1. Knife
Fault analysis and solution: The reason is that the turning tool is installed too high or too low, the workpiece is not clamped firmly or the turning tool is too worn.
The turning tool is installed too high or too low
If it is too high, when the cutting tool reaches a certain depth, the flank of the turning tool will bear against the workpiece, increase the friction force, and even bend the workpiece, resulting in the phenomenon of biting the tool; if it is too low, the chips will not be easily discharged, and the radial force of the turning tool will increase. The direction of the workpiece is the center of the workpiece, and the gap between the traverse screw and the nut is too large, which causes the depth of the knife to automatically tend to deepen, thereby lifting the workpiece and gnawing the knife. At this time, the height of the turning tool should be adjusted in time, so that the tool tip is the same height as the axis of the workpiece (the tip of the tailstock can be used to set the tool). During rough turning and semi-finishing, the position of the tool tip is about 1% D higher than the center of the workpiece (D represents the diameter of the workpiece to be machined).
The workpiece is not clamped firmly
The rigidity of the workpiece itself cannot withstand the cutting force during turning, resulting in excessive deflection, which changes the center height of the turning tool and the workpiece (the workpiece is raised), resulting in a sudden increase in the depth of cut and the occurrence of gnawing. The workpiece is firmly clamped, and the tailstock center can be used to increase the rigidity of the workpiece.
Too much wear on the turning tool
Cause the cutting force to increase, the workpiece is bent, and the knife appears. At this time, the turning tool should be ground.
2. Analysis and solution of random buckle failure: The reason is that when the lead screw turns one turn, the workpiece does not turn over an integer.
When the ratio of the screw pitch of the lathe to the workpiece pitch is not an integral multiple
If the opening and closing nut is used when the tool is retracted and the saddle is shaken to the starting position, then when the opening and closing nut is closed again, the tool tip of the turning tool will not be in the spiral groove of the previous tool, resulting in the occurrence of Random buckle.
The solution is to use the forward and reverse turning method to retract the tool, that is, at the end of the first stroke, without lifting the opening and closing nut, after withdrawing the tool in the radial direction, reverse the spindle to make the turning tool retract in the longitudinal direction, and then carry out the first step. The second stroke, in the reciprocating process, because the transmission between the spindle, the screw and the tool holder has not been separated, the turning tool is always in the original spiral groove, and there will be no random buckles.
For the thread where the ratio of the lead screw pitch of the turning lathe to the workpiece pitch ratio is an integral multiple
Both the workpiece and the lead screw are rotating. After lifting the opening and closing nut, the opening and closing nut can be closed again after at least one revolution of the lead screw. In this way, when the lead screw rotates one revolution, the workpiece rotates an integer multiple, and the turning tool It can enter into the spiral groove of the previous tool, and there will be no random buckles, so that the opening and closing nut can be opened and the tool can be manually retracted. In this way, the tool retracts quickly, which is conducive to improving productivity and maintaining the accuracy of the lead screw, and the lead screw is also safer.