diff --git a/UrumbotXYZ/fixed_axis/README.md b/UrumbotXYZ/fixed_axis/README.md index 739833e7a897d3197c6340c500f32727e7f938da..facb1ffaaade66ae0e529312c60dfc73cc2bae04 100644 --- a/UrumbotXYZ/fixed_axis/README.md +++ b/UrumbotXYZ/fixed_axis/README.md @@ -81,3 +81,13 @@ This configuration almost works for both PCBs and wax, with dF/dz = 30 N/mm at s - Better string, two strings, belt, leadscrew. - Evaluate bearing design and improve if it makes sense to do so. - Measure plate compliance (better word than stiffness?) and increase roller separation to stabilize if it makes sense. + + ### Evaluating and adding stiffness to z-axis. + + #### Adding more string + + - Confirmed about 30 N/mm stiffness on z axis at the spindle axis. + - Measured force and motion with a force sensor attaced to the plate that move the z-spindle, so that little torquing of the bearing was involved. The result is identical to the spindle measurement, about 30 N/mm, indicating that most of the axis compliance is associated with the belt and motor, rather than the rubber bearings. + - Braided three strands together. Upon reassembling, the stiffness increased by ~20 percent - not significant. I can see that the motor is turning slightly as force is applied. Looks like stepper motor torque is the limiting factor. I will reduce the motor spindle diameter by a factor of three or so. + +<img src=./img/braided_braid.jpg width=40%>