IE 1255 --LABORATORY 1
INTRODUCTION:
Metrology is the study of instrumentation and measurement. As such, it explores the techniques and tools of accurate and precise measurement. During this laboratory, we will begin exploring the use of these tools and instruments that were developed to make accurate assessment of product length. We will make up a set if varying length stacks of Johansson Gage Blocks (one by each team member) ranging from fractions of an inch to several inches and measure them using steel rules, vernier calipers and micrometers. These readings will (eventually) be compared to the expected values and instrument accuracy and repeatability assessed. Assessment will be most accurately performed using absolute deviation error of the measurement from the expected (built length) or absolute percentage deviation between these two values. Using this data, we will try to develop a preliminary “Cost of Quality Measurement” rating by studying the time it took to make a measurement using an instrument versus error inherent in the measurement. Work in your engineering teams as “Pairs” to assist each other while getting comfortable with making these measurements.
EQUIPMENT:
Gage Block Set (grades 2, 3 or 4)
Linear Steel Rule
Vernier Caliper
Micrometers, set: 0-1" 1-2", 2-3"
(Metric micrometers as available)
PC and EXCEL Software
Procedure:
Each Engineering Team will measure several stacks of gage blocks to bracket 0.1111" to 2.9999". Your team members will build (“wring”) these stacks (and actual height recorded but not revealed during measurement). These will be measured using all of the instruments and each of them by all team members. The resulting measurements for each member will be saved in a spreadsheet (EXCEL). Errors, as an absolute value and/or absolute percent deviation from the stack expected values should be calculated and plotted. Using your error measurements, comment on the following issues:
1. Relative accuracy of each measurement tool
2. Ease of use versus Accuracy (try to build a “Cost of Quality” measurement!)
3. Who is “Best” (most accurate) instrumentation user on the team (was it luck or skill??)
As a team, prepare a graph of measurement error for your team “average” error for each gage block stack found using each of the measurement tools, ie. three lines on a single graph. In addition, plot each team member’s graph of instrument usage – ie. all three instrument for a single user on one graph. Prepare a short summary of the results of the accuracy assessment. These should aid in answering the 3 questions above. Finally, be sure to include your personal observations relating to gage block and instrument use in a laboratory notebook. Also include a table of your measurements and error plots for each instrument in a notebook for future reference.