Metrology and Interchangeability

Opublikowano: 05.04.2014 19:15

Subject name Metrology and Interchangeability
Type of subject               Basic
Summary ECTS 2
Form of course 15h lecture, 15h exercises
Lecturer                           Zbigniew Humienny, Ph.D.
A brief outline:
Lecture
  • Measurements and their uncertainty. Measurement and measurement principle. Quantity intended to be measured (measurand) in the measurement of length and angle. Direct and indirect measurement methods. Direct comparison, differential and deflection methods of measurement. The main causes of measurement errors: method, equipment and personnel. Measurement result as random variable. Systematic and random errors. Mistakes. Corrections. Assessment of the standard and expanded measurement uncertainty of the single and average measurement result. Type A and B evaluation of measurement uncertainty. Evaluation of measurement uncertainty by a statistical analysis of measured quantity values (type A evaluation) – big number of measurements in series (usage of Student’s distribution) and small number of measurements in series (usage of Gaussian distribution). Combined uncertainty of indirect measurements.
  • Dimensional chains. Simple and 2D dimensional chains. Assembly and technological dimensional chains. Identification of the dependent dimension. The tolerance stuck up sketch. Equation of the nominal dimension, equations of upper and lower limit dimensions. Tolerance stuck up equation. Calculation of the limit dimensions – worst-case tolerance analysis and statistical tolerance analysis. Min-max method. Expansion of dimensional chain equation to Taylor series. Calculating of the selected dimension limits when all other dimensions are given. Calculating of the component dimensions limits when only dependent dimension limits are known. Rule of the shortest dimensional chain. Total and statistical interchangeability. Interchangeability due to fixing, additional cutting or selection.
  • Geometrical tolerancing according to ISO GPS system. Features of the workpice – nominal, actual, extracted (integral and derived). Partition of the extracted profile. Tolerance indicator. Datum indicator. Tolerances and deviations of form – straightness, flatness, circularity & cylindricity. Datums, datum features, datum simulators. Single datums, common datums & datum systems. Datum targets. Tolerances and deviations of orientation – parallelism, perpendicularity or angularity of a feature to one or more datums. Tolerances and deviations of location – position, concentricity & symmetry. Tolerances and deviations of profile of a line/surface used to control form or combinations of size, form, orientation & location of a feature(s) relative to a true profile. Tolerances and deviations of circular runout tolerance and total run-out tolerance – radial and axial. Relations between selected geometrical tolerances. Fundamental ISO GPS system principles. Maximum material requirement for toleranced feature and datum feature. Envelope requirement.
  • Measurement equipment and auxiliary equipment. General concepts and requirements for GPS measuring equipment. GPS measuring equipment classification – material measures, transducers, indicating measuring instruments. Metrological characteristics and design characteristics (scale range, measuring range, scale interval maximum permissible error MPE, measuring force). Calibration.
  • Selected examples of measurement of the geometrical characteristics. Gauge blocks and their usage. Testing of sizes by calipers and micrometers. Differential measurements with dial gauges. Measurement of form deviations. Measuring microscopes. Coordinate measuring systems (CMM, ACCMM, 3D optical scaners, metrotomography). Cloud of points used for assessment of the conformity with specifications. Criteria for the selection of measuring equipment.
Exercises
  • Tolerances and fits. ISO code system for tolerances on linear sizes. Basic terminology (feature of size, nominal size. limits of size, upper limit deviation, lower limit deviation, fundamental deviation). Tolerance interval – minmax interpretation and statistical interpretation). Tolerance class – combination of a fundamental deviation and a standard tolerance grade. Clearance fit. Interference fit. Transition fit. Hole-basis fit system. Shaft-basis fit system.
  • Systematic errors and contributions to measurement uncertainty of linear dimensional measurements due to thermal influences. Calculations of the measurement uncertainty for direct and indirect measurement methods. Calculation of the standard and expanded measurement uncertainty of the single and average measurement result.
  • Dimensional chains. Identification of the dependent dimension. The tolerance stuck up sketch. Calculations of the limit dimensions for 1D assembly and technological dimensional chains. Calculations of the component dimensions limits when only dependent dimension limits are known. Calculations of the limit dimensions for 1D dimensional chain due to fixing or additional cutting.
  • Practice in form, orientation, location, run out and MMR tolerance specification and interpretation for given workpieces.