The combination fixture is a kind of standardized, highly serialized flexible fixture, and has been commercialized. It consists of a set of pre-made high-precision components and assemblies with different geometries and different sizes. According to the processing requirements of the workpiece, the required fixtures are assembled in a combined manner during use. According to the shape of the base surface of the combined fixture assembly, it can be divided into two categories: slot system and hole system. The connecting base surface of the slot system combined fixture is a T-shaped slot, and the components are positioned and fastened by keys and bolts. The connection base surface of the hole system combination fixture is a coordinate hole system composed of cylindrical holes. The T-slot combination fixture series are divided into three types according to their size: small, medium and large. The main differences are the external dimensions of the components, the width of the T-slot and the diameter specifications of the bolts and screw holes.
1. Small series
The small series of combined fixtures are mainly suitable for instruments, meters, telecommunications, and electronics industries, and can also be used for smaller workpieces. The bolt diameter of this series of components is M8x1.25mm, the fitting size of the positioning key and the width of the key groove is 8H7 / h6, and the distance between the T-shaped groove is 30mm.
The medium series combination fixture is mainly suitable for the machinery manufacturing industry. The bolt diameter of this series of components is M12x1.5mm, the fitting size of the positioning key and the width of the key groove is 12H7 / h6, and the distance between the T-shaped groove is 60mm. This is currently the most widely used series.
The large series of combined fixtures are mainly suitable for the heavy machinery manufacturing industry. The bolt diameter of this series of components is M16x2mm, the fitting size of the positioning key and the width of the key slot is 16H7 / h6, and the distance between the T-shaped slots is 60mm.
The base part is the largest component in the combined fixture, and it includes square, rectangular, circular base plates and corner irons of various sizes, as shown in Figure a. The basic part is mainly used to clamp the concrete, and is also the basis for the assembly of various components.
There are many specifications of the support, which mainly include various square supports, rectangular supports, elongated plates, angle irons, angle supports and angle pads, as shown in the outline of Figure b. The support usually plays the role of supporting and lowering in the fixture, that is, the other components are connected with the base through the support to form a whole. The support member can also be used as a positioning member and a base member.
3. Positioning piece
The positioning parts include various positioning pins, positioning disks, positioning keys, etc., which are mainly used for workpiece positioning and positioning between the components of the combined fixture, as shown in outline c.
The guide includes various drill templates, drill sleeves, sleeves, and guide supports.It is mainly used to determine the relative position of the tool and the part. It plays the role of guiding the tool during processing and can also be used as a positioning part, as shown in the overview diagram d. .
The clamping parts include various shapes of pressure plates and washers, etc., which are mainly used to clamp the workpiece on the fixture to ensure the correct position of the workpiece after positioning. It can also be used as a backing plate and a stopper, as shown in the overview diagram e.
Fasteners include various bolts, nuts, and washers, and are mainly used to connect various components and fastening components in the combined fixture. The materials, accuracy, surface roughness and heat treatment of the fasteners of the combined fixture are better than the general standard fasteners to ensure the connection strength, reliability and combined rigidity of the combined fixture.
7. Other pieces
Other parts include springs, joints, sector plates, weights, etc., as shown in the overview diagram g. These components have no fixed purpose. If used properly, they can play an extremely effective auxiliary role in assembly.
The assembly is a separate part that is assembled from parts and is not used during assembly, as shown in outline h. According to its use classification, there are positioning assembly, guide assembly, indexing assembly, support assembly and clamping assembly and other assembly is an important assembly element of the combination fixture.
The above types of components have been standardized, serialized, and generalized. There are about 1500 to 2500 components in the complete set of fixtures.