Here’s a good conversation starter: Stop what you are doing and look around you for anything and everything that is a thin film or sheet made of paper, plastic or metal. In my office space I have a calendar (paper), a computer display (film), a crumpled wrapper of a roast beef sandwich (metal foil), sticky notes (paper), office memos (paper), a trash can liner (plastic)…you get the idea. Products like these, manufactured from the noted raw materials (metal, plastic, wood) are all around us, within the touch of our finger tips. They are so commonplace that we don’t give much thought as to how they were made, and what some of the challenges might have been to convert the raw materials into something useful for us.
None of the materials that are converted into the thin film or web formats we touch every day start out in this shape or geometry. Whether its aluminum or copper ingots to make foil, polyethylene pellets to make plastic film, or wood pulp to process into office paper, there exists an installed equipment base to process or convert our three solids into thin, flexible webs. These lines require a science unto themselves that govern their design and operation. You would think that for products that are ubiquitous, equipment to make it on would also be well understood, easy to design, and readily available to own and operate. However, this is not the case.
What drives the industry is equipment that can turn out massive quantities of these products, to keep Unit Manufacturing Costs low. So, the machines that make these Roll To Roll based goods (hereafter referred as RTR) are large, high powered, and complex. The know-how to get a continuous flat web to flow through the machine that processes it is derived mostly by companies that invest in building their own internal knowledge base, are those select few who can actually build the machines, and some limited professional societies and colleges that offer a special curriculum to teach the science that governs the forces and motions of web conveyance.
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Now, one of the interesting things about pulling a thin film of paper, plastic, or foil through an RTR production line is that these materials are relatively stiff in the lateral plane. One way to envision this is to try and bend a sheet of paper horizontally that is laying flat…the paper resists being bent, it will tear first. Of course, if we slide the paper partially off of the edge table, we will notice that it bends easily in the vertical axis. Understanding how a web will respond to inputs that are required to process it (like pulling on it, or steering it) is fundamental to how to design and maintain web handling machines.
Where does our understanding of RTR machinery begin? Or, you might ask, what are the basics, the blocking and tackling, of web handling? Well, resident web handling consultant Dr. Kevin Cole would tell us (as he does all of his clients whose factories he visits) that it is unnecessarily difficult to tune up a web line that isn’t first and foremost “true.” What he means by this is, that all the rolling elements that support, pull on, or steer the web should be level, perpendicular to the centerline of the web in the direction of travel, and parallel to each other. If they are not, they could be imparting unwanted forces into the web, that serve to create defects or unwanted web behavior.
Many times Dr. Cole will be called to a client’s manufacturing plant because the customer is wrestling with a product or process problem that they have not been able to remediate on their own. As you might expect, Dr. Cole is very likely to ask early on in his visit this question “When was the last time you checked the machine for roller alignment?” If the customer cannot produce a timely report, Dr. Cole will recommend that Optimation mobilize a couple of our millwrights/machinists to optically shoot the rollers in the machine, and adjust rollers that aren’t true, so that the negative influence of misaligned rollers is eliminated. This is the quickest path to eliminating one potential problem, and allowing Dr. Cole and the customer to diagnose the true root cause of the issue at hand.
You see, in web machines, like in life, it is very important to keep things like rollers “on the level.”
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