Reduced scrap rates. Increased throughput of first quality material. Product consistency. Increased productivity. Cost efficiencies. These are some of the requirements that nonwovens producers must meet as their customers increasingly demand high-quality, defect-free materials. These days an increasing number of nonwovens producers are turning to automated quality control (QC) inspection systems to ensure that they can satisfy these demands.
QC equipment can reduce or prevent the cost of sorting and re-inspecting or re-packaging products as well as derail the costs of supplying a package of defective products to the consumer.
While there’s no argument that the systems are reliable, easy to use and easily integrated into the factory automation system, makers and users of nonwovens who are considering making an investment in these systems need to know what type of return on investment (ROI) they can reap.
Where’s The Beef?
To critics who argue that QC systems are more of a luxury than a necessity, Brian Heil, president of Isra Surface Vision said, “In the hygiene market, nonwovens producers are forced to have this technology to ensure that they can maintain and ship the quality that their customers require. It’s a necessity just like putting gas in your car. You can’t produce material unless it’s being inspected. You don’t know what could potentially reach the customer who is very sensitive to defects and has a certain specification and there’s a contract in place that says, ‘If we find a problem, we’ll send back the whole lot number.’ What would that cost relative to an inspection system if they get truckloads of material back? If it’s a diaper or fem hygiene product or a medical product (medical disposables), it has to be very high quality.”
Emphasizing that nonwovens producers have greater quality requirements for their goods because end users have less tolerance for inferior products, Todd Guzzardo, Erhardt-Leimer’s (E-L) North American sales and marketing manager also asserted that inspection systems are becoming more of a requirement than an option. “In the past years, inspection systems with high resolution requirements were not as easily attained and they were much more cost prohibitive. Due to the high investment required for accurate inspection capabilities, it was more economical to produce extra material to compensate for potentially defective materials than to inspect them with automated systems. Currently, with the economies of scale with regard to technological advancements in both camera and computer technologies, the ROI is clearly much more cost effective in savings on waste from defective materials,” Mr. Guzzardo said.
Pointing out that the industry is running at approximately a 5% scrap level, AccuSentry’s president and CEO, Wei-Siong Tan said the scrap level can be reduced to 2% by analyzing data generated from the inspection. “That 3% spread is tremendous in terms of adding to manufacturers’ bottom lines. One percent in a diaper line could represent $250,000 in terms of revenues. The payback is very quick. The manufacturing equipment is expensive and you want to protect your investment. In a recession, the most important thing you can look at is how to improve efficiency. You are putting in a control mechanism that will increase efficiency with a very, very fast payback cycle. Adding automated inspection equipment also leads to process improvements and a higher overall efficiency based on equipment efficiency and reduced waste levels. A good target is 85% OEE with only 2% scrap,” said Dr. Tan.
As nonwovens producers’ and end users’ requirements for lightweight spunbond continue to increase, QC equipment suppliers have developed innovative tools to enhance detection of defects on high speed lines. These tools include high-resolution systems and new lighting techniques.
One such supplier, Isra Parsytec, has developed the Smash System. “We have a very high-resolution system for high-speed processes such as lightweight spunbond which is typically being produced at speeds of around 1000 meters per minute. We’ve developed some new lighting techniques that enable us to see the full range of defects required by the hygiene market. The speeds of the material— especially for lightweight spunbond— are being produced much more quickly. We can scan our cameras much more quickly to keep up with these speeds and offer our customers and nonwovens producers the highest resolution system with a new lighting technique that reports a complete range of defects that are of interest to nonwovens producers’ customers,” said Mr. Heil.
Dr. Tan also sees an increased need to find defects in high-speed lines as diaper technology has improved in recent years. “Inspection equipment gained traction in the diaper industry in the last three years. All of the major machinery manufacturers are very interested in this kind of technology. Now one of the factors that’s contributing to the popularity and speeding up the adoption cycle is the increasing speed of diaper lines. Not too long ago something that was running at 600 diapers per minute was considered high speed. Now if it’s anything below 1000, it’s considered regular speed,” said Dr. Tan.
Lighting The Way
Another trend in QC equipment that is gaining momentum is the development of lighting advancements. According to Mr. Heil, Isra Parsytec’s new lighting technique features an advancement in LED lighting technology that allows companies to be able to see a broader range of lightweight spunbond defects.
E-L is also making inroads when it comes to lighting. According to Mr. Guzzardo, E-L has developed its own lighting systems so it can supply customers with exact lighting replacements when they are needed.
Inspection of printed material such as logos and designs that are now commonly featured on hygiene and medical products is another trend that is taking hold.
“We see an increased amount of printing on nonwovens,” said Mr. Heil, adding, “Isra Parsytec’s PrintStar system inspects 100% of the printed pattern and also does color trending. It inspects 100% of every print repeat online at high speeds and highlights and classifies print defects, such as void, splash, misprint and mis-registration. PrintStar also monitors color to ensure that it meets the customer’s specifications.”
Color inspections for unprinted nonwovens are another noticeable trend. “If they switch over colors and have some fiber contamination of a separate color, we can detect that with color inspection,” said Mr. Heil.
E-L has also received more requests from nonwovens players for print inspections of logos and designs. The company’s NYSCAN system provides 100% print inspection.
Another important trend taking root is performing inspections early in the production process instead of when the product is finished. Dr. Tan said this trend is beneficial when it comes to features such as the elastic strands in leg elastics. “When the strands break down from one to three strands, the product is almost defective from a functional perspective. If the breakage is allowed to continue and the strands completely break, it may take 30 minutes to restrand the elastic. People are asking, why don’t we put an inspection unit at the very source—at the earliest point?” said Dr. Tan.
Automation To The Rescue
Mr. Guzzardo foresees automation as a dominant trend. “The interface ability with operating systems with the technology today is much easier than in the past. Closing the loop with regard to direct interfaces with machine control is the true savings and trend for the future,” he said.
ELSIS (Erhardt + Leimer’s Surface Inspection System) has the benefit of automatically calibrating and focusing the CCD camera across the material for simple and accurate set-up of all cameras. “The smart cameras have built in multidirectional motors for precise positioning of the CCD chip. This takes the manual adjustment out of the hands of the operator,”Mr. Guzzardo said.
This function is also beneficial with regards to post calibration verification, for example, annual ISO audits. It has an automatic calibration template and on systems like this that look at a wide materials or webs, they have multiple cameras that go across the web. “All E + L systems are supplied with a calibration template that serves as calibration reference and can be accessed through the Internet or a modem for diagnostic purposes and upgrades.”
Flexibility is a Fave
Technology integrating event capturing systems working with defect inspection systems has also been emerging. E + L is offering WMS (Web Monitoring System), which is an event capturing camera system. “These systems are designed to interface with each other to facilitate the various in-line corrections to assist the operator to find the root cause of defects and provide a much more progressive response to prompt an immediate corrective action,” said Mr. Guzzardo.
In addition to providing quality control, inspection systems generate important information about the production lines they are monitoring. “When every single product is being inspected a tremendous amount of information is generated. The initial reason for getting the system may be to address quality, but the biggest benefit of the system is its ability to collect information, such as statistical information and trends. People are able to utilize the system to pinpoint the area that needs to be fixed as well as the maintenance schedule from a starting point,” said Dr. Tan.
Dr. Tan went on to add that nonwovens producers are seeing much greater ROI from the overall equipment efficiency and the reduced scrap rate. “The scrap is not only wasting capacity. The time that was used to produce those scraps cannot be used to produce products. Those are wasted materials that go down the drain. Once we are able to compile a Pareto chart of the different type of defects, we can pinpoint the root cause of the defects and correct the machine settings, optimize it and reduce the scrap,” said Dr. Tan.
More Inspection Points
Another important trend underway is adding more inspection points early on in the process so if anything is wrong the machine stops immediately.
Dr. Tan said,” We are able to trace the position of the core, the tapes and all the different components that we can see at that point. People are saying that if they can inspect one position it already generates a benefit, what other things can they inspect along the line?”
Space Is Not An Issue
To skeptics who wonder what mechanical constraints they may face when adding systems to equipment that was designed without an inspection point, Dr. Tan said, “You need to retrofit to put that inspection point in there. One of the challenges is space constraint.” In response, AccuSentry has introduced the Sentry Line Scan camera, which requires a very narrow space.
“It can scan the product as the product moves underneath the camera. It can be fitted into a very tight space. It scans the product one line at a time to build up the image of the entire product. It has a higher resolution, which is another benefit,” said Dr. Tan.
The Global View
Where is the most investment activity occurring?
Mr. Heil said he is seeing the most investment activity in QC systems in Asia. “We don’t see a higher level of inspection in Europe versus U.S. versus Asia. The Asian market is also in tune with achieving these high levels of quality that are required for the disposable medical and hygienic nonwovens market. We have a few lines out of the Czech Republic. We don’t see emerging markets as shirking the quality responsibilities because that particular market (medical and hygienic disposables) is very demanding and to have any kind of meaningful penetration of that market from a market share standpoint they have to meet these quality standards.”
Dr. Tan said the largest markets are the U.S, followed by Europe, South and Central America, and finally, Asia. “The adoption of diapers in the overall populations is still not as high in terms of the penetration. In the U.S. they may have ten, 12 or even 30 lines making a particular product; in Asia there may be three lines. There’s still that type of discrepancy between developing countries and here,” Dr. Tan said.
So where are quality and control inspection systems headed in the future?
One area of inspection that is becoming more important is glue application. “In the past no one was interested in inspecting the elastic and how the glue is being applied on it,” said Dr. Tan, adding, “I am beginning to see interest in doing that kind of inspection. If the glue is not smack in the center of the elastic strand and they are offset a little bit the strength of the glue is compromised. It means additional cameras along the line—one camera to check the elastic strand and the glue, another camera checking the acquisition layer, frontal tape, and monitoring the end product before it goes into packing.”
Another trend that is gaining popularity is the integration of a warning system in machines so that when there is a problem the machine can make the adjustment automatically. “If this information is useful for the operator, why can’t we automatically fit it in the machine so it can make the adjustment automatically?” said Dr. Tan.
Web marking systems, which allow defects to be marked for later removal are also becoming prevalent. One such company offering a marking system is Ryeco. A defect marker places a mark at the location of each defect or process upset. The mark can be placed over the web in the same slitting lane as the defect or along the edge, which creates a ring when viewed from the end of the roll. The defect marks are visible to the operator or can be detected by sensors to activate automatic stopping or rejection of defects. The marks can be any color or invisible except under ultraviolet lighting. The length of the defect mark can be adjusted to give early warning of the approaching defect.
Another recent Ryeco development is to use a web marker to lace length codes along the edge of a moving web. A binary value is encoded onto the web at preset intervals and is later decoded to give precise footage regardless of stretch or shrinkage of the web. Defect locations are saved in a file and are synchronized to the web using the footage code marks. Not only are all defects removed but the exact length of good product in all rolls can be tracked for better inventory control.
Quality control equipment has certainly come a long way in helping makers and users of nonwovens meet increasingly stringent quality requirements. Whether or not more companies will purchase quality control equipment remains to be seen. Mr. Guzzardo advised, “Once we supply inspection systems to a company their sales force uses it to their benefit because they can tell the customer, ‘we are not going to be shipping you defective material.’”
Perhaps Mr. Heil summed up the reason for installing quality equipment best when he said, “Anyone who wants to play in this market has to deliver quality. It’s a very competitive market and you have to maintain a consistent level of quality. If you can’t do that you are going to lose your customers.”