ISE 370: Industrial Automation and Control



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Co-ordinate Measuring Machine Lab (M-Pod)

Topics Covered:

CMM Fundamentals

Control Charts (UCL, CL, LCL, Cp specifications)

Equipment Required:

Brown & Sharpe CMM (M-Pod)

PCB to measure metal pads

Optical Probe (Camera), Video Crosshair, TV monitor

Lab Objective:

This lab will cover the basic functionality and operation of a Machine Vision Inspection System. The Brown & Sharpe Co-ordinate Measuring Machine (CMM) can be used for non-contact measurement of critical printing parameters. Viewing CMM’s image and analyzing measurements can identify various possible defects. Specific industrial and electronic packaging applications include: Solder paste, Stencil apertures, Solder joints, & Component placement accuracy.

A coordinate measuring machine (CMM) is a device for measuring the physical geometrical characteristics of an object. This machine may be manually controlled by an operator or it may be computer controlled. Measurements are defined by a probe attached to the third moving axis of this machine. Probes may be mechanical, optical, laser, or white light, amongst others. The typical "bridge" CMM is composed of three axes, an X, Y and Z. These axes are orthogonal to each other in a typical three dimensional coordinate system. Each axis has a scale system that indicates the location of that axis. The machine will read the input from the touch probe, as directed by the operator or programmer. The machine then uses the X,Y,Z coordinates of each of these points to determine size and position. Typical precision of a coordinate measuring machine is measured in microns.

Coordinate-measuring machines include three main components:

• The main structure which include three axes of motion

• Probing system

• Data collection and Reduction system - typically includes a machine controller, desktop computer and application software.

Lab Assignment:

On the demonstration printed circuit board (PCB >> Square BGA 225):

1. Measure 30 random pad diameters. Calculate the area of each pad. Calculate the mean area & standard deviation for your sample of 30 pads. You are interested in building an x-bar quality control chart for production. Supply the controls limits (UCL, CL, and LCL) for a proper control chart while providing a Cp measure of process capability. (n =5)

Engineering Specifications for Diameter of Pad = 0.024 - 0.032 inches

2. Measure 20 random pitch dimensions. The pitch is measured by finding the distance from the center of one pad to the center of the pad next to it (not attached by metal line). Calculate the mean pitch & standard deviation. You are interested in testing that the true pitch is less than 1.750 mm. Again, you are interested in building an x-bar quality control chart for production. Supply the controls limits (UCL, CL, and LCL) for a proper control chart while providing a Cp measure of process capability. (Sample Size n = 5) (Note: There is a limit of 100 readings, use Delete to delete last readings if needed).

Pitch Engineering Specifications = 0.058 - 0.060 inches

Note: 1 mil = 1/ 1,000 inch 25.4 mm = 1 inch

Button used to Define the Relationship between the last 2 circles (Line):

>>>Top Selection on Computer Panel

Lab Instructions:

1. Sign In (Notebook) & use a key to open the storage area on the right side of the CMM. (The key is stored in the blue safety box on wall between M-2 & M-4. See your instructor for code).

2. Storage area contains: >> 2-Memory cards (Reflex-memory cards) stored in a box on shelf. >> Optical Camera is stored in a black plastic case. >> CMM machine manual & Software Instructions stored in case.

3. Load/click both Memory cards into the Control Box (Front Side of Control Box) >> The Reflex memory card goes into bottom slot (follow arrow direction on card) >> The other memory card goes into the top slot

4. Turn On: >> TV (Panasonic) >> Video Crosshair >> Control Box (near memory slots, left side then wait for boot-up) >> Air Pressure (Blue Handle Valve on LH side of CMM >> ¼ turn CC to horizontal position)

5. Move Upper Support to the Home position (Back – Left – Up) >> x-axis is the left to right movements >> y-axis is the back to front movements >> z-axis is the Up & Down movements Note: X-Y-Z Buttons on the Left side of upper support are locks. Any x-y-z lock employed will not allow movement in that direction. (Very important to have the Z lock employed until camera is balanced).

6. Control Box (Buttons correspond to the boxes next to it on the screen)

After finding the Home position with the upper support; push button for “Check”

7. Select Probe Type: Optical

8. Manually Place Camera onto Upper Support. >> The spindle on the Camera holder goes into the slot underneath the support. >> Point Camera Down – Spindle up. >> Tighten down with handle on support.

9. Connect the two cables from the optical camera. >> VC 1000 label – “Long” Cable goes to the power supply transformer. >> VC 1000 label – “Short” Cable goes to the Video Crosshair (middle of rear box).

10. Connect the optic reader cable from the Video Illuminator to the Camera. >> Back of camera near bottom of camera >> insert & lightly tighten down knob.

11. WARNING: The Optical probe is a delicate instrument. Always hold the camera/z-rail when unlocking the Z-axis. The optical camera will break if the Z-rail is allowed to crash to the work table. Always lock the machine axes when leaving the machine unattended.

NOW: Support the camera while unlocking the Z switch. Use the Black Knob (Top side under Browne & Sharpe text) to counter-balance the Camera’s weight. Turn until the camera stabilizes!

12. On the Control Box: >> Select Sphere >> Select Insert Probe >> Select Optical Probe type (x-y-z axes locked) >> Set Y offset at – 4.5 >> Set X offset at 0.00 >>> PRESS DONE

13. Now Startup Options Display on Control Box >> Press Measurements

14. Turn On camera lights by pushing the Surface Button On (Fiber-optic Controller) >> A light should be shining on your PCB.

15. Measure any feature on your PCB. >> Release x-y locks to move camera to a convenient position. >> Release z lock for rough focus on object; you will see features on the TV monitor. >> X-Y-Z knobs to fine tune position of camera for taking measurements.

16. Measurement types on silver circular metal pads located on PCB: >> Find 3 points on a circle for a Diameter or Radius measurement. After finding each point on the circle, L-click the little mouse buttons just above the camera holder on the optical probe. [Enter on control box)… "Circle" should appear in the title box. Continue... >> For Pitch: L-click/select 3 points on a circle [Enter] then L-click/select 3 points of un-connected pad circle [Enter]. Now you must Define the Relationship: This will define the relationship between the last 2 circles (a Line Measurement). Use the horizontal arrow button if the “1D & 2D Distances” option does not appear in the Title Box. Change in XY is your distance measurement on control box.

17. CMM Clean-Up: Control Box> Clear Readings & Turn Off, Remove Memory Cards, Remove Cameras, Turn Off TV, Turn Off Crosshair, Turn Off Illuminator, Re-balance Z- axis with camera returned to box, Cut off air pressure (1/4 Turn Clockwise to Up position), Return Camera and Memory Cards to Lock Box, Return Key, Hand in Hypothesis analysis.

For "Circle" For "Pitch"

Circle 1D & 2D Distances

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