| 摘要 |
<p>An apparatus (40) for positioning a guide slidably mounted on a machine wherein the guide is driven by a lead screw (43) turned by a DC motor (51) through a worm drive gearhead (50). The DC motor (51) is controlled by a programmable logic controller (PLC) (54) with input from an operator interface (56) and feedback from a hollow shaft encoder (53) attached directly to a shaft (48) extending from the lead screw (43). Ladder logic programming in the PLC (54) directs the motor (51) to run or stop based on comparing a target position for the guide with the current position based on electrical signals from the encoder (53). A home position of each guide corresponds to the guide's position when it has moved fully outward encountering an outward stop (44). The programming takes up mechanical backlash in the apparatus on each move by overshooting the target position a predetermined amount when a move is made in an outward direction. Moves in an inward direction proceed directly to the target position. A changeover cycle moves all guides to positions selected from previously stored positions.</p> |
