Central to any discussion about 3D laminating is a discussion of press types, and what makes them distinct from one another. Deeper into that discussion is a dialog on the function of each press and what the advantages/disadvantages are. The following is an attempt to clear up some of the mystery behind 3D laminating.
All 3D laminating is a result of heat and pressure over time, just like fossil fuels, only no animals have been killed in the process of making 3D laminated components. The heat and pressure that is applied in the process of 3D laminating (let’s use 3DL as an acronym) is different based on the type of machine being operating. The type of machine being operated is often determined by product volume, and/or required definition of that product. So let’s start at the beginning - entry-level machines.
For a shop just starting out with 3DL it has been a common practice to purchase a vacuum press. Vacuum presses are entry-level machines that provide adequate heat and pressure to get the job of 3DL done, however, there are limitations to what they can do.
A vacuum press is also referred to as a “single-chamber” machine. In other words, there is only one area in the press that affects the forming of the overlay. We call this area a chamber, or zone if you will. The way a vacuum press works is strictly through heat and vacuum within a single chamber. The heat is supplied through an external element in the hood, or top of the press. The overlay is heated through radiant heat, and when it is ready to be formed there is a vacuum drawn through the lower chamber to form the overlay around the components that are staged on the bed of the machine.
The process is fairly simple, but the ability to get high definition of shapes and tight corners is difficult with a vacuum press. Both the tooling and the procedure need to be modified in order to have good success with a vacuum press, which is why many companies look to a positive pressure machine to do their work.
2 vs. 3 chambers
In the area of positive pressure presses, there are two categories: two-chamber machines and three-chamber machines. To keep things simple I will keep them as separate categories. Suffice it to say that there was a time when all positive pressure machines were two-chamber machines, but then the industry changed and three-chamber machines were born. Today you can still purchase a simple two-chamber machine at a price point substantially less than the three-chamber press.
Two-chamber machines provide vacuum from below and positive pressure from above. They can be used with or without a membrane, and typically have a heat source that is a radiant platen. You can achieve very high definition with a two-chamber machine because you are pushing the surface with positive air pressure and not just a vacuum. A two-chamber machine is a dramatic step up from a vacuum press and should be seriously considered before purchasing a press based on price.
With a two-chamber machine, fitted with a membrane kit, you can get the most common advantages that come with a membrane, i.e., consistent heat to the glue line, reduction in wrinkle, and some assurance against blowouts. However, you will not truly reap the benefit of a membrane that a three-chamber press provides, which brings us to the three-machine.
In a three-chamber machine there are three active zones/chambers in the machine that influence the cycle, and the final product. In the first chamber, like that of the vacuum press and two-machine, you have a vacuum draw to do the initial work of pulling/wrapping the overlay around the components placed on the bed of the machine.
In the upper chamber of a three-chamber press it is much like that of the two-chamber machine, there is positive air pressure to press against the surface of the overlay to form it tightly to the substrate. This provides the pressure needed to do details that a vacuum press cannot achieve. However, the real beauty of the three-chamber press is in the middle chamber.
The middle chamber provides the technology to allow true membrane function in a machine that has affectionately been termed a membrane press. The middle chamber offers air flow in both directions. When a membrane is being used on-board the first cycle function is to draw a vacuum in the middle chamber to bring the overlay and membrane together. This helps to thoroughly heat the overlay, along with drawing out potential wrinkles. Once the overlay is heated, both the membrane and overlay are drawn around the substrate in a single step – vacuum draw. Next, the upper chamber provides positive pressure to drive the details into the shape of the component. Finally, the membrane is separated from the overlay by an introduction of positive air pressure in the middle chamber. This releases the overlay from the membrane and starts the cooling process.
True three-chamber presses can be used with or without a membrane. They function freely between two- and three-chamber machines, based on requirements. The best high-gloss product is achieved in a two-chamber process without a membrane. Presses with proportional valves and cycles developed to facilitate this process will yield the best results.
In today’s world of 3D laminating it is important to understand your press and how the cycle functions affect the end product. By understanding these functions it will better help the operator in troubleshooting and developing new products. The industry has never seen the wide range of products like it does today. With the emphasis on surface design, texture, and new materials, 3D laminating has reached a place far beyond the days of white on white.
Source: Ed Strahota is with Choice Machinery Group: Evans Machinery, Evans Midwest and Ritter Machinery. For more information call 616-546-8225 or visit choicemachinerygroup.com.
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