Research on High-speed Precision Grinding of Non-circular Parts Based on PMAC

This paper presented a new grinding method in relation to the focus of high-speed precision machining for non-circular parts. We designed and integrated a set of grinder NC system, refitted an experimental NC grinder and researched into the control core of the NC grinder-open Programmable Multi-Axis Controller (PMAC), linear motor feed unit and high-speed electrical spindle unit. The numerical PID principle was used to adjust the system’s dynamic and static performance. Time-base method of PMAC and the linear motor’s micro-feed motion and the electrical spindle’s high-speed performance were used to accomplish the grinding manufacture of high-speed performance of non-circular parts. Experiment researches have demonstrated this method could suffice part manufacture precision and provide a fine method for achieving the precision grinding of non-circle parts. Introduction With the improvement of engineering productions’ performance and quality, the high precision and complicated of parts is required. These require NC machine tools to have high performance, high accuracy and the ability to process steadily the complicated form parts. In recent years, with the development of new technology, high speed precision machining of non-circular parts becomes a new research focus because of the application of linear motor of fine properties. However, most of the researches and applications are based on lathe and the researches of high precise grinding are very few. Grinding as a method of accuracy machining plays an important role in modern manufacturing industry. The research on high speed precise grinding of non-circular parts has profound significance. The NC System’s Integration for High Speed Precision Grinding of Non-circular Parts The Choice of Open Controller. The controller is the core of grinder NC system, which is composed of various kinds of element for grinding according to standard and simple method. In this research we choose the PMAC (Programmable Multi-Axis controller) movement controller. It exploits the high function and high flexibility of DSP in an all-round way. It can manipulate one to eight axes at the same time by drawing support from DSP56001 of Motorola. We choose a two-axis Mini-PMAC in this grinder system. The PMAC’s structure principle is shown in Fig.1. Fig.1 PMAC structure principle Key Engineering Materials Vols. 259-260 (2004) pp 370-373 online at http://www.scientific.net © (2004) Trans Tech Publications, Switzerland Online availa le since 2004/Mar/15 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 130.203.133.33-16/04/08,10:52:39) Journal Title and Volume Number (to be inserted by the publisher) 371 In Fig.1, J8 port is a two-axis slot, which can control two motors and connect four inputs of encoders; J1 port is a display slot, which can indicate the machining process by connecting display; J2 port is a control panel slot, which can connect an external control panel; J4 port is a RS232/RS422 slot, which can serially communicate with PC; J5 port is a I/O slot, which can connect the input/output appliance; JE port is an expansion card slot of PMAC; JS port is a 16-bit A/D slot. High Speed Precise Feed Unit. The feed unit includes the servo drive unit, the rolling unit and the position monitor unit. The feed unit is the essential condition that keeps the grinding wheel in normal work and is one of the important indicators that appraises the performance of high speed, high efficiency and super high speed grinder. So the feed unit is demanded to have flexible operation, high resolution, high positional accuracy, large travel range, high rigidity, fast dynamic respondence, and to have not only larger acceleration but also enough power. As to non-circular parts, direct drive linear motor is used. The linear motor of high dynamic performance with numerical control technology can obtain higher quality of adjustment and satisfy the above-mentioned requirements as well. We choose the permanent magnet linear motor of IL06-030A1 model, which is produced by Kollmorgen Corporation. It can realize the feed reciprocal motion at micron level. The precise grinding of non-circular surface can be achieved therefore. High Speed Spindle Unit. High speed spindle unit is a core element to achieve high speed machining. Its cardinal type is an electric spindle. The spindle unit is an important element that determines high speed and high efficiency of machine tools and is the basis of machine tools’ technical development. It influences precision, stability and applicable range of machining system. Its dynamic performance and stability play a role in high speed and high efficiency grinding and in precision and super precision grinding. Enhancement of the grinding wheel’s rotation speed is primarily to enhance the rotation speed of spindle that connects the grinding wheel. So the spindle unit which is applicable to high precision, high speed and super high speed grinder is the key element of grinder. The support core of the electric spindle is the bearing for high speed precision spindle. We have developed the high speed and high power electric spindle unit by use of B7009C/HQ series ceramic bearing developed and manufactured by ourselves, which can achieve 30000 r/min, 15~20 KW and has been applied to this experimental grinder. Fig.2 The integration figure of grinder NC system The Integration of Grinder NC System. The integration figure of grinder NC system is shown as Fig.2. On the base of the lathe Mini-PMAC controller is used as control interface of NC. Mini-PMAC Variable Speed driver 1 Asynchronous motor