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Machine Vision in the Printing Industry
by Nello Zuech, Contributing Editor - AIA Posted 11/23/2004
Optical and electro-optical techniques for inspection have been around for a generation or more in the printing industry. Today there is a definite migration path to substituting machine vision techniques for these earlier approaches to monitoring pattern registration, color registration, web registration, etc. Missing a trend can lead to the production of much scrap as well as adding unnecessary value to scrap.
One can find a range of imaging-based products. These include web viewers, which are essentially closed-circuit televisions that an operator views and makes a decision on when to make changes; frame grabber or smart camera-based systems with intelligence to alarm an operator when taught conditions have changed; mark registration where a machine vision system monitors the pattern to control color and pattern registration; web registration where often a line scan-based system monitors wander.
Today there are machine vision-based systems that can perform 100% inspection, although there is some confusion associated with this terminology. Some suppliers suggest 100% inspection when they are actually performing sample inspection but across the entire web one sample at a time. This approach will detect recurring concerns rather quickly but not detect random concerns. On the other hand there are systems today that will actually inspect 100% of the entire printed web as it is being printed. These systems will not only detect trends that could ultimately result in reject conditions but also detect random concerns such as ink blotches, random print omissions and paper concerns, etc.
In addition to these types of application-specific machine vision systems for the printing industry, one can also find machine vision being applied to proofreading of printed materials. This is especially important to the pharmaceutical industry where all printed materials must accurately reflect the contents being packaged. Another application related to printing involves name and address reconciliation in conjunction with the high-speed printing of mailers and envelope addresses at facilities stuffing mass mailings.
Given all this machine vision activity in the printing industry, input for this article was canvassed from all companies known to supply one type or another of machine vision systems addressing applications in the printing industry. The following responded to our questions and what follows is their responses.
- Gal Shamri – Advanced Vision Technology
- Dave Kunz – PC Industries
- Ignatius (Iggy) Manning – PrintVision Systems
- Warren Friedersdorf - Tekmatex
1. What are some specific applications in the PRINTING industry that your company addresses with machine vision technology?
[Gal Shamri – Advanced Vision Technology] AVT provides machine vision-based Automatic Inspection solutions, targeted for the Packaging, Converting and Label Printing markets. Our solutions include on line Process Control and 100% Quality Assurance as well as off line Quality Verification solutions for the pre press, press and post press machines and workflows. Incorporating area and Line CCD cameras, sophisticated image processing algorithms and industry know-how, AVT’s PrintVision systems reduce printing waste, increase product quality and press productivity and provide full Quality Assurance. Installed on a press, laminator or rewinder machine, the AVT PrintVision system automatically detects, classifies and alerts for any print defect such as color variation, mis-register, spot or streak exceeding the pre-defined quality threshold. The system can also perform press and rewinder control tasks.
AVT’s PrintVision main proven capabilities are:
- Automatic Defect Detection for Process Control and 100% Quality Assurance
- Barcode verification
- In-line Color Measurement and Management
- ColdSeal print monitoring
- Press control (register control, pressure control)
- Rewinder machine control
- Full workflow support (such as: detect defect on press and automatic control of the defective material removal down stream, on a rewinder)
- Quality Information management.
In addition to the PrintVision family of solutions, AVT offers off line automatic verification solutions for ensuring that print product matches the original digital data. This tool is targeted for pre-press, press and consumer product companies (especially in the pharmaceutical field).
[Dave Kunz] PC Industries focuses on both narrow and wide web printing applications that require 100% web inspection, specifically for print defect detection, OCR, and color measurements. The applications include offline inspection, on press inspection, final inspection on rewind equipment, and incoming inspection for pharmaceutical and non-pharmaceutical products.
[Ignatius Manning – PrintVision Systems] At PVS, we take a global approach to the application of inspection technology in the printing industry; as a result we offer Inspection technology for pre-press, press and post-press. In addition, our solutions offer both process and quality control functionality. The only way a printer/converter can make a statement of validated 100% inspection compliance is to implement such an approach.
[Warren Friedersdorf – Tekmatex] We target almost any printed application you can imagine - rotogravure and flexographic are the two largest applications. Package printing in the form of shrink or sticky labels is very popular. These can be both opaque and transparent. We’ve also just completed an installation at a major laminate flooring supplier.
2. What are critical machine vision system performance criteria for each of the applications that you address?
[Dave] To insure success in the full range of applications, PC Industries has standardized on a hardened platform that includes processing equipment and cameras. This platform is customized for the customer’s specific applications.
[Iggy] Validation, Validation, Validation! Since the pharmaceutical industry drives most of the inspection applications to date, this is the most critical factor. Specifically, it is mandatory to 100% inspect to the specified and applied specifications - 100% of the job, 100% of the time of a job.
[Warren] In our case:
1) 100% inspection,
2) Fast camera (ours is 40 Mhz with 4,000 bits),
3) Sensitivity settings to allow the customer to customize what defects are to be detected and how they are classified without causing false calls,
4) Good lighting techniques to illuminate defects,
5) Algorithms to detect and classify defects.
[Gal] Based on the experience we gathered from more than 850 automatic inspection installations, the basic and most critical elements are:
- Objective and consistent detection of relevant defects. Defect detection is performed based on objective sensitivity settings determined per defect type.
- Minimum false alarm ratio. AVT’s PrintVision system uses powerful and sophisticated image processing algorithms to handle standard web movement and reduce to a minimum the false alarm ratio. Dedicated detection algorithms per defect type ensure full control over quality threshold avoiding alarms on unimportant variations.
- Ease of use and automation.
- Full integration into the specific printing workflow.
- One system can do it all (one system – multiple capabilities).
3. What changes have been taking place (in the technologies that are the basis of the machine vision systems used in the PRINTING industry) that have resulted in improved performance?
[Iggy] The biggest single factor that has had such a great impact is the advancement of the PC. Just a couple of years ago, Vision companies were saddled with extensive development of proprietary hardware to process the data generated for 100% Inspection - now this is done on a high performance commercial computer.
In addition, the camera technology has also advanced, offering higher performance - higher resolutions, higher scan or frame rates and standard interfaces.
The result on the development side is that inspection companies can now focus on the application -optimizing algorithms and so on. The result on the customer side is products are coming to market faster, costs are reducing, performance is increasing, a win - win for all!
[Warren] Our systems are computer controlled, so the big change has been increases in speed of the systems. We are able to detect smaller defects running at faster speeds.
[Dave] With the improvements in digital camera technology, combined with processing power, systems are able to detect smaller defects at faster speeds for less money.
4. Where do you see breakthroughs coming (in the specific technologies that are the basis of machine vision systems used in the PRINTING industry) that will result in further improvements in the near future – next three years?
[Warren] Systems will get smaller, faster, and smarter with added conveniences for the user. Also, we will see color proofing integrated with defect detection. In addition, saving a master sample for use anywhere and at any later time may become reality.
[Dave] PC Industries has recently developed an offline proofing station that can be wheeled from press to press to check the consistency of print jobs. This proofer can check the print for defects, misregistration, and color matching in a minute or two. This will save time and eliminate human error from proofing.
[Iggy] Continued advancements in PC technology and camera technology will continually offer incremental advancements. However, the notable advancements will be in the area of smart algorithms; embedding more intelligence is the future.
5. Are there market changes in the PRINTING industry that are driving the adoption of machine vision?
[Gal] Shorter print runs, growing quality demands, increased pressure on profit margins and growing competition have led printers to search for innovative technologies to reduce internal waste and increase product quality. The market awareness and acceptance of machine vision-based solutions is growing as more and more printers adopt this technology. Along with improvements in production machines and workflows, machine vision-based solutions are becoming an integral part of the printing production process.
[Dave] Vision systems, as an aid to increased productivity and quality, can’t be overlooked in the future. The insistence by the end user for 100% defect free printing products will continue to drive vision systems.
[Iggy] Changes maybe in some cases but mostly market acceptance. The need has been there for a long time - the acceptance has been slow mostly due to cost/performance - but this ratio has changed drastically. The technology has now entered into the growth stage in the market - already companies without 100% inspection are feeling the pinch from their customers.
[Warren] Yes, the end-user is requiring 100% inspection to eliminate their bad/return product. Therefore, printers are now adopting 100% inspection instead of the typical scanning technology.
6. How will machine vision systems have to change to meet emerging applications in the PRINTING industry?
[Iggy] Higher speeds, smarter algorithms.
[Warren] Systems are becoming more and more automated for downstream applications such as sending defect data directly to the slitter/rewinder for automatic location of any defects and integration into the user’s LAN system to allow manipulation of the data.
[Dave] Machine Vision systems must meet the demanding needs of the new presses, which are faster, wider, and higher quality. The vision systems need to be easy to use, operator friendly, and fast. If they burden the operators, they will not be used. PC Industries offers an easy to use operator interface combined with the latest technology in our Viper® and other vision systems.
7. As a supplier of machine vision systems for the PRINTING industry what are some challenges you face in marketing machine vision systems?
[Warren] First is cost, as 100% inspections systems can be 5-7 times more expensive than the standard scanning mechanism. Second, is competition as there are numerous companies now serving this market.
[Dave] The printing market is expanding globally. Serving new companies and foreign markets is always a challenge.
[Iggy] Much of the market is stuck in “Show Me”. In the past, there have been too many claims and too many promises. The single most important factor in selling 100% inspection is not to overstate the facts and to understand the specific customer’s needs and expectations.
[Gal] During the last few years, the main challenge we faced was to educate the market and to prove that machine vision-based solutions do work properly in the printing production environment, providing real benefits and positive influence to the printing house bottom line.
Now the main challenge is to provide better integration to the printer’s workflow and to provide additional added-value features such as in line color measurement and press control.
8. What are your thoughts on the future of machine vision in the PRINTING industry?
[Warren] The future looks very promising for 100% inspection systems. The requirement for zero defects and no product returns means better quality and cost savings for all involved.
[Gal] The future of machine vision solutions for the printing market is promising. We are pushing the machine vision technology envelope to provide our customer with more and better Process Control and 100% Quality Assurance solutions:
- More production machine automation and control
- Automatic inspection on additional production machines along the process
- Enlarge in-line color measurement and management capabilities
- Full Quality Management solution, from pre press to press production and finishing
[Dave] I believe that machine vision will become the standard for printers who demand perfection. Machine vision saves time, reduces scrap, and helps retain customers.
[Iggy] “The future is bright”! We expect to see the technology being adapted widely in the printing and converting industry – both web and sheet. Modernized work flow, lean manufacturing, JDF - as the industry embraces such technology then 100% inspection will be an integral component of this. 100% inspection technology will be standard on much of the printing and converting lines within a few short years!
9. What advice would you give to a company investigating the purchase of a machine vision system for a PRINTING industry application?
[Gal] Internal Analysis:
When purchasing an automatic inspection solution, it is highly recommended to first understand what are the specific requirements that a print house has; what are the main defects needed to be detected? On which machines? Is on-press 100% inspection needed?
What is the preferred workflow to remove the defective material? Is 100% quality assurance needed on the finishing side as well?
Other than basic automatic defect detection needs, it is important to analyze and prioritize other requirements such as in-line barcode verification, in-line color measurement, ColdSeal monitoring, register control, etc. As some of the machine vision based solutions (such as the AVT PrintVision) can do all the above-mentioned tasks, it is important to analyze in depth the complete production quality requirements and to make sure that the system can grow together with the printer’s needs.
Full production workflow analysis is important too. Machine vision-based solutions can be integrated at several points along the production process. For example, defects detected on press by AVT’s PrintVision system can be automatically removed down stream, on a rewinder, using AVT’s WorkFlow Link technology.
Machine vision technology becomes a real solution only if it works at a production site. No laboratory system or product brochure can demonstrate the specific system’s ability to perform acceptable defect detection with minimal false alarm ratio under the complexity of a running press or other production machines. Evaluating the specific solution offered at one or more production sites is highly recommended.
[Dave] Confirm that the machine vision company will provide the service and support required to insure ongoing performance. Is the machine vision company only interested in selling hardware, or will they become your partner for the current and future requirements? Ask for references and confirm the quality of the company and its personnel and products. Make sure your system is custom designed for your application(s). This will insure quick return on investment and operator satisfaction. Get a written money back agreement guaranteeing that the system can be returned if the specifications are not achieved.
[Iggy] Read our paper TQPC understand your needs, make a global implementation plan, select your entry points in accordance with short term goals working to your long-term goals. Educate yourself on the basics of the technology and choose a knowledge business partner.
[Warren] Always go with 100% inspection as anything else is just sampling and will not guarantee the quality of your product. Think about your ROI when investigating these systems. Although they initially cost more the ROI can be quick. Second, go with a company that has been in the business for some time and has real life experience with 100% inspection applications. There are many new vendors in this industry and it’s anybody’s guess how long they will stay around.
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