Web Coating Blog

Measurement of Paint Coating Thickness on Different Materials

Measurement of Paint Coating Thickness on Different Materials
Javier Marín Zafrilla
PCE Group Ibérica S.L.

Ultrasonic Principle
An ultrasonic technique is used when measuring the thickness of paint. The probe of the instrument contains an ultrasonic transducer that sends a pulse through the coating. The pulse reflects back from the substrate to the transducer and is converted into a high frequency electrical signal that is analyzed to determine coating thickness.
A example is the PCE-CT 28 coating thickness meter / gauge for cars is for measuring the thickness of paint and plastic on ferrous or non-ferrous materials without damaging the coating's surface. The coating thickness meter / gauge stands out due to its high range of measurement. This coating thickness meter / gauge should be one of the tools used by technicians in areas of paint or lacquering such as in production, automotive body repair or quality control.
The coating thickness meter / gauge is particularly useful in detecting damage to vehicles produced by an accident, for preventing possible damage or as a toll in auto body repair. Also, in the industrial sector, this device is essential for quality control in shipping and receiving and during production. It is ergonomincal with an integrated sensor and it shows results of measurements quickly and accurately. It was designed for non-magnetic coatings such as plastic, chrome, zinc, copper, etc. and insulation such as rubber, plastic, glass and paper over steel, iron, aluminium, brass and stainless steel. Thanks to its wide measurement range, the coating thickness detector is ideal for the naval and metal industries.

Paint thickness over exterior automotive materials is best measured with hand-held, electronic instruments.

The Importance Of Accurately Quantifying Defect Losses

37. The Importance Of Accurately Quantifying Defect Losses

There are many essential factors in the effective running of a high quality and economically effective web coating process. One of these factors is to maintain a quantitative detailed accurate database of defect losses in the process. This analysis should provide an ongoing:

• Accurate summary of product yield losses
• What caused the specific losses, streaks, bubbles scratches coverage etc?
• Summary of losses by product and defect type type.
• Specific losses for coating line down, product change, start-up losses
• The ability to calculate dollar losses for each defect
• Easy access to the data for all personnel

Utilization of this database will provide:
• Understanding of defect types in process and where they occur
• The ability to compare product performance and identify better performing products
• The ability to dentify process elements that need upgrading
• With accurate yield loss number the economic Justification for programs and new hardware can be calculated
• A priority list to work on
• An aid in understand mechanisms and

A barrier to developing this database is that often, the yield data collected can be rudimentary and does not accurately reflect the total losses and is not very helpful in identifying the potential causes for defects. The losses are characterized by where they are detected, i.e. in slitting or sheeting process and when the customer uses the product and return the product because it is defective. The classification also can be very general categories, which are not very helpful in finding the sources of the defect, and quantifying losses.

The following is an example of a basic yield loss summary, which provides insufficient information:

• Finishing yield loss 9-62 % of square feet processed
o Pattern length loss 2-14%
o Pattern width loss 1.5-35 %
o Quality yield loss 0-22 %
• Customer returns 10-15 %

For example, what is needed is the exact defects, which resulted in the loss. In regard to pattern width loss there are several potential losses and each may require different corrective action:

• Poor coating weight profile in either machine or transverse direction
• A streak or scratches which prevents using optimum slitting pattern
• Substrate defect such as gauge bands
• Poor edge coverage profile
• Quality Defects
• Missing coating

The database must be maintained in a computer system with intranet access for all company personnel. With advent of computer process control systems, on-line thickness gauges and on-line inspection systems; a significant amount of the data required can be added to the database without requiring personnel costs to add data.

The following is some of the typical data that is needed for an effective database:

• Identification information
• Roll number
• Raw material batches
• slit location
• Defect type
• Amount lost in sq.ft. for each defect type
• Segregated according to product
• Type classification
• Downtime losses,
• Time lost
• Causes such as
• Mechanical failure
• Product change
• Start-up times
• Getting on target for coverage and drying conditions
• Best estimate of defect origination, not where detecte
• Bubble detected in sheeting is coating defect
• Data for each product

The sources of data for the database are:
• Coater logs & inspection data
• Losses from slitters and sheeting
• Customer complaints
• Quality control testing
• On-line inspection data
• On-line thickness gauges

Another requirement of the database design is the ability to interact with other quality control and process databases so that losses can be correlated with process variables to determine defect causes.

One of the difficulties with this database is that there are no standard names and occasionally jargon names are used. This can result in different names for the same defect. One way to minimize this effect is to classify defect by attributes as well as the name. Figure 1 is an example of a classification scheme. An advantage of this approach is that the loss from general defect classes can be identifies and the cost of losses identified, such as streaks, chatter, base defects, etc. In addition, coater losses for operational variables can be determined.

Figure 1

DEFECT CLASSIFICATION

1. Linear Continuous
a. Machine direction
i. STREAKS
ii. RIBBING
b. Transverse direction
i. CHATTER
c. Diagonal
i. DIAGONAL CHATTER
2. Linear Intermittent
a. Machine direction
i. SCRATCHES
b. Transverse direction
c. Diagonal
3. Discrete point defect
a. Spot
i. BUBBLE SPOTS
ii. GELS
b. Contamination coating
i. REPELLENT SPOTS
ii. DIRT
c. Contamination substrate
i. REPELLENT SPOTS
d. Other types
i. REPEAT SPOTS

4. Pattern & diffuse defects
a. MOTTLE
b. DRYER BANDS
c. ORANGE PEEL
5. Process specific defects
a. Raw Materials
i. REPELLENTS
ii. BENARD CELLS
b. Coating
i. AIR ENTRAINMENT
c. Drying
i. MOTTLE
ii. DRYER BANDS
d. Web Transport & winding
i. WRINKLES
ii. SCRATCHES
iii. REPEAT SPOTS
e. Metallizing process
i. BLOOMING
6. Substrate defects
a. Plastic
i. GAUGE BANDS
ii. POLYMER SPOTS
iii. COATING NON-UNIFORMITY
b. Paper
i. WRINKLES
c. MEtalized

T

Recession Impact on Converting Technology

There is no doubt that the current economic slowdown, recession, or economic adjustment is presenting a major challenge for all businesses, Volume for most converting products are down significantly and profits are only fond memories. Businesses are responding to the changing scenario by the typical reaction of layoffs, reducing forces, and cost
cutting and a little bit of wishful thinking. The federal and local governments are also responding with a variety of actions. The Arizona legislature has taken several steps including reducing funding for all levels of education. It seems ironic that at time when we need more educated people to solve these problems, they are trying to reduce the supply

My interest is to try and ascertain what the effect is going to be on the industries’ manufacturing facilities and particularly on the personnel from R&D to Manufacturing. I expect that there will be:

• A major focus on short-term earnings, by improving quality and productivity and reducing losses
• Modernizing of existing equipment
• A reduction in long term capital projects for new facilities
• A need for personnel to rapidly acquire additional new skills as people in their companies are reduced
• A focus on energy savings in all aspects of the process.
• A reduction in support activities, instruments, analytical tests, education and travel expenses as management views their people as a cost and liability instead of an asset which can be optimized.

There are several technologies that can rapidly be implemented in the coating lines to improve efficiency and reduce costs. On-line coating weight thickness gauges will improve thickness control and can reduce product variability and save on raw material costs, An out of specification thickness can rapidly be determined and corrective action taken immediately. The devices can be used as part of a closed loop control system. Thus reducing amount of scrap produced.

On line-inspection devices can rapidly detect defects and permit rapid corrective actions. A major attribute is that they can detect small defects which are difficult for the human eye to detect, but will result in scrap product when the customer uses. Also, given an accurate position of defects, the final conversion of roll stock to the sizes required by customers can be optimized.

Both of these technologies if utilized correctly can have rapid payoffs and return of investments. They can also be used to develop a true quantitative estimate of real production losses. I have often found that the loss data is not in sufficient detail to identify the root causes. These technologies will rapidly provide reliable information can then permit technical effort on the real problems. These process detection devices can be integrated with computer technology to process data and reduce the burden on people.

Other technologies that should be investigated and upgraded are the ancillary support equipment, such as surface treatment, improved coater line speed and tension control, statistical process control, solution handling equipment and instrument performance and accurate easy to understand procedures. Improvements in these areas often require small expenditures and can resulting rapid process improvement and coat savings.

The process is very dependent on fossil fuels, as a source of energy. There has been an unlimited of fuels at reasonable prices.
However, in recent years the energy costs have increased dramatically, leading to higher energy costs for the convertor. The operating personnel need to focus on the newly available energy conservation technologies. To reduce costs.

One of the issues in the evaluation, selection and installation of the above technologies is that there will be less people to do these functions. In addition, the remaining people may not have expertise in the needed areas. The reduction in travel will reduce the ability of personnel to travel to technical meetings and continuing education courses to learn these technologies. I believe that this need will be met by more effective utilization of the Internet technology in which no one travels. All will have to get more comfortable with the computer and internet technology so they can institute and attend webinars, on-line courses, the use of sharing software. Technical meetings, which are currently almost exclusively face-to-face events will change to include a virtual meeting component. Some of the face-to-face component will gradually be replaced by remote participation by both attendees and presenter. This will permit rapid and less costly information transfer,

The Importance of Coating Process Support Systems

                             The Importance of Coating Process Support Systems
                                            Edward Cohen

Ongoing technical projects are needed to improve the quality, cost & productivity of a coating line in order to remain competitive and rapidly develop new products. There are several important considerations when developing and identifying coater needs and deciding on the most effective programs too work on. These are:

One Thing to Optimize Process

A question that is often asked about the Web Coating Process is “ What are the one or two most critical areas of the process that I should concentrate on to obtain a coated product with high quality and low cost?”. A possible basis for this question can be found in an interchange in the 1991 movie “City Slickers”, between Billy Crystal and Jack Palance

NEW YEAR ANNOUNCEMENT

NEW BI-MONTHLY POSTINGS WILL FOCUS ON THE DRYING PROCESS

Daniel Bemi Megtec Systems, is joining the Web Coating Blog as a contributing author. His focus will be on new bimonthly postings on all aspects of the Drying Process.

Drying and curing of coatings, along with other drying and annealing applications, are often a critical component of the coating and laminating process. While there are several good texts available on drying theory, there is a shortage of written materials focusing on application “know-how” and real world drying challenges. As such, AIMCAL will be introducing a bi-monthly posting of dryer-related technical articles beginning in January 2007. These postings will be aimed at bridging the gap between drying theory and application-based, process knowledge.

If you have a topic of interest that you would like to see addressed by our experts, please send your suggestions to Ed Cohen email cohened146@aol.com

Consider Modernizing an Existing Coater to obtain Improved Performance

As a coater ages, often it cannot meet current productivity, quality and cost needs. When this occurs, consideration should be given to modernizing the coater to meet these current and future needs.

Some of the problems that can lead to the poor performance are:

• Increased sales resulting in insufficient manufacturing capacity to meet sales demand.
• The current quality requirements cannot be met by the existing coater.
• New theology is required to manufacture products.
• Cannot meet the requirements for new products being developed.
• Product costs are increasing and are not competitive.
• Increasing yield losses.
• Equipment is wearing out and design conditions can not be achieved and maintained.
• Coater is becoming hard to run consistently.
• Downtime in the coater is increasing.

Summary of AIMCAL Fall Meeting

The October AIMCAL Fall Technical Meeting provided a forum for the exchange of Information between technical personnel in the web coating Industry. 60 papers were presented in three sessions as follows:

• Web Coating & Laminating
• Vacuum Web Coating
• Emerging technologies

In addition there were table to exhibits, which also provide an opportunity for additional technical discussions.

I found all of the presentations were outstanding and provided me with useful technology about the web coating process.

Defect Characterization Techniques: Microscopy

The ability to characterize a defect and to determine why it is different from the surrounding acceptable material is essential to determining the proper corrective action to eliminate it. There are a wide variety of analytical techniques that are in routine use to characterize defects and to help determine its physical and chemical characteristics. In this article the use of three microscopic techniques to determine these properties will be discussed.

The microscope is an instrument that produces magnified images of small objects that are too small to be seen with the naked eye.  An optical microscope uses visible light and combination of lenses to produce magnified images of small objects. Microscopes can also use other types of radiation infrared, electrons  and X-ray to  produce the magnified images.

More Than Defect Detection – The Real Value of Web Inspection

Brian W. Heil, Vice President – Sales
ISRA Surface Vision
4357 Park Drive Suite J, Norcross, GA USA
www.isravision.com

This article explores opportunities to maximize the value of automated on-line film inspection. Examples are presented of implemented inspection systems that provide critical real time process and converting information to maximize yield, improve raw material quality, and strengthen customer relationships. A solution for automated re-wind control for defect removal that increases converting throughput is discussed. The implementation of this technology offers its users a variety of methods to achieve value. The user realizes the maximum value when all of the possible methods are implemented.

INTRODUCTION
Implementation…this is the difference between success and failure of any plan. The best plans, ideas, technologies, strategies, directives, and mandates are useless unless they are implemented. The top performing companies are top performers because they spend much effort on new ideas and technologies and much more effort in implementing these ideas and technologies. This comes from the top of the organization and sets an example of follow through. We can all think about a capital project that was a failure, a piece of equipment that “never worked” or the “person left the company” that had the project, or the “operators never used it”. Occasionally this can be the result of a bad idea, but in an overwhelming majority of cases, good ideas and technology failed because they were never implemented.

This stated, we arrive at the topic of this paper – The Real Value of Web Inspection. We will explore how web inspection systems can be implemented to achieve maximum value. When defects occur in an extrusion process they can be just a nuisance and have no cost ramifications or they can be catastrophic in terms of causing product performance or aesthetic issues. An example of nuisance defects would be small gels and carbon specks in plastic grocery sacks. If your process only creates nuisance defects you are fortunate in this respect, however, these products usually are high volume, low margin commodity products that are purchased primarily on price and involve high customer turnover. <

Of greater concern and cost are defects that affect the aesthetics and/or the functionality of the extruded product. Examples would be carbon specks that affect the appearance and holes that affect the function of flexible food packaging. Functional defects are always catastrophic by causing the product to fail its intended use or required specification. Aesthetic defects can sometimes be catastrophic by prompting customers to return the product or change vendors. When aesthetic and functional defects are not controlled, returns occur, customers are lost, yields shrink, manufacturing costs rise, and the ability to compete in the market place is compromised. The cost of identifying and removing defective product from finished rolls is significant. The cost of failing to accomplish this is also significant. Inspection or lack thereof carries a high cost. Various opportunities exist to turn this cost into a profitable investment.

LIMITATIONS OF STATISTICAL SAMPLING
Controlling extrusion related defect occurrences is sometimes attempted by statistical sampling. A small piece of the film from the end of each roll is analyzed in the lab and the roll is considered to be acceptable or unacceptable. This strategy has many limitations. The occasional catastrophic defect cannot be controlled and real time process improvement is not possible as many rolls can be produced before the lab results are analyzed. In addition, rapidly changing process variations are missed, as the lab sample represents only a snapshot in time equating to as little as 0.001 percent of the produced product.

Figure I shows the variation of gel counts for a single roll of blown film. The data was collected with an on-line ISRA SURFACE INSPECTION SYSTEM that classifies, maps, and trends defect counts. The system counts gel, speck, and gels containing specks per square foot of inspected film. The trend graph in Figure I shows defect counts for each size class and type of defect per square foot of film. Within a five minute interval the total gel counts range from 2.5 to 20 gels per square foot of film and every ten minutes the counts are similar. In this case, statistical sampling, in terms of analyzing the gel count of a piece of film from the end of this roll, would provide erroneous results that would initiate the wrong process control action.

By itself, statistical sampling may provide a low cost alternative to inspection, but its limitations result in higher risks with regards to missed catastrophic defects and higher costs due to reduced process efficiency.

Figure I – Trend graph of defect counts per square foot of inspected film showing short term variation of gel counts

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