IPD Technical ConferenceFebruary 19th 2008

Industry: Automotive – Circuit Board Mounting Screw

Application: Screw with Silicon Rubber Collar Assembly Inspection

Presented by: Scott Montgomery / DALSA - IPD

Metal Screw with Green Silicon Rubber Collar

Assembly and Measurement Inspection

Thread

Silicon Rubber Collar

Automotive part – used to bolt mini circuit board to center console inside a JeepWrangler. Silicon collar used to keep water from penetrating. i.e. four-wheeling

Inspection Requirements

Measure Silicon Rubber Collar Rib Diameter:

12.05 mm + / - 0.13 mm

Check Silicon Collar for Following Surface Flaws (or defects):

Yellow Pigment Stains

Foreign Material, i.e. fibers, thread, etc.

Gas Pockets in the silicon mold

Flash and Short Shots

Missing, Rotated, Misplaced or Reversed Collars

Check for Following Thread Defects: Foreign or Extra Material in Shoulder

Missing Threads

Critical Measure: Rib Diameter

Rib Diameter

+ / - 0.13 mm

Surface Flaws in Collar

Yellow Pigment Stains Foreign Material Gas Pockets

Flash Short Shots

Misplaced and Reversed Collar

Reversed CollarCollar Properly Placed Misplaced Collar (pushed downward)

Head Diameter LargerHead Diameter Smaller

Thread Defects

Missing ThreadsForeign Material in Shoulder

Vision System Overview

Vision System : VA-41 w/ Sherlock

2 Cameras, TM2 640 H x 480 V Camera 1: Lighting and Optics:

TML 56676 Telecentric Lens

24v. White LED Pad Light, size 75mm x 75mm

Aluminum Polished Block

Camera 2: Lighting and Optics Fujinon 35 mm Lens w / 5mm ext. ring

24v. White LED Ring Ling ( 45 deg. angled LEDs )

Initial trigger pulse sent from PLC, then custom DALSA IPD I/O trigger module – generates a trigger pulse train

User Interface – Visual Basic front end

Camera 1: Collar and Thread Inspection

Aluminum Block( simulates a backlight )

Front Pad Light( white LED )

Camera 2: Insertion Inspection(misplaced collars)

Ring Light( 45 deg., white LED )

Machine Overview

Screws and green silicon collars are “bowl fed” independently to pick-and-place grippers

Screws are dropped into a pocket on an indexing rotary table

As the table indexes, a gripper inserts a silicon collar over the screw head

At the next station, a motorized drive engages, lifts, and presents the screw assembly to the vision system – CAMERA (1)

The completed assembly is spun 360 degrees to perform 100% surface flaw and thread inspection, and rib diameter measurement The vision system snaps a picture every 18 deg. of rotation – 20

triggers total for one completed revolution

Machine Overview (continued)

The table indexes the assembly to the next station to check for proper collar insertion – CAMERA 2

The vision system outputs a separate “PASS” signal at each inspection station to the PLC

If the assembly failed either inspection, a pick-and-place gripper will discard the part at the next indexed station

Otherwise, the part moves to the final station and is placed onto a conveyor that drops the completed assembly into a shipping carton

Once the desired lot quantity is reached the carton is sealed and ready for delivery.

Application Challenges

Achieving Full 360 degree, 100% Surface Inspection Using a pulse train of input triggers from DALSA IPD trigger

module ‘matched’ to the desired speed of rotation – 1 sec.

Finding a “One Light Fits All” Solution Green collar absorbs standard ‘RED’ LED wavelength of light Motion blur and minimal background contrast Lighting on a cylindrical surface produces centerline hotspot

Detecting Subtle Surface Flaws and True Flash Defects Discriminating between real defects and acceptable surface

imperfections – TEXTURE TOOL Discriminating between true flash and acceptable flash

Keeping Within Rib Diameter Tolerances Minimizing drive wobble and slippage Detecting drive slippage Minimizing perspective distortion

Capturing a Full 360 degree Field of View(using a pulse train of input triggers)

PLC VA-41DALSA IPD

CustomI/O Module

1 Trigger Pulse 20 Trigger Pulses **

1 2 3 20

** Input triggers are fed to the trigger input on VA-41 I/O breakout board( PIN 2 )

Begins Inspection Cycle

Begin to Capture and Process Images

Finding a “One Light Fits All” Solution

Aluminum Block( simulates a backlight )

Front Pad Light( white LED )

Lighting Challenges( creating a well-contrasted background with diffuse foreground )

Center line hotspots ( skunk stripe )

Polished aluminum block reflects light, providing a bright background

Green silicon rubber absorbs most

LED light

White LED Pad Lighting Suits All Inspections Requirements

Edge ProfilingSurface Inspection

Flash

TEXTURE TOOL ( Detecting Subtle Surface Flaws )

Gas Pockets

TEXTURE tool is effective for measuring texture based on edge density wherethe edge sensitivity can be ‘tuned’ to discriminate between true defects and natural surface variations - TOTAL EDGE COUNT is primary measure

Other Surface Flaws

Foreign Material

True Flash vs. Acceptable Flash

Acceptable Flash True Flash

Tracking Independent Reference Points

Left side Reference Point Right side Reference Point

Flash Tools( tracks laterally )

Minimizing Drive Wobble ( critical for rib diameter measurements )

Measuring Rib DiameterTracking Spin Motion

Detecting Drive Slippage

Tracking thread motion to detect drive slippage

Minimizing Perspective Distortion

Conventional Lens Telecentric Lens

Conventional vs. Telecentric Lens

Conventional Lens

Perspective Distortion

Telecentric Lens

Flat - No Distortion

User Interface

Summary

Overall cycle time per part : 2.0 seconds

Inspection time – 800 msec.

Shuttling part in and out – 1.2 seconds

Machine runs at less than 1.0% percent scrap rate

Produces about 40,000+ parts per week

Customer Quote :

“ Thanks to IPD, now I can sleep at night “

O.K. Guys, It’s a Wrap ! ! !

Tom “ the builder ”

“Vision Guy”

“ Dr. V.B. ”