Indicators of reproducibility and suitability for assessing the quality of production services

<p>A technique is proposed for estimating the probability of the possible appearance of defective products or the inconsistency of the production service on the basis of indexes of suitability and reproducibility of the production process.</p><p>The index of reproduction is recommended to be calculated on the basis of the standard deviation, which can be established by the average span of the control map and the limits of the tolerance field. At the same time, the production process must necessarily be in a state of statistical controllability. The suitability index cannot be calculated on the basis of the control card characteristics, but it is evaluated solely on the basis of the total of the standard deviation, which is calculated by the Bessel formula and the tolerance limits. The production process does not need to be statistically controllable. Conclusions on the suitability or insufficiency of the products (production services) are based on the value of the indexes of reproduction and suitability, which can take values less than or greater than one. On the basis of these indexes of obtained values, the probability of production appearance or characteristics of the production process, that does not match the established requirements, is established.</p>

DETERMINING NOMINAL VALUES OF INPUT PARAMETERS FOR PRODUCTION PROCESS USING DOE

Application of statistical methods in quality improvement of molded parts is presented in this paper. Implementation of two stages of DMAIC improvement cycle in a pre-production process is analysed in detail. DOE method is performed to define nominal values of process parameters of injection molding process. A fraction-factorial design with a single central point is used. A linear mathematical model with included elements of second-order interaction is defined. Finally, control stage is performed using prior defined nominal values. Process capability test is conducted in order to determine whether the process is capable of producing parts within specified tolerance field.

DETERMINATION OF THE MAXIMUM DEVIATIONS FROM THE NOMINAL DIMENSIONS OF THE PARTS OF DOUGH-DIVIDING MACHINES VACUUM-PISTON TYPE

The main method for determining the wear of parts is micrometer measurements of the output of the nominal size for the maximum deviations of the tolerance field. To determine the wear of parts during micrometric measurements, difficulties arise due to the lack of regulatory and technical documentation for equipment with design drawings of parts. One of the possible ways to determine the maximum deviations of the nominal size of parts was the method of calculating the size chain when solving the "direct" or "reverse" problem. (Research purpose) The research purpose is in determining the maximum deviations of the nominal dimensions of the parts for the suction chamber of the test separation machines of the vacuum-piston type by calculating the size chain. (Materials and methods) A caliper ShTs-II 0-160 was used to measure the external and internal nominal dimensions of the suction chamber parts. The input parameter for the calculation was the minimum technological gap in the joints of the parts equal to 50 micrometers, and the maximum one equal to 100 micrometers. The article presents the tolerance of the closing link by the probabilistic method of calculating the components of the links. (Results and discussion) The maximum deviations of the nominal dimensions of the parts for the suction chamber were determined by calculating the dimensional chains for the width and height of the parts when solving the "direct" problem. (Conclusions) The obtained limit deviations allow us to determine the wear of the parts for the suction chamber of the vacuum-piston type dough separating machines when the outer size of the part exceeds the lower limit deviation, and the inner size of the part exceeds the upper limit deviation.

The calculation of the allowable diametrical inaccuracy of the cycloidal driving bores in a cycloidal drive with a given profile error and transmission ratio fluctuation

Cycloidal drives are getting more and more widespread due to their beneficial properties. The greatest advantage of these transmissions compared to other general-purpose industrial transmissions, but even compared to the more widespread types of planetary gears, is their ability to operate with large transmission ratios and good efficiency under larger performance density. A smaller amount of play and the minimal fluctuation of transmission ratios, which fundamentally define the kinematic properties of these high precision premium transmissions, can only be achieved by increasing the manufacturing accuracy, decreasing the magnitude of manufacturing errors and limiting the tolerance field. The current research, has focused on finding the allowable manufacturing accuracy of transmissions that are primarily manufactured by small scale or by one-off production, and discusses the effect of the cycloidal driving bores diametrical inaccuracy in a cycloidal disc, that was manufactured with wire electrical discharge machining and contains profile defects.

RELIABILITY OF QUALITY CONTROL OF BUILDING MATERIALS AND PRODUCTS

The article deals with the issues of reliability of quality control of building materials and products. The structural diagram of the reliability of control of building materials is presented as a combination of series-connected technological operations. The purpose of the work is to assess the regulatory security of quality control of the production of building materials and products. The block diagram of quality control of concrete blocks for basement walls is presented. On the example of concrete blocks for basement walls, an assessment of the normative provision of product quality indicators is given. It has been established that the quality assurance of concrete blocks for FBS basement walls if all production parameters and quality indicators meet the requirements of regulatory documents and the condition: the mathematical expectation is in the middle of the product tolerance field and ± 3σ in the tolerance field is 0.9576, and the probability the appearance of marriage - 4.238%. The influence of the spread of indicators on the quality assurance is considered. It is found that with an increase in the value of the standard deviation to a value that is within the tolerance range of ± 2.5σ, the quality assurance decreases and amounts to 0,8092, and the probability of the appearance of defects is 19.08 %. It is shown that the application of the Six Sigma methodology at the enterprise will contribute to improving the quality of products

Determination of the errors first component in the tolerance field structure of the inter-transition size for the transformation of geometric elements in the structure of the initial blanks

To determine the errors first component in the tolerance field structure of the inter-transition size the knowledge base of the production technological preparation by seven levels of its basic objects of functionally different types is used. The task is solved in the working space of working machines, in the structure of which two technological schemes are built: for basing the initial blanks in working machines and for basing form elements in working machines and their geometric forming on working machines. Technological schemes for basing the initial blanks into working machines in the general case have a significant impact on the geometric and dimensional errors (the considered component) of the shape elements to be converted in the technological schemes for basing form elements into working machines and their geometric forming on working machines. It is shown that the determination of the errors first component in the tolerance field structure of the inter-junction size must be carried out by means of specialized intelligent control and measuring systems, embedding them in the structure of working machines. Determination of the first component in the tolerance field structure of the inter-transition size is relevant, has scientific novelty and practical significance. Keywords technological preparation of production; cutting processing; system analysis; information technology; modeling solutions; systems technology

Normalization of reproducibility and suitability indexes for assessment of products or production services quality

A technique is proposed for estimating the probability of the possible appearance of defective products (or the inconsistency of the production service) on the basis of the suitability and reproducibility indexes of the production process. The index of reproduction is recommended to be calculated on the basis of the standard deviation, which can be established by the average span of the control map and the limits of the tolerance field. At the same time, the production process must necessarily be in a state of statistical controllability. The suitability index can not be calculated on the basis of the control card characteristics, but is calculated solely on the basis of the total of the standard deviation, which is calculated on the basis of the Bessel formula and tolerance limits. The production process does not need to be statistically controllable. Conclusions on the suitability or insufficiency of the products (production services) are based on the value of the indexes of reproduction and suitability, which can take values less than or greater than one. On the basis of the obtained values of these indexes, the probability of production appearance or characteristics of the production process, that does not match the established requirements, is established.

Marginal superiority of maize: an indicator for density tolerance under high plant density

Marginal superiority is a common phenomenon in crops, and is caused by the competitiveness of individual plant for resources and crop adaptability to crowded growth conditions. In this study, in order to clarify the response of marginal superiority to maize morphology and plant-density tolerance, field experiments without water and nutrition stress were conducted at Qitai Farm in Xinjiang, China, in 2013–2014 and 2016–2019. The results showed that no more than three border rows of all the cultivars had marginal superiority under high density, about 90% of all the cultivars had no more than two border row that had marginal superiority and a significant negative correlation was observed between marginal superiority and population grain yield (first border row: y = − 2.193x + 213.9, p < 0.05; second border row: y = − 2.076x + 159.2, p < 0.01). Additionally, marginal superiority was found to have a significant positive relationship with plant density (first border row: y = 6.049x + 73.76, p < 0.01; second border row: y = 1.88x + 95.41, p < 0.05) and the average leaf angle above the ear (first border row: y = 2.306x + 103.1, p < 0.01). These results indicated that the smaller the leaf angle above the ear, the weaker the marginal superiority and the higher the grain yield. It suggests that the magnitude of marginal superiority in the border rows can be an indicator for plant-density tolerance under high density. What’s more, cultivars with small leaf angle above the ear can be selected to weaken the marginal superiority and improve grain yield under high plant density. Conversely, cultivars with a large leaf angle above the ear can be selected to achieve higher individual yield in intercropping systems with no more than four rows alternated with other crops.

The Research of Processing Methods of Thin-Walled Waffle Constructions Taking into Account Technological Deformations

Technologists often notice deformations after machining waffle construction of the shell. In that case, size characteristics go beyond tolerance field. Waffle constructions are widely used in aviation and rocket science, because thin-walled constructions allow decreasing mass of products. Results of calculations of standard machining parameters are given in the article. Review of literature sources allow to summarize the main solutions of the problems with deformations. Author has made a conclusion of technological restrictions and field of application of selected approaches.