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First, the basic principles of fixture design:
1, to meet the stability and reliability of the workpiece positioning in the process of use;
2, there is enough load or clamping force to ensure that the workpiece in the tooling and fixture processing process;
3, satisfy the simple and fast operation in the clamping process;
4. Damable parts must be the structure that can be quickly replaced. When conditions are sufficient, it is best not to use other tools.
5, to meet the fixture in the adjustment or replacement process of repeated positioning reliability;
6. Avoid complex structure and high cost as far as possible;
7, as far as possible to choose standard parts as components;
8. Formed the systematization and standardization of the company's internal products.
Second, the basic knowledge of fixture design
A good machine fixture must meet the following basic requirements:
1, ensure the processing accuracy of the workpiece to ensure the processing accuracy of the key, first is to correctly select the positioning datum, positioning method and positioning components, if necessary, also need to carry out positioning error analysis, but also pay attention to the structure of other parts of the fixture on the processing accuracy, to ensure that the fixture can meet the requirements of the workpiece processing accuracy.
2, improve the production efficiency of the special fixture complexity should be adapted to the capacity situation, should try to use a variety of fast and efficient clamping mechanism, to ensure easy operation, shorten the auxiliary time, improve production efficiency.
3, process performance good special fixture structure should be simple, reasonable, easy to manufacture, assembly, adjustment, inspection, maintenance and so on.
4, the use of good performance of the fixture should have enough strength and stiffness, the operation should be simple, labor-saving, safe and reliable. In the objective conditions and the premise of economic applicability, pneumatic, hydraulic and other mechanized clamping devices should be used as far as possible to reduce the labor intensity of the operator. Fixtures and fixtures should also be convenient for chip removal. When necessary, the chip discharge structure can be set to prevent the chip from destroying the positioning of the workpiece and damaging the cutter, and prevent the accumulation of chips from bringing a lot of heat and causing the deformation of the process system.
5, good economy special fixture should use standard components and standard structure as far as possible, and strive to simple structure, easy manufacturing, in order to reduce the manufacturing cost of fixture. Therefore, the design should be based on the order and capacity of the necessary technical and economic analysis of the fixture scheme, in order to improve the fixture in the production of economic benefits.
III. Overview of standardization of tooling and fixture design
1. The basic methods and steps of tooling and fixture design
The original data of the design of the fixture and fixture include the following contents:
A) Design notice, drawings of finished parts, rough drawings and process routes and other technical data, to understand the processing technical requirements of each process, positioning and clamping scheme, processing content of the previous process, rough conditions, machine tools, cutting tools, inspection gauges used in processing, processing allowance and cutting amount, etc.;
B) Understand the production batch and fixture requirements;
C) Understand the main technical parameters, performance, specifications, precision of the machine tool used and the connection size of the structure of the part connected with the fixture;
D) Standard material inventory of fixture.
2, fixture design consideration
Fixture design general structure is single, give a person the feeling that the structure is not very complex, especially now the popular hydraulic fixture, so that its original mechanical structure is greatly simplified, but if the design process is not considered in detail, there will be unnecessary trouble:
A) The blank allowance of the workpiece to be processed. The blank size is too large, resulting in interference. So before the design must be prepared to rough drawings. Leave plenty of space.
B) Chip removal fluency of the fixture. Due to the limitation of the processing space of the machine tool, the space of the fixture is often designed to be compact. At this time, it is often ignored that the iron chips produced in the processing process are stored at the dead corner of the fixture, including the flow of chip fluid is not smooth, which brings a lot of trouble to the future processing. So at the beginning of the actual processing should be considered in the process of the problem, after all, the fixture is to improve efficiency, convenient operation for this.
C) The overall openness of the fixture. Ignoring the open, causing the operator to install the card difficult, time-consuming and laborious, design taboo.
D) Basic theoretical principles of fixture design. Each fixture has to experience numerous times of clamping and loosening action, so it may be able to meet the user's requirements at the beginning, but the fixture should have its accuracy retention, so do not design something against the principle of things. Even if luck can now, also won't have long lasting. A good design should be tempered with time.
E) Replacement of positioning elements. Positioning components wear seriously, so should consider quick and convenient replacement. It is best not to design large parts.
The accumulation of fixture design experience is very important, sometimes the design is one thing, in the practical application is the same thing, so good design is a process of continuous accumulation and summary.
The commonly used tooling and fixtures are mainly divided into the following categories according to their functionality:
01 die
02 drilling and milling surface tooling
03 CNC, instrument chuck
04 gas test and water test tooling
Edge trimming and punching tooling
06 Welding Tooling
07 Polishing fixture
08 Assembly tooling
09 pad printing, laser lettering tooling
01 die
Definition: a tool for positioning and clamping with the shape of the product
Design points:
1. This kind of clamping die is mainly used in vise, and its length can be cut according to the need;
2. Other auxiliary positioning devices can be designed on the clamping die. The clamping die is generally connected by welding.
3. The figure above is a schematic diagram. The size of the cavity structure is determined by the specific situation.
4. The locating pin with diameter of 12 is tightly matched at the appropriate position on the moving die, and the locating hole at the corresponding position of the fixed die is sliding with the locating pin;
5. The assembly cavity should be offset and enlarged by 0.1mm on the basis of the shape surface of the non-shrinking blank drawing file during the design.
02 drilling and milling surface tooling
Design points:
1. If necessary, some auxiliary positioning devices can be designed on the fixed core and its fixed plate;
2, the above diagram is the structure diagram, the actual situation needs to do the corresponding design according to the product structure;
3, cylinder according to the size of the product and processing force, commonly used SDA50X50;
03 CNC, instrument chuck
A CNC chuck
The beam clamp
Design points:
1. The size not marked in the above figure is determined according to the size and structure of the inner hole of the actual product;
2. The outer circle in contact with the inner hole of the product should be left with a one-sided margin of 0.5mm during the production, and finally installed on the CNC machine to finish the car to the size, to prevent the deformation and eccentricity caused by the quenching process;
3, the assembly part of the material recommended to use spring steel, pull rod part 45#;
4. The thread M20 of the pull rod part is commonly used, which can be adjusted according to the actual situation
Instrument inner bundle chuck
Design points:
1. The figure above is the reference diagram. The assembly size and structure are determined according to the external size and structure of the actual product.
2, the material use 45#, quenching treatment.
Instrument outer bundle chuck
Design points:
1. The figure above is the reference diagram. The actual size is determined according to the size and structure of the inner hole of the product.
2. The outer circle in contact with the inner hole of the product should be left with a one-sided margin of 0.5mm during production, and finally installed on the instrument lathe to finish the turning to size to prevent the deformation and eccentricity caused by the quenching process;
3, the material use 45#, quenching treatment.
04 gas test tooling
Design points:
1. The figure above is the reference diagram of the gas test tooling. The specific structure needs to be designed according to the actual structure of the product.
2, the size of the cylinder can be adjusted according to the actual size of the product, but also need to consider whether the stroke of the cylinder can meet the convenience of taking and putting the product;
3. The sealing surface in contact with the product is generally made of materials with good compression such as Yuli adhesive and NBR apron. At the same time, attention should be paid to the use of plastic blocks of white adhesive as far as possible for positioning blocks in contact with the appearance of the product, and cotton cloth should be covered during the use to prevent the appearance of the product from being damaged.
4, the design needs to consider the positioning direction of the product, to prevent the leakage of gas inside the product cavity and the misdetection of the situation.
05 punching tooling
Design points: the above figure is the common structure of punching tooling. The bottom plate is conveniently fixed on the table of the punch press; The function of the positioning block is to fix the product, the specific structure is designed according to the actual situation of the product, and the center point can be convenient and safe to take and place the product; The baffle acts to facilitate the product to be detached from the punching knife; The struts serve to hold the baffle in place. The assembly position and size of the above parts can be designed according to the actual situation of the product.
06 Welding Tooling
Welding tooling is mainly fixed in the position of the parts of the welding assembly, control the relative size of the parts of the welding assembly, its structure is mainly positioning block, need to be designed according to the actual structure of the product. It is worth noting that the sealing space shall not be created between the welding tooling when the product is placed on the welding tooling to prevent the excessive pressure of the sealing space during the welding heating process from affecting the size of the parts after welding.
07 Polishing fixture
08 Assembly tooling
Assembly tooling is mainly used in the assembly of components in the process of auxiliary positioning device. The design idea is that according to the assembly structure of the components, the product can be easily picked up and put off. During the assembly process, the appearance surface of the product can not be damaged. During the use process, the product can be protected by covering with cotton cloth. In the selection of materials above as far as possible with white glue and other non-metallic materials.
09 pad printing, laser lettering tooling
Design points: according to the actual situation of the product engraving requirements to design the positioning structure of the tooling, it is necessary to pay attention to the convenience of the product to take and put, and the protection of the product appearance, positioning block and the auxiliary positioning device in contact with the product as far as possible to use white glue and other non-metallic materials.