Unlocking the Secrets of Advanced CNC Machining: A Deep Dive into the Design of the Main Transmission System
In the world of computer numerical control (CNC) machining, the lathes are highly automated machine tools that can often change speed, but must have sufficient rigidity and precision of rotation. The maximum speed of the pin depends on the eligible limit of the transmission element in the main transmission system, while the minimum speed is determined by the material treatment requirements, particularly for difficult-to-machine materials such as stainless steel. In this blog post, we will take a closer look at the design of the main transmission system of the DS11, a CNC lathe designed and produced by our factory.
Choosing the Right Main Transmission Method
The DS11’s main transmission system employs a separate transmission method, which transmits movement from the 15 kW DC main engine to the transmission through a triangle belt. This allows for a range of four speed settings, making it ideal for a variety of machining tasks. The change in mechanical speed is achieved by pushing the sliding gear with a cylinder, with the main engine running at low speed during the speed change. This process also prevents the engine from swinging and allows the movement of the spindle to start.
The Gearbox: A Compact and Rigid Solution
The gearbox is fixed to the pin box and centered by the flange, with the inner hole of the flange matching the outer circle of the intermediate bearing of the spindle. This ensures that the three bearing holes of the spindle are concentric and that the gears are properly meshed. By placing the gearbox directly on the spindle box, we eliminate intermediate connections and achieve a more compact design. Additionally, the pin and gear change equipment are packed into two boxes, reducing thermal deformation of the spindle and improving its rigidity and precision.
Power and Torque Characteristics
The maximum speed of the main engine is 3500 RPM, with a nominal speed of 1160 RPM. The regulation range of constant power is 3, and the transmission ratio of the pulley is 133:236. From the characteristic power curve, we can see that the power curve rides without notch, achieving a maximum power of 13 kW (mechanical efficiency 0.87) at a calculated speed of 142R/min or more. However, there are some parts that overlap the power curve, which may be a little wasted.
Spindle Support: A System of Three Bearings
The pin is supported by three bearings, with the front and intermediate bearings in the pin box, which is the main support, and the rear bearing in the gearbox, which is the auxiliary support. The front bearing is NN3024SKM-SP, and the intermediate bearing is NN3022SKM-CP. This bearing assembly has high rigidity, with the axial and radial forces supported by different bearings respectively, and the axial thermal expansion absorbed by cylindrical rolls. The rear bearing is a D220 centripetal bearing. Since the coaxiality of the three rolling holes is difficult to ensure, the coordination between the rear bearing and the box hole is more loose, which are adjusted by two semi-circular pads at the front end of the spindle, ground during assembly to adjust the preload of the front bearing. The opening of the pin is 70mm.
In conclusion, the design of the main transmission system in the DS11 CNC lathe is a key component in achieving precise and efficient machining. By understanding the principles behind this design, we can better appreciate the challenges and advantages of this advanced technology. In the next blog post, we will explore more topics related to CNC machining and advanced manufacturing techniques, so stay tuned!
