the Technique of aquantitative estimation of components of the revealed deviation of key figure of merit
At the analysis of the valid value of the handheld computer gained by measurement, pertinently to use definition from International Organization for Standardization 9000-08: «Products - result of process».
In this case products is the revealed deviation of a handheld computer from ideal value. Its magnitude is total result of processes of affecting of all without exclusion of factors of the technological system acting in those points of a surface where then measurement [17] has been spent. Generally it is necessary to present it in a following aspect:
- Value of a deviation of a handheld computer / / AK.
- Geometrical sum of the making deviations called to lapses of the equipment and equipment, revealed by diagnosing.
- Geometrical sum mизмеренных making lapses of adjustment.
- Geometrical sum of making deviations of the handheld computers called by act nконтрольных of characteristics in the course of creation AK. Their magnitudes should be gained by calculation on the turned out empirical models.
It becomes frequent enough necessary in processes formoobrazovanija cutting. After all in many transitions it is necessary to provide exclusively close tolerances on parametres of accuracy of workpieces, besides, that in technological system a little KHH all three groups (table 2.1) simultaneously acts. Therefore in this area from the old
Pores the mathematical apparatus of definition of values of separate characteristics of process is applied, and also are turned out extensive databases.
For technological transition of machining of a spherical surface (drawing 2.4) a deviation of radius 80 ±0,03 the mm is a geometrical sum of technological components (1). Therefore unmistakably to appoint the tool of decrease of a deviation it is possible only, knowing act mechanisms at least the most significant factors of process.
Act of each factor on magnitude of the future deviation submits to the regularity so in each point of the processed surface their significance is various. Therefore for exarticulation of their contribution in the given point it is necessary to carry out by the organisation of co-ordinate measurements (in a technique of measurement of a handheld computer registration of co-ordinates of points of measurement on the processed surface should be provided).
The control characteristics caused by a condition of the equipment and equipment, act during long time spans (table 2.1). That it is reliable to size up the contribution to a handheld computer deviation, them periodically enough to measure.
Let's present, that for the next calendar year it is planned two operations of diagnosing of parametres of accuracy of the rig (drawing 2.5). By results of first, on that section of the frame where the support is based at sphere machining, the deviation of a rule of an axis of a spindle owing to parallel misalignment directing Δδ e.g.
(drawing 2.5) is revealed. It is possible to consider it as a constant for volume of the details processed during a cycle of diagnosing. If at following diagnosing this magnitude considerably changes, the component of a deviation of radius will accept new value for the subsequent volume of details.One or the several significant naladochnyh making Δδ a cash. It is necessary to identify upon termination of adjustment process (drawing 2.6). It is enough to accept their magnitude of a constant for all volume of details more often,
Made before the following adjustment. In drawing 2.6 it is conditionally shown, that this component reduces value of radius.
Thus, by the moment of the beginning of performance of the task already there is an information on two groups of components of a measured deviation. Their total value (Δ R beliefs.) directly influences magnitude of radius.
At close tolerances on accuracy of a processed surface in many transitions formoobrazovanija it is necessary to consider the components called by dimensional deterioration of the tool and deformations of technological system under the influence of force of cutting. They act directly only in the course of cutter and preparation interacting. Generally they are individual for each elementary platform of the processed surface of preparation.
In today's conditions of the Russian factories piece identification of characteristics of preparations is practically impossible, so for definition of these components it is necessary to be restricted to likelihood calculation on the basis of empirical models of process of machining.
Let's present, that at performance of the task for party AK manufacturing on a work station the management plot provides measurement of a handheld computer of / / details. We will have in view of, that the party of work pieces is characterised by own variability of sizes and hardness. We will assume also, that preparations of various hardness and arrive diameter on machining in a casual order.
Characteristics of the law of normal distribution of these control characteristics (h and an average quadric deviation bh) in volume of party N of pieces should be defined a mean in advance experimentally. Further all range of distribution of the characteristic should be broken into intervals in which it is possible to consider its value to constants (width of an interval it is possible to accept equal, for example, to the price of division of a gauge) (drawing 2.7).
The design procedure of probable quantity of the whole pieces of preparations in each interval (drawing 2.7) is offered I.P.Balabanov [12].
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Drawing 2.5 - Identification stanochnoj a component of the measured deviation in a diagnosing scraper (Δδ e.g. a deviation of a rule of an axis of a spindle owing to parallel misalignment directing)
Drawing 2.6 - Identification of a component of figure of merit in naladochnom to a scraper (Δδ a cash. An increment of diameter from naladochnoj a component)
Drawing 2.7 - the Circuit design of a digitization of a range of variability of control characteristic H of party of preparations N of pieces. (J - width of an interval of a digitization, bh - an average quadric deviation of the characteristic)
Further we will appropriate to preparations a serial number. Using the random number generator, we make feeding into in each interval matching quantity of preparations with the direction of their serial number. The instance of distribution of party of preparations of 50 pieces on intervals of values of characteristics (N=50 pieces) is given in table 2.2. The alternative of sequence of delivery of preparations with certain characteristics on machining in a casual order is conducted with random number generator application. The instance is specified in table 2.3.
Value of an increment of radius of measured / / details ⅛. ξx., a micron, as a result of deterioration of a form-building element of a cutter:
Where - an increment of magnitude of deterioration on a back surface
The tool, a micron;
α - a cutter end-clearance angle, grade.
Initial empirical dependence ("speed-firmness"), m/mines, [12]: where - empirical constants.
T - the period of durability of a cutter (to optimum magnitude zatuplenija on a back surface [LDopt.), minute
S' - Supply, mm/about.
t - Nominal magnitude of an overmeasure on preparation, mm.
Wear rate of the tool at detail machining, microns/mines, [12]:
Where [⅛] - the accepted criterion zatuplenija the tool, a micron.
Table 2.2 - the Instance of distribution of party of preparations on intervals of values of characteristics (N=50 pieces)
Hardness, NV | Overmeasure, mm | ||||
Number interyovala | Quantity of preparations | Numbers of preparations in party | Number interyovala | Quantity of preparations | Numbers of preparations in party |
1 | 1 | 26 | 1 | 1 | 11 |
2 | 3 | 2, 12, 25 | 2 | 4 | 2, 22, 32, 36 |
3 | 5 | 6, 15, 22, 29, 38 | 3 | 8 | 4, 10, 16, 21, 27, 33, 38, 43 |
4 | 7 | 1, 10, 18, 35, 40, 42, 50 | 4 | 12 | 6, 8, 13, 15, 19, 23, 30, 37, 31, 48, 50, 49 |
5 | 8 | 8, 14, 21, 30, 34, 43, 45, 48 | 5 | 10 | 1, 3, 7, 9, 18, 26, 34, 39, 44, 47 |
6 | 9 | 347 11 17 23, 32, 41, 44 | 6 | 9 | 5, 12, 17, 24, 31, 35, 40, 45, 48 |
7 | 7 | 9, 20, 27, 31, 44, 46, 49 | 7 | 5 | 14, 20, 25, 29, 42 |
8 | 5 | 5, 19, 37, 39, 47 | 8 | 1 | 28 |
9 | 3 | 16, 28, 36 | - | ||
10 | 2 | 13, 33 | - |
Table 2.3 - Characteristics of work pieces at machining
Kits of parts
After transformation (3) settlement increment of magnitude of deterioration on a back surface of the tool at machining of each / / details, the micron, will make [12]:
Where Trez - a cutting time at a surfacing of one detail, minute
Increment of a deviation of radius of / / details of a micron, from deterioration
The tool (2) taking into account (5) will make [12]:
Then an increment of diameter of / / details δ ' ⅛. ι.5мкм, in measured cross-section:
The circuit design of gradual decrease of magnitude of radius at machining of preparations with the different characteristics which are given out on machining in a casual order is shown in drawing 2.8. This component is added after machining of each detail, as though accumulating on already certain earlier making deviations (drawings 2.6, 2.5). For the given transition it is last of considered factors (drawing 2.8).
Technique approbation has industrially proved to be true, that in the absence of significant stanochnyh lapses and stable adjustment in the given technological transition one reason of variability of radius - deterioration of the tool predominates only. Thus, for stability maintenance it is the most important to trace chafing of the tool and if necessary to carry out podnastrojku on a size.
At machining of nonrigid details, for example, long shafts it is necessary to consider one more significant component of a deviation - a bend of an axis of preparation
Drawing 2.8 - Identification of an increment of a deviation at machining of party of preparations owing to the radial deterioration of the tool (Δδ izn.і - a radius increment і details from deterioration of the tool, R verifitsir. - value naladochnogo a size on accomplishments of technological transition)
Under the influence of force of cutting. Its magnitude also pays off on the basis of the empirical formula.
Magnitude of bending force Ru, N:
ti - A cutting depth of measured / / preparations, mm;
S - supply, mm/about;
HB/-Hardness of measured i preparations, NV;
- Correction index depending on the saved up magnitude of deterioration of the tool on a back surface.
For a case of cantilevered attaching of preparation of type of the shaft at outdoor turning an axis bend ⅛⅛ι., the micron, in a point of measurement of diameter under the influence of a bending force of cutting R will be equal [12]:
Then an increment of diameter i ⅛, 1, a micron, in the measured cross-section:
Where E - a material modulus, MPa;
J - A moment of inertia of round cross-section? <
lизм. - distance of a point of measurement from a support, mm;
L - Length of a work piece, mm.
The circuit design of an increment of components of a measured deviation owing to deformations in technological system is resulted in drawing 2.9.
The general circuit design of identification of structure of the measured deviation is presented in drawing 2.10. Once again we will note, that from accepted to consideration
Drawing 2.9 - Identification of components of a deviation as a result of deformation of technological system at machining of the is cantilevered-fixed preparation in party (Δδ def. і an increment of diameter in the measured cross-section)
Drawing 2.10 - Stage-by-stage formation of structure of the deviation measured on / / details (Δδ e.g. - a deviation of a rule of an axis of a spindle owing to parallel misalignment directing, Δδ a cash. - an increment of diameter from naladochnoj a component, Δδ izn.і - an increment of radius of / / details from deterioration of the tool, R beliefs - value naladochnogo a size on performance TP, Δδ def.і - an increment of diameter of / / details from deformation of technological system)
Four KKH, two of them will be constants for all processed party, and components of deterioration and deformations - individual for each preparation. The given technique allows to define their probable magnitudes with comprehensible accuracy.
To choose the most productive alternative of correction at act in transition in the presence of several significant factors, by results of calculations of all components of a deviation it is expedient to build diagramme Pareto and the diagramme of these saved up sums making (drawing 2.11 and,). These schedules allow to begin correction with the most significant factor. But also, under the diagramme of the saved up sums it is possible to predict set KHH which it is necessary to affect for achievement of the necessary extent of decrease of a deviation.
So, under diagrammes in drawing 2.11 () for deviation decrease diametrana the following is expedient to make 70 %:
- To inject compulsory periodic podnastrojku a cutter on a size for deterioration compensation;
- To analyse possibility of decrease of force of cutting or raise of rigidity of technological system;
- To develop provisions on raise of accuracy of adjustment.
Dynamics of development of modern means of reception of the information and data transfer allows to hope, that the proximal decades practically all significant factors of deviations will be put under a positive control.
Drawing 2.11 - Diagram Pareto of components of the measured deviation of / / details. The diagramme of the saved up sums making measured deviation of a handheld computer (Δ∙
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