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Scheme design of positioning mechanism of NC lathe tool post

CNC lathes currently use taper pin positioning and end face gear positioning in the positioning mechanism of the tool holder. Due to the higher positioning accuracy of the conical pin, it usually relies on spring force or hydraulic pressure or aerodynamic force when it enters the positioning hole.

After the conical pin is worn, it can still eliminate the gap to achieve higher positioning accuracy. The positioning of the end gear disc is formed by the meshing of two end gear discs with opposite tooth shapes. Since the errors of each tooth compensate each other when the teeth are engaged, they play the role of error equalization and high positioning accuracy.

The characteristics of the positioning of the tooth disc at the end of the CNC lathe tool holder:

(1) High positioning accuracy.

Due to the large number of positioning teeth on the end sprocket, and the uniform distribution along the circumference, the centripetal multi-tooth structure, the indexing accuracy of the tooth disc after grinding is generally up to about ± 3 ‘, and the highest can exceed’ ‘4.0 or more. It has the function of self-centering when meshing. Therefore, the rotation accuracy, clearance and wear of the central shaft have no effect on the centering accuracy, the accuracy of the central shaft is low, and the installation is easy.

(2) Repeated positioning accuracy is good.

Since multi-tooth meshing is equivalent to the repeated running-in of upper and lower gear discs, the higher the running-in accuracy is, the better the repeated positioning accuracy is.

(3) The positioning rigidity is good, the bearing capacity is large, and the two tooth discs are meshed with multiple teeth.

Due to the high strength of the toothed portion of the gear disc, and the meshing rate of the common teeth is not less than 90%, the meshing length of the tooth surface is not less than 60%, so the positioning rigidity is good and the load carrying capacity is large. Thinking about the end face gear has the above various advantages, so the tool holder designed this time uses end face gear positioning.

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