servo - based fast linear actuator

A fast linear actuator for servo : servo 180° rotation on XY plane -> 58mm on Z plane
2 versions of the rings are available

A: linear_ring_1.stl has wide tolerance, about 0.8mm away the inside worm screw
B: linear_ring_T.stl has a small tolerance, about 0.25mm

"A" version needs rough sanding only, but has more axial parasitic move tolerance
"B" version needs clean sanding of the worm screw + the ring, but it gives far less parasitic moves on the direction of the push/pull