Precision Design and Error Distribution of Shenzhen Double Ten Instrument

Date:2020/12/11 8:56:55 / Read: / Source:本站

Precision Design and Error Distribution of Shenzhen Double Ten Instrument
    Instrument accuracy design includes two aspects: on the one hand, it is necessary to study and allocate the total error allowed by the known instrument, and make it economical and reasonable.
 Allocate the ground to the parts, and formulate the tolerances and technical requirements of each part. On the other hand, it is necessary to try to use the "error compensation" method
 To expand the allowable tolerances, to solve the problem that the allowable error (tolerance) of some parts is too strict due to the small total error value.
 1. Formulation of the precision index
    The total accuracy of the instrument should be determined by the requirements for use. In the past, the accuracy of the instrument tip was often taken as 1/3 of the accuracy of the measured result.
Or determine the data based on experience. This is unscientific.
    When formulating the accuracy index of the instrument tip, the application occasion of the instrument should be considered. For example, the instrument should use the data of one measurement as the measurement result.
 When the limit error is used as the total error of the instrument. If the average value of multiple side quantities is used as the measurement result, the mean square error should be used as the instrument
 The total precision index of the instrument; at this time, the division value of the instrument can be taken as the total allowable error of the instrument 1/2^-1/10.
     Second, the basis for the distribution of instrument accuracy
    The basis of precision distribution is Shenzhen Double Ten
     1. The accuracy index and general technical conditions of the instrument;
     2. The working principle of the instrument, the photoelectric system diagram, the assembly diagram of the mechanical structure and the related parts diagram. They provide the source of error
 The total number, the degree of influence of each error source on the instrument error and the possibility of mutual compensation between errors, etc.
     3. The technical level of the instrument manufacturer (such as processing, assembly, inspection, etc.), the environmental conditions of the product use, etc.;
     Diao. Economical;
     5. Relevant tolerance technical standards of countries, departments and factories.
    Precision distribution step-by-step
    1. Clarify the total accuracy index;
     2. When forming the working principle of the product and the overall plan, the theoretical error and the plan error are mainly considered;
When arranging the overall layout and the electro-optical system, the principle error should be considered separately.
 Complete the structural design of each part, calculate the total accuracy, find out all the error sources, and write their respective error representations
 Formula, formulate component tolerances and technical conditions, and determine the compensation plan;
     5. Mark the given tolerance technical conditions on the part work drawing. Write the technical design specification.
 Third, the distribution method of error Shenzhen Double Ten
     Total instrument error 2 total system error 10 total random error.
    Due to the different nature of the error, its allocation method is also different.
    (1) Total system error:
     The system error has a greater impact and a small number. When the system error is a function of a certain variable, the instrument error equation can be used to
 Means. If the length measuring machine performs length measurement, the error is a function of the length. The instrument error is ±((1+-total-)um. Measuring the length of the part

Then the error of measuring f is also larger.
    The process of system error tolerance formulation is: first calculate the principle system error, and give the principle error according to the general economic technology level.
 Difference tolerance value. Calculate the local system error of the instrument, and finally synthesize the total system error.
     If the total system error is too large or close to the total error allowed by the instrument, the tolerance is unreasonable, and technical measures should be considered
 To solve or overthrow the original plan, redesign.
     If the total system error is greater than 1/2 or less than the total error allowed by the instrument, generally the tolerances of the relevant parts can be increased first
 Level before considering some compensation measures.
     If the total system error is less than or close to 1/3 of the total allowable error of the instrument, it is preliminarily considered that the assigned tolerance is reasonable, pending
 When the tolerance of random error is determined, comprehensive balance is performed.
     (2) Random error Shenzhen Double Ten
     Random errors are characterized by a large number, generally integrated by the root mean square method. The total error of the system is subtracted from the total error, and the rest is
 The random total error is shown in the following formula.
                                      J: Two.1, one entry (2-72)
In the formula, the total error of the instrument. 4L-total system error; Ar-random total error.
     There are usually two methods of random total error allocation: one is based on the original moment of equal action; the other is based on the principle of unequal action.
     Principle of equal action: the error of each part acts equally on the total error. Then each individual error is
    (3) Tolerance adjustment
    The error distribution method based on the principle of equal action does not consider the actual situation of each component, which causes some tolerances to be loose, and some
 Too tight. Very uneconomical. Shenzhen Double Ten
     Usually, three tolerance evaluations are determined on the basis of investigating the actual process level and technical level of the manufacturing industry.
 Class. That is, economic tolerance limit, production tolerance limit and technical tolerance limit, used as scale 2 standard.
     Economic tolerance limit-the precision that can be achieved by the most economical processing method on general equipment.
    Production tolerance limit—On general equipment, special process equipment is used. It does not consider the efficiency that can be achieved by processing
 The precision.
    Technical tolerance limit-on special equipment, under good laboratory conditions, when processing and inspection, can reach
 The precision.
    When adjusting the tolerance, first determine the adjustment object. Generally, the system error is adjusted first, and the error transmission coefficient is large and easy
 Adjusted items.
    The tolerance values below the economic tolerance limit should be increased to the economic tolerance limit. From the total limit tolerance △:, combine it
 Value deduction. Then a new allowable error Ge’ is obtained. After repeated adjustments, the tolerances of most parts are within the economic tolerance range.
 Within the limit. At this time, there may be a few exceeding the technical tolerance limit. For this kind of error, compensation can be used to solve it.
     When adjusted to the extent that most are within the economic tolerance limit, a few are within the production tolerance limit. Very few in technical tolerance limits
 The tolerance level of the system error is higher than the random error. The compensation is less and the economic effect is significant, and it can be considered qualified.
     If the above requirements are still not met after repeated adjustments, the design plan should be changed.
    (4) Error compensation
    Error compensation is an effective means to adjust tolerances. Generally, the following three compensation methods are often used
    1. Error compensation method
    It is a way to directly reduce the source of error. Its compensation forms are
    (1) Grading compensation: Divide the size of the compensation parts into several levels, and by selecting the compensation parts of different sizes, the error can be obtained
 The stepped reduction is achieved by grinding the size of the compensation pad to meet the expected accuracy requirements.
     (2) Continuous compensation: such as guide rail inserts, can be used to continuously adjust the gap.
     (3) Automatic compensation: If the error correction board is used, the error can be automatically corrected.
    2. Error transfer coefficient compensation method: usually the following three methods are used
    (1) Choose the best working area: if there is sinw or in the eccentricity error transfer coefficient. , Item (9,-eccentric phase angle). When zero
 When the working angle range of the piece is not large, you can choose to work in the area outside the maximum eccentric zone to reduce the error.
     (2) Change the error transfer coefficient: as shown in Figure 2-12, when the error of the pitch t is quasi-time.
Changing the angle a can change the error transfer coefficient.
    (3) Comprehensive compensation
  Using mechanical, optical, electrical and other technical means to offset certain errors. So as to achieve the purpose of comprehensive compensation.


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