Abstract: PMAC (programmable multi-axis controller) is used as the CNC system for a machine tool. A CNC lathe was designed and built. This machine tool uses PMAC to drive its cutting axis to the spindle encoder, enabling the tool speed to track the spindle speed, thus achieving a constant pitch and precise driving. Keywords: Programmable multi-axis controller; Drive; CNC Introduction Turning, as the most basic machining method, has received widespread attention and vigorous research and development. General lathe CNC systems can only use G-code programming, and the CNC system is not an open system. PMAC is used as the CNC system, which has an open platform. It can not only use G-code, but also C or BASIC languages ​​for programming, and can run PLC programs. PMAC uses a Motorola DSP 56001/56002 digital signal processor as its CPU, which can handle calculations for 8 axes and can be expanded to control 128 axes. It is essentially a computer, which can be installed in a PC slot for control or run completely offline. PMAC can control any type of motor. It also has a feedback function. It is a high-performance control system with a high cost-effectiveness and should be vigorously promoted in CNC machine tools. 1. CNC Lathe Structure The structural principle of the CNC lathe is shown in Figure 1. It adopts a four-axis PMAC-PC as the CNC system. The x and z axes use servo motors as drive devices, and the spindle is controlled by a frequency converter. [align=center] Figure 1 Schematic diagram of CNC lathe[/align] 2. PMAC Structure and Working Principle This system uses PMAC-PC as the CNC system controller of the CNC lathe. Its system structure is shown in Figure 2. Its CPU is [align=center] Figure 2 PMAC system structure diagram[/align] J8—a four-axis wiring slot that can control 4 motors and connect 4 encoder inputs. The following slots can also be connected to the D/A output: J1 – Display slot for connecting a display to show the machining process; J2 – Control board slot for connecting an external control board; J3 – Handwheel slot for connecting a pulse generator; J4 – RS-23T/RS-422 slot for serial communication with a computer; J5 – I/O slot for connecting input/output variables; JE – PMAC expansion card slot; JS – 16-bit A/D input interface slot. The M56001/56002 digital signal processor controls the DSP-GATE gate array, which can control various slots. Because the gate array outputs in parallel, it can control not only one axis of independent motion but also eight axes simultaneously. Software can also be programmed to perform curve interpolation motion, thus completing the machining of irregular surfaces. 3. Application Example Taking the turning of a screw as an example, a PMAC application program was developed to machine a 5mm screw. Assuming the spindle speed is 3000 r/min, the cutting speed is 50 (rev/see) / 2 (rev/cm) - 25 cm/sec. To ensure tool alignment with each thread (50 rev/see (>20 msec/rev), the program time for each cycle must be a multiple of 20 msec. 4. Conclusion This paper introduces the use of PMAC as a machine tool CNC system, develops a program for turning screws, and conducts practical machining applications on a self-designed and manufactured CNC lathe. The results demonstrate that by controlling the machine tool with PMAC, the tool speed can track the spindle speed, achieving a constant pitch, precise follower operation, and improved machining accuracy. PMAC also has the following characteristics: a. PMAC can be used not only on lathes but also on grinding machines and other machine tools as a controller for CNC systems. b. PMAC has various structural forms; a suitable and inexpensive structure can be selected according to system requirements. c. Using PMAC, linear motors, and laser interferometer feedback, a precision X-Y platform can be moved at a speed of 25.4 cm/s, with a resolution of 0.0254 m, making it suitable for designing high-precision machine tools.