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Reasonable application of milling tools

Release time:May 10, 2019 Visits:

Key words: milling tool; tool parameters; cost control


   1 Overview 

The current development of the manufacturing industry is characterized by intensified competition. How to continuously improve production efficiency, reduce manufacturing costs, provide high-quality products to customers at competitive prices, and meet the increasing demands of users in a timely manner has become a common concern of all manufacturing companies. Focus.

Cutting tools and machine tools are two subsystems of the manufacturing technology system. They are independent and complementary, and they continue to promote the productivity of manufacturing. When a machine with high-speed cutting capability is provided, the key problem is transferred to the tool. In foreign manufacturing, there is a saying that “the dividend of the enterprise is on the cutting edge”. In the Chinese idiom, “the job is to be good, the tool must be sharpened first”, and “the knife is not mistakenly cut.” The importance has been vividly and profoundly described.

CNC milling machine cutting has high speed and high efficiency. Compared with traditional milling machine cutting, CNC milling machine has higher requirements for cutting tools. The rigidity, strength, durability and installation adjustment methods of milling tools will directly affect the cutting work. Efficiency; the accuracy and dimensional stability of the tool itself will directly affect the machining accuracy of the workpiece and the quality of the surface. Reasonable selection of cutting tools is also an important part of the CNC machining process.

2 Problems encountered in production

There are often problems with the tool during milling, such as chipping, cutting edge wear, breakage, etc. When these problems occur, production efficiency will be affected to varying degrees, resulting in an increase in production costs.

Example: Machining parts - encountered some problems when connecting the ears (Figure 1).

Figure 1 Area view of the part

(1) The blade is easy to chip; (2) the production efficiency is low, and the production plan cannot be met; (3) the tool life is short, and the service life is T=35min.

The actual working conditions at the time were as follows:

Equipment Name: Hanchuan Machine Tool HANDLAND XK714G

Cooling method: air cooling

Parts material: precipitation hardening stainless steel 15-5 (AMS5659)

Tool holder: BT40

Knife body: C211.25R.03-11-A-32-165

Blade: XDKT11T320SR-F50

The cutting parameters used were: cutting speed vc=80 m/min, feed per tooth fz=0.06 mm, radial depth of cut ae=12 mm, axial depth of cut ap=2 mm, tool diameter Dc=25 mm, number of teeth Zn=3.

3 Analysis and improvement plan

Since the depth of the cavity is deep, the depth of the cutter body reaches 100 mm. When the cutter is milled to the bottom, the knife has vibration. To solve the problem of excessive overhang, the following methods can be adopted: (1) the overhang is reduced; (2) use a sparse cutter with unequal pitch; (3) balance radial and axial cutting forces; (4) improve split tooth feed; (5) use light cutter insert geometry; (6) reduce Axial depth of cut af. There are many reasons for the chipping, which is not purely a kind of wear mechanism, and more is the end result of not optimizing the process. In order to solve the problem of chipping, the following methods can be adopted: (1) reviewing the programming strategy; (2) selecting a brand with better toughness; (3) selecting a blade with a stronger cutting edge; (4) increasing the cutting speed vc; (5) Choose a more rigid trough; (6) reduce the feed rate or radial depth of cut; (7) use coolant or compressed air during chipping; (8) improve stability.

Combined with the above analysis, we carried out a large number of experiments, using the method of changing the tool, adjusting the cutting parameters and replacing the machine tool. The specific scheme is as follows:

  Option One: 

Machine tool: Hanchuan machine tool HANDLAND XK714G; cutter body: R390-025A25-11L; insert: R390-11T308M-MM GC2040; parameters: cutting speed vc=80m/min, feed per tooth fz=0.1mm, chip thickness hex=0.1 Mm, radial depth of cut ae = 12 ~ 25mm, axial depth of cut ap = 4mm

The tool life obtained by the experiment was T=30 min.

  Option II: 

Machine tool: Hanchuan machine tool HANDLAND XK714G; cutter body: R390-025A25-11L; insert: R390-11T308M-MM GC2030; parameters: cutting speed vc=80m/min, feed per tooth fz=0.1mm, chip thickness hex=0.1 Mm, radial depth of cut ae = 12-25 mm, axial depth of cut ap = 4 mm.

The tool life obtained by the experiment was T=50 min.

  third solution: 

Machine tool: XHA788 Beijing No. 1 Machine Tool Plant; cooling method: water emulsion; holder: JT50; cutter body: R390-025A25-11L; insert: R390-11T308E-PM GC1030; parameters: cutting speed vc=55m/min, each The tooth feed fz = 0.1 mm, the chip thickness hex = 0.1 mm, the radial depth of cut ae = 12 ~ 25 mm, and the axial depth of cut ap = 4 mm.

The tool life obtained by the experiment was T=120 min.

Through experiments, we obtained a more optimized solution, reduced tool costs (as shown in Table 1) and improved production efficiency. It is concluded that the service life of GC1030 material on this material is worthy of recognition, and it shows the extraordinary ability of this coating to enhance the blade edge toughness, especially in the case of large overhang and small diameter; in large overhang milling In order to obtain a larger ae, a 90° lead angle and a small rounded insert should be chosen to reduce the cutting force. Moreover, when loading and unloading the blade, use a torque wrench, which can improve the quality of the tool and extend the service life of the tool body and the screw.

4 Summary

For the cost control of manufacturing, manufacturing economics has changed the view of cost control in normal production. Lowering the price of production parts does not significantly reduce costs. In fact, some fixed costs are difficult to reduce, such as equipment depreciation and labor costs. Etc. Therefore, the key to lowering prices is the use of good tools and good processes.

The choice of milling tool is reasonable or not, which directly determines the processing quality and processing efficiency. The selection of the tool is carried out under the human-computer interaction state of the NC programming. The tool should be selected according to the material properties, the amount of milling, the shape of the workpiece, the machining method, the machining capacity of the machine and the load and other relevant factors.

  5 Conclusion 

According to the data, the production cost distribution of mold manufacturing can be summarized as: cutting cost 65%, workpiece material cost 20%, heat treatment cost 5%, assembly / adjustment cost 10%, which also clearly shows the excellent cutting plan The importance of economic production of molds. Therefore, increasing cutting parameters and process improvements can significantly reduce the cost per part, thereby increasing corporate profitability. Modern and efficient tools play a key and irreplaceable role in leveraging the comprehensive advantages of digital manufacturing technology. Reasonable selection and application of modern cutting tools is the key to reducing costs and achieving major economic benefits.

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