What is CNC boring? CNC boring refers to expanding or refining the original holes on the workpiece. The boring feature of CNC machining is to correct the eccentricity of the lower hole, to obtain the precise position of the hole, and to obtain high-precision roundness, cylindricity and surface finish. Therefore, boring is often used in the final process.
Compared with other machining, CNC boring is a kind of difficult machining. By adjusting only one blade (or blade holder), it processes micron sized holes like H7 and H6.
What are the characteristics of CNC boring?
1. Tool rotation
CNC machining is different from lathe machining. Because of the tool rotation, it is impossible to control the condition of the tool tip in time to adjust the feed amount. It is also impossible to change the machining diameter just by adjusting the CNC button like the CNC lathe. This has become a big obstacle to fully automated processing. Because the machining center does not have the function of automatic machining diameter adjustment (except for the one with U-axis function), it is required that the boring cutter must have a fine adjustment mechanism or automatic compensation function, especially in the case of fine boring, sometimes it must be adjusted at the micron level according to the tolerance requirements.
In addition, the direction of chip flow out is constantly changing when boring in machining center, so the cooling of tool tip, workpiece and chip discharge are much more difficult than when machining in lathe. Especially when the vertical machining center is used for steel blind hole rough boring, this problem has not been completely solved up to now.
2. Spring knife
The most common and troublesome problem in boring is the spring knife. The main reasons for the spring knife in the machining center are as follows
① Rigidity of tool system: including the rigidity of tool handle, boring bar, boring head and intermediate connecting part. Because it is cantilever machining, especially the machining of small holes, deep holes and hard workpieces, the rigidity of the tool is particularly important.
② Dynamic balance of tool system: relative to the rotating axis of tool system, if the tool itself has an unbalanced mass, it will cause chatter due to the effect of unbalanced centrifugal force during rotation. Especially in high-speed machining, the dynamic balance of tools has a great influence.
③ Fixed rigidity of workpiece itself or workpiece: for example, some smaller and thinner parts cannot be fully fixed with reasonable jigs due to insufficient rigidity or workpiece shape.
④ Blade tip shape: the cutting resistance is also different due to the different front angle, escape angle, tip radius and chip breaking groove shape of the blade.
