Move green slider carrying a rack that turns grey shaft to mill an Archimedean spiral groove on the work (not shown) fixed to the grey shaft.
Violet and yellow sliders are connected together by a revolute joint.
Adjust oblique angle α of the popcorn runway to get various constant distances of the Archimedean spiral. If α = 0 the spiral turns into a circle.
This device can be considered as a mechanism for converting a straight line (in blue) in a Castesian coordinate system into an Archimedean spiral (in pink) in polar coordinate system.