ANTISHICNC CNC Turning Milling Machines,CNC Lathes
A vertical machining center is a vertical CNC milling machine with a tool magazine.
The components of a vertical machining center are highly integrated and standardized. If disassembled, the vertical machining center can be divided into eight parts: CNC system, electrical appliances, bed, spindle, tool magazine, guide rail, lead screw, and sheet metal. These eight parts are produced by professional manufacturers.
1. CNC system
The high-end system is Siemens 840D from Germany. The mid-range system is dominated by Fanuc and Mitsubishi from Japan
Selection method: Siemens 840D or Fanuc 31i is recommended for five-axis vertical machining center system.
Fanuc 18i and Mitsubishi M700 are recommended for three-axis and four-axis vertical machining centers for high-speed and high-precision machining. For three-axis vertical machining centers for general applications, Fanuc 0i MD-A is suitable for mold processing, Fanuc 0i MD-B is suitable for product processing, and Fanuc 0i Mate-MD is an economical system, Mitsubishi M70-A is used for mold machines, and Mitsubishi M70-B is suitable for product machines. It is generally believed that Fanuc is easier to operate and more stable, and Mitsubishi of the same level has more powerful functions; in occasions with low requirements and budget constraints, domestic CNC systems can also show their talents. To be fair, in recent years, domestic machining center systems have developed rapidly, and it is their progress that has forced the prices of foreign CNC system brands to drop sharply;
2. Electrical system
In the electrical system of vertical machining centers, GE of the United States, Schneider of France, and Omron of Japan occupy the mainstream position.
3. Central lubrication system
Good lubrication is a necessary condition to ensure the smooth mechanical movement of the vertical machining center. All parts that have contact movement need to be lubricated. Without the lubrication system of the machine tool, the life and accuracy of the machine tool will be greatly affected. Carefully observing the oil lubrication system of the machine tool is a compulsory course before purchasing a vertical machining center.
4. Bed (including guide rails)
Selection method: hard rails for mold machines and linear rails for product machines. This is the industry-recognized selection method.
The bed of the vertical machining center can be divided into single-column type (C type) and double-column type (gantry type). The single-column vertical machining center has a C-shaped structure when viewed from the side. This structure is only suitable for vertical machining centers with a Y axis less than 1200mm. If it is larger than this value, the spindle head will be too long to overhang, which will cause insufficient rigidity of the spindle head and vibration during processing. Therefore, vertical machining centers with large Y-axis travel are rarely seen. The gantry type has better rigidity and unrestricted Y-axis travel. It is generally used in large vertical machining centers and high-speed engraving and milling machines. This article only talks about single-column vertical machining centers.
The bed of a vertical machining center is divided into two types: fixed column type and movable column type according to whether the column moves. Conventional vertical machining centers are fixed column type, that is, the column is fixed, and the entire movement is composed of the X-axis and Y-axis movement of the workbench, plus the Z-axis movement of the spindle on the column. The movable column vertical machining center has a fixed worktable, and the three-way movement of the X-axis, Y-axis, and Z-axis is realized by the column. The advantage of the movable column type is that it occupies a small area, and the operator’s actions are not affected by the movement of the worktable. It is generally used in situations where there are double workbenches or additional rotating exchange workbenches. CNC exchange workbenches can be selected from Taiwan’s Tanxing and domestic Yantai Huanqiu.
Heavy cutting generally uses rectangular guides (i.e. hard rails), and high-speed feeding generally uses linear guides (i.e. linear guides). In order to increase the support rigidity of the machine tool, some vertical machining centers use a four-guide or even six-guide structure.
5. Screw
The characteristics of linear motor drive are fast speed, high efficiency and good rigidity. The problems are expensive, high heat generation and slightly poor transmission stability, so the traditional ball screw is still the mainstream in conventional CNC machine tools. However, as the linear motor technology gradually matures and the price gradually decreases, it can be foreseen that the application of ball screws in CNC machine tools will gradually decrease.
The pitch of the ball screw directly determines the feed speed of the machine tool. Large pitch corresponds to high speed, but the sacrifice is precision. There are gains and losses.
There are two ways to install the ball screw on the vertical machining center: one is to fix one end and move the other end. The axial clearance of the ball screw is eliminated by pre-stretching the ball screw at the moving end to avoid thermal deformation caused by temperature rise. This is the most common installation method; the other is to fix both ends, which is suitable for high-speed and high-precision machine tools. It is difficult to install and debug, but it can solve the problem of pre-stretching affecting the bearing life.
The structure of the ball screw nut seat also has a great influence on the rigidity of the machine tool. The overall nut seat is difficult to manufacture and has good rigidity, but the entire workbench needs to be replaced after damage.
6.Spindle
The spindle is the most critical functional component of the vertical machining center. The spindle is generally divided into four categories according to the transmission structure.
Gear-driven spindle: high rigidity, suitable for heavy cutting occasions, the speed is generally less than 6000 rpm.
Synchronous belt-driven spindle: simple structure, easy to manufacture, strong buffering capacity, overload sliding protection can effectively protect the spindle. It is one of the mainstream spindle structures of vertical machining centers. The speed is generally 6000-12000 rpm.
Direct-connected spindle: The servo motor directly drives the spindle through the coupling, with high torque and low energy consumption. It is also the mainstream structure of the vertical machining center. The speed is generally 8000-15000 rpm.
Electric spindle: also called spindle unit, Taiwan called internal expansion spindle. That is, the motor is built into the spindle, the motor and the spindle are combined into one, and the length of the main transmission chain is shortened to zero. The speed is generally 18000-40000 rpm.
7. Vertical machining center tool magazine
The most common vertical machining center tool magazines are bamboo hat-type tool magazines and robot tool magazines. They have been introduced in detail in previous articles, so I won’t go into details here.
8. Protection shield of vertical machining center
Sheet metal and paint are the clothes of machine tools. The air-tightness of sheet metal of vertical machining center is particularly important. Water and oil leakage will make workshop management difficult and may even cause safety accidents. Poor dust prevention will directly affect the electrical life.
Selection method: The sheet metal thickness should be more than 1 mm, the seam gap should be small and uniform, and the paint should be thick and flat. The door should be tight, there should be buffer when pushing and pulling, and the power will be automatically cut off when the electric cabinet door is opened.
9. Control of vertical machining center
In fact, a large part of the control is related to the CNC system. Excellent machine tool factories have the ability to carry out secondary development of CNC systems, and can even allow operators to automatically generate programs by simply filling in forms and entering parameters, truly realizing programming-free control. In addition, the position of the control box, the rotation method, the position and opening and closing method of the sliding door, the placement of tools and tools, etc., all need to be designed from the perspective of the operator, so that such a design will bring humanized control.
Selection method: Give priority to machine tools that can achieve programming-free control. In addition, please actually operate the machine tool to see if the structural components of the machine tool will interfere with the processing. Excellent machine tools will make people use them with ease.
10. Optional accessories
Reasonable optional accessories can make machine tools more efficient! Such as CNC rotary tables, oil coolers, chip conveyors, oil mist separators, high-precision universal fixtures, in-machine measuring devices, etc., are indispensable killers in many processing occasions.
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