Gaging and measurement of axis parallelism of connecting rod holes.
Bachelor Thesis(B. Eng)writer:Praveen Rguides:Prof. Dr. Matthias DeckertDr. N Ramaniduration:01.
01.2018 – 15.06.2018Abstract.ITable of contents.IIList of abbreviations and symbols. IIITable of contents.
Introduction.Introduction to Geometric dimensioning and Tolerancing.5-6Schematic representation of GD&T families and their members.7Geometric dimensioning and tolerancing.Relation diagram of GD&T. 8Factors influencing GD&T.9GD&T tolerances and fits.10-15GD&T symbols and their functions (table).
16Parallelism.Plane to Plane parallelism.17-18Plane to Axis parallelism.18Axis to Axis parallelism.
19Axis to Axis parallelism.Parallelism doesn’t control position.Types of measuring and gaging the axis to axis parallelism.Examples of gaging and measuring axis to axis parallelism.
Connecting Rod.Introduction.Material and Manufacturing of connecting rods.Importance of connecting rod.Forces on connecting rod.Different types of loads on connecting rod.Possible Failures.
Gauges types and their application.Different types of gauges.How are Gauges used?Difference Between Gauging and measuring.
Measuring Methods and technicsDifferent types of measuring.Importance and value of measuring.Designing of Actual mating envelope(AME) for connecting rod.Understanding the need for Gauge.Design of AME for Easy interpretation.
Working manual for the Gauge(AME) of Connecting rod.10.1 Setting up the Gauge.
10.2 Procedure for checking.10.3 Checking for error.Observation11.1 Checking the Values and making notes of the reading.
Correctness of the Measurement.End results.12.1Wrapping up and drawing conclusion.
Summary.Technical glossary.List of references.Gauging and measuring of axis parallelism of connecting rod holesIntroductionIntroduction to geometric dimensioning and tolerancing.The word Geometry is derived from two words ‘Geo’ means earth and ‘Metry’ means measurement. It is also a branch of mathematics that deals with the property of the object in which angle, line, points of contact…, etc.
are measured in order to know the object.Geometric dimensioning and tolerancing (GD;T) is one of the mostly used tool where quality is improved, cost is reduced and in-time delivery of products are being controlled. GD;T is a symbolic language.GD;T has an influence on the design as the drawings drawn are to be specified with the GD;T symbols and the respective tolerances have to be mentioned. To achieve functional quality.
e-g., relationship between features of a component like parallelism, perpendicularity…etc. or components.Today GD;T is considered as a bible of standards which can be directly used in the drawings based on the requirement and moreover it’s like a language for designer. If a designer knows what GD&T means then he knows what drawing is meant to be. GD&T mainly is of.
SymbolsRulesMathematical definitionsInternationally recognized standards.VocabularyDimensioning is expressing the intended geometry (shape and size) in numbers to make it as a model.Tolerancing decides the allowable variations in the dimension to achieve quality in terms of precision and accuracy .GD&T has five main families of tolerances,Form toleranceOrientation toleranceRunout tolerancesLocation tolerancesProfile tolerances So, we know the five families and, in this thesis, the main theme is study of parallelism tolerance.Parallelism is an orientation tolerance that relates to a surface, center plane or an axis parallel to an axis or plane.
Parallelism is classified into three types they are,Plane to plane parallelism (PPP)Axis to plane parallelism (APP)Axis to axis parallelism (AAP)Axis to axis parallelism will be discussed in depth for a better understanding of the gauging and measuring of connecting rod holes.Connecting rod is an important part in an internal combustion engine. A connecting rod connects the piston on to the crank pin of the crankshaft. Piston reciprocates and crankshaft rotates but connecting rod performs both the action so the stress induced in it are very highFor the connecting rod to work smoothly under this forces the consideration of parallelism of the holes of the connecting rod is very important. In short, we can say it as AAP of connecting rod holes. (AAP – Axis to Axis parallelism) To know the different types of tolerance available in the five families a hierarchy chart will help us to know the different tolerances under these five families.
This five families have 14 features which control the engineering drawing.1.2Schematic representation of GD&T families and their members.Geometric Dimensioning and Tolerancing (GD&T)GD&T is known as the universal symbolic language for engineering drawing.
A designer can convey his ideas to all users of the drawing without ambiguity.Tolerancing is the permissible variation that is allowed or permitted by the designer on a part which is to be controlled. Why tolerance is required?No part in the world is perfect even though they may look identical still there will be some variations. Why does GD&T become important?Engineers or designers by specifying the geometric tolerances.
Ensure that the functionality of the feature is achieved. Also, in the places of assembly and interchangeability the tolerancing plays an important role. Where the parts produced at one shop has to match the corresponding parts which are produced at a different shop.2.1 Relation diagram of GD&T.The tolerance factors which affects the productivity are,Parts having larger/coarse tolerance are always easy to produce and the chances of failure of the part are also high.
Parts having very tight tolerance range are very difficult to produce and may require special production methods. It is also advised not to give a tolerance which is very tighter than the required because it may add up the cost so designer has to choose wisely in such cases.Now we have some idea about tolerancing but still we have not explored how this tolerance are being specified.
They are specified by the following.SizeGeometryValue of toleranceGeneral toleranceTolerance specified for size2.2 Factors influencing GD&TSizeIn this type of tolerance, the variations are specified to allowed variation in the dimension.
Examples length, width, diameter, height, etc.GeometryIn this type of tolerance, the tolerance for a geometry of a part separate from its size is specified. GD&T symbols are used to control different geometric features of the part.
Value of toleranceIn this type of the tolerance, tolerance for a single dimension may be specified with the dimension and then the tolerance. Tolerance is just the variation between the upper and the lower limit.General toleranceIn this type of tolerance, it is applicable for dimension of drawing without explicit specification of tolerances. General tolerance is to promote drawing clarity by reducing the number of dimensions required on a drawing.Tolerance specified for sizeIn this type of tolerance there are two types,Limit size specification.Plus/minus tolerancesUnilateral toleranceBilateral tolerance.
2.3 GD&T tolerances and fits.Limit toleranceIn this type of tolerance, it is done by specifying the both upper and lower limits and placing them above and below the dimension line. This is one of the best methods for general use. E.g.
20.1/19.9Plus / minus toleranceUnilateral toleranceIn this type of tolerance, the dimensionVariation is shown only on one side of the dimension from the basic line. This type of dimension may be either positive from the basic line or negative from the basic line in terms of tolerances in which they are to be mentioned.e.
g. 19.9+0.2 or 20.
2-0.2Bilateral toleranceIn this type of tolerance, the dimensionvariation is shown on the both sides of the basic line i.e. this type of tolerance may have both positive as well as negative variation.
e.g. 20 plus or minus 0.1Allowance in an assemblyIt is defined as the intentional difference between the maximum material limits of mating parts.
It is the minimum positive allowance or maximum negative allowance between mating parts.Minimum clearance – positive allowance.Maximum interference – negative allowance.The formula to calculate allowance is,Allowance = maximum material condition of hole – maximum material condition of shaft.Clearance It is defined as the maximum intended difference or loosest fit between the mating parts. The formula to calculate the clearance,Clearance = least material condition of hole – least material condition of shaft.
To get a better understanding of the allowance and clearance we have to know about the fits available.There are three types of fits.Fit is the relationship existing between the mating parts which are to be assembled i.e. hole and shaft.
All the internal features of a part irrespective of profile may be cylindrical or not cylindrical can be referred to as hole and all the external features of those which are cylindrical or non-cylindrical can be referred as shaft.Clearance fitInterference fitTransition fitClearance fitIt is defined as the fit which always provide the clearance is called clearance fit. The tolerance zone of the hole is always over that of the shaft. It is also called as running or sliding fit as per the ANSI standard fits.Interference fitIt is defined as the fit which always provide the interference is called as interference fit. In this the tolerance zone of the hole is entirely below that of the shaft.
Also called as force fit as per ANSI standard fits.To calculate the interference,Minimum interference = least material condition of shaft – least material condition of holeMaximum interference = maximum material condition of shaft – maximum material condition of hole.Transition fitIt is defined as the fit which either provides an interference or a clearance is called as a transition fit. In this type the tolerance of the hole and shaft overlaps.Some of the GD&T symbolsPreviously we have discussed about the five families of tolerance and the different features they control and here are is the table of all the features and their symbols as per the GD&T standards.Five families are,Form toleranceProfile toleranceOrientation toleranceLocation toleranceRunout tolerance2.
4 GD&T symbols and their functions.ParallelismParallelism is an orientation tolerance that defines the angular relationship between two planes or two axes or between an axis and a plane.Parallelism is classified into three types they are,Plane to plane / Planar parallelismAxis to plane parallelismAxis to axis parallelism3.1 Plane to plane / Planar parallelismThe direct way of measuring parallelism is plane to plane parallelism it has been misunderstood that various thickness measurements were carried out to inspect parallelism.Parallelism is measured with respect to a datum plane which is in proper contact with surface plate or inspection equipment in order to make a perfect measurement.Misconception,Many of us think that parallelism can be measured with a micrometer. In fact, we are not measuring parallelism we are measuring thickness at different places of the workpiece to know the difference between the thickness. The reason why a caliper or micrometer cannot give you the parallelism measurement is that primary reference surface or the datum is not contacted properly (highest points are not in proper relation).
But still parallelism measurement is simple in the case of plane to plane parallelism. 3.2 Axis to surface parallelism / axis to plane parallelismIn this type of parallelism, the axis of a hole is to be parallel to the datum surface. The axis of the hole is an orientation tolerance that ensures that the hole is aligned to a datum plane and it does not control the location it only controls the orientation of the hole.3.3 Axis to axis parallelismIn this type parallelism, the axis of one hole is to be parallel with the axis of the other hole. A datum surface is not required for this parallelism measurement but a functional gauging is required to measure the parallelism.
And the gauge pin in the datum axis should be an Actual Mating Envelope ( A tight fitting pin for the datum hole in this example, to establish the datum axis).Parallelism does not control location.