The CNC grinding machine is a machine tool that grinds the surface of the workpiece with a grinding tool.
Most of the grinding machines are ground using high-speed rotating grinding wheels. A few are processed with other abrasives such as oilstone, abrasive belts and free abrasives, such as honing machines, superfinishing machines, belt grinding machines, grinding machines and polishing machine and so on.
CNC grinding machines also have CNC surface grinders, CNC centerless grinders, CNC internal and external cylindrical grinders, CNC vertical universal grinders, CNC coordinate grinders, CNC forming grinders, etc.
CNC machines are the combination of information technology and mechanical manufacturing technology, representing the technical level and development trend of modern basic machinery.
China’s CNC machine tool industry has developed rapidly, and there are nearly one hundred CNC machine tool manufacturers. By the year 2000, the number of CNC machine tools has grown to 1,000, of which 100 have reached the international level in the early 1990s.
The average time between failures of CNC machine tools and CNC systems is 10,000 hours, and the annual output reaches 20,000 units. The popular products are basically based in China.
Grinding machines can process harder materials such as hardened steel and hard alloys; they can also process brittle materials such as glass and granite.
Grinding machines can be used for grinding with high precision and surface roughness, as well as for highly efficient grinding such as strong grinding.
History of grinding machine
In the 1830s, in order to adapt to the hardening of parts such as watches, bicycles, sewing machines and firearms, the United Kingdom, Germany and the United States developed grinding machines using natural abrasive wheels.
These grinding machines were made by adding grinding heads to existing ready-made machine tools such as lathes and planers.
They are simple in structure, low in rigidity, and prone to vibration during grinding, requiring the operator to have a high skill in order to grind out precise workpieces.
The universal cylindrical grinding machine manufactured by Brown-Sharp Company of the United States exhibited at the Paris Exposition in 1876 was the first machine to have the basic characteristics of a modern grinding machine.
Its workpiece headstock and tailstock are mounted on a reciprocating table that increases machine rigidity and has an internal grinding accessory.
In 1883, the company made a surface grinder with a grinding head mounted on a column and a reciprocating table.
Around 1900, the development of artificial abrasives and the application of hydraulic transmissions have greatly promoted the development of grinding machines.
With the development of modern industry, especially the automotive industry, various types of grinding machines have been introduced.
For example, at the beginning of the 20th century, planetary inner grinding machines, crankshaft grinding machines, camshaft grinding machines and piston ring grinding machines with electromagnetic chucks were developed.
The automatic measuring device was applied to the grinding machine in 1908.
Around 1920, centerless grinders, double-face grinders, roll grinders, guide grinders, honing machines and superfinishing machines were used.
In the 1950s, there was a high-precision cylindrical grinding machine that could be used for mirror grinding.
At the end of the 1960s, high-speed grinders with a line speed of 60-80 m/s and large depth-cutting and slow-feed grinding surface grinders appeared.
In the 1970s, technologies such as digital control and adaptive control of microprocessors were widely used in grinding machines.
- Suitable for the processing of complex shaped parts.
- Implement computer control to eliminate human error.
- Accuracy compensation and optimization control can be realized by computer software.
- The machining center, turning center, grinding center, and electric machining center have the functions of tool magazine and tool change, which reduces the number of clamping and improves the machining accuracy.
- CNC machine tools have increased the flexibility of machining equipment.
Flexible processing is not only suitable for multi-variety, medium and small batch production, but also suitable for mass production, and can alternately process two or more different parts.
The function of automatically changing the workpiece is added, which enables unattended operation at night.
The Flexible Manufacturing System (FMS) consisting of several CNC machine tools (machining centers) has a more flexible automated manufacturing system, including machining, assembly and inspection.
(1) Spindle components
The line speed of the grinding wheel is generally 30~60m/s, the CBN grinding wheel can be as high as 150~200m/s, and the highest spindle speed is 15000r/min.
The spindle unit is the pivotal component of the grinding machine. For high-speed and high-precision unit systems, it should have the characteristics of good rigidity, high rotation precision, small temperature rise, good chaos, low power consumption, long life and moderate cost.
The bearings of the grinding wheel spindle unit often use high-precision dynamic elastic bearings, hydrostatic bearings, hydrodynamic bearings, and message compression bearings.
High-speed and ultra-high-speed grinding machines are increasingly using electric spindle unit components.
(2) Feeding unit
The feed unit includes a servo drive unit, a moving member, a position monitoring unit.
The feed unit is a necessary prerequisite for maintaining the normal operation of the grinding wheel and is one of the important indicators for evaluating the performance of the grinding machine.
The feed unit is required to be flexible in operation, high in resolution, high in positioning accuracy, and fast in dynamic response. It requires both a large acceleration and a sufficient driving force.
The common scheme of the feed unit is the feed scheme of the combination of the AC and DC servo motor and the dynamic screw, or the direct drive of the linear servo motor.
The transmission chain of the two solutions is very short, mainly to reduce the mechanical transmission error.
Both solutions rely on the idea of speed regulation and commutation.
The grinding wheel frame, the head frame, the tail frame, the work table, the bed body and the column are the basic components of the CNC grinding machine, and the design and manufacturing technology is the basis for ensuring the quality of the grinding machine.
(4) Auxiliary unit
Auxiliary units include workpiece quick clamping device, high-efficiency grinding fluid supply system, safety protection device, spindle and grinding wheel dynamic balance system, chip handling system and so on.