With the widespread use of PCD, CBN and other superhard material tools in the automotive, motorcycle, air conditioning compressor, wood processing industries, the market demand for such tools is increasing. At present, about 20 companies in China have been engaged in the development, processing and sharpening of superhard tools, but most of them are limited to the processing of low-end products (such as blade-mounted super-hard tools with low precision requirements). This has led to fierce competition in such products. However, some high-end products (such as high-precision welded PCD tools, etc.) are mainly due to high technical requirements and difficult processing, and the products still rely mainly on imports. According to statistics, the cost of imported high-precision welded PCD tools consumed by the 2VQS engine production line of Shanghai Volkswagen Automotive Co., Ltd. in 2001 has exceeded RMB 1 million (the cost of engine machining tools for Passat and Polo models has not been counted). FAW-Volkswagen's 2VQS engine production line is basically the same as Shanghai Volkswagen. The consumption of such tools is also very large. Together with the tool consumption of other automobile, motorcycle manufacturers and related industries in the country, it can be seen that there are high-precision welding PCD tools. Huge market demand. In order to reduce production costs, enterprises are eager to achieve localized processing and sharpening of such tools.

1. High-precision welding type PCD tool technical requirements

High-precision welding PCD tools have high technical requirements. The tool holder adopts HSK adapter or straight shank installed in HSK hydraulic chuck; PCD tool length is less than 150mm, diameter is less than 50mm, blade diameter tolerance is 0.003mm, accuracy grade is IT2~IT3, and the coaxiality tolerance of IT3 precision is 0.003mm.

The coaxiality error between the cutting edge of the welded PCD tool and the tool holder is a combination of grinding machining error and tool mounting error. It is quite difficult to control it within the range of 0.003 mm. In order to guarantee a tool outer diameter tolerance of 0.003 mm, high precision is also required for the machining accuracy of the machining machine and the grinding process. In addition, in order to achieve accurate measurement of high-precision welded PCD tools, the comprehensive measurement accuracy of the measuring instrument is required to reach the micron level, and the measuring force acting on the cutting edge of the tool should be controlled within 150 mN.

2. High precision PCD tool grinding machine

Taking the FC-500D PCD&CBN tool grinding machine produced by Yuanshan Machinery Co., Ltd. as an example, the structural characteristics and processing performance of high-precision PCD tool grinding machine are briefly introduced.

(1) Machine tool features

The grinding wheel travel of the FC-500D PCD & CBN tool grinding machine is 500mm, which can meet the grinding stroke requirements of the 150mm tool. With the rotary table of the machine tool and its corner display function, the reverse taper grinding requirement of the cutting edge of the tool 1:1000~1:1500 can be realized. Both the wheel base and the table rail are Swiss SchneeBerger high-precision roller linear guides. The table feed mode is pneumatic flexible feed, and the feed amount per handle is 1 μm (display display). The contact pressure between the grinding wheel and the tool is adjustable during sharpening. The height of the grinding head is adjustable to grind large diameter PCD saw blade milling cutters. The grinding machine is equipped with a high-precision camera system (CCD), which can clearly display the tool sharpening process (magnification 15~120 times) through the screen. At the same time, the tool edge arc can be detected through the display screen (the minimum arc R0 can be measured. 05mm).

(2) Indexing work head

In order to achieve precise sharpening of high-precision PCD tools, the grinding machine is designed with an indexing work head that can be fine-tuned. The working head adopts the spindle fine adjustment mechanism of the SK40 spindle inner hole and the worm gear. When the worm is disengaged from the worm wheel, the spindle can be rotated quickly. The 24 aliquots of the indexing plate and the spindle can be empty or interlocked. The pin fixed on the clip can be inserted into the gap of the indexing plate, so that the indexing plate and the main shaft are positioned and fixed on the circumference (the indexing plate and the main shaft are interlocked at this time). The 24 equalizing indexing plate is suitable for machining 2, 3, 4, 6, and 8 equal parts. If you need to machine 5 or 7 equal parts, you need to use 20 equal parts or 28 equal parts.

(3) Reducer sleeve

Since the indexing work head adopts the inner hole of the SK40 spindle, when machining the tool of the HSK handle, the reducer sleeve must be used to fix the tool in the inner hole of the working spindle. When machining the straight shank tool, the tool can also be installed first. The hydraulic shank clamp of the HSK handle is then inserted into the bore of the main shaft of the working head through a variable diameter). Since there are coaxiality errors in the inner bore of the spindle and the reducer sleeve, in order to meet the coaxiality requirement of the tool processing (0003mm), a new technology of adjustable center reduction sleeve developed by foreign countries is adopted. The reducer sleeve structure consists of two parts, the SK40 part on the left side, which can be installed in the inner hole of the indexing work head spindle; the HSK part on the right side can be connected with the HSK handle of the tool. The shaft and the hole are positioned and connected between the left and right parts, and are fixed by four hexagon socket screws. The gap between the shaft and the hole is a clearance fit, and the fit clearance is the center adjustment range. There are four facets on the shaft. The coaxiality deviation of the left and right axes is adjusted by the hexagonal set screws facing the facets, and the parallelism of the axes is adjusted by the set screws. After the adjustment sleeve is adjusted, mark the circumference of the inner hole of the SK40 handle and the indexing work head SK40 with which it is matched to determine the installation position of the reducer sleeve, and avoid repeating the adjustment of the coaxiality when reinstalling the reducer sleeve. .

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