"If a worker wants to do good things, he must first use his tools." Tools are the symbol of the progress of human civilization. Since the end of the 20th century, modern manufacturing technology and mechanical manufacturing process automation have made great progress. But the function of tools (including clamps, tools, measuring tools and auxiliary tools) is still very significant in the continuous innovation. The fixture of machine tool has a direct influence on the quality, productivity and product cost of parts processing. Therefore, fixture is an important process equipment in both traditional manufacturing and modern manufacturing system.

1. The function of machine tool clamp

(1) To ensure the machining accuracy, the workpiece can be clamped with machine tool clamp, and the relative position relationship between workpiece and tool and machine tool can be accurately determined, and the machining accuracy can be guaranteed.

(2) The improvement of production efficiency machine tool fixture can quickly position and clamp the workpiece, reduce the auxiliary time and improve the production

Production efficiency.

(3) The mechanical, pneumatic and hydraulic clamping devices are used to reduce the labor intensity of the workers.

(4) Expanding the technological range of machine tools, using machine tools and fixtures can expand the machining range of the machine tools. For example, using boring die on lathe or drill machine can replace boring machine boring, so that lathe and drill machine have boring function.

2. Classification of machine tool clamps

2.1. classification according to the application scope of fixture

(1) General fixture is a fixture with standardized structure and wide application range, such as three jaw chuck and four jaw chuck for lathe, flat tongs and indexing head for milling machine.

(2) Special machine tool fixture is a fixture designed and manufactured for a certain process of a workpiece. Special machine tool clamp is suitable for application in the situation of relatively stable products and large production.

(3) The combination fixture is a set of pre-made standard components and assembly parts. The combination fixture has flexible structure, short design and assembly period, and can be reused for a long time. It is suitable for many kinds of single piece small batch production or new product trial production.

(4) Group fixture is a fixture designed and manufactured for each part group when group processing is adopted. When another part in the same group is changed, only individual components on the fixture need to be adjusted or replaced to process. The group clamp is suitable for the application in the production of multi varieties and small batch.

(5) The traveling fixture is a mobile fixture used on the automatic line. Before the workpiece enters the automatic line processing, the workpiece is installed in the fixture, and then the fixture along the automatic line along the automatic line moves from one position to the next station together with the workpiece being processed. The workpiece is not removed from the fixture until the workpiece exits the automatic line processing. The traveling fixture is a fixture which always moves along the automatic line with the workpiece.

2.2 classification by machine type used

The types of machine tools are different, and the fixture structure is different. Therefore, the fixture can be divided into lathe fixture, drilling machine clamp, milling machine clamp, boring machine clamp, grinder clamp and combined machine tool clamp.

2.3 classification by fixture power source

According to the clamping power source used by the clamp, the clamp can be divided into manual clamping fixture, pneumatic clamp, hydraulic clamp, pneumatic clamp, pneumatic clamp, electromagnetic clamp, vacuum clamp, etc.

3. The composition of special machine tool clamp

The fixture is generally composed of the following elements or devices:

(1) Positioning element is a component used to determine the correct position of the workpiece. The positioning base surface of the processed workpiece is directly in contact with or in coordination with the fixture positioning element.

(2) The clamping device is a device which can keep the workpiece in the correct position under the action of external force.

(3) Tool alignment element, guide element alignment element and guide element refer to the components in the fixture which are used to determine (or guide) that the tool has the correct position relationship with respect to the fixture positioning element, such as drilling sleeve, boring sleeve, tool alignment block, etc.

(4) Connecting element fixture connecting element refers to the element used to determine the correct position and connection of the fixture on the machine tool, such as the positioning key installed on the bottom surface of the milling machine clamp.

(5) Other components and devices shall be equipped with indexing and shifting device, profiling device, workpiece lifting device and auxiliary support device according to the processing requirements.

(6) The clamp is a basic part for connecting fixture elements and related devices to make it a whole. The clamp is connected with the machine tool by the clamp.

Positioning elements, clamping devices and clamps are the basic components of the fixture, and other parts can be set as required.