Machine vision can boost productivity

Simplot Australia, which offers a range of food products under well known brands such as Edgell, Birds Eye, John West, Leggo’s, Ally, Seakist, Harvest and Chiko, has six manufacturing facilities around Australia including at Echuca in country Victoria.

The company says there is a constant effort to maximise quality control systems and processes through new and innovative technologies.

At the Echuca plant, which employs some 140 people, machine vision technology from Omron has been installed as part of the quality control system on the glass line that produces Leggo’s pasta sauces.

The design and implementation of the system was undertaken by an in-house team led by mechanical project engineer Jimmy D’Alessio who advised the team on how to implement the system.

Other team members included electrician and programmer Paul Baker who was involved with the actual programming that needed to be coded, and control system engineer Wes Brown who was also involved with the programming codes.

Input to the project was also provided by electricians from the electrical department to wire the system, and fitters from the mechanical department to manufacture bracket fittings to support the system.

The system consists of a ZFX-C15 vision controller with one camera connection, PNP, IP20, integrated 3.5" TFT LCD colour touchscreen, RS232, 422, USB2.0, Ethernet outputs, 32 banks, 24Vdc supply 1.5A, together with a FX-S vision monochrome camera, and a programmable logic controller (PLC) (also from Omron) to automate the system at high speeds.

Other elements of the system include CCTV lenses to suit FZ series vision, a red LED backlight, a S8VS-12024 power supply, a photo-electric sensor, and a reflector for long distance photo-electric switch.

D’Alessio says that the purpose of the vision system is to give even greater assurance on the quality of the glass jars containing the product supplied to customers.

"The system has to inspect 320 glass jars per minute as they pass through the gripper conveyor and if an imperfection is detected the system output displays the detected jar and signals the operator to physically inspect the item. The vision system is then reset to continue inspecting each jar under automation," he explained.

"As the jars pass along the conveyor, the system takes a 2D monochrome photo and inspects for any imperfections on the glass with the aim of ensuring that only good quality glass goes through to the filler.

"This new automated vision system provides another element to our focus on total quality control, adding to the existing critical control point (CCP) safeguards, including X-ray machine checks at the end of the line."

D’Alessio points out that the team was faced with some significant challenges in designing and installing an effective vision system. For example, the speed of the conveyor that grips the jars can vary, which created issues.

The system has to inspect 320 glass jars per minute as they pass through the gripper conveyor."Every jar has to be photographed, so operation of the system needs to be precise. Initially, the sensor was positioned at an angle to the field of view of the inspection system, making it difficult to take an accurate photo.

"The solution was to move the sensor away from the camera field of view and relocate it 40 mm away in a parallel line to the field of view.

"This eliminated the time delay fluctuations created by the gripper conveyor and enabled accurate detection of the following jar coming up close with a small gap, making both critical points parallel to cope with high speed inspection of each jar.

High-speed time delay

According to D’Alessio, another issue was that the main PLC was doing a lot of processing, which caused delays, particularly when the line was running at high speed.

These problems were overcome by utilising a micro PLC with high speed time delay and programming it to deliver a high speed signal to the vision system from the photo-electric sensor, thus forming a close loop system away from the main PLC to deal with the high speed operation.

The theory was to create a loop within a loop in order to automate each system under a deterministic time nature."If detection occurs, a signal goes out of the loop enabling the main PLC to initiate ‘inspect jar condition’, stopping the jar at a pre-determined inspection point. The theory was to create a loop within a loop in order to automate each system under a deterministic time nature," he said.

D’Alessio explains: "The biggest difficulty with the project was re-programming each product with different specifications, time delays and memory banks data under automation so that when a particular product was selected through the main PLC it also changed the selection at the vision system

However, with Omron providing support and assistance, we were able to get the system up and running.

"It was found that the best way to detect defects in the glass was to illuminate the jars from the back, and laboratory testing helped us to determine which camera and lens needed to be used."

According to D’Alessio, total investment cost of the vision system, including labour, was $25,000 and significant productivity improvement benefits are flowing from the project, particularly by ensuring first time quality of all products and eliminating the need for rework.

Advanced technology

Machine vision specialist at Omron, Panfilo Tarulli, says the ZFX Machine Vision Sensor is a total image processing system that includes everything from a camera with an integrated light source to an image processing unit.

"The ZFX can use a C-mount camera which enables you to choose the correct lens to match the field of view, and it can be used in combination with optical lighting, such as transmitted lighting, low angle lighting, and bar lighting to support different inspection types," he said.

"The ZFX Machine Vision Sensor stores up to 100 files of image data in the main memory without slowing measurement speed, and images data can be remeasured, so even with a high speed line the results of the measurements can be checked at leisure afterwards.

"Omron’s ZFX unique sensitive search capability can observe and detect the smallest detail in an object and display it on a screen, including smears, scratches, chips and burrs.

The system can provide a valuable quality control function for a wide range of manufacturing industry applications."

Omron recently released the new FZ4 Machine Vision Sensor which has a large touch screen and has many filtering features as well as code reading functions.

It also has HDR (high dynamic range) function and OCR (optical character recognition) capability, as well as remote access, which enables the user to log into the vision system to take full control, either from their office or off site.

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