On the contrary, cold extrusion taps are used for chip-free machining of internal threads. In this process, the thread is not formed by cutting, but by cold extrusion, and the workpiece material is extruded into the required thread profile.
With the development of CNC machine tools, thread milling is introduced into internal thread machining as another optional process. When machining, the thread is milled in the hole by using the specific circular motion and feed motion of the cutter. These three processing methods are suitable for different processing conditions.
"Traditional" Machining Method: Tapping
In the traditional tapping process, the workpiece material is removed by continuous cutting. When the hardness of workpiece material is greater than HRC60, the application of tapping in deep hole thread processing is greatly limited due to the dimensional accuracy and tool damage caused by chip removal difficulties.
Chip-free processing method: cold extrusion molding
Thread cold extrusion processing is suitable for workpiece materials with strength less than 1200N/mm2 and elongation at break greater than 8%. Due to the effect of cold extrusion, the thread processed by this chip-free process can achieve higher static and dynamic strength and better surface quality.
But the disadvantage of cold extrusion thread forming is that it needs more torque and high quality lubricant than traditional tapping.
Efficient precision machining method: thread milling
Thread milling is suitable for almost all workpiece materials, with the best machining flexibility and the highest productivity. The machined thread surface is clean and smooth, and there will be no axial misalignment. For difficult-to-machine materials, thread milling is often the best processing method. Another underrated advantage is that when the tool is broken, it is easy to take it out of the hole. The limitation of thread milling is related to thread depth. Generally speaking, the thread depth can not exceed 3 times the thread diameter.
No matter which thread processing method is adopted, it is certain that the thread cycle in the advanced CNC software module can be used to compile the processing program quickly and conveniently.
Internal thread machining cycle
The actual programming requirements of internal thread are complicated, because many parameter values must be considered. Advanced CNC thread circulation can effectively deal with this complexity. These machining cycles need to input some elements, including the required tools, thread depth and cutting speed, and specific program parameters.
These specific program inputs take into account the unique characteristics of specific tapping processing, for example, whether this traditional tapping is completed by one-time cutting or chip breaking. If chip breaking is needed, the tool retracting movement and rotation can be automatically programmed into the machining program.
Connection of processing steps
Internal thread processing usually requires a separate processing step. For example, before machining internal threads, centering holes and pre-drilling holes should be made first. If several identical internal threads need to be machined on the workpiece, these machining steps must be repeated at each machining position. To reduce the related programming workload, you can create subroutines that can be called in different locations.
In fact, if proper CNC software is used, these processing steps can be programmed more efficiently. As long as all the processing steps are programmed at one time and then connected through a position mode. The programming of centering hole, drilling and tapping can be completed at one time, which is suitable for all machining positions of this mode. These position modes can use combinable machining cycles for lines, holes, grids, frames and special positions.