Abstract : This article takes the Automatic Table Change (APC) control of a horizontal machining center as an example to introduce the characteristics of Siemens 840 channel control technology. Keywords : CNC system, channel control, APC control 1 Introduction The so-called channel control technology of a CNC system is essentially parallel processing. It allows the system to process multiple programs simultaneously, improving system performance and reliability while reducing costs. This advanced technology can effectively solve the control problems of multi-unit multi-axis machine tools. Siemens has used channel control technology since the 810 system, and this technology is more mature in the 840 system. It not only increases the number of channels but also introduces the concept of operating mode groups, enabling six channels to work simultaneously in six different operating modes. It can execute all auxiliary functions (such as M, S, T, H, D, etc.) and control the spindle through the 840 system's unique "program and axis coordination" commands (NC program instructions). It can also flexibly control and coordinate the movement and control of each channel and axis. The following section uses the automatic table exchange control of the TMA-55 OPN6 horizontal machining center as an example to introduce the characteristics of Siemens 840 multi-channel control technology. 2. Machine Tool Control Requirements: The TMA-55 OPN6 horizontal machining center is a full-function horizontal machining center imported from Italy by our factory, using the Siemens 840 CNC system. It has a 6-position rotary table magazine with 64 tools and is capable of seven-axis control. In addition to the five basic CNC axes (x, r, z, B (rotary table), and c (spindle position control) found in ordinary horizontal machining centers, to improve reliability and efficiency and simplify the hydraulic and mechanical transmission system, the rotation of the tool magazine and the table magazine are controlled by CNC axes. The E-axis is the table magazine rotation axis, and the x-axis is the tool magazine rotation axis. Because tool pre-selection by the random tool magazine and table transport must be performed simultaneously during machine processing, this cannot be satisfied by multi-axis linkage functions (since the seven axes are not simultaneously in position). For this purpose, TMA adopted Siemens' 840-channel control technology. [b][align=center]For details, please click: Siemens 840-channel control technology and APC control[/align][/b]