1 Select manufacturers and brands should pay attention to their market share at home and abroad; sales performance and operating conditions in recent years, financial conditions; service capabilities, especially remote service capabilities; to prevent the risk of factory failure. Example: A factory purchased a floor-standing CNC boring and milling machine from a Spanish company in 1995. The machine tool has not yet been installed and the company has closed down. To choose more than three manufacturers - shop around. Make a thorough investigation of its product performance, characteristics, accuracy, main specifications and prices. In addition to traditional user surveys, manufacturer exchanges and inspections, the research methods must pay particular attention to the visits to authoritative international machine tool exhibitions held in China, such as CIMT; at the same time, they should give full play to the role of domestic and foreign authorities and neutral market intermediary organizations; Use Internet features. For open tendering, the preparation of bids is very important. In particular, the main technical indicators for asterisks must adhere to the principle of “fair, reasonable, and advanced”. Fairness is non-discriminatory: it is the best or better basis for the protection of selected equipment. The ultimate benefit is self. At the same time, this is also the precondition for passing the national tender review. Rationality avoids over-indexing, causing waste and deterring manufacturers of equipment that is best or better. The excessively high indicators both have blindly pursued advancement and omnipotence issues; they also have problems such as inadequate process analysis. The advanced nature is to avoid bids with low prices but poor quality and low performance. 2 About the price With the realization of the industrialization of CNC machine tools in developed countries and regions of the machine tool and the gradual price reduction of CNC equipment worldwide, in the past ten years, the price of international CNC machine tools has dropped by an average of about half (thus, some people believe that the low price is also an international machine tool). Development trend). When purchasing, we often find that the price of similar CNC machine tools may be very different. The important reason is that there is a big gap between the manufacturers' production volumes. A manufacturer with an annual output of dozens of units will have twice the difference in the purchased parts (parts) as compared with a manufacturer with annual production of more than one thousand units. The purchased parts account for about half of the total price of CNC machine tools. Therefore, it can be said that "cheap and good goods." To investigate international fair prices and prevent fraud risks. Also pay attention to the performance/price ratio—choose the equipment with excellent performance in the low price; prevent the low price trap. 3 About the selection of positioning accuracy standards and authentication methods The four internationally-accepted positioning accuracy standards are ISO, JIS, ASME and VDI (International, Japan, United States, and Germany, respectively). In addition, there are Chinese GB and British BS. In addition to the JIS standards, the above-mentioned six standards use mathematical statistics methods for multiple and multi-point measurements, with little difference in measurement results. However, JIS only measures once, and its accuracy value is the smallest. For example, a machining center sample provided by the German HELLER company indicates that the positioning accuracy is measured according to JIS and VDI standards, which are respectively ±4 μm and 14 μm; the repeat positioning accuracy is ±2 μm and 10 μm, respectively. The BOSTON DIGITAL company in the United States has listed the accuracy of the machining center positioning accuracy using ISO and JIS standards, as shown in the following table. Positioning accuracy JIS ISO Open loop machine positioning accuracy ±3μm 10μm/300mm Repeatability positioning accuracy ±1μm 5μm Semi-closed loop machine resolution 1μm Positioning accuracy ±2μm 7μm/300mm Repeatability positioning accuracy ±1μm 4μm Full-closed-loop machine tool resolution 0.5μm Positioning accuracy ±1.5 Μm 5μm/300mm Repeatability ±1μm 4μm In addition, pay attention to the factory precision reserve (can not trust measurement accuracy). 4 About Choosing the CNC Since the computer technology was applied to the machine tool, it has gone through two stages and six generations of products. Namely: NC (CNC) stage, including tubes, transistors, small-scale integrated circuit systems; CNC (computer numerical control) stages, including small computers, microprocessors, and PC-based systems. At present, many machine tools in the world use the sixth-generation PC-based numerical control system. This is because it can be developed almost at the same time as the world level of PC development. Therefore, it has the following advantages: Thousands of component factories and hardware factories all over the world can develop and improve components for PCs. On the system, its components have the highest integration, reliability, and high performance. Technological progress is fast and upgrading is easy. Many PC features such as touch panel input, voice input, networking, and mass storage can all be implemented on PC-based CNC systems. Provides an open foundation with rich available hardware and software resources. In this way, the CNC function has been expanded. Now that some of the factories in foreign countries are implementing network manufacturing, these extensions are used. For CNC systems, the advantage lies in having good performance, a wide variety of development tools and environments, such as the use of high-level language development; hardware production has been simplified (turn to outsourcing) and so on. At present, many users prefer FANUC and SIEMENS CNC systems. This of course makes sense because they have the highest market share. However, on the PC-based digital control system, the national products are at the same level of development as foreign countries. 5 To study the technological development trend so that the selected equipment will not be eliminated in 10 years: When Guangzhou Peugeot Automobile Company disintegrates, China seeks new partners. Japan Honda found that China has a flexible engine production line and soon reached a joint venture agreement. In another large-scale automobile joint venture, the new engine production line is just behind the production line, because it is a rigid production line and cannot meet the requirements of engine replacement. The obvious contrast between these two things is self-evident, so we must pay attention to its advanced nature when purchasing equipment.
