PINCH TURNING – SYNCHRONIZED UPPER & LOWER Pinch Turning is a way to employ 2 independent and opposing tools on a CNC lathe in order to cut more quickly. When Pinch Turning, one tool follows 180° of spindle rotation behind the other. Each opposing tool is only engaged in the cut for 180° of spindle rotation. The Doosan Puma MX Series T & ST configurations fully support Pinch Turning. The feed rate that is calculated for each tool is doubled. The tools cut at the same time but are 180° out of phase so that the amount of time needed for the Pinch Turned Operation is 50% less than a standard turning operation. The tools used in Pinch Turning must be identical in configuration.
The opposing tools should both share the same orientation (Right or Left Handed), clearance and relief angles, and most importantly, the inserts used must be identical. Pinch Turning is also referred to as Balanced Turning. It can be used for either roughing or finishing. With Pinch Turning, both the opposing tools use the same programmed path. However, each program is independent and is a separate control system. These different control systems are typical classified as Upper & Lower and are synchronized during automatic operation. This synchronization is achieved by the use of Wait Codes (M900-M999) that are placed strategically within the NC code.
A Wait Code is included on a line of NC Code where we wish to begin the synchronization. The same wait code is placed at the corresponding point in the NC Code for the opposing tool. When the Upper and Lower Control Systems reach the same point, both Upper and Lower Tools will begin their motion at the same time. If either Control System reaches a Wait Code before the other Control System, that Control System will wait for the other system to “catch up” before beginning synchronized operations. - 16 -