Checking Fixture
The checking fixture mainly measures various specified shapes of fixtures such as surfaces, holes, shafts, gears, etc. There are two main types of fixture inspection fixtures: one is to measure the surface of the fixture inspection fixture and check the flatness of the workpiece; Another type is the hole fixture inspection fixture, which checks the position and size of part holes.
What is Fixture Testing？
Fixture testing is a type of precision mechanical manufacturing equipment. Because checking fixture is specialized and high-tech precision testing equipment with added value, they mainly have high precision and high surface quality requirements. The purpose is to ensure the quality of the product, improve the surface quality of the product, and have high requirements for relative positional accuracy between relevant structural components.
Structural Design of Automotive Fixture Testing
The structural design of automotive fixture testings includes determining the positioning scheme, clamping scheme, product placement scheme, bottom plate material, material and heat treatment, detection scheme, and determining the positioning device. The overall structural design plays a crucial role in the design of automotive fixture testings, taking into account the selection of standard components, design assembly, operation and maintenance, usage time, as well as the efficiency, safety, and reliability of production work.
The overall structural design of automotive fixture testing must consider analytical functions that can meet the requirements of product and process quality. For example, the function of automotive fixture testing is to meet the requirements of product quality, such as the product fitting surface, sealing surface, sealing surface, and fitting position.
It is necessary to meet the requirements of standards, such as the shape and size of the product, as well as various considerations such as processing methods and manufacturing measurement techniques. Design from the perspectives of operation and users, such as installation methods, inspection of parts to be inspected, and implementation of measurement methods, to avoid affecting the repeatability of inspection during the operation process. Emphasis is placed on the need for later maintenance and replacement of workpieces, to improve the structural design of automotive fixture testings. The basic requirements for the structural design of automotive fixture testing are as follows.
- The Overall Structure of the Fixture Testing Should Have Stability and Balance
1.The overall structure should be as simple as possible and easy to operate. If the structure is as simple and lightweight as possible while meeting functional requirements, product quality can be improved, and the usage time of fixture testing can be increased, effectively improving accuracy.
2.The thickness of the overall structure should meet the requirements, and the thickness should not be too thin, otherwise it will have an impact. There is a standard strength to meet accuracy and usage time requirements.
3.The overall structure should not have too many convex and concave parts, and stress should not be concentrated, otherwise it will cause the workpiece to fracture.
4.The overall external dimensions should be within the range of error, and the measuring tool components must be within the range of the base of the measuring tool in their working position. It is necessary to ensure that the measuring tool is easy to move, facilitate the retrieval and placement of components, and ensure smooth clamping actions.
- The Structure Has High Strength and Sufficient Rigidity
1.The installed components are sturdy and reliable. Under the premise of ensuring mechanical performance, reducing the impact of gravity on the accuracy of the measuring tool is generally done by opening weight-reducing holes or process grooves.
2.The structure has high stiffness, and high reliability, and is not prone to shape changes, which is conducive to improving the geometric and positional accuracy during assembly measurement, and can meet the normal use time. Generally, lightweight and high-quality manufacturing are used in design.
3.To have sufficient load-bearing capacity, the supporting and connecting components must meet the standard thickness and larger contact area.
4.The material selected for the working components of the fixture testing has the characteristics of high hardness, good toughness, and high wear resistance.
- Strong Universality and Good Structural Interchangeability
1.The operation of the fixture testing has convenient, safe, and reliable performance and high detection efficiency. Even in frequent use, the fixture testing can still maintain high-precision operation.
2.The selected standard components are universal components that are convenient to purchase in the market, including corner frames, hinges, guide plates, etc., or use high-standard fixture testing structures or standard structures.
3.Workpieces can be replaced in a short period, and each part should be accurately and reliably installed with firmness.
4.Easily damaged parts are easy to disassemble, install, and maintain, with good positional accuracy and repeatability.
The Assembly Method of Fixture Testing
There are many assembly methods for fixture testings, which are determined based on factors such as the assembly accuracy requirements, processing conditions, structural design, precision, and manufacturing requirements of different fixture testings. In most cases, the assembly accuracy of fixture testing is closely related to the accuracy of fixture testing parts. If the assembly accuracy of the fixture testing is higher, the accuracy of the fixture testing parts will be higher. However, a reasonable assembly method is to choose according to the actual requirements of the fixture manufacturing. Choosing a reasonable assembly method has played a major role in the assembly of fixture testings, enabling the assembly of high-precision fixture testings with lower-precision parts.
The assembly method of fixture testings and the assembly method of molds have similarities, with general process methods such as interchangeable assembly. The production of fixture testings is used for single-piece small batch production, with the characteristics of complete sets and high assembly accuracy. So, currently, the commonly used methods for fixture assembly are repair and exchange assembly. In the future, if modular fixture standard parts are used, the exchange assembly method will be more commonly used. Whether it is the repair method or the exchange assembly method, try to minimize the occurrence of benchmark problems, and if problems occur, they should be resolved promptly. To ensure the assembly and measurement of the fixture testing have good processability, it is necessary to operate by the requirements, with the basic surface of the fixture testing as the unified benchmark, to improve the manufacturing accuracy of the fixture testing during assembly and measurement.
Interchange assembly method
Interchange assembly method: During assembly, after processing each matching part, the manufacturing tolerance must be within the range. A method of achieving assembly accuracy without the need for adjustment, selection, or adjustment.
The characteristic of this method is that the quality of the assembled parts is stable and reliable, easy to assemble, and has high production efficiency, but it requires high machining accuracy of the parts. The interchangeability of components is aimed at improving organizational assembly and automated assembly and is a practical and advanced assembly method. Therefore, this method should be prioritized.
The complete exchange assembly method refers to the method of achieving assembly accuracy by directly assembling various parts without selection, repair, and adjustment during the assembly of fixture testings. This method has the characteristics of simple assembly work, high quality, high production efficiency, simple operation technology, and convenient fixture testing maintenance. This assembly method has limitations in fixture assembly and is mostly suitable for large-scale automation equipment and other machine manufacturing industries. If high assembly accuracy is required, the tolerance range required for each part is relatively small, which will increase the difficulty of part processing.
Assembly Content of Fixture Testing
The quality of fixture assembly plays a crucial role in the overall quality of the fixture, ensuring that it has the prescribed repair accuracy, predetermined usage functions, and quality requirements. It is necessary to operate according to the requirements. If the assembly is improper, the assembly task is not valued, and the assembly is not carried out according to the process and technical requirements, even if the quality of the replacement and repair parts is qualified, it may not be possible to assemble intact fixture testings. The work of fixture assembly is very important and requires careful attention. It is necessary to carefully follow the fixture assembly design diagram and design reasonable assembly process procedures.
The assembly of automotive fixture testing mainly includes two aspects: the first aspect is to assemble the processed fixture testing parts as a whole according to the drawing requirements. The second aspect is to make partial adjustments or supplementary processing during the assembly process. Mainly includes component assembly, adjustment, and repair.
Component connection and fixation:During the assembly process of automotive fixture testings, individual parts need to be fixed through a large number of connection combinations. The connection methods can be divided into two types, such as detachable connection and nondetachable connection.
The commonly used detachable connection is a pin connection. Welding is used for nonremovable connections. It is necessary to connect and fix the fixture testing to become whole, improve the firmness of the system, and effectively ensure normal use function.
Preparation, adjustment, and calibration:Matching refers to drilling and grinding, which are additional steps for fitters and mechanical processing in the assembly of fixture testings. Drilling is mainly used for threaded connections, and grinding is mostly used on the joint surface of the motion pair. In general, coordination is carried out in combination with calibration and adjustment.
Adjustment is the specific adjustment work carried out during the assembly process of the fixture testing to ensure the mutual position, fit clearance, and tightness of the relevant parts, as well as the adjustment of the clearance of the moving pair to ensure the motion accuracy of the moving parts. Its purpose is to coordinate the work of the fixture testing or machine.
Correction refers to the preliminary inspection of the relative positions of relevant parts through the overall design drawing, and the adjustment of some inaccurate positions. Leveling and corresponding adjustment work are generally applied in the assembly of basic components of large fixture testings.
Check the fitting dimensions of matching parts:During assembly, it is important to perform retesting or spot checks on certain important mating dimensions. If it is necessary to know the actual fit clearance or interference, the connection of interference fit is generally not removed and reassembled after assembly, so the accuracy of the actual interference amount should be highly valued in pre-inspection.
Automobile fixture testing is mainly used in single-piece products and small-batch production. The function of specialized fixture testing is to provide testing process equipment for large-scale production. Generally, each pair of fixture tests corresponds to a specific product. Place the product on the inspection fixture and visually inspect the surface and shape of the product using a stop fixture testing or caliper.
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