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Discussion on the basic principles of selecting measuring instruments for machined parts

With the development and progress of society, machining and production in the process of social and economic development occupies an increasingly large influence, and thanks to the development of social industry, the production and development needs of various social industries can be met. From the analysis of machining, for a component processing and production process, its quality is the most critical, and how to protect the quality of production and processing, it is necessary to use the relevant measuring instruments to do a good job of measuring and production specifications control, so that processing and production can be more standardized, more reasonable, more efficient, and ultimately improve the economic benefits of enterprise production. Therefore, based on this paper, the basic principles of the selection of measuring instruments for machined parts are discussed. The overall first from the selection of measuring instruments considerations, and then to elaborate and analyze the use of measuring instruments considerations, and finally is to put forward the basic principles of the selection of machined parts measuring instruments.

20230305122908 36191 - Discussion on the basic principles of selecting measuring instruments for machined parts

1. The basic principles of selecting measuring instruments for machined parts

(A) the size of the part, surface quality and material properties
For the selected measuring apparatus, it is necessary to ensure that the measurement range is larger than the size of the parts, so that the parts can be measured effectively. At the same time, the surface quality and material properties of different parts are also different, so in the process of selecting measuring instruments, more practical consideration should be given to the quality of the material surface, if the surface quality of the parts is good, then choose to use high-precision measuring instruments, if the surface quality is slightly poor, then avoid the use of high precision measuring instruments. And the nature of the material itself will also show the characteristics of hard and soft, according to the actual hard and soft degree to choose the measurement strength of measuring instruments, so as to complete the measurement, but also to protect the quality of the parts are not destroyed.
(B) Parts processing process specifications and production batch
The actual choice of measuring instruments, also need to be based on the actual parts of the processing specifications and production batch how much to decide. If the mass production of parts, in the absence of special processing and measurement requirements, you can choose the common measuring instruments to complete the measurement, if there are special processing requirements and measurement needs of the parts, it is necessary to choose the corresponding measuring instruments to complete the measurement, so as to ensure the measurement effect. For example, small batch production of L = 80mm parts using a 150mm Vernier caliper, but to mass production, you need special inspection fixtures and gauges to improve the efficiency and accuracy of measurement. In addition, different weights and parts structure of the workpiece also need to use different measurement methods, for some small lightweight parts using length measuring machine calibration can be, but the weight of large, complex parts need to use the level measurement.
(C) Clarify the error of the measuring apparatus itself
For the production of parts for measurement work, in the process of selecting the corresponding measuring apparatus, it is necessary to seriously consider and clarify the error of each measuring apparatus itself, so as to make a good choice on the basis of advance understanding, to avoid the impact of the final measurement accuracy due to the unclear information on the error. Different processing needs and the use of standard parts have different error standards, which is related to the production scale of the workpiece, the degree of refinement, some production scale is small, precision is not high parts, production caused by the error will certainly be large, but the mass production and measuring instruments error is small workpiece, its production error is small, production staff need to be based on their own production needs, the error control within a reasonable range, the use of gauges It is also important to use gauges with errors within the allowable range of production.
(D) The range of measuring instruments
Specifically, the measuring instruments are divided into working range and effective range, so whether the selected measuring instruments can meet the needs of the measured parts need to be carefully analyzed to ensure that the working range and effective range of its measurement meet the measurement needs of the parts, so as to effectively complete the measurement work. All workpiece production should be established on the basis of accurate and standardized, and if the problem of insufficient range of measuring instruments should be solved in time to avoid the impact of the range on the accuracy of the production workpiece itself.

2. The use of measuring instruments precautions

(A) The use of safety aspects and measurement before the parts clean up
In the process of measuring the relevant processing parts on the machine tool, the machine tool and the processed parts must be guaranteed to be completely stable before measuring, so that the purpose of two, one is to ensure the safety and stability of the measurement work, to avoid the negative impact of the actual work because of the instability of the measurement tool, if placed unstable, may cause inaccurate measurement, or because of the placement of unstable personal safety of the measurement personnel The second is to reduce the wear and tear of the moving parts on the measuring instruments, thus reducing the accuracy of their measurement. Therefore, the use of safety issues need to be taken seriously.
Before the measurement of the relevant parts, the parts to be measured surface and the surface of the measuring apparatus need to be effectively cleaned, the surface will be clean of debris, to avoid the existence of fine debris affect the accuracy of the measurement, especially for some high-precision measuring apparatus and the need for high-precision measurement of the parts, more attention needs to be paid to the clean-up work before the measurement.
(B) Storage and special tools for measuring instruments
Regarding the use and storage of measuring instruments, the specific measuring instruments should be placed in the special apparatus box. Avoid placing together with other tools and equipment. Such as with files, turning tools, hammers, etc., so as to prevent such tools on the measuring instruments caused by collision damage, and thus affect the measurement accuracy. At the same time, also avoid placing in the machine tool and other moving machinery, so as to avoid the vibration caused by the movement of machinery measuring instruments fall, thus affecting the accuracy of measurement.
In addition, for the machining and production of common vernier calipers, percentage rulers and rulers, etc., to do special tools, remember to use professional measuring instruments for other purposes, such as the use of straightedge scribing, turning screws, etc.. At the same time, professional measuring tools in the use of the process should also pay more attention to the use of norms, avoid random measurement and random use.
In order to avoid damage to the measuring instruments in the production process, all the instruments should be properly managed, the measuring instruments should be identified before use to ensure the safety and stability of the instruments before use, do not meet the use of the specifications of the instruments strictly shall not be used. In the following cases, measuring instruments are considered unqualified:

  • (1) The surface of the apparatus is obviously damaged;
  • (2) Previously had an overload or misuse of the apparatus;
  • (3) Abnormal display of the apparatus;
  • (4) The function of suspicious but can not troubleshoot the apparatus;
  • (5) Apparatus that exceeds the time interval specified in the weekly inspection;
  • (6) The integrity of the instrument seal is broken.

Measuring instruments and tools with the above-mentioned non-conformities must be stopped, stored separately, and marked.
(C) Measuring instruments using the environment
Some measuring instruments have high requirements for the use of the environment, especially high-precision measuring instruments for the use of the environment requirements are more stringent, such as the use of ambient temperature, the use of the environment whether there is a large magnetic field, etc., may have an impact on the measurement accuracy of measuring instruments. Thus the actual use of the process requires careful consideration of the use of environmental temperature factors, magnetic field factors.

3. The general way to choose measuring instruments and the main measures to improve accuracy

(A) the general way to choose measuring instruments
First of all, the need to observe the appearance of measuring instruments, such as the existence of manufacturing licenses, which is an effective way to test whether the regular manufacturers of measuring instruments. For example, the first four digits belong to the manufacturer’s area code, the next four digits are the order number of the license, “Jin” indicates the issuance code, that is, the province, autonomous region, municipality directly under the Central Government for short. If the measuring device is not clearly or clearly marked, the equipment may belong to counterfeit.
Secondly, to measure the accuracy of measuring instruments and the use of quality testing, such as surface burrs, corrosion inspection, as well as the inspection of the elasticity of the moving parts, if the regular manufacturer of measuring instruments, the surface burr treatment is cleaner, the corresponding elasticity is also appropriate.
Finally, also observe and analyze whether the measuring apparatus is running smoothly during the quality inspection, if there is a large noise and excessive clearance, the quality is not reliable. Further, with other measuring instruments have been measured reliably for comparison experiments, if the results measured by both in the same measurement conditions are the same, you can determine the measuring accuracy of the measuring instruments qualified, if there is a large deviation, it is necessary to consider whether there are quality problems or unreasonable precision adjustment.
(B) The main measures to improve the accuracy of measuring instruments
1. Improve the skill level of the operator
For the actual parts processing and measurement work, the important production quality and measurement work effect embodiment, to a large extent, will be affected by the main measurement operator, so for the measurement work, the relevant operators need to improve their own skills and work ability, as well as for the degree of familiarity and proficiency in the use of measuring instruments. Thus, the enterprise has the responsibility to conduct professional training and education for the operation and use of measuring instruments, so that they can be improved in terms of basic working ability and working level, thus ensuring the effective implementation of the measurement work, and also ensuring the safety of the use of measuring instruments and the use of norms.
2. Comply with the process specifications and basic requirements of measurement work
The main measuring personnel should use the same way to load the relevant measuring workpiece, and the measuring process should be standardized and standardized to ensure that each part measured is based on the same process. And for some parts with high measurement accuracy requirements, it is also more important to ensure the standardization and reasonableness of the intensified strength and angle, so as to ensure the overall measurement effect.
3. Do the inspection and calibration of measuring instruments
As the production of mechanical processing and production parts are generally more, so in the face of mass production sampling testing process, the use of measuring instruments more frequently, over time will reduce the accuracy of measurement, thus reducing the accuracy of measurement will certainly affect the effect of measurement, but also affect the stable production of enterprises, so for the relevant measuring instruments necessary to do a good job of inspection and calibration, and regular maintenance work, so as to To reduce the measurement accuracy of measuring instruments to occur in the case of misalignment.
4. Establish instrument use account
The general account of the instrument, the use account and the verification ledger should be established, and the measurement group should also establish the corresponding sub-account for the use of measuring instruments. The original file of measuring instruments shall be kept by the technical department of the project, and the copy shall be kept by the measurement team and the team leader. Copies shall be packed with the instruments. The user of the instrument shall be responsible for the custody and maintenance of the instrument during use and shall prevent moisture and loss of the measuring instrument. After use, the measuring instrument shall be handed over to the relevant department for safekeeping and registered return. Without permission, it shall not be used by others or lent out without permission.

4. Conclusion

Although industrial processing and production and related workpiece measurement, the state and relevant departments have norms and standards proposed, and enterprises in the actual production and measurement process will also be in accordance with the norms and standards for production and measurement, but fundamentally affect the accuracy of the measurement of machined parts measuring instruments also lies in whether the measuring instruments are reasonably selected, so that based on enterprise production, processing and processing parts measurement needs, the necessary According to the basic principles of selecting the measuring instruments for machined parts, and do a good job of using the process of quality inspection and improve the measurement accuracy, so as to promote the stable production and development of enterprises.



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