Due to the particularity of the valve seat material, the tool wears quickly, consumes a large amount, and the production cost is high. If the processing cost of the part can be reduced, it has certain significance for controlling the processing cost of the engine. Ways to reduce tooling costs:
First, design new tools:
1. Design points: The basic idea of designing this tool is that the structure should be simple to reduce the manufacturing cost of the tool; the number of re-grinding of the tool can be increased, and the total life of the tool can be increased to reduce the cost of the tool. This tool achieves this goal in two ways.
2. The processing valve seat adopts forming processing to simplify the structure of the cutter body, reduce the difficulty of making the cutter and improve the processing efficiency. 1. Blade 2. Blade 3. Blade 4. Knife 5. Adjusting screw 6. Pressing block Figure 1 Tool structure The blade is designed to grow in a strip shape, which can make the tool regrind many times.
3. Tool structure: The structure of the tool is shown in the figure. The three elongated blades 1, 2, 3 are respectively fixed on the cutter body by a pressing block, and the axial dimension of the blade is adjusted by adjusting screws. The radial dimensions of the blades do not need to be adjusted. Therefore, the presetting of this tool is very simple. The inner bore fD can be used to mount a valve guide reamer to achieve simultaneous processing of the valve seat and the valve guide.
Blade: The shape and size of the blade, the width L of the three blades must be larger than the three cone sizes ab, bc and cd of the valve seat, respectively, in order to achieve the forming process. The three blades have the same dimensions except for the angle q. Blade material: CBN insert Because the tool is formed by forming, the blade must have sufficient wear resistance to ensure the machining accuracy of the valve seat and prevent the valve seat from leaking. The blade material is preferably CBN.
Second, the processing technology:
1. Processing procedure: When using CBN inserts, each of the intake and exhaust valves can be machined and formed in one process with a single tool, and the precision requirements are met. It is not necessary to perform roughing and finishing on multiple processes.
2. Since the cutting parameters are formed by one-time processing, there are certain requirements for the cutting parameters. The cutting speed is too low to meet the accuracy requirements, especially the valve seat leakage;
3. The cutting speed is too high and the tool wears too fast. Practice has proved that when the material hardness of the valve seat is about 280HB, the cutting speed is about 200m/min.
Third, the re-grinding of the blade:
The economics of regrinding inserts are generally more than 30 times. A blade can be reground more than 30 times. Compared with the triangular indexable non-reground blade, the cost of regrind can be reduced by more than 70%.
Note on blade regrind:
1. The straightness of the cutting edge must be controlled within 0.01/100. If the straightness does not meet the requirements, the valve seat will leak.
2. A diamond grinding wheel with a particle size of 600# is used. The grinding wheel of this size is easy to meet the requirements of blade straightness and roughness.
3. Use grinding fluid to prevent the durability of the tool from decreasing.
4. The tool grinder has sufficient rigidity. Domestic tool grinding machines can meet the requirements.
