Design points of special clamps for fixture tooling

The fixture design is generally carried out according to the specific requirements of a particular process after the machining process of the part is formulated. When formulating the process, it should fully consider the possibility of fixture realization, and when designing the fixture, if necessary, can revise the process. The design quality of the fixture should be measured by whether it can stably guarantee the processing quality of the work-piece, high production efficiency, low cost, convenient chip removal, safe operation, labor-saving, and easy manufacturing and maintenance.

Basic principles of fixture design

1. Satisfy the stability and reliability of work-piece positioning during use;

2. There is enough load-bearing or clamping force to ensure the processing of the work-piece on the fixture;

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

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

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

6. Avoid complex structures and high costs as much as possible;

7. Use standard parts as much as possible;

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

Basic knowledge of fixture design

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

1. The key to ensuring the machining accuracy of the work-piece is to correctly select the positioning datum, positioning method, and positioning components. If necessary, it is necessary to analyze the positioning error. It is also necessary to pay attention to the influence of the structure of other parts in the fixture on the machining accuracy. Influence to ensure that the fixture can meet the machining accuracy requirements of the work-piece.

2. The complexity of the particular fixture for improving production efficiency to the production capacity. Should use various fast and efficient clamping mechanisms as much as possible to ensure convenient operation, shorten the additional time and improve production efficiency.

3. The structure of the particular fixture should be reasonable and straightforward, and it should be easy to manufacture, assemble, adjust, inspect and maintain.

4. The tooling fixture with good performance should have sufficient strength and rigidity, and the operation should be simple, labor-saving, safe, and reliable. Under the premise of objective conditions and should use the economical application, pneumatic, hydraulic, and other mechanized clamping devices as much as possible to reduce the operator's labor intensity.

The tooling fixture should also be convenient for chip evacuation. If necessary, a chip removal structure can be set up to prevent chips from damaging the positioning of the work-piece and damaging the tool, and prevent the accumulation of chips from bringing a lot of heat and causing deformation of the processing system.

5. Good economy The particular fixture should use standard components and structure as much as possible and strive to be simple in structure and easy to manufacture to reduce the manufacturing cost of the fixture. 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 fixture's economic benefits in production.

An overview of the standardization of fixture design

Basic methods and steps of fixture design

Preparation before design The source material for fixture design includes the following:

a) Technical information such as design notice, finished part drawing, blank drawing, and process route, understanding the technical processing requirements of each process, positioning and clamping plan, processing content of the previous process, blank condition, machine tools, and 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, accuracy of the machine tool used, and the size of the connection with the structure of the fixture connection;

d) Standard stock of fixtures.

Problems to be considered in the design of tooling fixtures

The structure of the fixture design is generally single, and the structure is not very complicated. Especially now that the hydraulic fixture is widespread, its original mechanical structure is greatly simplified. Still, if it is not considered in detail in the design process; unnecessary troubles will inevitably occur:

a) The blank allowance of the work-piece. Cause the blank size is too large, resulting in interference. So be sure to prepare the rough drawing before designing. Leave enough space.

b) The chip removal smoothness of the fixture fixture.

During the design, due to the limited processing space of the machine tool, the fixture is often designed with relatively compact space. At this time, it is often ignored that the iron filings generated during the machining process are accumulated in the dead corner of the fixture, including the poor flow of the cutting fluid, which will use later.

Processing brings a lot of trouble. Therefore, should consider problems in the processing process at the beginning of practice. 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, labor-intensive, and design taboo.

d) Basic theoretical principles of fixture design. Each set of fixtures has to undergo numerous clamping and loosen actions so that it may meet the user's requirements at the beginning. Still, the fixture should have its accuracy retention, so don't design something that goes against the principle. Even if you can get away with it right now, it won't last long. A good design should stand the test of time.

e) Replace-ability of positioning elements. The positioning elements are seriously worn and should consider a quick and easy replacement. It is best not to design into more prominent parts.

The accumulation of fixture design experience is significant. Sometimes design is one thing, but it is another thing in practical application, so good design is a process of continuous accumulation and summarization.

Commonly used tooling fixtures are mainly divided into the following types according to their functions:

01 Clamp

02 Drilling and milling tooling

03CNC, instrument chuck

04Gas test, water test tooling

05 Trimming and punching tooling

06Welding tooling

07 Polishing jig

08 Assembly tooling

09 Pad printing, laser engraving tooling

01 Clamp

Definition: a tool for positioning and clamping with the product shape

Design Points:

1. This type of clamping die is mainly used on the vice, and its length can be cut off as needed;

2. Other auxiliary positioning devices can be designed on the clamping die, and the clamping die is generally connected by welding;

3. The above picture is a schematic diagram, and the specific situation determines the size of the cavity structure;

4. Fit the locating pin with a diameter of 12 in the proper position on the movable die, and the locating hole at the corresponding position of the fixed die is slidably fitted with the locating pin;

5. When designing the assembly cavity, it is necessary to offset and enlarge 0.1mm based on the outline surface of the blank without shrinkage.

02 Drilling and milling tooling

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 schematic diagram of the structure, and the actual situation needs to be designed according to the product structure;

3. The product size and the force determine the cylinder during processing, and SDA50X50 is commonly used;

03 CNC, instrument chuck

A CNC chuck

Inner bundle chuck

Design Points:

1. The size not marked in the above picture is determined according to the inner hole size structure of the actual product;

2. The outer circle that is in contact with the inner hole of the product needs to leave a margin of 0.5mm on one side during production, and finally installed on the CNC machine tool and finished turning to size to prevent deformation and eccentricity caused by the quenching process;

3. The material of the assembly part is recommended to use spring steel, and the tie rod part is 45#;

4. The thread M20 of the tie rod part is a common thread, which can adjust according to the actual situation

In-instrument collet

Design Points:

1. The above picture is a reference diagram; the assembly size and structure are determined according to the actual product size and structure;

2. The material is 45#, quenched.

Instrument outboard collet

Design Points:

1. The above picture is for reference, and the actual size depends on the inner hole size structure of the product;

2. The outer circle that is in contact with the inner hole of the product needs to leave a margin of 0.5mm on one side during production, and finally installed on the instrument lathe and finished turning to size to prevent deformation and eccentricity caused by the quenching process;

3. The material is 45#, quenched.

04 Gas test tooling

Design Points:

1. The above picture is a reference drawing of the gas test tooling. The specific structure needs to be designed according to the actual structure of the product. The idea is  the simplest way possible to sell the product, so it needs to  test, and the seal is filled with gas to confirm its tightness;

2. Can adjust the size of the cylinder  according to the actual size of the product, and it is also necessary to consider

der whether the stroke of the cylinder can meet the convenience of picking and placing the product;

3. The sealing surface in contact with the product is generally made of materials with good compressions, such as Uli glue, NBR rubber ring, etc. At the same time, pay attention to the use of white glue-type plastic blocks if there are any positioning blocks in contact with the appearance surface of the product. Cover with a cotton cloth to prevent bumping the appearance of the product;

4. Should consider the positioning direction of the product in the design to prevent the gas leakage from being trapped in the product cavity and false detection.

05 Punching tooling

Design points: The above picture shows the typical structure of punching tooling. The bottom plate is used to facilitate fixing on the workbench of the punching machine; the positioning block is used to fix the product. The specific structure is designed according to the actual situation of the product, and the center point is around the product, which can be quickly and safely taken and placed; the baffle plate is used to facilitate the separation of the product from the punching knife. ; The pillar acts as a fixed baffle. Design the assembly position and size of the parts mentioned above and the actual situation of the product.

06Welding tooling

The welding tool is mainly used to fix the position of each component in the welding assembly and control 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 tool, it is not allowed to create a sealed space between the tooling to prevent excessive pressure in the sealed space during the welding healing process and affect the size of the parts after welding.

07 Polishing jig

Hand polished mold and handle

08 Assembly tooling

Assembly tooling is mainly used as a device to assist positioning in the assembly process of components. The design idea is that the product can be quickly taken and placed according to the structure of the assembly, cannot damage the appearance surface of the product during the assembly process, and can be covered with a cotton cloth to protect the product during use. In selecting materials, try to use non-metallic materials such as white glue.

09 Pad printing, laser engraving tooling

Design points: Design the positioning structure of the tooling according to the lettering requirements of the actual situation of the product. Pay attention to the convenience of product handling and the protection of product appearance. The positioning block and the auxiliary positioning device in contact with the product should use non-metallic materials such as white glue as much as possible.