Originally shared by Lewihe
ADDITIONAL COMPONENTS for Kit Play 3D
That belt path will cause the belt tension to change as it moves, resulting in a nonlinear relationship between motor rotation and linear movement, as well as increased wear on the belts.
I use exactly the same belt setup on my quadrap core xy for over a year now. It works fine so far and I don’t see why tension should change when the HE travels. What is important in this setup is to have equal tension on both belts as they both end at the carriage. Not so easy to achieve, I added belt tensioners for this purpose. No wear so far. Tension is quite strong in my setup, each loop measures about 1.8m.
The run of belt going from the motor to the Y carriage is not parallel to the direction of travel, so the angle of the belt will change as it moves. Here, the belt’s length is the hypotenuse of a triangle where one side is a fixed length and the other side is variable, and the length of the hypotenuse does not vary linearly with the length of the side.
A more extreme version of the same problem can be seen here: https://plus.google.com/+BrianBenchoff/posts/STXGy69HS7Q
In that case, the belt (or spectra line, in this case) gets so loose when it moves in the -Y direction that it visibly loses all tension and almost falls off they pulleys. What is shown here is just a less extreme case of the same problem.
@Whosa_whatsis thanks for your explanation, I see the point now. I didn’t see that the belt from the stepper to the gantry is not parallel in Y direction. My setup is allmost identical with the difference that the belts are parallel in Y direction.