IPD Technical ConferenceFebruary 19th 2008

Flat Ribbon Cable Ends

The Product

Company X manufactures flat ribbon cables and connectors.

The cable ends must meet extremely high tolerance requirements – hundredths of millimeters – to ensure that when they are mated with connectors, the conductors in the cable ends mate with the pins in the connectors.

Inspection Requirement

Typical measurements

Width: 30.99 mm

Span: 29.39 mm

Left stripping: 4.98 mm

Right stripping: 4.96 mm

Inspection Requirement

Currently, inspection of the cable ends on randomly-selected cables is performed with an optical comparator. This approach is highly subjective.

The measurements must be automated. (Inspection is still performed on a sample of cables; 100% inspection is not a requirement.)

Prototype System

A cable is inserted into an inspection station that constrains the position of the cable end within the field of view of a high-resolution camera. (In a 1376 x 1035 image, each pixel equals about 0.02 mm.)

The cable is back-lighted.

Prototype System

Various Sherlock ROIs and algorithms are applied to make the measurements.

ProblemsBecause the measurement tolerances are so

strict, vibration or movement of the camera can throw off a “static” calibration and result in bad readings. Therefore, Sherlock must be recalibrated on every image acquisition…

BUT, the integrator assumes that the cable being inspected meets the manufacturing specification for “average width”, and uses this as the calibration target.

Solution: Calibrate on every image using a calibration target of a known size

30 mm-wide calibration bar

Line ROI executing Inside Caliper algorithm

Calibration bar width (pixels)

Calibration bar width (mm)

mm/pixel

(Instance of Numeric : Divide)

Test Results

Width Left stripping Right stripping SpanAverage 31.3063 5.1465 5.0828 29.3044Variance 7.83374E-06 3.31749E-06 7.26716E-06 5.08572E-06Min 31.2996 5.1424 5.0770 29.3004Max 31.3123 5.1499 5.0891 29.3089Range 0.0127 0.0076 0.0122 0.0085

Cumulative results from three sets of images of the same cable end.

Within each set of about 20 images, the cable is stationary; this is a test of Sherlock's measurement repeatability on the "same" image.

From image set to image set, the cable was moved slightly; this is a test of Sherlock's measurement repeatability on the same part in different positions.

Left margin Right margin0.9503 1.05151.35926E-05 1.72484E-050.9436 1.04580.9572 1.05950.0136 0.0137

AverageVarianceMinMaxRange