MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous) (ISO/IEC - 27001 - 2005 Certified) __________________________________________________________________________________________________ Page No: ____/ N WINTER– 16 EXAMINATION Model Answer Subject Code: Important Instructions to examiners: 1) The answers should be examined by key words and not as word-to-word as given in the model answer scheme. 2) The model answer and the answer written by candidate may vary but the examiner may try to assess the understanding level of the candidate. 3) The language errors such as grammatical, spelling errors should not be given more Importance (Not applicable for subject English and Communication Skills. 4) While assessing figures, examiner may give credit for principal components indicated in the figure. The figures drawn by candidate and model answer may vary. The examiner may give credit for any equivalent figure drawn. 5) Credits may be given step wise for numerical problems. In some cases, the assumed constant values may vary and there may be some difference in the candidate’s answers and model answer. 6) In case of some questions credit may be given by judgement on part of examiner of relevant answer based on candidate’s understanding. 7) For programming language papers, credit may be given to any other program based on equivalent concept. Q. No. Sub Q. N. Answer Marking Scheme 1 a Metrology: Metrology is the science of measurement. Metrology is primarily concerned with the establishment, reproduction, conservation and transfer of units of measurement and their standards. Necessity Of metrology: 1. Metrology can be used for selection of proper measuring instrument in industries. 2. Metrology can be used for deciding the proper measuring standards. 3. Metrology can be used for minimizing cost of inspection. 4. Metrology can be used for determining process capabilities. 5. Metrology can be used for deciding or finding out tolerances. 6. Metrology can be used for maintaining accuracy and precision at the time of inspection. 02+02 17530
20
Embed
16 EXAMINATION Model Answer 17530msbte.engg-info.website/sites/default/files/w16mo c/17530...Sine bar is not used for measurement of angle greater than 450 : We know that angle is
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)
Important Instructions to examiners: 1) The answers should be examined by key words and not as word-to-word as given in the model answer
scheme. 2) The model answer and the answer written by candidate may vary but the examiner may try to assess the
understanding level of the candidate. 3) The language errors such as grammatical, spelling errors should not be given more Importance (Not
applicable for subject English and Communication Skills. 4) While assessing figures, examiner may give credit for principal components indicated in the figure. The
figures drawn by candidate and model answer may vary. The examiner may give credit for any equivalent figure drawn.
5) Credits may be given step wise for numerical problems. In some cases, the assumed constant values may vary and there may be some difference in the candidate’s answers and model answer.
6) In case of some questions credit may be given by judgement on part of examiner of relevant answer based on candidate’s understanding.
7) For programming language papers, credit may be given to any other program based on equivalent concept.
Q. No.
Sub Q. N.
Answer Marking Scheme
1
a
Metrology: Metrology is the science of measurement. Metrology is primarily concerned with the establishment, reproduction, conservation and transfer of units of measurement and their standards.
Necessity Of metrology:
1. Metrology can be used for selection of proper measuring instrument in industries.
2. Metrology can be used for deciding the proper measuring standards.
3. Metrology can be used for minimizing cost of inspection.
4. Metrology can be used for determining process capabilities.
5. Metrology can be used for deciding or finding out tolerances.
6. Metrology can be used for maintaining accuracy and precision at the time of inspection.
02+02
17530
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)
Difference between hole basis system and shaft basis system :
Sine bar is not used for measurement of angle greater than 450 :
We know that angle is measured by using sine bar is based on sine principle,
sin θ = h / l
Where, h = Required slip gauge combination
l = center distance of rollers.
The relationship between the angular setting accuracy (dθ) and any error which may be present in the slip gauge combination (dh) or the center distance between roller
(dl) can be determined by differentiating the equation sin θ = h / l .
Or h = l sin θ
The effect of error in specing of roller centres ( dl ) or error in combination of slip gauges dh on angular setting accuracy can be obtained by partial differentiation of the above equation
Hole basis system Shaft basis system
1.hole size is kept constant and shaft size is
Varied for obtaining different fits.
1.shaft size is kept constant and hole size is
Varied for obtaining different fits.
2. Hole whose lower deviation is zero (H hole) is used.
2. Shaft whose upper deviation is zero (h hole) is used.
3. Preferred in mass production. 3. Not Preferred in mass production.
4. Initial cost is less as fewer drills and reamers are required.
4. Initial cost is more as many drills and reamers are required.
5. Space required is less. 5. Space required is more.
01 for each
02 + 02 for
equation
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)
From above it is clear that error is the function of tan θ. Below 450 errors is smaller
which increases rapidly above 450, as tan 450 is equal to one.
Thus in general it is preferable not to use the sin bar for measuring angles greater than 45 o if high accuracy is required
Process Capability: The process capability can be defined as the minimum tolerance to which the machine can possibly be expected to work and produce no defectives under the specified conditions.
Or
Process Capability: The process capability can be defined as the minimum spread of a specific measurement variation which will include 99.73 % of the measurements of given process. The process capability =6σ.
The process capability is achieved as follows: 1. Selecting a part to be produced that is representative of the type of operation performed by the machine.
2. Inspecting each part (total of at least 100) as it is produced and noting its characteristics with a measuring instrument.
02+02
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)
4. Error caused by measuring forces of instrument.
Unilateral Tolerance System Bilateral Tolerance System
1. Both limit of variation are on same side of zero line.
1. Both limit of variation are on different side of zero line.
2. Both limits are having same sign i.e. +ve or –ve.
2. Both limits are having different sign i.e. +ve and –ve.
3. Where mating parts must be interchangeable unilateral tolerances are preferred.
3.Not preferred for interchangeable parts.
4. For Example
4. For Example
Clinometer: A Clinometer is angle measuring device. Clinometer is a special case of application of spirit level, used for determining the included angle of two adjacent faces of work piece.
Use of Clinometer: Determining the included angle of two adjacent faces of work piece.
1. First the clinometer is placed on surface A and rotary arm is adjusted to horizontal position as shown in fig. Measure the angle α.
2. Place the Clinometer on surface B, adjusts the rotary arm to horizontal position.
01 for each
02+02
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)
Construction: 1. One fixed spindle and other movable spindle is mounted on a flat base.
2. The movable spindle moves along with base by rolling action on the main base plate.
3. A Master gear is mounted on the fixed spindle and gear to be tested is mounted on movable spindle.
4. The dial gauge is set to note the errors.
Working: when master gear is rotated slowly, a gear to be tested will also get rotation movement because of their meshing. Errors in the manufactured gear cause the gear to move away from the centerline of spindle. When gear to be tested moves the floating body also moves by the same distance. Because of displacement of floating body dial gauge gives displacement. The variation in the readings can be observed and plotted in the graphical format.
100 % Inspection is not preferred in the industry for mass production due to following reasons.
1. Cost required for inspection is more as compared to sampling inspection.
02+02
04
MAHARASHTRA STATE BOARD OF TECHNICAL EDUCATION (Autonomous)