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Abstract Modern production of die and mold tools is quite different in comparison with conventional machining. The basic theory of cutting process and cutting geometry is similar, but the techniques and technology is quite different. High-speed cutting (HSC) principles are not applicable with conventional machine-tools. Difference between conventional and high-speed cutting velocity is analysed on chip formation. The comparison between EDM and HSM has been made and shows great HSC benefits. Usage of modern software (CAM) optimises tool production and helps us to save unnecessary additional machining time and costs.68748
Keywords: High-speed cutting (HSC); Die and mold manufacturing; Time and costs of machining
1. Introduction
High-speed machining (thereinafter HSM) is a relatively new production technology that allows a higher productivity, an excellent surface finish and a good dimensional accuracy in the manufacturing process. Slovenian die tools production mainly contains: plastic molds, die casting molds, vacuum molds and forging dies. High-speed milling is one of the most important of all high-speed cutting (HSC) methods [1–3]. Thanks to the advances in machine-tool performance as a re- sult of improvements to the main spindle, feed drives, etc., high-speed milling has become a cost-effective manufactur- ing process that produces products with a high surface qual- ity, low variations in the machined surface and dimensional accuracy. High-speed milling was first used successfully in the aircraft and automotive industries for machining complex machine parts made of aluminium and its alloys. Recently, with the advances in cutting-tool materials and technologies, high-speed milling has also been used in the machining of al- loy steels in their hardened state (above 30 HRC up to 60–65 HRC) [4,5].
Customer expectations are striving to: high-quality prod- ucts, short machining times and low machining costs. Euro- pean machine-tool market is getting stronger and stronger in
∗ Corresponding author. Tel.: +386 611771200; fax: +386 12518567.
E-mail address: peter.krajnik@fs.uni-lj.si (P. Krajnik).
favor of HSC machine-tools in comparison with EDM ma- chines.
2. HSM in tool-making industry
High-speed machining assures two times more efficient productivity, which is achieved at first with the cutting speed and secondly with feed-rate. Conventional feed-rate is in- creased with software solutions and modern machine-tool design up to 1600 mm/min.
Fig. 1 shows water bottle mold machined with HSC by using modern CAM programs. By deep cavity the machined surface quality is very uncertain, especially the second part where polishing is used as a finish operation.
More exacting machining of 3D (three-dimensional) workpiece surfaces is successful only with five-axis machine- tools, which enables milling of any surface. Five-axis NC programming is similar to the one applied with three-axis par- allel machining. Five-axis machining enables additional cut- ter side deviations and onward–backwards deviations from the normal, which orientates the surface. Among many CAD–CAM possibilities, five-axis machining is the most uni- versal machining procedure, which enables side or tip milling of any shapes.
Fig. 2 is presenting an example of rather complex sur- face machining. The surface is curved in all directions and contains concavoconvex spheres.
0924-0136/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2004.07.146
Fig. 1. Water bottle mold.
Five-axis milling machine-tool enables main spindle slope, thus ball-nose pencil cutter can be used at a defined angle. In this way we can avoid null cutting speed on a cutter tip.