High-speed milling of dies and precision and complex parts

For the past few years, high speed milling has been used as an alternative and complement to traditional milling or electrical discharge machining. High-speed milling firmly establishes a state of catching up with traditional machining processes. Due to its great advantages in processing 3D curved surfaces and carbide materials, it is mainly used in the mold making, small lot precision and complex parts processing industries. In the automobile industry, which requires the production of large quantities of parts, high-speed milling also has its own characteristics. Especially in the field of automobile mold processing, the recent boom in the automobile industry has brought severe challenges to Chinese automobile mold companies. It is reflected not only in the stringent requirements of the delivery cycle, but also in the comprehensive challenges of the automotive mold industry for design, process and manufacturing capabilities. From a breakthrough in process and manufacturing capacity, high speed milling technology has the important machining advantage of shortening the mold manufacturing cycle and improving manufacturing accuracy.

1.Rapid prototyping parts rapid manufacturing

With the boom in the automobile market, automobile replacement is becoming faster and new product development cycles need to be as short as possible. The high speed milling process is efficient and can cut cavities with complex profiles. Especially, in combination with flexible machining methods such as vertical and horizontal conversion 5-axis linkage, it is the best solution for rapid manufacturing of prototype parts.

2.Die processing of automobile parts

Cars require thousands of molds, but the manufacturing cycle and mold quality have a direct impact on the car’s production cycle and quality. High speed milling has unique advantages in the manufacture of complex parts for automotive parts. For example, if a high speed milling center processes an injection mold for safety door locks, the hardness of the material used in the mold is 54HRC. The minimum tool used is 0.6 mm, the maximum depth of cut is 4.8 mm, and the surface roughness is Ra 0.4 mm. In addition, it eliminates the benching process and reduces machining time. Another example is when processing an injection mold for the gearbox of an automatic window lifting system, the hardness of the material used in the mold is 58HRC. The workpiece is directly milled up to 85%, the remaining 15% is completed by electrical machining, the total machining time is 16 hours and the machining time is reduced by 50%.

3.Mold processing for automobile interior parts

Car replacement is reflected in improved performance More than updated Exterior, interior and auto parts are not reflected. Most of the automobile interior parts are injection molded parts, and the consumption of molds is large. High-speed milling improves mold manufacturing accuracy and extends mold life, thereby improving the quality of injection molded parts.

It can be seen that high speed milling shows great technical advantages in the machining of molds for automobile parts and molds for interior parts. From a processing technology point of view, high speed milling is mainly used in the following aspects of automobile mold processing.

a.High speed milled electrode

The electric discharge machining process basically requires two electrodes to machine the workpiece. To improve EDM, it is necessary to duplicate the same electrode and distinguish between rough and finished electrodes by surface quality. Stable electrodes reduce the time required for electrical discharge machining.

Traditionally milled electrodes require inconsistent manual polishing, manually polished electrodes always have sharp angles, and tip discharge affects the quality of electromachining.

High-speed milling of the electrodes eliminates the need for manual polishing, and near-perfect consistency between the rough and finished electrodes optimizes the efficiency of EDM.

At the same time, high-speed milling can handle thin walls, so it can handle integrated electrodes with ribs. This eliminates the cumulative position error caused by multiple clamps in traditional milling, saving time and improving quality.

Comparison of conventional milling and high-speed milling

Machining method-Total number of processes-Total time (h) -Groove machining (h) -Machining accuracy (mm) -Surface roughness
Conventional milling — 22—256—179— ± 0.2 to ± 0.5—Ra 1.6
High-speed milling — 17—120—44— ± 0.10—Ra0.4

b. Roughing and semi-finishing of the mold

Since high-speed milling can be processed directly on hardened steel, it is theoretically possible to directly mill dies. However, if there are special requirements for the mold cavity, electromachining cooperation is also required. Therefore, roughing and semi-finishing of the mold cavity can be performed on a high speed mill after the material has been heat treated. Leave a small margin, EDM to complete the final finish molding.

c. Direct high speed milling to complete the cured mold

This method is the greatest manifestation of the benefits of high speed milling in mold machining. Take, for example, a micron high-speed milling crankshaft and connecting rod forging die at Dongfeng Motor’s commercial vehicle forging plant.
The traditional milling process is as follows: Roughing of shape → Shape processing Roughing groove → Heat treatment → Shape finishing → Numerical control Electric spark roughing, finishing groove → Fitter polishing groove → Surface strengthening treatment.

The process for fast milling is as follows: Roughing of shape → heat treatment → shape finishing → high-speed milling groove → surface strengthening treatment.

Completing hardened steel molds using high speed milling direct machining has obvious machining advantages. The total processing cost has been reduced from more than 27,000 yuan in the conventional processing to 22,000 yuan.

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