The fixture is a kind of process equipment for clamping workpieces. It is widely used in machining, heat treatment, assembly, welding and inspection and other processes in the mechanical manufacturing process.
The fixtures used on metal cutting machine tools are collectively called machine tool fixtures. In modern production, machine tool fixtures are an indispensable process equipment, which directly affects the accuracy of workpiece processing, labor productivity and product manufacturing costs.
There are many types of machine tool clamps, which can be classified from different angles. Commonly used classification methods include the following.
(1) Classification according to the use characteristics of the fixture.
According to the common characteristics of the fixture in different production types, machine tool fixtures can be divided into five categories: general fixtures, special fixtures, adjustable fixtures, combination fixtures and assembly fixtures.
① Universal fixtures are standardized fixtures that can process different workpieces within a certain range. They are called universal fixtures. Their structures and dimensions have been standardized, and they have certain versatility, such as three-jaw self-centering chucks, flat-mouth vise for machine tools, Four-jaw single-action chuck, bench vise, universal indexing head, center, center frame and magnetic workbench, etc. This type of clamp is highly adaptable and can be used to clamp various workpieces within a certain shape and size range. These fixtures have been manufactured and supplied by specialized factories as machine tool accessories. Their accuracy is not high, productivity is low, and it is difficult to clamp workpieces with complex shapes, so they are generally suitable for single-piece and small-batch production.
②Special fixtures: Fixtures designed and manufactured specifically for a certain process of a certain workpiece are called special fixtures. In the production of relatively stable products and large batches, using various special fixtures can achieve higher productivity and processing accuracy. The design cycle of special fixtures is long and the investment is large. Special fixtures are generally used in mass production. In addition to mass production, some special fixtures are also needed in small and medium-sized batch production, but specific technical and economic analysis must be carried out during structural design.
③ Some components of the adjustable fixture can be adjusted or replaced to adapt to the processing of various workpieces, which is called an adjustable fixture. Adjustable clamps are a new type of clamp developed to address the shortcomings of general clamps and special clamps. For workpieces of different types and sizes, just adjust or replace individual positioning elements and clamping elements on the original fixture. It can generally be divided into two types: universal adjustable clamps and group clamps. The former has a larger general range than the general-purpose clamp; the latter is a special adjustable clamp, designed according to the grouping principle and can process a group of similar workpieces, so it is better used in multi-variety, medium and small batch production. economic effect.
④ Combination fixtures use standard combination components and components. The fixtures that are specially assembled for a certain process of a certain workpiece are called combination fixtures. The combination clamp is a modular clamp. Standard modular components have high precision and wear resistance and can be assembled into various fixtures. The clamp is removable after use and can be left to assemble a new clamp after cleaning. Since the use of combination fixtures can shorten the production preparation cycle, components can be reused multiple times, and has the advantages of reducing the number of special fixtures, combination fixtures are a more economical method for single-piece, medium and small batch multi-variety production and CNC processing. clamp.
⑤Assembled fixtures are assembled with specialized standardized and serialized assembly parts, which are called assembly fixtures. It has the advantages of a combination clamp, but has higher precision, higher efficiency and compact structure than the combination clamp. It often has small hydraulic cylinders in its base plate and clamping components. This type of fixture is more suitable for use on CNC machine tools.
(2) Classification by machine tools used
According to the machine tools used, fixtures can be divided into lathe fixtures, milling machine fixtures, boring machine fixtures, gear machine tool fixtures, CNC machine tool fixtures, automatic machine tool fixtures, automatic line accompanying fixtures and other machine tool fixtures.
(3) Classification according to clamping power source
Clamps can be divided into manual clamps, pneumatic clamps, hydraulic clamps, magnetic clamps, etc. according to the power source of clamping.