The CNC milling machine is an automated processing equipment developed based on the general milling machine.
The processing techniques of the two are essentially the same, and their structures are somewhat similar.
CNC milling machines can be categorized into two types: those without a tool magazine and those with a tool magazine.
The CNC milling machine equipped with a tool magazine is also known as a machining center.
Features
CNC milling machines offer distinct advantages over ordinary milling machines, including:
- Adaptability and Flexibility: CNC milling machines can process parts with intricate contour shapes or challenging dimensions, such as mold and shell parts.
- Capability to Process Complex Parts: They can machine parts that are difficult to process with ordinary machines, such as three-dimensional space surface parts described by mathematical models and complex curve parts.
- Ability to Process Parts in Multiple Stages: CNC milling machines can process parts in multiple stages without the need to unclamp and reposition the part.
- High Precision and Processing Quality: CNC milling machines offer high precision, with pulse equivalents of the numerical control device generally being 0.001mm. High-precision numerical control systems can reach 0.1μm. Moreover, numerical control processing reduces the operator’s operation errors.
- High Degree of Automation: CNC milling machines offer high production automation, reducing the labor intensity of the operator and conducive to the automation of production management.
- High Production Efficiency: CNC milling machines do not require any special process equipment such as special fixtures. Replacing workpieces is only a matter of calling the machining program, clamping tool, and tool data stored in the numerical control device, greatly shortening the production cycle.
CNC milling machines have multiple functions, including milling, boring, and drilling, resulting in a highly concentrated process that significantly enhances production efficiency. Additionally, the CNC milling machine allows for infinitely variable spindle and feed speeds, enabling optimal cutting amounts to be chosen.
Structure and composition
(1) Basic structure
There are several types of CNC milling machines that share similarities, despite their differences in composition. In this article, we will take the XK5040A CNC vertical lifting table milling machine as an example to introduce its components.
The XK5040A model is equipped with an IV3MA numerical control system and utilizes a full digital AC servo drive. It comprises six main parts: the bed, milling head, worktable, cross feed, lift, and cooling and lubrication components.
The interior of the bed is well-arranged and has excellent rigidity. In addition, there are four adjusting bolts on the base that facilitate the horizontal adjustment of the machine. The cutting fluid reservoir is also located inside the machine base.
(2) System classification
- Cooling System
The cooling system of the machine tool consists of a cooling pump, an outlet pipe, a return pipe, a switch, and a nozzle.
The cooling pump is located in the inner cavity of the machine base. It pumps the cutting fluid from the reservoir in the base to the outlet pipe, which then sprays it through the nozzle to cool the cutting zone.
- Lubrication System and Method
The lubrication system is composed of a manual oil pump, oil separator, throttle valve, and oil pipe.
The machine tool uses the periodic lubrication method and the manual lubricating oil pump to lubricate the main shaft sleeve, the vertical and horizontal guide rails, and the three-way ball screw through the oil separator. This process enhances the service life of the machine tool.
Considering the Features of Digital Control Technology
Thanks to the adoption of servo motors and digital technology, the CNC machine can directly control the working sequence and motion displacement of the machine tool. The traditional machine tool’s gearbox structure is partially or entirely eliminated, and the mechanical structure is significantly simplified.
Digital control requires mechanical systems with high transmission stiffness and no drive clearance to ensure the execution of control commands and quality.
Moreover, as computer levels and control capabilities continue to improve, it is now possible to allow more functional components to perform various auxiliary functions on the same machine tool simultaneously. Therefore, the mechanical structure of the CNC machine tool must have a higher integration function requirement than that of the traditional machine tool.
Considering the Requirements for the Development of Manufacturing Technology
With the introduction of new materials and processes and the market demand for lower costs, metal cutting is advancing towards higher cutting speeds, precision, production efficiency, and more dependable systems.
This requires the development of CNC machine tools with increased precision and driving power based on traditional machine tools. The mechanical mechanisms must be quieter and hotter, the thermal stiffness must be better, the work must be more reliable, and long-term continuous operation with minimal downtime must be achievable.
(3) Milling head
The milling head section consists of a stepped or stepless gearbox and a milling head. The milling head spindle is supported by a high-precision bearing that provides high rotational accuracy and excellent rigidity. In addition, the spindle is equipped with a quick tool changer, and the front cone has a 1° 50′ taper. The spindle also features a mechanical stepless speed change mechanism that offers a wide adjustment range, stable transmission, and convenient operation.
The brake mechanism enables quick spindle braking, which saves auxiliary time. To brake, the brake ring opens the stop ring, which immediately brakes the spindle. However, careful attention must be paid to loosen the spindle brake handle when starting the main motor.
The milling head assembly also has a servo motor, an internal toothed pulley, a ball screw pair, and a spindle sleeve that form a vertical direction (z-direction) feed drive chain to enable vertical spindle movement.
The table and saddle rest on a wide horizontal rail of the lifting platform, and the longitudinal feed of the table is driven by a servo motor mounted at the right end of the table. The precision ball screw provides longitudinal feed of the table, driven by the internal toothed pulley. Handwheels and dials are mounted on the left end of the table for manual operation.
The saddle’s vertical and horizontal guide surfaces are made of TURCITE B plastic, enhancing wear resistance, smoothness, and precision of the guide rail, and eliminating the phenomenon of low-speed creep.
(4) Basic parts
The fundamental components of CNC milling machines typically include structural parts such as the bed, column, beam, workbench, and base. These components are significant in size and form the primary framework of the machine tool.
Other components are attached to the base member, and some of them require movement along the base member. As the base member acts as a support and guide, it must have good rigidity.
A frequency converter is an application of frequency conversion technology and microelectronic technology. By changing the frequency of the motor operating power source, the power control device of the AC motor is controlled.
In CNC machine tools, the frequency converter is mainly used to manage the spindle’s motion.
I found it interesting when you talked bout how CNC machines are very efficient in their production rates. If I were to guess, getting a CNC machine to work probably entails a bit of software programming in order to tell it what to do. It would be interesting to learn more about how this kind of manufacturing is programmed.