- June 30, 2005, E. Lawrence Gogolin, Gogolin & Assoc.
Not too long ago, a question was posed to me: What are some ideas for cost reduction projects in a coating operation? Very often coating costs are characterized in terms of dollars per square foot. Products of high volume and low technology have values under $0.05/sq ft. In narrow web, slow speed, and high technology applications, cost can exceed $1.00/sq ft. To be competitive, there is a need to find ways to lower these costs.
#1 Having a great relationship with all your raw material suppliers is a must. They need to know and understand your requirements, and you need to know their capabilities. Problems often arise when specifications are unrealistically tight.
Try setting up partnerships with critical suppliers to do joint tours of each other’s facilities so everyone can understand the process requirements and capabilities.
Can you loosen up some of your specifications to reduce the vendors’ scrap losses (and your material costs) by testing some of the "off-grade materials?"
Fluid Mixing & Delivery
#2 Make sure mixing equipment is correctly sized, properly agitated, and temperature controlled. Do whatever it takes to keep air bubbles out of the mix. Defects arise and time is lost if they get into the mix.
#3 Consider using in-line mixers to help deliver a more uniform fluid to the coating head. Are the filters efficient to do the job and to minimize waste during a changeover?
#4 If possible, increase the solids content of the mix to reduce the drying load and speed up the web. If an organic solvent system is used, another benefit is the reduction in solvent consumption and savings in the recovery or disposal efforts.
There are lots of mechanical upgrades that can be done to improve productivity. Some of them include:
#5 Speed up the coater with new drive systems. This is particularly beneficial on machines with old or obsolete drives.
#6 Better drying may help. A major source for capacity limits can be traced to the dryers. Simple things like improved air filtration or higher fan speed will help. New and larger heat exchangers and nozzles can do wonders. Consider the addition of IR heaters at the oven entrance or in between the nozzles inside the oven zones to speed up the drying rate.
#7 If you shut down the coater after each coated roll to put up a new one, consider installing a dual unwind and rewind to allow continuous operation.
#8 If time is lost at changeover because of extensive cleaning or interchange of coating heads, analyze changeover procedures in order to find better ways to do it faster. Downtime on the coater, especially during changeovers, can be a major source of cost reduction.
There are many ways to look at speeding up the switch from one product to another. Try setting up a team made up of mechanics, operators, material handling and lab staff, and engineers. Utilizing a video camera to document what really happens during a typical changeover and then dissecting the steps can be very enlightening. Then list the suggestions for time reduction; there will be many.
Retrofitting the Line
#9 Consider the addition of new process units to help with increasing web speed (new drives), roll changes (accumulators), quality (web cleaners), and coatability (corona treatment).
#10 Can you replace older or worn out components on the coating line with newer or more modern versions?
#11 How long does it take to get the ovens up to equilibrium in both web temperature and concentration of the evaporated solvents? The drying curve of both temperature and solvent retained in the coating can change during the initial startup. Does this factor have an effect on quality or startup scrap losses? Should you run less expensive leader stock initially to bring the system into equilibrium?
Reducing Utility Consumption
#12 Energy consumption is a major cost factor, especially in the dryers. Check energy balances. Regardless if the source is gas, oil, or electric, major cost savings may be had in utilities if energy balances show a problem.
#13 What is the efficiency of the dryers and can it be improved? Look at filter cleanliness and fan efficiency (for pulley drives, are all the belts in place and in good shape?). Are heat exchangers plugged or too small?
Defect Reduction (Quality Improvements)
#14 Defects are either the ones you have seen before or brand new ones with no history of cause or cure. They are here today and gone tomorrow but often seem to come back later on. Much has been written about defect detectors, documentation methods, identification systems, and more. Before jumping into costly fixes, the important step is to create a Pareto bar chart, by lost dollars, of the top five or so defects. Then concentrate on finding the cause and a cure.
#15 Scrap losses are taken when a defect exceeds a dimensional or visual standard level for acceptance. Often these standards are old and possibly obsolete. Review the standards levels periodically with the customer or end-user. You may be scrapping defects in the coated web that are never seen in the product application.
#16 Don’t give up on preventive maintenance and wait for a seasonal plant shutdown or a failure. Proper lubrication, bearing monitoring, cleaning, alignments checks, periodic shutdown, and inspections are invaluable to top performance of a coating line.
#17 The poor or infrequent care for rubber rolls also has been a major source of quality problems. These rolls are used in many places on the coater including tension nips or S-wraps, backing, and laminator pressure rolls. When these rolls get hard and shiny and slip, the resulting tension or speed issues can plague the process. When the rubber is rough, crazed or pitted, and cut, coating quality can be affected, especially if it is a backing roll.
#18 Many mature web coating processes can achieve a yield of 99.0% or better. Classify yield losses, which come from many sources. Some are designed into the process and are all but impossible to eliminate. These include inspection and retain samples required by the customer, sheet left on core at a splice, and edge trim losses. Others, however, are caused by poor materials, equipment failures, operator error, and the like.
Dictionary of Defects
AIMCAL has created a Coating Defects Lexicon that provides standard naming conventions for web coaters to use to identify and resolve coating defects.
This CD-based reference offers a variety of information including representative images of the defects, their causes and cures, and standardized definitions of the defects as well as web coating process terms.
The lexicon includes an alphabetized glossary section, and it can be searched by key word.
For information on obtaining the lexicon, contact AIMCAL at aimcal.org.
Larry Gogolin is a consultant to the coating industries with more than 30 years of experience. He works with clients in the areas of product and process development, manufacturing improvements, equipment selection, company evaluations, and project management. He is an independent consultant and on the technical advisory panel for the Assn. of Industrial Metallizers, Coaters and Laminators (AIMCAL). Larry can be reached at Gogolin & Assoc., 978/779-9845, e-mail: firstname.lastname@example.org.