"When a worker wants to do something good, he must first sharpen his tools." Tools are the hallmark 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. However, the tools (including fixtures, knives, measuring tools and accessories) are still innovating, and their functions are still very significant. Machine tool fixtures have a direct impact on the quality, productivity and cost of part processing. Therefore, fixtures are important process equipment in both traditional manufacturing and modern manufacturing systems.

1, the role of machine tool fixture

(1) Guarantee the machining accuracy The workpiece is clamped by the machine tool fixture, which can accurately determine the relative positional relationship between the workpiece and the tool and the machine tool, and can ensure the machining accuracy.

(2) Improve production efficiency Machine tool fixtures can quickly position and clamp workpieces, which can reduce auxiliary time and increase production efficiency.

(3) Reducing labor intensity Machine tool fixtures use mechanical, pneumatic and hydraulic clamping devices to reduce the labor intensity of workers.

(4) Expanding the technological scope of the machine tool The machine tool fixture can be used to expand the processing range of the machine tool. For example, the use of a die on a lathe or a drill press can replace the boring of the boring machine, so that the lathe and the drilling machine have the function of a boring machine.

2. Classification of machine tool fixtures

2.1. Classified by the application range of the fixture

(1) General-purpose fixtures General-purpose fixtures are fixtures that have been standardized and have a wide range of applications, such as three-jaw chucks and four-jaw chucks for lathes, flat-end pliers for milling machines, and indexing heads.

(2) Special machine tool fixture The special machine tool fixture is a fixture specially designed and manufactured for a certain process of a certain workpiece. Special machine tool holders are suitable for applications where the product is relatively stable and the output is large.

(3) Combined fixture The combination fixture is a fixture assembled from a set of pre-manufactured standard components and fittings. The structure of the combined fixture is flexible and flexible, and the design and assembly cycle are short. The fixture parts can be reused for a long time, and it is suitable for applications in multi-variety single-piece small batch production or new product trial production.

(4) Grouping jigs Grouping jigs are jigs designed and manufactured for each part group when using group processing. When changing another part in the same group, only need to adjust or replace individual components on the jig. It can be processed. The group fixture is suitable for application in multi-variety, medium and small batch production.

(5) The pallet is a mobile fixture used on the automatic line. Before the workpiece enters the automatic line processing, the workpiece is loaded into the fixture, and then the fixture is moved along with the workpiece along the automatic line from one work to the next. A station stops the workpiece from the fixture until the workpiece exits the automatic line machining. A pallet is a fixture that always moves along the workpiece along the automatic line.

2.2 Classification by machine type

Different types of machine tools and different fixture structures make it possible to divide fixtures into lathe fixtures, drill chucks, milling fixtures, boring fixtures, grinding fixtures and combination machine tool fixtures.

2.3 Classification by fixture power source

According to the clamping power source used by the fixture, the fixture can be divided into a manual clamping fixture, a pneumatic clamping fixture, a hydraulic clamping fixture, a gas-liquid linkage clamping fixture, an electromagnetic fixture, a vacuum fixture, and the like.

3. Composition of special machine tool fixtures

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

(1) Positioning element The positioning element is an element used to determine the correct position of the workpiece. The positioning base of the workpiece to be machined is in direct contact with or mates with the fixture positioning element.

(2) Clamping device The clamping device is a device that allows the workpiece to maintain its correct positioning position under external force.

(3) Tool setting element, guiding element The tool setting element and guiding element refer to the element in the fixture for determining (or guiding) the correct positional relationship of the tool relative to the fixture positioning element, such as drill sleeve, boring sleeve, tool holder block, etc. .

(4) Connecting element The jig connecting element is an element for determining that the jig has the correct position on the machine tool and is connected thereto, such as a positioning key mounted on the bottom surface of the milling jig.

(5) Other components and devices According to the processing requirements, some fixtures still need to be equipped with indexing indexing device, master device, workpiece lifting device and auxiliary support.

(6) The clip specific clip is specifically a basic member for connecting the clamp member and the related device to make it integral, and the clamp is specifically connected to the machine tool through the clamp.

The positioning element, the clamping device and the clamp are in particular the basic components of the clamp, and the other parts can be arranged as required.