(a) Explain with the aid of a sketch the principle of an automated coordinate measuring machine. [20%] (b) What is meant
Posted: Sat May 21, 2022 8:47 am
(a) Explain with the aid of a sketch the principle of an
automated coordinate measuring machine. [20%] (b) What is meant by
Abbe principle? Describe why CMM does not conform to Abbe
principle. [30%] (c) A large horizontal arm CMM is used to measure
a steel bar of a nominal length of 3 m. The bar is moved from a 25
oC manufacturing floor to a 20oC metrology lab. If the bar is
measured immediately after it enters the metrology lab, what will
be the measurement error due to the temperature difference? How
long should you wait before you can properly measure the steel bar?
Assume the thermal expansion coefficient is approximately 10 ppm
per oC for steel bar and the time constant for steel to reach the
thermal equilibrium is 1700×L2 (L in m). [30%] (d) Describe briefly
the typical thermal error sources of CMMs and the technology for
minimising the thermal errors on CMMs.
automated coordinate measuring machine. [20%] (b) What is meant by
Abbe principle? Describe why CMM does not conform to Abbe
principle. [30%] (c) A large horizontal arm CMM is used to measure
a steel bar of a nominal length of 3 m. The bar is moved from a 25
oC manufacturing floor to a 20oC metrology lab. If the bar is
measured immediately after it enters the metrology lab, what will
be the measurement error due to the temperature difference? How
long should you wait before you can properly measure the steel bar?
Assume the thermal expansion coefficient is approximately 10 ppm
per oC for steel bar and the time constant for steel to reach the
thermal equilibrium is 1700×L2 (L in m). [30%] (d) Describe briefly
the typical thermal error sources of CMMs and the technology for
minimising the thermal errors on CMMs.