Trapped Heat
Before cutting to size, remember to release heat from the panel
By David Welch
Panel processing, born in Europe and continuing to make progressive inroads in the U.S., particularly in the cabinetry industry, presents its own particular question marks in the manufacturing process from time to time. The cause of and cure to distortions in laminated panel cuts, when to bring laminates in-house, the advantages of engineered board and its future are discussed by industry experts.
Imagine this scenario: You have purchased a state-of-the-art saw for your panel processing operation. You arm the saw with the best blades on the market. However, when you place the panel on the saw and make your cut, the cut is not square. Before blaming the saw or the tools, the problem might be in the panel itself.
Panels that have been laminated on both sides tend to trap heat, according to Jon Elvrum, director of distribution and sales for Ritter Manufacturing.
“Two-sided melamine panels tend to trap heat inside the center of the board as a function of the bonding process,” he says. “So, when you go to make the cuts and reduce the parts down to panel parts, you expose a lot of interior heat that has not had the chance to escape through the plastic on the top and the bottom. That heat will cause a distortion in the cut as you get to the center of the panel and a reduction of heat as the cut leaves the center and exits the other side of the panel.”
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| The accuracy of CNC machining centers, like this one from Northwood, make true panel processing possible. |
The result is two panels that curve slightly away from the cut, so if the two pieces are brought back together there will be a wider separation at the center than at the outside edges. This results in what Elvrum terms, “the banana cut.” Obviously, panels that are curved slightly cause problems in the assembly and banding processes.
“If you were able to put a high resolution microscopic camera right at the top of the blade as it was going through the panel, what you would see is the board actually exploding in front of the cut. The heat is so intense that it blows out as the knife-edge comes through. You can see evidence of splitting three to six inches in front of the blade. So, it is not a shear cut. It happens so fast, the blade comes behind it and trims it so that it is not rough. The closer you get to the edge of the panel, the less heat there is and it comes back to a straight cut,” Elvrum explains.
Balancing the panel
There are methods to get the heat out of these panels. “The Europeans have perfected a method and used it for a long time,” says Elvrum. “They balance the panel. They run the panel through a double-end tenoner, which produces vibration. Vibration releases the heat on both sides where the cut is happening. It actually shakes it out and the impact of that is that the heat spreads itself from the center outward to where you now have a panel that is sized to the opening created by the sawblades.”
| Advantages of panel processing |
1. Conserves natural resources –engineered panels are a high efficiency use of timber resources.
2. The material is made in board mills that use a fraction of the energy required by kiln drying solid wood based on same amounts of raw material.
3. The engineered panels are delivered in a form that is readily machinable using the same chip removal technologies used with traditional solid wood: sawing, drilling, routing, sanding, etc.
4. The machining of panels is usually less demanding than the machining of solid wood, contributing to plant automatization and lower manufacturing costs.
5. Its panel format satisfies the design requirements of most furniture manufacturers
and millworks.
6. Panel processing requires fewer piece parts that go together more systematically.
7. There is less guess-work involved, which leads to a higher level of performance accuracy. |
Panel balancing is not widely performed in the U.S. market, according to Elvrum. “The American market remains blissfully ignorant to this problem and they tend to blame the saw manufacturers or the tooling. The truth is that melamine is laid up flat and kept in a flat position. Nobody ever turns it on its edge because they might ruin the edges. If you could successfully turn it on its edge and leave it for six to twelve weeks, most of the heat would migrate out. But because these panels are kept flat, the heat inside the board is trapped. There is a period of time between pressing and when the material is supposed to be taken to market and that is when some of the heat is to migrate out.”
When should a panel processing company laminate its own board?
The panel process actually begins before the cut-to-size operation. Depending upon the company, the panel is either bought and immediately sent into the cut-to-size operation, or companies may choose to invest in the ability to lay-up panels themselves.
“As companies get larger and volume grows, it makes sense for many to consider bringing their laminating capabilities in-house,” says Ken Holley, president of Midwest Automation. “The panel process begins with these companies at the lay-up operation, which is beneficial because companies that perform their own lay-up operation get to control supply, costs and quality. They control their own destiny.”
When does a company know to make the investment in laminating equipment? “Usually a company knows it is time to make the investment in panel lay-up when it begins to have serious problems with supplier reliability,” says Holley.
The laminating process has changed dramatically in recent years. “Traditionally, people that lay-up their own panels would use a glue spreader and a cold press,” says Holley. “They would lay-up hundreds of panels a day and cold press them overnight. The industry had a batch mentality, which leads to lots of inventory.”
The just-in-time environment in manufacturing is all the more reason to control panel lay-up in-house. “What has changed is that companies need to make smaller, more customized batches,” Holley explains. “Now instead of warehousing the material, it goes from laminating to machining to edgebanding to packaging as it is ordered. This process is conducive for faster delivery of product and it reduces expensive inventory. However, to manufacture in a JIT environment, a company has to have tremendous flexibility and quick set-up times.”
Using engineered panels conserves natural resources without sacrificing quality
Forest conservation is a major advantage found in the use of engineered wood panels according to Giordano Checchi, president of Giben America. “Engineered wood makes high efficiency use of timber resources, using the most of the tree, including tree limbs and small rounds. The material is made in highly efficient board mills that use a fraction of the energy required by kiln drying solid wood based on the same amounts of raw material.”
“Cheap, abundant wood species can be used to make the boards, which can in turn be finished with expensive veneers to give them the rich look of solid wood without taking anything away from the quality of the finished product,” Checchi says.
Checchi dispels the stigma that remains with many U.S. consumers that engineered wood is a step down in quality from solid wood. “Panels that are laminated with paper or melamine impregnated paper can give life to a number of furnishing products that still combine high quality with very reasonable pricing. HPL (high pressure laminate) boards can achieve performances that were not even known before, with stain, acid, caustic, temperature resistant surfaces that find their perfect application in institutions, hospitals and science labs because of the highly hygienic features of these materials. Panels that are laminated with specific colors or other optically pleasing surfaces find innumerable applications in the store fixtures sector of the woodworking industry, creating environments that appeal to the consumer,” he says.
Industry sees a continual revolution substrate technology
Almost every four or five years, there are new breakthroughs in board material technology, according to Elvrum.
“Once upon a time it was filled with formaldehyde, which isn’t particularly true anymore. Once, panels were filled with a highly resinous pitch pine and that isn’t necessarily true anymore. In the early days in Europe, they used just about anything they could get their hands on – including forest trimmings. We are now going back to that as in the use of strawboard, which is a lighter material. The technology of the board and the glues is the one part that continues to change and develop.”
Panel processing continues to see growth in U.S.
Now estimated at 85% of woodworking production
Many of the existing mills are capable now of handling recycled wood, in part or at 100% recycled wood, giving wood fibers a second or even a third life, says Checchi. “These technologies are truly remarkable because they contribute more and more to wood and forest conservation with tangible benefits for the environment, without negatively influencing jobs or creating unemployment. It is an evolution, not a reduction.”
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