I've also read many success stories with various configurations of utilizing belts on a long Y axis - with a couple successful 4x8 belt driven builds being on this forum. From a simplicity and cost standpoint, there are some advantages. I have been unable to find anything specifically about the belt and pinion design - which I think has some unique advantages over other belt assemblies I've seen. I think the distinct advantage to the "belt & pinion" set up over other belt set up's I've seen done is that since the motor is traveling with the gantry, the total length of the belt is only marginally longer than the Y axis, where many set ups have a belt that loops back and is 2X the length of the axis it serves. OpenBuilds lists the accuracy of this assembly as 0.003" ~0.007". Let's assume the greater inaccuracy of 0.007" is referencing the longest configuration shown on the site of 1500mm. If we multiply that by double the length (3000mm Y axis), we have an accuracy of 0.014". I'm going venture to assume that multiplying length of belt doesn't exactly translate to a 1:1 ratio of length to inaccuracy like that, so for the sake of a pretty unscientific conversation, lets multiply that result by 2x again, with a result of 0.028" inaccuracy or 0.712mm - something that I believe I'd be pretty satisfied to achieve with a project like this. I don't believe that I have any illusion about the fact that the belts will be a regular maintenance item, something of concern that I will have to pay attention to regularly, and I'm also just building a hobby machine for me to mess around with - nothing in a demanding production environment. In fact, my primary use will be 2D cutting of plywood and MDF parts. That all said, does anyone have some thoughts on if I'm crazy for thinking this might be a reasonable approach to achieve a simple Y axis actuator that is about 114" long on a hobby level machine? Thanks for any input!
There is a method called double belting where you mount a belt inside the slot. This belt meshes with the regular drive belt. What this does is reduce the belt length from whatever the length is (500mm, 1500mm, 3000mm, whatever), to whatever the distance is between the wheels and motor. This method pretty much eliminates belt stretch. I can't find the exact example I was looking for though. Maybe someone else can follow up.
maybe Fitting Dual Belt ? Searching for Dual Belt above in the search box is good start too, used to be a very popular mod in the old Ox days
