Fixtures used on metal cutting machine tools are collectively called machine tool fixtures. In modern production, machine tool fixture is an indispensable process equipment, which directly affects machining accuracy, labor productivity and product manufacturing cost.
There are many kinds of machine tool fixtures, which can be classified from different angles. Commonly used classification methods are as follows.
(1) According to the use characteristics of the fixture.
According to the general characteristics of different types of jigs, machine tool jigs can be divided into five categories: general jigs, special jigs, adjustable jigs, combined jigs and combined jigs.
(1) Universal fixture The fixture that can process different workpieces within a certain range has been standardized and is called universal fixture. Its structure and size have been standardized, and it has certain universality, such as three-jaw self-centering chuck, flat-mouth vice for machine tools, four-jaw single-acting chuck, vice, Universal dividing head, top, center frame, magnetic workbench and so on. This fixture has strong adaptability and can be used to clamp various workpieces in a certain shape and size range. These fixtures have been manufactured and supplied by special factories as machine tool accessories, and only need to be purchased. Its disadvantages are low precision, low productivity and difficulty in clamping workpieces with complex shapes, and it is generally suitable for single piece and small batch production.
(2) Special fixture A fixture designed and manufactured for a certain process of the workpiece is called a special fixture. In the production of relatively stable products and large quantities, high productivity and machining accuracy can be obtained by using various special fixtures. The design cycle of special fixture is long and the investment is large.
Special fixtures are generally used for mass production. In addition to mass production, small and medium-sized batch production also needs some special fixtures, but specific technical and economic analysis is needed in structural design.
(3) Adjustable fixture Some parts can be adjusted or replaced to adapt to various workpiece processing fixtures, which are called adjustable fixtures. Adjustable fixture is a new type of fixture developed for the defects of general fixture and special fixture. For different types and sizes of workpieces, only a single positioning element and clamping element on the original fixture need to be adjusted or replaced. Generally, it can be divided into universal adjustable fixture and group fixture. The universal range of the former is larger than that of the universal fixture; The latter is a special adjustable fixture designed according to the group principle, which can process a family of similar workpieces, so it has good economic effects in multi-variety and small and medium-sized batch production.
(4) The modular fixture adopts standard modular components and is specially assembled for a certain process of the workpiece, which is called modular fixture. The modular fixture is a modular fixture. The standard module components have high precision and wear resistance, and can be assembled into various fixtures. The fixture can be disassembled after use, and left to assemble a new fixture after cleaning. Because the use of combined fixture can shorten the production preparation cycle, parts can be reused many times, which has the advantage of reducing the number of special fixtures, combined fixture is an economical fixture in single-piece, small and medium-sized batch multi-variety production and NC machining.
⑤ Assembly fixture is a fixture assembled with specialized, standardized and serialized assembly parts, which is called assembly fixture. It has the advantages of combined fixture, but it is more accurate, efficient and compact than combined fixture. Its bottom plate and clamping part usually have small hydraulic cylinders. This fixture is more suitable for CNC machine tools.
(2) according to the classification of machine tools used
Fixtures can be divided into lathe fixture, milling fixture, drilling fixture, boring fixture, gear machine fixture, CNC machine fixture, automatic machine fixture, automatic line tracking fixture and other machine fixture.
(3) according to the classification of clamping power supply
According to the power source of clamping, the fixture can be divided into manual fixture, pneumatic fixture, hydraulic fixture, gas-liquid pressurization fixture, electromagnetic fixture and vacuum fixture.