To overcome the difficulty of hard materials
New kinds of tool use ceramic knife and cubic boron nitride (CBN) cutting tool in Machining Hardened Steel is very good. The tool has been rapid development in a short period of time, some tool manufacturers claim that: as long as the machine correctly, their tool than grinding can shorten the time of 300%, and can improve the cutting precision.
Ceramic knife these suppliers recommended with negative rake angle and larger T- chamfering, the chamfering only increase the pressure at the tool workpieceinterface. In contrast, CBN in accordance with the specific circumstances of the workpiece, may or may not have the negative T- chamfering. For example,incontinuous cutting with CBN, requires a larger T- chamfer to withstand vibration.
The use of ceramic cutting tools will be more prevalent than CBN more and more,this is because of its low cost, but also because more cutting edge for their sake.However, they are very easy to be heated up crack. In addition, if the bladegrinding is not the time, should not be interrupted cutting. Although CBN than ceramic is much more expensive, but it's much better cutting performance, high processing precision, long service life of some.
Choose between this two kind of tool material, is how to make the workpiece material, geometry and the cutting speed and sent people to adapt to their work.Some users are usually limited compared to the one by one, but with the tool onthe same processing cost of the structure, and can produce much benefit for theselection principle. These users with heat treatment of coarse ceramic knife pricewhen low residual rust and iron scale, then, finish machining with CBN tool better.Generally speaking, if the material depth of hardening depth than desire for the car to go to, it is best to choose CBN.
Choose the correct methods for processing
Consider from a practical standpoint, turning hard material is a process and the workpiece is closely related to the characteristics of. It is particularly suitable forcutting with intricate arc, angle, and radius of workpiece geometry is verycomplex. Methods you can use single pole tip programming turning, fast andeconomical finish machining, and do not have to go to the purchase of forming grinding wheel, according to the experience of most hard materials turning is tofeed rate 91-150 m/min cutting speed and the 0.05-0.13mm/min. Precision cuttingdepth is generally 0.08 - 0.5mm.
Therefore, how to control the purity of materials, heat treatment, machining andforming process and turning before, then becomes this processing can achieve the precision of the determinants of the size, if the workpiece hardness fluctuation of only three Rockwell hardness value (for example), the cutting pressure willchange tool enough to make your size M can not guarantee the accuracy of 5.The instability of the hardness and uneven depth, will damage the processing.Therefore, should the use of qualified materials, maintaining a constant rate ofmetal cutting, and insurance group of heat treatment hardness 2 HRC values in + 1 or + within.
Workpiece length diameter ratio will also affect the ability to maintain toleranceprecision machine tool. Fixed bed type lathe tailstock typical not of length diameter ratio of soft parts 5:l 6:1, can achieve very strict precision. Because therequired hardness, tool workpiece negative rake angle and cutting hard materialT- chamfering, makes considerable pressure on out, therefore, when the workpiece without tailstock support, should be restricted in the 3:1 4:1 the ratio of length to diameter of workpiece.
Of course, this limit will not change with the processing between -- that is to say,with the workpiece material, hardness and the roughness and precision requirements change. We had no workpiece tailstock support turning diameter 13mm, length 64mm, is the poor accuracy.
The tailstock can play a role, but it is the panacea to solve all the problems of non. For example, the top can not prevent the workpiece diameter 25mm, length300mm tremor. For this kind of workpiece, you can only use the grinding method.To ensure tighter tolerances and accuracy than 0.005mm, a better use of grinding process. Although say hard material turning can not completely replace the grinding, it can replace a considerable part, especially the workpiece length diameter is relatively small, relatively complicated so. |
