How to improve the precision machining efficiency?

Deshengrui Machinery Co., Ltd. analyzes the factors affecting the machining productivity according to the problems found in the actual production of the factory. The most important factors are: product design quality, blank forming method, machining technology and production management method and level. So how to improve the machining efficiency should start from the following points.

I. Process measures to improve the productivity of machining

(1) Shorten one-piece working hours

First, the process measures to shorten the basic time. In large-scale mass production, since the basic time accounts for a large proportion in unit time, productivity can be improved by shortening the basic time. The main ways to shorten the basic time are as follows:

1. Increasing the cutting amount, increasing the cutting speed, the feed rate and the amount of the backing knife can shorten the basic time, which is an effective method for improving productivity widely used in machining. However, the increase in cutting amount is limited by the durability of the tool and the power of the machine tool and the rigidity of the process system. With the advent of new tool materials, the cutting speed has been rapidly improved. At present, the cutting speed of cemented carbide turning tools can reach 200m/min, and the cutting speed of ceramic cutting tools reaches 500m/min. In recent years, the cutting speed of polycrystalline synthetic diamond and polycrystalline cubic boron nitride cutters for cutting ordinary steel reached 900 m/min. In terms of grinding, the trend in recent years has been high speed grinding and strong grinding.

2. Simultaneous cutting with multiple knives.

3. Multi-piece machining This method improves productivity by reducing the cutting-in, cutting-out time or the basic time of the tool, thereby shortening the basic time for each part. There are three ways to process multiple parts: sequential multi-piece machining, parallel multi-piece machining, and parallel sequential multi-piece machining.

4. Reduce machining allowance. Advanced processes such as precision casting, pressure casting, precision forging, etc. are used to improve the precision of blank manufacturing and reduce the machining allowance to shorten the basic time, sometimes without even machining, which can greatly improve production efficiency.

Second, shorten the auxiliary time. Auxiliary time also accounts for a large proportion in single-piece time, especially after greatly increasing the amount of cutting, the basic time is significantly reduced, and the auxiliary time is a higher proportion. At this time, taking measures to reduce the auxiliary time becomes an important direction for improving productivity. There are two different ways to shorten the auxiliary time. One is to make the auxiliary action mechanized and automated, so as to directly reduce the auxiliary time; the other is to make the auxiliary time coincide with the basic time and indirectly shorten the auxiliary time.

1. Directly reduce the auxiliary time. The workpiece is clamped by a special fixture, and the workpiece does not need to be aligned during the clamping, which can shorten the time for loading and unloading the workpiece. When mass production is carried out in large quantities, high-efficiency pneumatic and hydraulic clamps are widely used to shorten the time for loading and unloading workpieces. In the single-piece small batch production, due to the limitation of the manufacturing cost of the special fixture, in order to shorten the time for loading and unloading the workpiece, a combined fixture and an adjustable fixture can be used. In addition, in order to reduce the auxiliary time of the stop measurement during processing, an active detection device or a digital display device can be used for real-time measurement during the machining process to reduce the measurement time required in the process. The active detection device measures the actual size of the machined surface during machining and automatically adjusts and manages the machine according to the measurement results, such as grinding automatic measuring devices. The digital display device can continuously and accurately display the movement amount or angular displacement of the machine tool during the machining process or the machine tool adjustment process, which greatly saves the auxiliary time of the stop measurement.

2. Indirectly shorten the auxiliary time. In order to make the auxiliary time and the basic time coincide in whole or in part, a multi-station jig and a continuous machining method can be employed.

3. Shorten the time for laying work. Most of the work time is spent on changing the tool, so it is necessary to reduce the number of tool changes and reduce the time required for each tool change. Increasing the durability of the tool can reduce the number of tool changes. The reduction of the tool change time is mainly achieved by improving the tool mounting method and using the tool holder. For example, various quick change tool holders, tool fine adjustment mechanism, special tool setting or tool setting and automatic tool changer are used to reduce the time required for tool loading and unloading and tool setting. For example, the use of indexable carbide inserts on lathes and milling machines reduces the number of tool changes and reduces tool loading, unloading and sharpening time.

4. Process measures to shorten preparation and end time. There are two ways to shorten the preparation and termination time: first, expand the production batch to reduce the preparation and termination time allocated to each part; second, directly reduce the preparation and termination time. Expanding production batches can be achieved through standardization and generalization of parts, and can be organized by group technology.

(2) Implementing the care of multiple machine tools

The supervision of multiple machine tools is an advanced labor organization measure. It is obvious that a worker can manage several machines at the same time to improve productivity, but two necessary conditions should be met: First, if one person takes care of M machines, the sum of the working hours of workers on any M-1 machine should be less than the other. The maneuver time of the machine tool; the second is that each machine must have an automatic parking device.

(3) Adopting advanced technology

1. Blank preparation. New processes such as cold extrusion, hot extrusion, powder metallurgy, precision forging, and explosive forming can greatly improve the accuracy of blanks, reduce the amount of machining work, save raw materials, and significantly increase productivity.

2. Special processing. For difficult-to-machine materials or complex profiles such as extremely hard, tough, and extremely brittle, special processing methods can greatly increase productivity. If the general forging die is electrolytically processed, the processing time can be reduced from 40 to 50 hours to 1 to 2 hours.

3. Use less cutting without machining. Such as cold extrusion gears, rolling screws and so on.

4. Improve processing methods and reduce manual and inefficient processing methods. For example, in large-scale production, broaching and rolling are used instead of milling, reaming and grinding, and fine grinding, fine grinding and diamond slabs are used instead of scraping.

(4) Adopting an automated manufacturing system

The automated production system is an organic whole consisting of a range of processed objects, a variety of equipment with a certain level of flexibility and automation, and high-quality people. It accepts external information, energy, capital, accessories and raw materials, etc. Under the joint action of the computer control system, a certain degree of flexible automated manufacturing is realized, and finally the products, documents, wastes and environmental pollution are output. The use of automated manufacturing systems can effectively improve working conditions, significantly increase labor productivity, significantly improve product quality, effectively shorten production cycles, and significantly reduce manufacturing costs.

Second, design measures to improve the productivity of machining

When designing, under the premise of ensuring the performance of the parts of the product, the part structure should have a good processing technology, and the materials with good processing technology should be selected to reduce the processing difficulty and improve the labor productivity, thereby obtaining good economic benefits.

(1) Improve the structural craftability of the parts

In order to make mechanical products have good structural processability, the following measures are often used in design:

1. Improve the degree of “three-way” of parts and components (parts standardization, component generalization, product serialization), make full use of the existing technology and standardized and serialized parts and components, and try to borrow the existing production of the factory. The same type of parts make the designed structure have good inheritance.

2. Use parts with simple surface geometry and place them as much as possible on the same plane or on the same axis for processing and measurement.

3. Reasonably determine the manufacturing precision of the parts and the assembly accuracy of the products. Under the premise of ensuring the performance of the product, the manufacturing precision and assembly accuracy should be minimized.

4. Increase the proportion of parts made by non-cutting methods and parts made by less expensive cutting methods. Obviously, the greater the proportion of these two parts in the product, the better the processability of the product.

(2) Selecting workpiece materials with good cutting performance

The machinability of the workpiece material directly affects the cutting efficiency, power consumption and surface quality of the part. When designing the product, the workpiece material with good cutting performance and the heat treatment measures that can improve the cutting performance of the material should be selected as much as possible to ensure the productivity and reduce the cutting cost.

The machinability of a material depends primarily on the physical and mechanical properties of the material. In general, materials with high strength and hardness, good plasticity and toughness, and poor thermal conductivity have poor machinability, and vice versa.

In actual production, heat treatment methods are often used to change the metallographic structure and mechanical properties of the material to improve the machinability of the workpiece material. For high-hardness cast iron, high-temperature spheroidizing annealing is generally used to spheroidize the flake graphite to reduce the hardness and improve the machinability of the material.

Deshengrui Machinery is a professional CNC manufacturing and sheet metal fabrication company, including CNC machining services,CNC turning service, CNC milling services, CNC drilling services, laser cutting services, stamping services, die casting service and forging service. Call us +86-512 3687 0426 or email us bruce@desheng-precision.com for more details for your projects.

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