What is the concept of hard cutting?
Hard cutting refers to the use of CBN solid cutters, CBN cutters, or ceramic cutters to machine hardened workpieces. The new process of hard cutting can cut hardened steel, gray cast iron, ductile iron, powder metallurgy and special materials. Of course, some materials such as bronze are not suitable for hard cutting. Hard turning can be used for turning, surface machining, tapping, milling, grooving, mold machining, turning cones. According to reports in the United States, hard cutting keeps the workpiece finish at 16 um. Under normal conditions, the finish can reach 6 ~ 8um. At present, the new process of hard cutting is being adopted in many industrial sectors. For example, automobile manufacturers use this method to semi-finish and finish the drive shaft, various shaft drive chains, engines, brake discs and brake rotors; aircraft manufacturers Using this method to manufacture aileron gears and landing gear, the application of hard cutting methods can be seen everywhere from oil fields to steel mills. Machine tools, tools, heavy-duty trucks, agricultural machinery, medical equipment, cans, and automotive parts all make hard cutting an integral part of their production process.
Advantages of using hard cutting technology:
1. Hard cutting cost is low, generally only one quarter of grinding:
2. The use of hard cutting does not require the use of special tools, special machines and fixtures, while grinding requires the use of grinders, while hard cutting and lifting can be performed on existing NC or CNC turning centers;
3, high productivity, because the cutting speed of the CBN tool can be as high as 274m/min or more, so that productivity is greatly improved, saving a lot of time.
As the cost of CBN cutting tools has been greatly reduced in recent years, conditions have been created for hard cutting applications. The cost not only refers to the tool cost, but also to the manufacturing cost of each part. With long tool life and low cost per cutting head, CBN provides the most economical way for hard machining. For example, in the United States, a company previously used rough grinding to machine the end face of a hard gear, and then changed to hard machining as rough machining. After grinding, the cost was reduced by 40%. If both rough and fine grinding were changed to hard cutting, the machining time, fixture costs, tooling costs, and energy consumption could all be reduced, while productivity could be increased and the cost per part reduced by 55%. Another factory in the United States that produces pressure rings, the original process is grinding, including internal grinding, face grinding, cylindrical grinding and spherical grinding four processes, after hard cutting, only use VNMA332 and CNMA432 The tool, the processing speed increased by 10 times.
In addition, hard cutting is superior to grinding in terms of waste disposal and environmental protection. Grinding produces a mixture of abrasive debris and coolant, which is waste that cannot be reused and can pollute the environment. The waste generated by hard cutting can be reused, which is particularly important today when it comes to environmental protection.
In recent years, the space in the factory has received much attention. Compared with CBN tools, grinding wheels are relatively large and bulky and therefore difficult to store. The CBN tool is small and can be used for hard cutting without adding a new machine, thus saving the factory space.
The rapid development of hard cutting is based on the progress of CBN tool technology in the past few years. In the early 1990s, hard cutting was selected for only a few CBN tools. At present, the user's choice is 10 times more. In addition, the speed is greatly improved. The maximum cutting speed for cast iron in the early 1990s was approximately 152m/min. Now the maximum cutting speed is 1524m/min, and the most continuous hard steel cutting speed is 90 to 150m/min. 0.05 ~ 0.2mm/r, cutting depth of 0.1 ~ 0.5mm. The applicability of CBN has been expanded. In the past, it could not be used for brittle workpieces. Nowadays, workpieces with different hardnesses can be processed.
Given the many advantages of hard cutting mentioned above, foreign experts believe that this new technology represents today and heralds tomorrow. Some also issued the question "Why do you still use grinding?"
However, does high speed machining and hard cutting really replace grinding?
Grinding experts believe that it will not, because the grinding machine has its own advantages, high grinding precision, strict non-grinding tolerance of the non-grinding. The online measurement can be added during grinding and the cycle can be closed during the machining time. This method is difficult to achieve on other machine tools. And the most important point is that new materials have emerged in recent years. Replaced many traditional materials. Practice has proved that grinding is a good way to process this type of new material. Therefore, grinding and processing in the future are still indispensable. It is true that for general materials, grinding may encounter strong competitions such as milling, reaming, and turning. But for a new generation of materials such as ceramics, cermet composites, whisker reinforcements, and high-temperature superalloys, hard cutting is by no means an adversary of grinding, and it must be processed by grinding. For example, grinding is the only way to machine super alloy workpieces used in jet aircraft engines, and is the only way to machine ceramics, ceramics and glass made from automobiles and optical parts. New materials are generally hard, brittle, wear-resistant, heat-resistant, etc. Polymerized materials are absolutely required processing methods. For the heat-resistant and wear-resistant ceramic coatings, the more complicated problem is the simultaneous grinding of ceramics and metals.