Application of CNC machine tools in automobile manufacturing
In today's automobile production, the development cycle of new products is continuously shortened, and the cost is also continuously reduced. According to the data, a car product that requires a four-year development cycle ten years ago can be completed in two years. In addition to advanced technology development methods such as advanced new product development methods, virtual manufacturing, and synchronous engineering, it is important to benefit from the efforts of equipment suppliers that provide manufacturing equipment for automotive manufacturing, especially equipment suppliers. A variety of CNC machines are available that allow automakers to deliver products that meet market needs as quickly as possible.
CNC machine tools classification and features
There are many kinds of CNC machine tools; from the general category, there are special CNC machine tools, there are general-purpose CNC machine tools; from the processing varieties, there are CNC milling machines and machining centers for machining shells, CNC lathes with machining axes, turning centers , cam CNC grinding machine, etc.; from the processing control requirements, there is a single-axis CNC CNC belt polishing machine, there are five linkage CNC gear cutting machine, CNC hob grinding; from the complexity of control, there is simple CNC, There are multi-channel numerical control; from the driving mode, there are stepping motor, DC servo motor, AC synchronous servo motor, AC asynchronous servo motor, linear motor; from spindle drive mode, there is DC spindle motor, there are AC spindle motor, with AC main shaft; from the position feedback mode, there is full closed-loop feedback, semi-closed loop feedback, open loop control and so on.
The good flexibility of CNC machine tools, high adjustment, high processing precision, has long been concerned by car manufacturers, and began to enter the field of auto parts production in the 1960s. Due to its high cost, system function and efficiency are not ideal, and it has not been widely used. In the 1990s, with the intensification of market competition; multi-variety production to meet the diversified needs of the market to the greatest extent, until the needs of each user, to become the goal pursued by car manufacturers, with CNC machine tools as the main body Flexible manufacturing units are used in large quantities. There are two key development directions for CNC machine tools today:
High-speed CNC machine tools achieve high efficiency at high speeds. The current international level is spindle speed ≤ 25000 rpm, acceleration and deceleration ≤ 2.5g, fast movement ≤ 160m / min, to achieve this new level, CNC machine tool drive, mechanical transmission, mechanical structure, tools must have a large Improve. The main shaft of the machine tool must use the electric spindle. The main bearing is generally made of ceramic bearings. The difficulty is cooling and lubrication, and the service life is generally 20,000h. The drive generally uses linear motor plus linear guide (also used for static pressure guide), 90m/min, 1g machine is also driven by double servo motor with large pitch double ball screw pretensioning scheme. The mechanical structure generally adopts a frame box structure. The tool is made of high-hardness and high-heat-resistant tools, and the handle is HSK.
Solve the contradiction between flexibility and high efficiency by specializing in CNC machine tools or numerical control of special machine tools. At present, most of the European and American automobile production adopts an agile production system consisting of high-speed machining centers. This system can be produced in 100% flexible mixed flow, and is composed of a plurality of flexible processing units called islands. Each island is composed of multiple similar products. The machine tool and the robot that connects the machine tools are exchanged with the pallet and the machine tool with an electronic storage. It is worth noting that these equipment suppliers not only master the proprietary technology of equipment manufacturing, but also attach great importance to the development of automotive manufacturing processes. They can provide turnkey projects to users and have their own system development capabilities. The reliability index of the machine tool is extremely advanced, and the single machine actuation rate is over 98%. With this production system, the industrialization cycle of new products of automobile manufacturers is greatly shortened.
After more than 20 years of reform and opening up, in the field of domestic auto parts manufacturing, the use of CNC machine tools has become more and more extensive. However, most of them are imported from Europe, America and Japan. The characteristics of European and American machine tools are: good reliability and low failure rate; the design of the machine interface is humanized; with active measurement and compensation system; it can provide automatic loading and unloading device. Machining unit; modular design of machine tools. Although there are many domestic CNC machine tool manufacturers, from the perspective of varieties, there are still many low-level general-purpose CNC lathes. For multi-axis CNC machining centers suitable for high-volume automobile engines, gearboxes and chassis main components, there are few varieties, and Most of them have not withstood the test of mass production.
Application and deficiency
In the past two decades, China's machine tool design and styling has made great progress. If we look at the shape of the machine tool statically, we can't see much difference with similar foreign products. However, to adapt to the production of large-scale auto parts, we need high machine tools. Reliability. There are two main aspects affecting machine reliability: one is the design quality of the machine tool; the other is the process quality of the machining and assembly of the machine components and assemblies; in a sense, the process quality has a greater impact on the reliability of the machine tool. . Domestic machine tool manufacturers pay more attention to product design quality, generally adopting joint ventures or adopting imitation of foreign products. However, the quality of the manufacturing process, which has a greater impact on machine reliability, is ignored. As a result, some of our manufacturers have completed prototypes for many years, and the machine tools that are sold have small problems, high failure rates, or low accuracy, and poor service. User satisfaction is very low. Therefore, the developed products have formed economic benefits and achieved a small amount of sales. What I want to emphasize is that it pays attention to the control of process quality, standardizes the manufacturing process, quality control, and continuous improvement of product quality, which is the prerequisite for obtaining high reliability machine tools. In addition, we must establish a machine tool design and manufacturing standard that is synchronized with international advanced machine tool manufacturers. In the early 1980s, China introduced Xuer Wheeler's special machine manufacturing part of the standard, through digestion and absorption, produced such as Dongfeng Equipment Manufacturing Plant, Dalian Machine Tool Plant Such as the domestic excellent combination of special planes and automatic line production enterprises. However, at the same time as the introduction of technology, we did not immediately promote technological innovation, did not establish a complete technical standard through the introduction, and maintained a simultaneous development. As a result, in the Western countries in the early 1990s, when equipment was upgraded to CNC flexible equipment, we were still spending manpower and material resources to improve the level of special aircraft manufacturing. At present, most of the domestic CNC machine tool manufacturers adopt a strategy of joint venture or cooperation with foreign countries to introduce one or a few models, which cannot form a series of products, which makes auto parts manufacturers lack selectivity; today's automakers want to reduce costs. Shorten the development period, implement turnkey projects for industrialization, and domestic suppliers lack the ability to develop automotive parts manufacturing processes. Most of them lack the agile manufacturing systems for important automotive engine parts such as cylinder blocks, cylinder heads; crankshafts, connecting rods; camshafts. The experience of the complete line of parts, lack of auxiliary machine development and supporting capabilities and system connection design capabilities.
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