Lower cost vision success at spice manufacturer

When Spice Hunter looked at vision systems, it discovered the In-Sight vision sensor from Cognex, which in addition to being less expensive, seemed better suited to the application

Spice Hunter is a leading manufacturer of gourmet spice, offering one of the largest selections of spices and blends available, and producing roughly 45,000 jars of spice a day ranging from nutmeg to chili powder.

Each product, according to the company, is made with the freshest, all natural ingredients with no MSG, preservatives or irradiated ingredients.

With a strong commitment to producing high-quality spice, the company is also committed to the aesthetic quality of its distinctive square-shaped jars.

"How our products appear on the supermarket shelf is extremely important to us, and this year we have done a lot of work to figure out how to give our jars the best, most consistent shelf appearance," says Tim Ewen, Quality Manager at Spice Hunter.

"More specifically, we needed a way to ensure that the labels are on straight, the caps are properly applied, and the freshness seal on the cap is present and in tact." While the company had relied upon manual inspection to detect packaging flaws, the checks were conducted on a random sample basis.

As a result, less-than-perfect jars would occasionally get by.

"We needed to get as close to possible to zero defects, and quickly realised during our research that machine vision technology was a viable way to meet our packaging quality goals," according to Ewen.

With this realisation, the task of selecting a vision product was handed over to Pete Priebe, a Spice Hunter Manufacturing Engineer responsible for implementing and maintaining the plant's automation equipment.

According to Priebe, price was the first consideration.

"We had never used machine vision in the plant before, and wanted to get our feet wet with the technology at a relatively low price.

So, we looked at products in the five thousand-dollar range, and that's when we discovered the In-Sight vision sensor from Cognex.

It seemed to have the right tools for the job, and at the right price." Priebe contacted Cognex to get an application evaluation under way.

According to Christina Fein, the Cognex applications engineer assigned to the evaluation, in addition to being less expensive, a vision sensor seemed better suited for the application than a more expensive, PC-based vision system.

"When I first spoke with Spice Hunter, they intuitively felt that since they wanted to do multiple inspections, they needed a vision system with multiple cameras.

I explained that they could perform all the label, cap and freshness seal inspections all at once with In-Sight, which is a single-camera product." Said Fein.

The jars, according to Fein, presented a number of challenges for the vision sensor to overcome in order to inspect reliably.

"At fairly high speeds, the sensor had to deal with labels that were glossy, bottles that were glass, and caps that were shiny.

The customer also indicated that the ambient lighting in the factory can vary considerably, since there are windows and sunlight gets in.

For the evaluation, I received a variety of jar samples that they might actually see during production, not just good and bad jars, but marginal as well since marginal parts are where most vision systems fail." Explained Fein.

Having proved capable of performing all three inspections during evaluation, an In-Sight vision sensor was purchased and installed on the production line.

Having a basic understanding of conventional spreadsheets, Priebe was able to use In-Sight's patented vision spreadsheet environment to set up the application.

This involved selecting vision tools and parameters from drop-down menus using a video game-like handheld control pad.

The vision spreadsheet then automatically generates tool results into worksheet cells, which can easily be linked together to set up the label, cap, and freshness seal inspections.

The spreadsheet is transparent, which enabled Priebe to see a reference image of a spice jar, and the vision tools being applied to the image, without having to switch between separate screens.

On the production line, the vision sensor's digital camera is mounted perpendicular to the jars at a camera-to-subject distance of approximately 18 inches.

The camera connects to an industrial-hardened vision processor which links directly to a standard VGA monitor.

Because the vision processor is a standalone unit, it does not require the use of a PC during set up or runtime.

As the process begins, raw glass jars are first moved from boxes onto a turntable, which rotates them onto a feeding conveyor.

The jars move through various stations where they are filled, banded, capped, and labeled.

Once they leave the labeler, the jars move towards the inspection point spaced 2.5 inches apart from one another.

To achieve the highest image contrast, a bright white board is placed directly behind the inspection point, and basic front-lighting is used to illuminate each jar as it comes into view.

When a jar arrives at the inspection point, a sensor triggers the camera to capture an image of the moving jar and the image is instantly transmitted to the In-Sight processor.

The image is then processed and analysed using a variety of vision software tools.

When setting up the application, Priebe needed to pick two features common to all jars as reference points from which all measurements would be made.

The features that seemed to work best were the leading edge of the jar and the cap, since those two features are consistent in their positions no matter what type of jar is being run," explains Priebe.

In-Sight's PatFind pattern matching tool is used to verify that the cap and freshness seal are present, and that the cap is properly seated on the jar.

The PatFind tool was selected for its ability to locate patterns on the jars even as the jars move around on the loosely fixtured conveyor.

Labels are then checked for skew, which involves the use of edge detection tools to measure the distance between the leading edge of the jar and closest vertical label edge.

Labels position needs to fall within a tolerance of 3/16ths of an inch, which the company feels is necessary for the labels to line up perfectly as the jars sit on grocery store shelves.

The entire inspection sequence happens in approximately 300 milliseconds, keeping pace with a line speed of 200 jars per minute set by the labeling machine.

If a jar fails any of the inspections, the vision sensor sends a reject signal to a PLC, which then triggers a pneumatic gate to kick the jar off the line into a reject bin.

These jars are washed off and re-queued back into the line.

Jars that pass proceed down the line to a bundling station, where they are packaged up and shipped.

In addition to performing the inspections at required line speeds, the vision sensor helps improve process control.

If several label or cap problems in a row are detected, for example, this may alert line operators that the labeler or capping machine needs to be adjusted.

Operators can then stop the line and fix the problem before additional defects occur.

The sensor also records pass/fail data for each jar inspected, including data on the types of defects found, providing quality engineers with more information about the process.

Ultimately, Priebe anticipates that the vision sensor will be able to interactively link with other equipment when problems occur.

"If the vision sensor sees a trend in labels that are drifting too far to the right or left, we want it to be able to tell the labeler to move things in the other direction automatically without any operator intervention," he explains.

Most importantly, the vision sensor is helping Spice Hunter achieve its aesthetic quality goals, and according to Ewen, provides two primary benefits.

"First, we now have cumulative data on our manufacturing process, so we no longer have to rely on simple statistics based on sample spot checking.

And secondly, we can now actually pick out any bad jars that come through, thus ensuring that every jar leaving our facility is defect-free and has the greatest shelf-appeal.".

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