A turned part is simply a part that is machined on a lathe using a CNC lathe. It is through the rotary motion between the workpiece and the linear or curved motion between the tools to change the shape and size of the blank into parts that meet the requirements of the drawings.
Turning is the most common cutting method, suitable for most of the workpiece processing, can achieve high precision, there are many types of turning parts, of which hard turning is the most famous for high thermal stability, but also the most widely used. So let's learn more about hard turning.
Choosing the right hard turning system can reduce or even eliminate the high cost and processing time, while achieving high accuracy and thus maximizing the utilization of equipment. So when choosing a reasonable turning part we have to take into account the following factors.
1, coolant. No coolant cutting has a cost advantage, but in continuous cutting, coolant can improve the smoothness of the surface while extending the life of the tool, and the use of coolant to water-based. Take away most of the heat in the cutting process, to protect the machine while also avoiding operator burns.
2, whitening layer. Also called heat-affected zone, in the process of cutting, due to excessive heat transfer to the parts, whitening layer is often formed on the bearing steel, so the operator to randomly spot-check, to determine how many parts each insert can turn without forming a whitening layer.
3, machine tools. The stiffness of the machine largely determines the machining accuracy of hard cutting. In order to keep all parts as close as possible to the turret holder to maintain systematic, to minimize overhang, tool extension and parts out and eliminate the strip gap pieces and washers.
4、Turning threads. The use of appropriate inserts is key, the best being triangular inserts. Properly increase the number of tools and reduce the depth of cut, while the use of alternate side cutting can control the cutting force and extend the life of the tool.
5, workpiece. The most suitable for hard turning parts have a small length to diameter ratio (L/D), generally speaking, the ratio of L/D of unsupported workpiece is not more than 4:1, supported workpiece L/D ratio is not more than 8:1. Although slender parts have tailstock support, but due to excessive cutting pressure may still cause tool vibration. In order to maximize the rigidity of the system for hard turning, the overhang should be minimized. Tool extension length should not be greater than 1.5 times the height of the tool bar.
6、Boring. Boring hardened materials requires a lot of cutting pressure, so it is often necessary to multiply the torsional and tangential forces on the boring bar. The use of positive front angle (35 ° or 55 °), small tip radius inserts can reduce the cutting pressure. In increasing the cutting speed while reducing the depth of cut and feed rate, is also a way to reduce cutting pressure.
7, process. Because most of the heat generated by hard turning is carried away by the chips, inspection of the chips before and after processing can find out whether the whole process is coordinated. Continuous cutting, the chip should be blazing orange, and like a ribbon like floating out. If the chips are cooled and a basic break with the hand, indicating that the heat taken away by the chips is normal.
8, inserts. CBN inserts are the most suitable for hard turning, despite its expensive, but its continuous cutting process can provide the safest tool wear rate, relative to ceramic or metal ceramic inserts are far ahead of the performance.