Machine Tool Metrology
Laboratory Overview
Spring
2013
Pre Lab General Overview (Will be done in class),
LAB 1. Environmental and Dynamic Tests Jan 23-24
LAB
2. Machine Control and Table Bending Check
Jan 30-31
LAB
3. Angular Error Measurements with Levels
Feb 6-7
LAB 4.
Linear Displacement Measurements Feb 13-14
LAB
5. Angular and Straightness Error Measurements Feb 20-21
LAB
6. Notebook Quiz & Individual Laser
Setups Feb 25- Mar 15 (Sign up for
times)
LAB 7. X-Y Laser Diagonals for Squareness
Measurement Mar 20-21
LAB 8. Measurement of Y Carriage Errors Schedule Group Time (Mar 25- April 5)
LAB 9. API 6DOF Measurement Apr 10-11
LAB 10. Final Notebook Quiz Apr 15-26 (Set up 1hour appointment)
2. Machine Control and Table Bending
Check
Lab Preparation (Read this): that
you may be prepared
Parametric Handbook #1 (PH1):
Software Correction of a Vertical Spindle Machining
Center (p10-12).
Lab Discussion : that you may broaden your knowledge
A.
Discuss Laboratory Notebooks
i. info: machine,
measurements, observations, procedures .
B. Discuss machine
mechanics and operation - ball screws, motors, scales, ways, controller
(g-codes), jog, manual data input, program input (canned cycles), thermal
effects, etc.
i. Z-axis positive into
spindle.
C. Discuss Table bending, rigid body check
D. Discuss use of levels to obtain relative angular
measurement.
Lab Measurements: that you may
develop experience
A. Record machine general
information (PH1 page 5) .
B. Demonstration of
machine operation basics : Referencing (home position, switches), jogging,
manual g-codes, initial codes (metric/inch, rapid traverse, coordinate system
(absolute/relative etc.).
C. Measurement of Table bending
(PH1 pages 10-12)
Lab Homework: that you may develop understanding
A.
Write CNC program [in ASCII (DOS) file] to move x in 50 mm increments and
dwell for five seconds to do data acquisition -2 mm, 0, 50, 100... to 750 mm
with 2 mm overshoot and reverse. The program should make 3 bidirectional runs
with a feedrate of 1000 mm/min.
B. Write CNC program as in A
using variables and DO WHILE commands for arbitrary step, dwell, and number of
bidirectional runs along a 3D linear path.
C. Calculate
Bending Coefficient for the table of the VMC45.
D.
Review table bending data. Consider the design of the VMC 45 and give an
explanation with illustration of why you think the table bends the way that it
does.
3. Coordinate Systems and Measurements with
Levels
Lab Preparation (Read
this): PH1 (p13-27).
Lab Discussion :
A. Coordinate
systems, defining and alignment, relation.
B. Machine
errors, error directions, geometric, dynamic (contouring), spindle, thermal
errors.
C. Rigid Body assumptions, (table, non-moving
axes).
D. Level operation and measurement of Angles.
Operation manual for levels is available.
E. Angular error
measurements with levels.
Lab Measurements:
A. Assignment of coordinate systems (Error, Tool etc.) and
correction zone relative to machine coordinates.
B.
exx(x), Roll of x-axis measurement with levels.
C. exy(y),
exz(z) as time permits.
Lab Homework:
A. Graph angular data sets as a function of scale
reading.
4. Coordinate Systems and Linear Displacement Accuracy
measurements
Lab Preparation (Read this):PH1 (p27-31)[Opt.B5.54 Standard Section
5.5].
Lab Discussion :
A. Coordinate systems, transformations of point
definition.
B. Laser positioning measurement, simple
theory.
C. Origin to origin measurement and effect of
position of optics (therefore must know positions of gages)
D. Thermal expansion of scale, ball screw etc.
E. Laser correction for humidity temperature and pressure.
Lab Measurements:
A.
Record, temperature, humidity, and pressure.
B. Laser
alignment techniques (all must align).
C. Linear
displacement accuracy measurement (x-axis).
D. Minimum step
(resolution) check.
Lab Homework:
A. Correct linear displacement laser readings for
T, P, H and the machine readings for thermal expansion due to deviation from
20o C.
B. Graph all measured and corrected
errors.
C. Correcting errors for optics offset from
origin: Assume a 4 arcsec error at 400mm what would the additional error be?
Explain and show math.
5. Angular and
Straightness Error Measurements
Lab Preparation (Read this): PH1 (p 31-35) [Opt. B5.54 Standard Sections 5.8.2.2.5,
5.8.2.3. (all subsections)]
Lab Discussion :
A. Angular measurement with lasers:
theory.
B. Straightness measurement with lasers:
theory.
Lab Measurements:
A. Angular measurement with laser (x-axis pitch and
yaw).
B. Straightness measurement with laser (along x, in y
or z).
Lab Homework:
A. Graph all measured and corrected errors.
B. Be ready next week to align laser and do setups for linear,
angular and straightness.
6. Notebook and Practical
Quiz
A. Setup and
Alignment quiz. Each person will be required to separately align the
laser and setup the optics as if you were going to do an actual measurement run.
You will be required to do setups for measuring linear displacement accuracy,
anglular errors, and straightness errors.
B. First Notebook quiz: You will be required to use your notebook and most answers
will be required to be referenced to your notebook.
7.
Squareness measurements
Lab Preparation (Read this): PH1 (p46-52)[Opt. B5.54 Standard Section 5.8.4,
5.8.4.1(& subsections)].
Lab Discussion
:
A. Carpenters check for square.
B. Laser Diagonal Measurements.
C.
Correction for optics positions, temperature, pressure, humidity (scale and
laser).
D. Laser mount on table.
Lab
Measurements:
A. XY
diagonal measurement.
B. YZ diagonal
setup.
C. XZ diagonal setup.
Lab Homework:
A. Do squareness
extraction from XY diagonals.
B. Outline each step for
doing A.
C. Prepare for final lab exam (diagonal setup).
8. Measurement of the Y axis
Lab
Group Assignment:
A. Do necessary measurements to
obtain dyy(y), dxy(y), dzy(y), exy(y), eyy(y), ezy(y)
B. Do
calculations to get above parameters. Discuss and show all work in
journal.
9.API 6 DOF Laser Measurement
Lab Discussion
The Automated Precison Inc six-degree of
freedom measurement system will be used to measure the X-carriage of the machine
tool.
Lab Measurements: (as many as practical)
A. Static measurements at positions measured
before.
B. Some dynamic measurments at different speeds
Lab Homework:
A. Graphically compare API static measurements to
those obtained with the HP laser after THP correction. Graph data and
differences
B. Graphically compare the API dynamic
measurements. Data and differences.
10. Final quiz
A. Final notebook quiz.
B. Turn in
Notebooks
Construction began on this site 12-17-97
Last
Update Jan 212
Jimmie A. Miller
Chief Engineer
Center for Precision
Metrology
Department of Mechanical Engineering and Engineering Science
The University of North Carolina at Charlotte 9201 University City Blvd.
Charlotte NC, 28223
E-Mail: jamiller@uncc.edu