421/521 Lab 5 Total Station, Laser Tracker and Coordinate Measuring Machine CMM

Motivation Become familiar with three types of precision 3D measuring devices Not to become experts, but to be aware of their existence and their potential to solve problems To large extent computers make these instruments useful to the common person They can be lifesavers in certain situations –Total stations and laser trackers can be leased –Can buy time on a CMM, or contract inspection

Total station Read instructions Go through set up Measure length of a ruler at end of lab Measure distance to ruler with tape measure Does math make sense? Don’t believe any measurement with a new instrument Try measuring size of light fixture –Does the math rectify the shape?

Total Station

More fun with the TS Set the TS up outside behind the East Wing There is a bench mark in the sidewalk to the garage Measure some features of the buildings visible Check that dimensions make sense by measuring a brick Pick a easily identified point and do a reversal –Do you get the same answer both times? –This is the classic check of a theodolite or transit

Laser tracker Get help from the TA or knowledgeable user These are very expensive instruments Use the LT to measure some of the same features measured with the total station How do the two sets of measurements compare? Which measurements are more precise, axial or lateral (azimuthal)? Why?

Laser Tracker Adopting spherical coordinate system, R(radius), Θ(Azimuthal angle), Φ (Elevation angle) –R: measured by IFM: distance measuring laser interferferometer ADM: measuring time taking the light travel between the tracker and SMR –Θ(Azimuthal angle), Φ (Elevation angle) Precision rotary encoder Versatile precision measuring tool in large volumetric target SMR(Sphere Mounted Retroreflector)

Lab: Measure OD and ROC of an optic Install and set up Laser Tracker Home the Laser Tracker using a given SMR Sample OD of a given optic(Lens or Mirror) Establish coordinate frame Sample the surface of optic Query, –OD of the optic –RoC of the optic –Surface figure Compare the measured OD and RoC to the result from Vernier calipers and 3-ball spherometer

CMM Go through start up check list –Marco made up a nice couple pages on this –He is out but I will get this on-line asap Follow through with the measurement of the Master ball to establish the machine coordinate system Measure several artifacts and use the software to see the best fit shape

CMM Adopt Cartesian coordinate, X, Y, Z –Linear coordinates XYZ are implemented in a precision guide way(typically airbearing) –Each position is measured by a precision linear encoder –Touch trigger probe (a switch) trigger the signal to record position

Lab: Measurement features Install the part provided on CMM Establish coordinate frame Measure dimensions, write down the reading and see if the measured value meet the tolerance Compare the result to the result from the measurement using Vernier calipers, Micrometer and other mechanical measurement tools

Drawing

Important All the instruments are very expensive –Little to no money to fix them if broken –Money earning projects rely on the CMM and LT Do not force anything, move slowly and deliberately. Don’t drop anything Think about each step before making a move The CMM probe tip is very delicate, move up to work slowly and gently