Article by: Okuma Techno (Thailand) Ltd. & MEGA Tech
Lead time reduction and cost reduction are major issues in the manufacturing of die mold industry. On the other hand, the diversification of automotive design has led to very high shape accuracy and surface quality requirements for die mold. In the die mold manufacturing, the skillful know-how necessary for hand finish work such as polishing and mold matching is being lost, while high quality and improvement of production efficiency are required.
The Double-Column Machining Center “MCR-S (Super)” and related technology will be introduced in this article, which was developed to shorten the total lead time in the die mold manufacturing process.
Development Objectives
MCR-S is mainly responsible for large-scale die machining such as press dies for automotive. In die mold machining, shortening of machining time and reduction of step and corner area have been raised as issues. Further, as the design of automotive is continuously improving, the machined surface quality is required. It is necessary to solve these problems.
Key Technologies for Problem Solving
- Reduction in Machining Time
Outer type die mold such as bonnets and side panels have less undulations. And there is expected that the machining time will be shortened by improving the feed rate. In MCR-S, continuous cutting feed X, Y axis 20, and Z axis 10 m/min are standard specifications, achieving the fastest continuous cutting feed in its class.
When the design surface of the side panel is processed into die mold for automotive, it is possible to shorten machining time by 25% compared to the previous model. Optimal cooling is applied to the heat generating part to achieve stable machining performance for long time machining with feed rate of 20 m/min (Fig. 1).
- Improvement of Machining Surface Quality
To reduce the polishing process in the machining post process, high surf
ace quality machining without stripe is required. By using linear guide for Y-axis, and cooling of the slideway of ram for Z-axis to improve the trackability of each axis, the high quality surface machining is achieved. As an example, the evaluation result of machining area of Z-axis reversal part using 3D optical profiler, the stripe about 1 μm is occurred in the previous machine is become 0.5 μm or less in the MCR-S, and it is possible to improve to the invisible level (Fig. 2).
Moreover, not only the machine structure but also the machining program is a major factor in the quality improvement of machining surface. Therefore, by applying our machining program compensation function “Hyper-Surface”, the control device automatically correct NC data during machining to achieve high quality surface. Specifically, by compensating the uneven spaces between adjacent cutter paths, reducing inconsistent depths and edge widths, the depth of cut is arranged as uniform to suppress the occurrence of stripe (Fig. 3). As a result, the quality of the machined surface is improved and the polishing time of die mold can be considerably reduced.
Fig.2 Trackability Improvement Result