Workcentre

摘要

A workcenter comprises a track (14) having a carriage (24) moveable along the track by a screw (32) rotated by a motor (30). The carriage has a bore (42) surrounding the screw. Two sleeve members (160) are received in the bore at either end thereof and surround said screw. The sleeve members are segmented and have threads for engagement with the screw. The sleeve members are pressed radially into engagement with the screw by a spring ring (198). The sleeve members are constructed from deformable plastics material and are screwed onto the screw against the opposite shoulders (163) around the bore in the carriage sufficient to deform the threads so as to take up axial freedom of movement between the carriage and screw. This arrangement allows an inexpensive rolled steel screw having inherent inaccuracies to be employed without loss of positional accuracy.