The role of the fixture What the fixture consists of

1. Fixture function: install the workpiece quickly, conveniently and safely. Fixture refers to a device used to fix the processing object in the process of mechanical manufacturing, so that it occupies the correct position to accept construction or testing, also known as fixture (qiǎ jǜ).

Broadly speaking, any process in the process can be called a fixture for the device used to install the workpiece quickly, conveniently and safely.

2. The fixture is usually composed of a positioning element (to determine the correct position of the workpiece in the fixture), a clamping device, a tool setting guide element (to determine the relative position of the tool and the workpiece or the direction of the guiding tool), an indexing device (the workpiece can complete the processing of several stations in a single installation, and there are two types of rotary indexing device and linear moving indexing device), connecting elements and clamping body (fixture base), etc.

Usually it is a product part, there are thick steel plates, sheet metal parts, steel castings, and a small number of plastic parts, usually special fixtures are machined, welding, and some are used as inspection fixture clamping mechanisms.

1) Classification according to the process: machine tool fixture, assembly fixture, welding fixture, testing fixture; 2) Classification of machine tool types: lathe fixtures, milling machines, drilling machines, grinding machines, broaching fixtures, etc. 3) Classification according to the applicability and characteristics of fixtures:

General fixtures, disposable fixtures, multiple reuse fixtures, independent transmission devices, etc. 4) Classification according to the structural characteristics of fixtures: special fixtures, combined fixtures, adjustable fixtures, etc. 5) Classification according to the power source of clamping devices: manual fixtures, pneumatic fixtures, hydraulic fixtures, electromagnetic fixtures, vacuum fixtures, etc.

Combination fixtures are fixtures that are assembled from standard fixture parts (or specialized parts) that can be reused into easy attachment and disassembly.

Combined fixtures are divided into machine tools and welding.

Machine tools: In order to facilitate the combination and obtain high assembly accuracy, the manufacturing accuracy of the combined fixture element itself is IT6 7 level, and it must have good interchangeability and wear resistance. In general, the assembled fixture can process workpieces with IT8 accuracy, and if carefully adjusted, it can also process workpieces with IT6 and 7 accuracy.

Welding class using standardized technical requirements to make a standardized, serialized, generalized many modules, all modules of connection, fixing and pressing are to hole positioning with locking pins to achieve quick locking, between modules and modules can be adjusted according to the actual size of the workpiece, the combination of the whole set of tooling fixture system can realize the construction of two cavity and three-dimensional space.

The combination fixture is assembled from a set of pre-manufactured standard elements and components of different shapes, specifications and sizes. Figure 3-40 is the process diagram of the disc part to be processed.

Features of the combination fixture.

The combination fixture is generally a special fixture assembled for a certain process of a workpiece, and can also be assembled into a general adjustable fixture or a group fixture. Combination fixtures are suitable for all types of machine tools, but drill dies and lathe fixtures are the most used.

The combination fixture turns the one-way process of design, manufacturing, use, and scrapping of special fixtures into a circular process of assembly, disassembly, cleaning, storage, and reassembly. A few hours of assembly cycle can be used instead of several months of design and manufacturing cycle, thus shortening the production cycle; It saves man-hours and materials, and reduces production costs; It can also reduce the area of the fixture warehouse, which is conducive to management.

The components of the combination fixture are highly accurate, wear-resistant, and fully interchangeable, and the component accuracy is generally IT6 and IT7 level. The position accuracy of the workpiece processed with the combined fixture can generally reach IT8 and IT9, and if carefully adjusted, it can reach IT7.

Because the combination clamp has many advantages, and is especially suitable for new product trial production and multi-variety small batch production, it has developed rapidly in recent years and is widely used. The main disadvantages of the combined fixture are that the volume is larger, the stiffness is poor, the investment is more, and the cost is high, which makes the popularization and application of the combined fixture limited to a certain extent.

The combination fixture is divided into two categories: groove system and hole system.