Ways to improve milling efficiency

I. Introduction

Milling is one of the basic machining methods for machining. From the perspective of the overall mechanical processing industry, it accounts for about 20%-30% of the machining work , which shows its importance in machining. In addition to the workpiece on the surface of the cylinder, workpieces of various shapes and shapes can be milled. With the continuous advancement of science and technology, the wide application of CNC milling machines, the working range of milling processing continues to increase. Therefore, improving milling efficiency is not only the main means to reduce production costs, obtain greater economic benefits, but also the most effective way to reduce technical equipment. The way to improve milling efficiency is to use advanced and reasonable process equipment (tools, tooling, cutting fluid, etc.) to maximize and rationally improve the three elements of milling usage, and to minimize the basic time and auxiliary time to obtain unit time. Maximum productivity and maximum economic efficiency. This is also the basic measure to improve the survival and market competitiveness of enterprises.

Second, the main way to improve milling efficiency (using high-quality tool materials)

1. Replace high-speed steel milling cutters with high-performance high-speed steel milling cutters. Like high carbon, high vanadium, cobalt-containing, aluminum-containing, super-hard high-speed steel, their heat resistance is 4~6HRC higher than that of ordinary high-speed steel at 600°C, and the wear resistance is 2~4 times higher. It is suitable for milling of difficult-to-cut materials and can improve milling efficiency by about 30% . Used by the factory floor.

2. Replace the high speed steel milling cutter with a carbide milling cutter. The hardness of high speed steel tool material is HRC62~70 , heat resistance is 600~650 , bending strength is 3500~3800MPa, and hardness of hard alloy is HRA89.5~92.5 , heat resistance is 800~1000 , bending strength is 1500. ~4000MPa. The allowable cutting speed is more than 4 times that of high speed steel , which can increase the milling efficiency by about 4 times. Therefore, when using a milling cutter, use hard alloy as much as possible. Of course, cemented carbide tools are more expensive than high-speed steel milling cutters. However, due to its cutting efficiency and high life, the average cost per workpiece is much lower than that of high speed steel milling cutters. Furthermore, the technology for manufacturing carbide milling cutters in China is not worse than that of foreign countries. The price is 1/4-1/6 of imported ones , which creates favorable conditions for the widespread use of such milling cutters.

3 , using coated high speed steel and carbide milling cutter. PVD coating process using high-speed steel TiN, PVD and CVD processes using carbide coating TiN, after TiALN, TiC, the tool can (sheet) to improve surface hardness HV2000 ~ 3200 (co HRC83 or more), not only to improve the durability of the cutter More than 3 times, the cutting speed can be increased by 30%-50% , thus improving the milling efficiency.

4 , using ceramic blade milling. Modern ceramic blades have a flexural strength of 800 to 1100 MPa . The hardness is HRA94.5~95.5 , which is higher than the highest hardness of cemented carbide HRA2~ 3 , and its heat resistance is 1200 . And it does not bond with the metal. Various end mills made of it can mill hardened steel, various cast irons and steels at several times the cutting speed of cemented carbide. The cutting speed of milling cast iron can reach Vc=300 ~600m/min , and the Vc of milled hardened steel is 80 ~120m/min . Therefore, the cutting efficiency is improved by 3 to 5 times.

5 , using cubic boron nitride milling cutter. The hardness of cubic boron nitride (CBN) is second only to diamond , the hardness is HV8000~9000 , which is 4 ~5 times that of cemented carbide . The heat resistance is the highest among the tool materials , and it is the core of iron group metal. small. CBN and cemented carbide are used as composite sheets ( PCBN ), which are processed into indexable milling inserts and welded into milling cutters for milling corresponding materials such as cast iron and difficult-to-cut materials. High-speed milling can be performed several times faster than carbide milling cutters to improve milling efficiency.

6. Artificial polycrystalline diamond ( PCD ) and synthetic diamond thick film brazing cutters. It is used to mill all kinds of non-ferrous metals and non-metals and various composite materials. Its tool durability is extremely high (several times that of cemented carbide), and it can be 5 to 10 times higher than that of cemented carbide . The amplitude increases the milling efficiency.

7. Milling with a combination milling cutter. A combination milling cutter is a milling cutter that combines two or more milling cutters of the same type or different types on a cutter bar to simultaneously mill several surfaces of the workpiece in one feed pass. Milling and milling in this way not only reduces the number of passes, but also doubles the machining efficiency, while also ensuring the mutual positional accuracy of the machined surfaces.

Change the milling cutter structure to improve milling efficiency. What kind of milling cutter can be used to improve milling efficiency? Replacing the welding cutter with an indexable milling cutter not only saves the grinding time and the assisting time of the knife adjustment, but because of its many teeth, it can increase the feed speed several times; with a thin blade saw blade milling cutter (including closed Cutting the T -slot and other milling cutters) instead of the dense-tooth milling cutter, the chip space can be increased, and the milling efficiency can be improved by several to several tens of times. By replacing the general end mill with a wrong-tooth spiral corn cob milling cutter, the milling depth can be doubled. And improve milling efficiency.

8. Reduce the auxiliary time. The machining time quota of a workpiece, which consists of maneuver (also called basic) time and auxiliary time. Increasing the milling efficiency not only shortens the maneuvering time, but also greatly and reasonably shortens the auxiliary time. Measures to shorten the auxiliary time include: selecting tools with excellent performance (tool material, tool geometry, tool structure, etc.) to improve tool durability, reduce the number of sharpening and tool change, and increase the amount of cutting; in batch production, use more Work station, automatic positioning, clamping fixture, reduce workpiece installation time; use special measuring tools and automatic measuring tools; use CNC milling and so on.

9. Use a good cutting fluid. Cooling lubricants reduce cutting temperatures and friction, reducing cutting forces, heat, and tool durability. Why do all foreign cutting machines work with good cutting fluids? Through practice, using cutting fluid with good performance can improve cutting efficiency by 30%-50% . However, the milling of conventional milling machines in China mostly uses dry milling, so the milling efficiency is low.

Third, the conclusion

1. The main way to improve milling efficiency is also a simple and easy way. It is reasonable to select high-performance tool materials, tool geometry parameters and tool structure to improve the three factors of milling. As long as one element of the cutting speed, feed rate and depth of cut is doubled, the maneuver time is doubled.

2. In addition to the conditions of machine tools and tool cutting tools, the selection of tools, measuring tools and cutting fluids can greatly shorten the auxiliary time and improve the milling efficiency.

3 , improve the quality of operators, in order to rationally choose milling conditions and process parameters, is the fundamental way to improve milling efficiency.

Fourth, the reference

1, Xiao Shi Gang "reasonable choice of tool materials and" 2nd edition, Beijing: Mechanical Industry Press. 1990

2. Shanghai Science and Technology Exchange Station . Metal Cutting Manual . Shanghai: Shanghai People's Publishing House, 1974

3. Ai Xing . “High-speed Machining Technology . ” Beijing: National Defence Industry Press, 2003

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