Research On Open Numerical Control System Based On PMAC For Abrasive Water Jet Cutting Machine

As the only cold processing technology in the market, water jet cutting technology has significant advantages. A major advantage is its ability to cut virtually any material with strong adaptability and high controllability. Another advantage is that it doesn't superheat the area adjacent to the cut, so the material can be left intact. The large pieces of reusable scrap material can be cut off, that might have been lost using traditional cutting methods.Among all kinds of water cutting technologies, abrasive water jet cutting technology in particular has a remarkable development in the last few decades. However, conventional abrasive water jet cutting Machine is lack of reusable flexibility, it cannot provide the user with second development. Therefore, the research of an open Computer Numerical Control(CNC) system has a constructive significance to the improvement in the abrasive water cutting machine field.Aiming at the disadvantages of numerical control system of traditional abrasive water jet machine, this thesis puts forward open numerical control system structure that NC inserts into PC, utilize PMAC motion controller and IPC to configure dual CPU system with master slave distributed system structure.The necessary of controlling the pressure of water jet and abrasive flow rate is proposed according to the features of abrasive water jet machining. The pressure is measured by using a pressure transmitter and adjusted by applying an electromagnetic pressure regulator. The abrasive flow is controlled precisely through a CNC controlled spiral abrasive feeding system.In order to achieve a high accuracy, using a linear motor and grating scale to construct full closed-loop structure, and builds the dual compound control system with both feedback and feedforward. Specially, to eliminate the error, the PID parameters and feedforward parameter are adjusted through the step signal and parabola signal with the applying of a servo system. The method of adjusting the precision of the machine by establishing a wheelbase and clearance error compensation table is proposed.Initialization, manual-control, process monitoring, machine simulation, and parameter initialization are accomplished by using Windows platform VB6.0 and Pcomm32 Dynamic Link Library, in particular, a machine controlling software is designed. In addition, the use of a principal computer has accomplished the major performance of the abrasive water jet numerical controlling system. The water jet pressure and the abrasive flow rate are successfully controlled simply from the computerized monitor, where also its accordingparameters can be monitored directly.A standard G code of the machine tool is programmed and is recognizable and controllable by the PMAC motion controller. The simulation of the entire processing system is implemented by using the servo interpolating function of PMAC system. The experimental results are concluded and discussed, which demonstrates the possibility of applying the digital system to a new open abrasive water jet cutting technology.