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Metrology and Quality Control PDF Metrology and Quality Control by Avinash M. Badane Book PDF Book Description: Book: Metrology And Quality Control. Metrology and Quality Control. Time: 3 Hrs.] Prelim Question Also, inspection of shafts can be done easily and rapidly with the help of adjustable gauges. BME METROLOGY QUALITY CONTROL & RELIABILITY Engineering metrology (Defn): Measurement of dimension: length thickness, diameter.
The GUM method involves first considering all of the influences which might affect the measurement result. A mathematical model must then be determined giving the measurement result as a function of these influence quantities. The GUM approach is sometimes described as bottom-up, since it starts with a consideration of each individual influence. Each influence is normally listed in a table called an uncertainty budget which is used to calculate the combined uncertainty.
Example uncertainty budget. MSA involves performing Gage Studies in which repeated measurements are compared with a reference under different conditions to determine the bias, repeatability and sometimes reproducibility. A Type-1 Gage Study is the quick check normally carried out to initially understand the variation in a gage. It involves a single operator measuring a single calibrated reference part 25 or more times and then considers the variation and bias in the results.
This type of test is often called a repeatability study outside of MSA. Typically 10 parts are each measured twice by at least three different operators. This considers the change of operator and subsequent changes in time and environment to be a full representation of reproducibility conditions. MSA is sometimes referred to as top-down since it largely treats the measurement process as a black-box and experimentally determines systematic and random uncertainties. Two important concepts in MSA are accuracy, used as the equivalent of uncertainty; and precision, used as the equivalent of random uncertainty.
The advantage of uncertainty evaluation is that it is capable of considering all sources of uncertainty and, if done properly, gives the most accurate estimate of uncertainty. Problems with this approach include the fact that it requires a metrologist capable of producing the mathematical model and the risk of human error leading to significant influences being omitted or incorrectly estimated.
The GUM method is also only valid for an individual measurement which has been carried out with values known for any corrections applied. It is therefore difficult to correctly apply uncertainty evaluation to predict the uncertainty of an industrial measurement process. MSA can be much more easily applied and is intended to provide a prediction for the accuracy of an industrial measurement process.
The problem with this approach is that certain systematic effects are ignored and reproducibility conditions may not be fully represented, leading to an underestimate of uncertainty.
An example of the omission of systematic effects is that when determining the bias, a comparison is made with a reference which is treated as the true value—in reality the reference also has uncertainty, which should be included. This method relies on all reproducibility conditions being varied so that their effects can be seen in the variation of results when making repeated measurements.
It is likely that the way in which these conditions are varied will not fully reflect the variation seen during the life of the actual measurement process. Measurement and Quality Assurance So far, I have focused on quality control, i.
A process may be evaluated by making several parts and measuring them to determine the variation and bias in the manufacturing process. Rather than giving these results directly, it is normal to divide the part tolerance by the process precision to give the Machine Tool Capability CP or by the process accuracy to give the Process Capability CPK.
It takes a top-down approach to understand random and systematic effects. However, instead of evaluating measurements, it is used to evaluate process outputs. It generally has the same advantages and disadvantages as MSA, and a bottom-up uncertainty evaluation approach can be used if these are a concern.
However, common cause variation or chance cause variation in older literature is the equivalent of precision; short-term variability is the equivalent of repeatability; long-term variability is the equivalent of reproducibility; and special cause variation or assignable cause variation in older literature is the equivalent of bias.
In broad terms, this means that effects are random and normally distributed with any significant systematic effects corrected for. This gives a simple graphical view of a process where it can be easily spotted when a process is drifting or producing errors which cannot be explained by normal random variations.
For example, if several points are all increasing or decreasing then this would indicate the process is drifting. Example control chart. In a quality environment to check for consistency and accuracy in the manufacturing process.
On the workshop floor to initially set up or calibrate a machine, prior to a production run. Dial indicators help users measure the distance between two plates, but the readings given by the tool could be faulty.
Wipe the surface plate, the gauge blocks and the tip of the dial indicator's plunger to remove any dirt or debris. Rest the tip of the plunger directly on the surface plate.
Rotate the indicator's face until the "0" marking aligns with the dial. Raise the plunger and slip a inch gauge block underneath. Lower the plunger onto the surface of the gauge block. Check that the indicator reads inch. Raise and lower the plunger two more times to check that the dial indicator gives the same measurement in the same spot repeatedly.
Repeat the process with inch, inch, inch, inch, inch and 1-inch gauge blocks. Check each block three times to ensure the dial indicator's repeatability. It meets the iso requirements for periodic calibrations of one micron least count dial gauges [l. The equipment is useful for periodic calibration of plunger type dial gauge and lever types dial gauges and bore gauges.
Metrology, Quality control and reliability notes/ebook pdf download for ME/AU/IP
It includes rigid stand having dial gauge fitting arrangement on upper holder and micro screw with probe in the holder below the same. The dial gauge holding system is having mechanism of fine adjustment for setting the dial gauge. This is the specialty of the design.
The digital unit indicates movement of probe that is fitted in micro screw. The digital indication unit is having a required operating switch for setting different modes that consists of change of resolution either , 0. High point and low point of the wave are called as crest and trough resp. Maximum displacement of the wave is called as amplitude.
Wavelength has a precise value and form. If they have combined with each other, the resultant effect is production of maximum illuminator and the resultant amplitude of addition af A1 and An. However satisfactory operation requires use of light sources such as mercury, Krypton, Thallium, Helium and gases in this sources discharge lamp is charged with one particularly element excited elastically so that they radiate at a certain wavelength.
The importance of optical flat is operation in light wave measurement because all inspection operation are performed with reference to the surface of optical flat. If an optical flat is placed upon another optical flat facing the reflecting surface, it will not form an important contacting but will lie at some angle making and if optical flat now be illuminated by monochromatic surface of light, eye placed in proper position will observe number of bonds produced by interference of light wave reflected from lower surface of other flat through thin layer of air between two flats is monochromatic light of surface of wave of incident beam from 5 is particularly reflected thus recommended by the eye having traveled path whose length will differ by an amount ACD.
Type B: Both surfaces flat and parallel to each other. In eyepiece, particularly reflected light collimating lens which collimates through it. Further leveling arrangement is provided on a table.
The reflected light strikes illuminated lens which collimates it and through it further on optical flat under test. The flat under test is placed on the table provided with leaving arrangement. This is designed for measurement of parts of complex figure profiles of external threads, tool templates and gauges. It can be used to measure center to center difference of holes in dry plane as well as in co-ordinate measuring systems.
Basically it consists of the optical hand which can be adjusted vertically along the guide ways of the supporting column. The optical head can be in any portion by screw. The working table on which parts to be inspected are placed on a heavy hollow box. The table has a compound slide by means of which the measurement part has longitudinal and lateral movement.
The beam of the light passes through transparent glass plate on which parts to be checked are placed. Determination of relative position by using protractor. Measurement of angle by using protector eyepiece. Comparison in eyepiece measurement of pitch and effective diameter. Comparison of an enlarged protector image with a tracing fixed to projecting image. This is measured by measuring the travel of the work table necessary to transfer a second point to the position previously occupied by the first and so on.
The enlarged image can be compared with accurate drawing made to the scale of magnification. Such a comparison can reveal any deviations in the sizes and contours of the objects and to get a numerical assessment of such deviations, measurements can be made on the enlarged shadow.
The measured dimensions on the shadow will then have to be divided by the multiplication factor. The projection apparatus used for this purpose is termed as an optical profile projector. The essential features of a profile projector are that, it should be accurately as stated and that there should be maximum latitude in holding and adjusting the work piece and examining the projected shadow. The application of a particular process is often customized to the production process.
A typical process may include: test of previous articles plan to improve design to include improvements and requirements manufacture with improvements review new item and improvements test of the new item Many organizations use statistical process control to bring the organization to Six Sigma levels of quality, in other words, so that the likelihood of an unexpected failure is confined to six standard deviations on the normal distribution.
This probability is less than four one-millionths.
Re: Metrology and Quality control By R. K. Jain
Items controlled often include clerical tasks such as order-entry as well as conventional manufacturing tasks. Traditional statistical process controls in manufacturing operations usually proceed by randomly sampling and testing a fraction of the output. Variances in critical tolerances are continuously tracked and where necessary corrected before bad parts are produced.
How to Use SPC :Statistical Process Control may be broadly broken down into three sets of activities: understanding the process, understanding the causes of variation, and elimination of the sources of special cause variation. In understanding a process, the process is typically mapped out and the process is monitored using control charts.
Aims and scope
Control charts are used to identify variation that may be due to special causes, and to free the user from concern over variation due to common causes. This is a continuous, ongoing activity. When a process is stable and does not trigger any of the detection rules for a control 29 chart, a process capability analysis may also be performed to predict the ability of the current process to produce conforming i.
When excessive variation is identified by the control chart detection rules, or the process capability is found lacking, additional effort is exerted to determine causes of that variance. Provide the means of finding out inadequacies in manufacture. The results of inspection are recorded and reported to the manufacturing department for further action to ensure production of acceptable parts and reduction in scrap.
Inspection 5. download good-quality raw materials, tools, and equipment that govern the quality of the finished products. Coordinate the functions of quality control, production, downloading, and other departments of the organizations.
Promote the spirit of competition, which leads to the manufacture of quality products in bulk by eliminating bottlenecks and adopting better production techniques. Measurand, a physical quantity such as length, weight, and angle to be measured.Threading of cylindrical pieces If triangular head is Dial gauge and mandrel 0.
Run out can rapidly ruin the disc if it exceeds the specified tolerance typically 0. Sustain customer goodwill by ensuring that no defective product reaches the customers. This method relies on all reproducibility conditions being varied so that their effects can be seen in the variation of results when making repeated measurements.
We measure it and get a result of Forums for working professionals. Coordinate the functions of quality control, production, downloading, and other departments of the organizations.
Since he has been developing novel metrology at the University of Bath, working closely with leading aerospace companies.
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