The design of tooling fixtures is generally carried out according to the specific requirements of a certain process after the machining process of the parts is formulated. When formulating the process, the possibility of fixture implementation should be fully considered. When designing the tooling fixture, you can also propose modifications to the process if necessary. The design quality of tooling fixtures should be measured by whether it can stably guarantee the processing quality of the workpiece, high production efficiency, low cost, convenient chip removal, safe operation, labor saving and easy manufacturing and maintenance.
1. Basic principles of tooling fixture design
1. Meet the stability and reliability of workpiece positioning during use;
2. There is sufficient load-bearing or clamping strength to ensure the processing of the workpiece on the fixture;
3. Meet the simple and fast operation during the clamping process;
4. Wearable parts must be of a structure that can be quickly replaced. It is best not to use other tools when conditions are sufficient;
5. Meet the reliability of repeated positioning of the fixture during adjustment or replacement;
6. Avoid complex structures and expensive costs as much as possible;
7. Use standard parts as component parts as much as possible;
8. Form the systematization and standardization of the company's internal products.
2. Basic knowledge of tooling and fixture design
An excellent machine tool fixture must meet the following basic requirements:
1. To ensure the machining accuracy of the workpiece, the key to ensuring the machining accuracy lies in correctly selecting the positioning reference, positioning method and positioning components. If necessary, it is also necessary to conduct positioning error analysis. It is also necessary to pay attention to the impact of the structure of other parts in the fixture on the machining accuracy. influence to ensure that the fixture can meet the processing accuracy requirements of the workpiece.
2. To improve production efficiency, the complexity of special fixtures should be adapted to the production capacity. Various fast and efficient clamping mechanisms should be used as much as possible to ensure easy operation, shorten auxiliary time, and improve production efficiency.
3. The structure of special fixtures with good process performance should be simple and reasonable to facilitate manufacturing, assembly, adjustment, inspection, maintenance, etc.
4. Work fixtures with good performance should have sufficient strength and rigidity, and should be easy, labor-saving, safe and reliable to operate. As long as objective conditions permit and it is economical and applicable, pneumatic, hydraulic and other mechanized clamping devices should be used as much as possible to reduce the labor intensity of the operator. The tooling fixture should also facilitate chip removal. If necessary, a chip removal structure can be set up to prevent chips from damaging the positioning of the workpiece and damaging the tool, and to prevent the accumulation of chips from bringing a large amount of heat and causing deformation of the process system.
5. Special fixtures with good economy should use standard components and standard structures as much as possible, and strive to have simple structures and easy manufacturing to reduce the manufacturing cost of the fixture. Therefore, the necessary technical and economic analysis of the fixture solution should be carried out based on the order and production capacity during design to improve the economic benefits of the fixture in production.
3. Overview of standardization of tooling and fixture design
1. Basic methods and steps of tooling and fixture design
Preparation before design The original data for tooling and fixture design include the following:
a) Design notice, finished part drawings, rough drawings and process routes and other technical information, understand the processing technical requirements of each process, positioning and clamping scheme, processing content of the previous process, rough condition, machine tools and tools used in processing , Inspection measuring tools, machining allowances and cutting quantities, etc.;
b) Understand the production batch size and the need for fixtures;
c) Understand the main technical parameters, performance, specifications, accuracy, and dimensions related to the structure of the fixture connection part of the machine tool used;
d)Standard material inventory of fixtures.
2. Issues to consider in the design of tooling fixtures
The clamp design generally has a single structure, which gives the impression that the structure is not very complicated. Especially now the popularity of hydraulic clamps has greatly simplified the original mechanical structure. However, if detailed considerations are not taken during the design process, unnecessary troubles will inevitably occur:
a) The blank margin of the workpiece to be processed. The size of the blank is too large and interference occurs. Therefore, you must prepare rough drawings before designing. Leave plenty of space.
b) Smooth chip removal of the fixture. Due to the limited processing space of the machine tool during design, the fixture is often designed in a relatively compact space. At this time, it is often ignored that the iron filings generated during the processing process accumulate in the dead corners of the fixture, including the poor outflow of the cutting fluid, which will cause problems in the future. Processing brings a lot of trouble. Therefore, problems arising during the processing should be considered at the beginning of practice. After all, the purpose of fixtures is to improve efficiency and facilitate operation.
c) Overall openness of the fixture. Ignoring the openness makes it difficult for the operator to install the card, which is time-consuming and labor-intensive, and is a taboo in the design.
d) Basic theoretical principles of fixture design. Each set of fixtures has to go through countless clamping and loosening actions, so it may be able to meet user requirements at the beginning, but the fixture should maintain its accuracy, so don't design something that goes against the principle. Even if it is possible right now, it will not last long. A good design should stand the test of time.
e) Replaceability of positioning components. The positioning components are severely worn, so quick and easy replacement should be considered. It is best not to design into larger parts.
The accumulation of fixture design experience is very important. Sometimes design is one thing and practical application is another, so good design is a process of continuous accumulation and summary.
Commonly used work fixtures are mainly divided into the following categories according to their functionality:
01 clamp mold
02Drilling and milling tooling
03CNC, instrument chuck
04 Gas testing and water testing tooling
05Trimming and punching tooling
06Welding tooling
07Polishing jig
08Assembly tooling
09 Pad printing, laser engraving tooling
01 clamp mold
Definition: A tool for positioning and clamping based on product shape
picture
Design Points:
1. This type of clamp is mainly used in vise, and its length can be cut as needed;
2. Other auxiliary positioning devices can be designed on the clamping mold, and the clamping mold is generally connected by welding;
3. The above picture is a simplified diagram, and the size of the mold cavity structure is determined by the specific situation;
4. Fit the locating pin with diameter 12 at the appropriate position on the movable mold, and the positioning hole at the corresponding position of the fixed mold slides to fit the locating pin;
5. The assembly cavity needs to be offset and enlarged by 0.1mm based on the outline surface of the non-shrunk blank drawing when designing.
02Drilling and milling tooling
picture
Design Points:
1. If necessary, some auxiliary positioning devices can be designed on the fixed core and its fixed plate;
2. The above picture is a simplified structural diagram. The actual situation requires corresponding design according to the product structure;
3. The cylinder depends on the size of the product and the stress during processing. SDA50X50 is commonly used;
03CNC, instrument chuck
A CNC chuck
Toe-in chuck
picture
Design Points:
1. The dimensions not marked in the above picture are based on the inner hole size structure of the actual product;
2. The outer circle that is in positioning contact with the inner hole of the product needs to leave a margin of 0.5mm on one side during production, and is finally installed on the CNC machine tool and finely turned to size to prevent deformation and eccentricity caused by the quenching process;
3. It is recommended to use spring steel as the material for the assembly part and 45# for the tie rod part;
4. The thread M20 on the tie rod part is a commonly used thread, which can be adjusted according to the actual situation.
Instrument toe-in chuck
picture
Design Points:
1. The above picture is a reference diagram, and the assembly dimensions and structure are based on the actual product's dimensions and structure;
2. The material is 45# and quenched.
Instrument external clamp
picture
Design Points:
1. The above picture is a reference diagram, and the actual size depends on the inner hole size structure of the product;
2. The outer circle that is in positioning contact with the inner hole of the product needs to leave a margin of 0.5mm on one side during production, and is finally installed on the instrument lathe and finely turned to size to prevent deformation and eccentricity caused by the quenching process;
3. The material is 45# and quenched.
04 Gas testing tooling
Design Points:
1. The picture above is a reference picture of the gas testing tooling. The specific structure needs to be designed according to the actual structure of the product. The idea is to seal the product in the simplest way possible, so that the part to be tested and sealed is filled with gas to confirm its tightness;
2. The size of the cylinder can be adjusted according to the actual size of the product, and it is also necessary to consider whether the stroke of the cylinder can meet the convenience of picking up and placing the product;
3. The sealing surface in contact with the product is generally made of materials with good compression capacity such as Uni glue and NBR rubber rings. At the same time, please note that if there are positioning blocks that are in contact with the appearance surface of the product, try to use white glue plastic blocks and use them during use. Cover the middle cover with cotton cloth to prevent damage to the appearance of the product;
4. The positioning direction of the product must be considered during design to prevent leakage of gas from being trapped inside the product cavity and causing false detection.
05Punching tooling
Design points: The picture above shows the common structure of punching tooling. The bottom plate is used to fix the workbench of the punch machine easily; the positioning block is used to fix the product. The specific structure is designed according to the actual situation of the product. The center point is surrounded by the center point to facilitate the safe and convenient picking and placing of the product; the baffle is used to facilitate the separation of the product from the punching knife. ; The pillars serve as fixed baffles. The assembly positions and sizes of the above parts can be designed according to the actual conditions of the product.
06Welding tooling
The welding tooling mainly fixes the position of each component in the welding assembly and controls the relative size of each component in the welding assembly. Its structure is mainly a positioning block, which needs to be designed according to the actual structure of the product. It is worth noting that when the product is placed on the welding tooling, a sealed space must not be created between the tooling to prevent excessive pressure in the sealed space from affecting the size of the parts after welding during the welding and heating process.
