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 the realization of the fixture should be fully considered, and when designing the tooling fixture, if necessary, the process can also be modified. The design quality of the tooling fixture should be measured by whether it can stably ensure 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 fixture design

1. Meet the stability and reliability of workpiece positioning during use;

2. There is enough bearing or clamping force to ensure the processing of the workpiece on the fixture;

3. Satisfy the simple and fast operation in the clamping process;

4. The vulnerable parts must be a structure that can be quickly replaced, and it is best not to use other tools when the conditions are sufficient;

5. Meet the reliability of repeated positioning of the fixture during adjustment or replacement;

6. Avoid complex structure and expensive cost as much as possible;

7. Use standard parts as components as much as possible;

8. Form the systematization and standardization of the company's internal products.

2. Basic knowledge of fixture design

An excellent machine tool fixture must meet the following basic requirements:

1. Ensure the machining accuracy of the workpiece The key to ensuring the machining accuracy is to correctly select the positioning reference, positioning method and positioning components. If necessary, it is necessary to carry out positioning error analysis, and also pay attention to the structure of other parts in the fixture on the machining accuracy. To ensure that the fixture can meet the machining accuracy requirements of the workpiece.

2. The complexity of the special fixture for improving production efficiency should be adapted to the production capacity, and various fast and efficient clamping mechanisms should be used as much as possible to ensure convenient operation, shorten auxiliary time, and improve production efficiency.

3. Good process performance The structure of the special fixture should be simple and reasonable, which is convenient for manufacture, assembly, adjustment, inspection and maintenance.

4. Good performance Tooling fixtures should have sufficient strength and stiffness, and the operation should be simple, labor-saving, safe and reliable. Under the premise of allowing objective conditions and being 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. Tooling fixtures should also be convenient for chip removal. If necessary, a chip removal structure can be set to prevent chips from destroying the positioning of the workpiece and damaging the tool, and to prevent the accumulation of chips from causing a large amount of heat and causing deformation of the process system.

5. Good economy Special fixtures should use standard components and standard structures as much as possible, and strive to be simple in structure and easy to manufacture, so as to reduce the manufacturing cost of fixtures. Therefore, the necessary technical and economic analysis of the fixture scheme should be carried out according to the order and production capacity in the design to improve the economic benefits of the fixture in production.

3. Overview of the standardization of fixture design

1. Basic methods and steps of fixture design

Preparation before design The original data for fixture design includes the following:

A) Technical data such as design notice, finished part drawing, blank drawing and process route, understand the processing technical requirements of each process, positioning and clamping plan, processing content of the previous process, blank situation, machine tools, tools used in processing, Inspection measuring tools, machining allowance and cutting amount, etc.;

B) Understand the production batch and the need for fixtures;

C) Understand the main technical parameters, performance, specifications, precision of the machine tool used, as well as the contact size with the structure of the connecting part of the fixture;

D) The stock of standard materials for fixtures.

2. Issues considered in the design of fixtures

The fixture design is generally single in structure, giving the impression that the structure is not very complicated, especially now that the hydraulic fixture is popular, the original mechanical structure is greatly simplified, but if the design process is not considered in detail, unnecessary troubles will inevitably occur:

A) The blank margin of the workpiece. Causes the blank size to be too large, resulting in interference. So be sure to prepare a blank drawing before designing. Leave enough space.

B) The smoothness of chip removal of the fixture. Due to the limited processing space of the machine tool during the design, the fixture is often designed with a relatively compact space. At this time, it is often ignored that the iron filings generated during the processing process will accumulate at the dead corner of the fixture, including the poor outflow of the chip fluid, which will give rise to future processing. bring a lot of trouble. Therefore, the problems in the processing process should be considered at the beginning of the actual situation. After all, the fixture is based on improving efficiency and facilitating operation.

C) The 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 the design is taboo.

D) The basic theoretical principles of fixture design. Each set of fixtures has to go through countless clamping and loosening actions, so it may meet the user's requirements at the beginning, but the fixture should have its accuracy retention, so don't design something that goes against the principle. Even if you are lucky enough to be able to do it now, it will not last long. A good design should be tempered by time.

E) Replaceability of positioning elements. The positioning components are severely worn, so quick and convenient 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 it is another thing in practical application, so good design is a process of continuous accumulation and summary.

Commonly used fixtures are mainly divided into the following categories according to their functionality:

01: Clamp 02: Drilling and milling tooling

03: numerical control, instrument chuck 04: gas test, water test tooling

05: Trimming and punching tooling 06: Welding tooling

07: Polishing jig 08: Assembly tooling

09: Pad printing, laser lettering tooling