CNC Grinding Machine Explained

The CNC grinding machine is a type of machine tool that uses a grinding tool to grind the surface of a workpiece.

Most grinding machines utilize high-speed rotating grinding wheels, while some employ other abrasives like oilstones, abrasive belts, and free abrasives. Honing machines, superfinishing machines, belt grinding machines, grinding machines, and polishing machines are also used for grinding purposes.

In addition, CNC grinding machines include various types such as CNC surface grinders, CNC centerless grinders, CNC internal and external cylindrical grinders, CNC vertical universal grinders, CNC coordinate grinders, and CNC forming grinders.

Introduction

CNC machines are the result of combining information technology and mechanical manufacturing technology, representing the current technical level and development trend of modern basic machinery.

In China, the CNC machine tool industry has experienced rapid growth with nearly a hundred CNC machine tool manufacturers. By the year 2000, the number of CNC machine tools had reached 1,000, of which 100 were at an international level in the early 1990s.

The average time between failures of CNC machine tools and CNC systems is 10,000 hours, with an annual output of 20,000 units. Many popular CNC machine tool products are manufactured in China.

Processing range

Grinding machines are capable of processing a wide range of materials, including harder materials like hardened steel and hard alloys, as well as brittle materials like glass and granite.

Grinding machines are commonly used for achieving high precision and surface roughness in grinding operations. They can also be used for highly efficient grinding tasks, such as in the case of strong grinding.

History of grinding machine

In the 1830s, the United Kingdom, Germany, and the United States developed grinding machines with natural abrasive wheels in order to adapt to the hardening of parts such as watches, bicycles, sewing machines, and firearms. These machines were created by adding grinding heads to existing machine tools like lathes and planers. They were simple in structure, low in rigidity, and prone to vibrations during grinding, requiring operators to have high skill levels to produce precise workpieces.

In 1876, the Brown-Sharp Company of the United States showcased the first grinding machine with the basic characteristics of modern machines, a universal cylindrical grinding machine, at the Paris Exposition. This machine featured a reciprocating table that increased machine rigidity, an internal grinding accessory, and workpiece headstock and tailstock.

In 1883, the company developed a surface grinder with a grinding head mounted on a column and a reciprocating table. The development of artificial abrasives and hydraulic transmissions around 1900 greatly promoted the advancement of grinding machines. Various types of grinding machines were introduced with the development of modern industry, particularly the automotive industry.

In the early 20th century, planetary inner grinding machines, crankshaft grinding machines, camshaft grinding machines, and piston ring grinding machines with electromagnetic chucks were developed. In 1908, automatic measuring devices were added to grinding machines. By around 1920, centerless grinders, double-face grinders, roll grinders, guide grinders, honing machines, and superfinishing machines were in use.

In the 1950s, a high-precision cylindrical grinding machine that could be used for mirror grinding was developed. 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, digital control and adaptive control of microprocessors were widely applied to grinding machines.

Characteristics

• Suitable for processing complex shaped parts.
• Implements computer control to eliminate human error.
• Enables accuracy compensation and optimization control through computer software.
• Machining centers, turning centers, grinding centers, and electric machining centers have tool magazine and tool change functions, reducing the number of clamping and improving machining accuracy.
• Increases the flexibility of machining equipment.

Flexible processing is suitable not only for multi-variety, medium and small batch production, but also for mass production. It can also alternately process two or more different parts.

The addition of the function of automatically changing the workpiece enables unattended operation at night.

The Flexible Manufacturing System (FMS) comprises several CNC machine tools (machining centers) and provides a more flexible automated manufacturing system, including machining, assembly, and inspection.

Structural features

(1) Spindle Components:

The grinding wheel typically operates at a line speed of 30-60 m/s, while the CBN grinding wheel can reach up to 150-200 m/s. The highest spindle speed is 15,000 r/min.

The spindle unit is a critical component of the grinding machine. For high-speed and high-precision unit systems, it should possess good rigidity, high rotational precision, low temperature rise, good vibration resistance, low power consumption, long lifespan, and moderate cost.

The bearings of the grinding wheel spindle unit often utilize high-precision dynamic elastic bearings, hydrostatic bearings, hydrodynamic bearings, and message compression bearings.

Electric spindle unit components are increasingly utilized in high-speed and ultra-high-speed grinding machines.

(2) Feeding Unit:

The feed unit consists of a servo drive unit, a moving member, and a position monitoring unit.

The feed unit is essential to maintaining the normal operation of the grinding wheel and is a crucial indicator for evaluating the performance of the grinding machine.

The feed unit must be flexible in operation, high in resolution, high in positioning accuracy, and fast in dynamic response. It requires both a large acceleration and sufficient driving force.

The common approach for the feed unit is the combination of the AC and DC servo motor and the dynamic screw feed system, or the direct drive of the linear servo motor.

The transmission chain of the two solutions is short, primarily to reduce mechanical transmission errors.

Both solutions rely on the concept of speed regulation and commutation.

(3) Components:

The grinding wheel frame, head frame, tail frame, work table, bed body, and column are the fundamental components of the CNC grinding machine. The design and manufacturing technology are the foundation for ensuring the quality of the grinding machine.

(4) Auxiliary Units:

Auxiliary units include a workpiece quick clamping device, high-efficiency grinding fluid supply system, safety protection device, spindle and grinding wheel dynamic balance system, and chip handling system.