Basic knowledge of fixture design

The design of fixture is generally in accordance with the specific requirements of a process after the formulation of the machining process of parts. The possibility of fixture realization should be taken into full consideration in the formulation of the process, and when designing the fixture, modification suggestions can be put forward to the process if necessary. Fixture design quality of the level, should be stable to ensure the workpiece processing quality, high production efficiency, low cost, convenient chip removal, safe operation, labor saving and manufacturing, maintenance easy for its measurement indicators.

1, 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 bearing or clamping strength to ensure that the workpiece in the fixture on the processing process;

3, meet the clamping process of simple and fast operation;

4, vulnerable parts must be able to quickly replace the structure, when the conditions are sufficient, it is best not to use other tools;

5, 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.

2. Basic knowledge of fixture design

A good machine tool fixture must meet the following basic requirements:

1, ensure the machining accuracy of the workpiece. The key to ensure the machining accuracy lies in the correct selection of positioning datum, positioning method and positioning components, positioning error analysis is necessary, but 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, improve production efficiency. The complexity of special fixture should be compatible with the capacity, should try to use a variety of fast and efficient clamping mechanism, to ensure convenient operation, shorten the auxiliary time, improve production efficiency.

3, good process performance. Special fixture structure should strive to be simple, reasonable, easy to manufacture, assembly, adjustment, inspection, maintenance and so on.

4, good performance. Fixture should have enough strength and stiffness, operation should be simple, labor-saving, safe and reliable. Under the premise of objective conditions and economic applicability, pneumatic, hydraulic and other mechanical clamping devices should be used as far as possible to reduce the labor intensity of operators. Fixture should also be convenient chip removal. When necessary, the chip removal structure can be set up to prevent the chip from destroying the positioning of the workpiece and damaging the tool, and prevent the chip from accumulating 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 for simple structure and easy manufacturing, in order to reduce the manufacturing cost of fixture. Therefore, the design should be based on the order and capacity of the fixture scheme for the necessary technical and economic analysis, in order to improve the fixture in the production of economic benefits.

3, the standardization of fixture design overview

1. Basic methods and steps of fixture design

Preparation before design The original information of fixture design includes the following:

(1) Design the technical data such as the notice, the finished part drawing, the blank drawing and the process route, understand the processing technical requirements of each process, the positioning and clamping scheme, the processing content of the previous process, the blank situation, the machine tool, the tool and the measuring tool used in the processing, the processing allowance and the cutting amount, etc.;

(2) Understand the production batch and the requirements of fixtures;

(3) Understand the main technical parameters, performance, specifications, accuracy of the machine tool used and the size of the connection with the structure of the fixture;

(4) Standard material inventory of fixtures.

2, fixture design considerations

Fixture design general structure is single, giving people the feeling that the structure is not very complex, especially now the popularity of hydraulic fixture, so that its original mechanical structure is greatly simplified, but if the design process is not considered in detail will inevitably appear unnecessary trouble:

(1) the blank allowance of the processed workpiece. The blank size is too large, resulting in interference. So before the design must prepare blank map. Leave plenty of space.

(2) Chip discharge smoothness of fixture. Design due to the limited processing space of machine tools, fixture is often designed space is relatively compact, then often will ignore in the process of processing iron filings in the fixture dead corner deposit, including chip fluid flow is not smooth, to bring a lot of trouble later processing. So in the beginning of the actual process should be considered in the process of the problem, after all, fixture is to improve efficiency, convenient operation for this.

(3) The overall openness of the fixture. Ignore the open, causing the operator to install the card difficult, time-consuming and laborious, design taboo.

(4) Basic theoretical principles of fixture design. Each set of fixtures should experience countless times of clamping, loosening action, so may be able to meet user requirements at the beginning, but the addition should have its precision retention, so do not design something that goes against the principle. Even if luck works right now, it won't last long. A good design should be tempered by time.

(5) replaceable positioning components. The positioning element is badly worn, so it should be considered fast 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 actual application is another thing, so good design is a continuous accumulation and summary of the process.