Assessment of Methods for Block Volume Measurement

1
Assessment of Methods forBlock Volume Measurement

• Carl R. F. Lund
• February 28, 1999

2
Business Opportunity with ABC Blocks

• ABC Blocks may contract with Big C Enterprises
  for the manufacture of ABCs blocks
• ABC Blocks requires production line monitoring of
  blocks
• Must meet volume specification
• Big C Enterprises currently does not have
  standardized methods for production line
  monitoring of block volume

3
Outline

• Project Objectives
• Summary of Findings
• Methods Tested
• Procedure
• Results
• Critical Examination of Methods
• Conclusions
• Recommendations

4
Project Objectives

• Identify different methods that could be used to
  check the volume of blocks as they come off the
  production line
• Compare the accuracy and other merits of the
  methods
• Select the best method for development and
  implementation in the process.

5
Summary

• Three methods for volume measurement were
  examined
• One based upon direct measurement
• Two based upon fluid displacement
• As tested, none were completely satisfactory
• A method based upon fluid displacement is
  recommended for further development
• Rapid, lowest cost
• Can be implemented with sufficient accuracy

6
Methods Considered

• Measure length, width and height multiply to get
  volume
• Displace fluid from a container, collect the
  displaced fluid and measure its volume
• Displace fluid within a container, measure volume
  of fluid only, add block and measure volume of
  block and fluid, find block volume from difference

7
Procedure

• A test block was machined from pure aluminum
• volume was found by weighing, using
  well-established density of pure aluminum
• Each method was used in the lab to measure the
  volume of this same block.
• assessed accuracy, ease of implementation, and
  reliability

8
Results

• Test block volume 3.83 cm3
• Volume by measuring dimensions 4.03 0.15 cm3
• Volume by collecting displaced fluid 3.06 0.05
  cm3
• Volume from change upon displacing fluid 3.0
  1.4 cm3

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Critical Evaluation of Method ofMeasuring
Dimensions

• The method is time-consuming and labor intensive
• There are multiple sources of error
• Each of 3 dimensional measurements
• Block may not be true
• Computational errors
• Any one of these errors can be significant enough
  invalidate the result
• Accuracy as tested is not satisfactory
• Measured 4.03 0.15 vs. 3.83 cm3 true volume
• Could be improved but might increase time
  required to make the measurement

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Critical Evaluation of Collecting Displaced Fluid

• Results were accurate but imprecise
• Measured 3.06 0.05 vs. 3.83 cm3 true volume
• Suspect systematic error in gradations of
  graduated cylinder
• Could repeat, dont recommend doing so
• Method is moderately time consuming
• Must top off container before each measurement
• Requires care not to spill or lose displaced fluid

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Critical Evaluation of Measuring the Change in
Volume

• As tested the accuracy was not sufficient
• Measured 3.0 1.4 vs. 3.83 cm3 true volume
• Can be improved by better design of equipment
• Method is rapid
• Potential operator errors are no worse than with
  other methods
• With improvement in accuracy this is the method
  of choice.

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Conclusions

• Measuring dimensions is not accurate enough, time
  consuming, and subject to several sources of
  error
• Collecting displaced fluid is awkward and
  time-consuming compared to measuring change in
  fluid volume due to adding block
• Further development of apparatus for measuring
  the change in fluid volume is necessary
• It is the method of choice
• It is accurate (with redesign), rapid, and
  inexpensive

13
Recommendations

• Design apparatus specifically for present
  purposes and ensure accuracy is adequate.
• Mark volume gradations on the vessel that are
  finer than the desired accuracy
• Make the container cross-section only slightly
  larger than the size of the blocks being measured
• If desired accuracy cant be attained consider
  collecting displaced fluid
• eliminate systematic errors in equipment.