Improvement of machining deep-hole tool for gray cast iron

Our company is a traditional enterprise that produces gold cutting machine tools. When machining the gray cast iron lifting box drive hole system of vertical lathe in the past, the machining time consumed is about 16h, and the processing quality is difficult to guarantee, which has become a constraint on production. bottleneck.

The machining time required to process other workpieces with the same amount of cutting is 3 to 4 hours. If a reasonable method is found, the machining time of the workpiece can be greatly reduced. YG8 cemented carbide tools are generally used for machining gray cast iron, but because the hole size of the workpiece is deep, and the φ 95js7 hole and φ 102j s7 hole are stepped holes that require clearing, the traditional machining method can only use the rhombic shank. (see picture 1). Carbide tools are hard and brittle, and they are prone to chipping during processing. Therefore, traditional angle cutters can only use high-speed steel tools. The shortcomings of high-speed steel tools are mainly caused by wear and tear, especially when processing deep-hole parts of gray cast iron, which cannot be discharged in time due to high heat generation, which accelerates the wear of the blade of high-speed steel cutters. Therefore, when the machine tool is machining parts, the spindle speed can only be below 80r/min, and the tool feed amount is about 0.10mm/r, that is, the workpiece cutting amount is only 8mm/min, and the machining efficiency is very low.

The fundamental reason for the limitation of the use of cemented carbide tools is that the cross-sectional area of ​​the rhombic cutter is small, the rigidity is insufficient to cause the body to vibrate, and the blade edge is unstable, resulting in chipping. By analyzing the force of the block (see Figure 2), it is found that the block on the bar is mainly affected by the force in the direction of the tool feed. The force in this direction can be decomposed into two forces. One is the force perpendicular to the block and the other is the force parallel to the block. The force perpendicular to the block has no effect on the positioning of the tool, and the force parallel to the block is the main cause of the block vibrating. Through the above analysis, the decision will mainly solve two problems: 1 to solve the problem of vibration during tool feed. 2 In turn, the high speed steel tool is changed to a cemented carbide tool.

Through practical experience, the smaller the angle α between the tool and the direction perpendicular to the tool bar, the smaller the force the tool is subjected to parallel to the block (see Figure 2), so reduce the tool and the direction perpendicular to the tool bar. Angle.

For the first improvement, the fixing groove of the blade and the shank is changed to be parallel to the front end surface, that is, the angle between the blade and the arbor is 0°, the block is processed into an L shape, and the shank hole is inserted. Two fixing screws are added to keep the tool feed rate 0.10mm/r unchanged, and the spindle speed is increased to 180r/min when machining parts, that is, the workpiece cutting amount is 18mm/min. The machining efficiency is improved, but the tool block is vibrated due to the force of the tool, and the tool stability is still not good. The main problem is that the phenomenon of tooling after the spindle speed exceeds 180r/min is significant, resulting in an average production time that is far from ideal.

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