Wire and Cable Technology International September/October 2013 : Page 158

High-Speed Machine Vision Applications in Cable & Shrink Tubing Industry Ananda V. Mysore, President Angle Systems LLC www.anglesystems.com Ramon Ware, Quality Engineering Manager TE Connectivity www.te.com The use of machine vision techniques for inspection and metrology applications has been continually increasing with the availability of high-speed and high-resolution cameras. However, the perception in the cable and tubing industry about the use of machine vision techniques has not been that great due to various factors including system speeds and complexity. The essential checks that most cable and tubing industries have are diameter, lump and neck-down, line speed and the length of cable or tubing produced. Most of these measurements use laser-based measurements and dedicated hardware. Though these are the absolutely needed inspection and measurements in the cable and tubing industry, there are other factors that are equally important that need to be monitored. These include the verification of print, cable jacket defects such as drag marks, pin holes, etc. as well as tube cut length and shape (in the case of electrical heat shrink tubing). This article presents two examples of these types of inspection that just started being used in the industry. These effects could lead to customer complaints and product returns depending on the severity of the is-sue. Another issue that may come up at high speeds from 200 to 1500 fpm is that an operator is not be able to see the print on a cable or tubing if it contains a typographic error. In order to reduce or eliminate the customer com-plaints, many manufacturers either scrap the prod-ucts or clean the product and reprint the entire product. Here are the issues: •Scrapping of the cable or tubing products results in reduction in yield and hence overall profitability. •The cleaning and reprinting operation involves more time to correctly produce the same product and hence increasing the manufacturing cost. This problem can be solved using a Print Quality Inspection system that either provides automatic real time feedback to the operator or automatically marks the defective parts so that they can be sepa-rated at a later time dur-ing the manufacturing process. Angle Systems has designed and suc-cessfully implemented these types of systems at cable manufacturing plants in the USA. These systems can read and locate defects on cables at speeds of up to 1500 fpm (see Figure 1 ). Fig. 1 — Print Quality Inspection system from Angle Systems, including example of good and bad parts, shown below. Print Quality Inspection Systems Ink jet printers printing on cable jackets require main-tenance from time to time. Usually, failures begin with a single jet blocking the ink and continuing the trend to block the entire set of jets so that there are partial or no characters printed on the cable or tub-ing. Also, due to the blockage of the jets and the ink pressure build up, there might be a splurge of ink on the cable or tubing. This has many effects including: •Missing print on the product. •Partial and unreadable characters. •Smudge on the entire length that can probably affect even good products when they are spooled. 158 Wire Harness & Cable Connector OK NOK September 2013

High-Speed Machine Vision Applications In Cable & Shrink Tubing Industry

Ananda V. Mysore

The use of machine vision techniques for inspection and metrology applications has been continually increasing with the availability of high-speed and high-resolution cameras. However, the perception in the cable and tubing industry about the use of machine vision techniques has not been that great due to various factors including system speeds and complexity. The essential checks that most cable and tubing industries have are diameter, lump and neck-down, line speed and the length of cable or tubing produced. Most of these measurements use laser-based measurements and dedicated hardware.Though these are the absolutely needed inspection and measurements in the cable and tubing industry, there are other factors that are equally important that need to be monitored. These include the verification of print, cable jacket defects such as drag marks, pin holes, etc. as well as tube cut length and shape (in the case of electrical heat shrink tubing). This article presents two examples of these types of inspection that just started being used in the industry.

Print Quality Inspection Systems

Ink jet printers printing on cable jackets require maintenance from time to time. Usually, failures begin with a single jet blocking the ink and continuing the trend to block the entire set of jets so that there are partial or no characters printed on the cable or tubing.Also, due to the blockage of the jets and the ink pressure build up, there might be a splurge of ink on the cable or tubing. This has many effects including:

• Missing print on the product.

• Partial and unreadable characters.

• Smudge on the entire length that can probably affect even good products when they are spooled.

These effects could lead to customer complaints and product returns depending on the severity of the issue.Another issue that may come up at high speeds from 200 to 1500 fpm is that an operator is not be able to see the print on a cable or tubing if it contains a typographic error.

In order to reduce or eliminate the customer complaints, many manufacturers either scrap the products or clean the product and reprint the entire product. Here are the issues:

• Scrapping of the cable or tubing products results in reduction in yield and hence overall profitability.

• The cleaning and reprinting operation involves more time to correctly produce the same product and hence increasing the manufacturing cost.

This problem can be solved using a Print Quality Inspection system that either provides automatic real time feedback to the operator or automatically marks the defective parts so that they can be separated at a later time during the manufacturing process. Angle Systems has designed and successfully implemented these types of systems at cable manufacturing plants in the USA. These systems can read and locate defects on cables at speeds of up to 1500 fpm (see Figure 1).

The Print Quality Inspection system consists of a high-speed camera continuously capturing images of the print on the cable. The camera control module triggers the camera based on the encoder signals on the cable lines. This ensures print quality verification is consistent even with the variation in the line speed.With Angle System’s image analysis application, alphanumeric print is digitally read and checked for defects (Figure 2). The defects or missing characters are analyzed based on a scoring system that can be set based on quality requirements of each manufacturer. Once the system detects the defects, it has two options:

• Alert an operator using an alarm.

• Mark cable/tubing with an ink (preferably invisible ink).

By alerting the operator at a very early stage of missing characters or ink dots, scraping of the cable or tubing can be avoided if the operator takes the immediate action of cleaning the ink jets.

Marking the cable/tubing locates the sections that are missing characters or have other defects. A marking detection unit installed at the tubing cutter/diverter unit can divert the defective parts. In case of cable manufacturing, these marking detection units can locate the position of the cable defect and alert the operator to cut those portions of cable (Figure 3).

End Cap Inspection System

Heat-shrinkable end caps provide mechanical and environmental protection to the cable and are mainly used in sealing the ends of the cable. Heat-shrinkable, dual-wall PD Caps encapsulate crimped electrical connections.

PD Caps are manufactured from radiation-cross-linked polyolefin. With heating, the outer jacket of the PD Cap shrinks while the inner wall flows into gaps in the crimp, creating an electrically insulated connection.

TE Connectivity is the world-leading producer of these types of shrink-tubing. Traditionally, the inspection method that was used by TE was a manual method wherein an operator looked for the defects such as short lengths, out-of-tolerance OD, tip length, presence or absence of tip, tip angle, etc. The images in Figure 4 indicate some examples of good and bad parts.

The inspection of these defects is a time-consuming process. Also, the chances of bad parts mixing with the good parts are very high. With the advancement of technology, crimping and heat shrink processes are automated and hence it is important to make sure that the defect rate is extremely small.

Angle Systems has custom designed and developed a defect sorting machine. This system is currently being used at TE Connectivity’s Menlo Park facility, and inspects heat shrink elements based on the shape parameters and separates them into good and bad parts. It consists of three main modules (Figure 5).Part Feeding Module. The part feeding module is a vibratory bowl that feeds the parts into an imaging system for inspection. The PD Caps are loaded in the vibratory bowl and made to slide down on a ramp.There is a gap specifically created in the ramp that separates the vibratory and nonvibratory parts of the ramp, which helps in separation of the individual parts. At the end of the ramp parts are made to fall vertically so they are presented to the camera for imaging (Figure 6).

Part Inspection/Analysis Module. The module consists of three camera and lighting units located so as to obtain synchronized images of a PD Cap from three different angles. A proximity sensor located at the end of the ramp signals the camera and lighting units, the availability of the part for imaging. Once the system captures images of the part (flying in air), a high-speed computer with Angle System’s image analysis custom application, analyzes the image for various parameters and tolerances and sends a signal to a part separation controller to accept or reject the part (Figure 7).

Part Separation Module. A part separation module consists of a controller for receiving signals from the system computer and relaying it to the part separation air jet module. A group of air jets blows high-pressure air ejecting the part to a box containing bad parts (Figure 8).System can take images, analyze and make a decision to accept or reject the part in less than 0.050 seconds. Due to the mechanical feeding and pneumatic part ejection system, throughput can be limited to about 3 to 4 parts a second. Www.anglesystems.com / www.te.com

The authors acknowledge the contribution of Robert Gerber of TE Connectivity and Michael Signorelli and Reid Berry of Angle Systems LLC.

Company Profile...

Angle Systems LLC, founded in 2009 designs, develops and integrates high-speed metrology, inspection and automation system solutions involving vision and laser-based sensor technologies. Www.anglesystems.com

Read the full article at http://www.bluetoad.com/article/High-Speed+Machine+Vision+Applications+In+Cable+%26amp%3B+Shrink+Tubing+Industry/1489708/172580/article.html.

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