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Automated 3D Machine Vision Seal Inspection

Brett Martin is one of Northern Ireland’s leading manufacturing companies and a global player supplying specialist plastic products such as plastic sheets. plumbing and drainage systems for the construction, fabrication, and other sectors worldwide.

Seeking to follow and implement the latest manufacturing technology and innovation trends, the company decided to automate the inspection of caps and seals for its push-fit soil systems. Each piece (bend, reducer, joint etc.) has a ‘cap’ clipped on with a rubber seal that allows a mating tube to fit for its inner diameter. The products may be buried in soil, which requires a high quality for a long life time.

Automated Quality Check of Seals

The rubber seals need to be inspected for short-shots. They are created by being inserted into a moulding machine – if the mould is not fully filled with rubber, the seal will have a dent or nick, which can cause leakage.

A robot has already been used for taking the parts out of the moulding machine and placing them onto a cooling conveyor. Now the customer decided to inspect them using a vision system while the robot holds the parts. The requirement was that after the quality check, the robot would place the seals to a location based on whether they passed or failed.

Vision System 3D Inspection

The machine vision solution for Brett Martin was delivered by Fisher Smith, a machine vision integrator that strives to supply only excellent, robust, and reliable products.

The vision system needed to meet the customer’s high requirements, including high resolution and accuracy, robust performance, and the ability to differentiate black rubber from black plastic background. Therefore, they decided for a 3D vision system from Photoneo – the industrial-grade PhoXi 3D Scanner.

PhoXi 3D Scanner provides high accuracy, a great level of detail, and a resolution of more than 3 million 3D points. It is available in five models (XS – XL), each offering a different scanning range suitable for different applications. Altogether, the PhoXi family covers a scanning range from 15 cm up to 4 m. The scanner’s robust performance ensures a high-quality output even for challenging surfaces, including black, shiny, or transparent materials.

Due to the technology suppressing ambient light, the scanner works reliably even in demanding light conditions of up to 20,000 lux. PhoXi 3D Scanner is designed to withstand challenging industrial environments, including exposure to dust, water, and varying temperatures, which is ensured by IP65 rating and thermal calibration. The scanner features two powering options – PoE (Power over Ethernet), enabling the use of a single cable with a length of over 30 m for both power and data connection, and a 24V power option.

Final solution

Fisher Smith uses its own machine vision software GenVis built on the MVTec vision library HALCON for image acquisition, image processing, display, and graphics for cameras from multiple vendors.

Because HALCON supports the interface of PhoXi 3D Scanner, Fisher Smith was able to quickly integrate the scanner into GenVis software, using standard tools they already had.

The automated inspection process process is as follows: The robot positions each seal in front of the 3D scanner to make a 3D scan and reveal potential short-shots. It takes less than 1 second to take each scan. If the seal passes the quality check, the robot places it onto a cooling conveyor. If it fails, the robot places it among rejected parts.

Initially, the process was very stop-start due to the robot not being able to hold the seals steadily in front of the vision system, which affected the quality of scans. A number of improvements needed to be made to keep the robotic head static.

Benefits of Automating Inspection Process

The main benefit of automating the inspection process is a decreased number of faulty seals that get to the end customers. Though the seals are manually handled later in the process, the operators do not always spot all short-shots.

The automated inspection keeps up with the existing process and fills in the dead cycle time, which means that it has not slowed down the production process. Another important fact is that the solution did not take up additional floor space and fitted into the existing cell, requiring minimum installation.

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