What is CNC machining boring? CNC machining boring refers to the expansion or refinement of the original hole on the workpiece. The feature of CNC machining is to correct the eccentricity of the lower hole, obtain precise hole position, and obtain high-precision roundness, cylindricity and surface finish. Therefore, boring is often used in the final process.
Compared with other mechanical processing, CNC boring is a kind of more difficult processing. It only depends on adjusting a blade (or blade seat) to process micron-level holes like H7 and H6.
What are the characteristics of CNC boring?
- Tool rotation CNC machining is different from lathe machining. Due to the rotation of the tool during machining of the machining center, it is impossible to grasp the tip of the tool in time during machining to adjust the amount of feed, etc. It is also impossible to change the machining diameter just by adjusting the CNC button like a CNC lathe. This has become a big obstacle to fully automated processing. It is also precisely because the machining center does not have the automatic machining diameter adjustment function (except for the U-axis function), it is required that the boring tool must have a fine-tuning mechanism or an automatic compensation function, especially during fine boring, sometimes it must be adjusted at the micron level according to the tolerance requirements. . In addition, because the outflow direction of the chips is constantly changing when the machining center is boring, the cooling of the tool tip, the workpiece, and the discharge of the chips are much more difficult than during lathe machining. Especially when a vertical machining center is used for rough boring of steel blind holes, this problem has not been completely solved so far.
- Bouncing knife
The most frequent and most troublesome problem in boring is the bullet knife. The main reasons for the bullet knife on the machining center are as follows
①The rigidity of the tool system: including the rigidity of the tool holder, boring bar, boring head and the intermediate connecting part. Because it is cantilever machining, the rigidity of the tool is particularly important when machining small holes, deep holes and hard workpieces.
②The dynamic balance of the tool system: relative to the axis of rotation of the tool system, if the tool itself has an unbalanced mass, chattering occurs due to the unbalanced centrifugal force during rotation. Especially in high-speed machining, the dynamic balance of the tool has a great influence.
③The fixing rigidity of the workpiece itself or the workpiece: For example, some small and thin parts cannot be sufficiently fixed with reasonable jigs due to insufficient rigidity of their own or due to the shape of the workpiece.
④The shape of the blade tip: the cutting resistance generated by the blade’s rake angle, escape angle, tip radius, and chip breaker shape is also different.