Shrink tunnels are too often overlooked in the buying process as it’s typically seen as a support piece to the shrink wrapper. When you think of package quality and appearance, think of the shrink tunnel as it plays a large role with the end product.
The use of energy is critical for shrink tunnels as the wrapped package must have maximum ballooning or pillowing to allow the bubble to collapse at the right rate. If not done correctly, you will notice imperfections with the shrink wrap resulting in a less than desirable end product not suitable for retail.
How does a shrink tunnel work?
Heater size, fan velocity, volume of air, ability to precisely control the volume and direction of the air, belt type, and tunnel length are all critical factors in the choice of a tunnel. Heat and volume of air without the ability to control the direction or, control of the direction without sufficient heat or volume, will produce less than satisfactory results. A tunnel’s internal “plumbing” is a subtle but very important factor. Much like the efficient air management in a home can make an enormous difference in the energy efficiency and comfort of the indoor environment with the proper choice and size of ducting and fans, proper tunnel design can make all the difference in how quickly and how well products can be shrunk. Tunnels with heaters that are too small, or with poor air flow design that fails to create enough turbulence in the tunnel can have a dramatic effect on production speed, energy usage, and package appearance.
Don’t forget about belt design
Belt choice is also very important in choosing a tunnel. Typical belt styles are stainless steel mesh, Teflon or fiberglass mesh, wire mesh, and various plastic grid types. In some tunnels, silicone covered live rollers are used in place of a belt. While producing a very nice package especially on the bottom cleanup, roller tunnels are more maintenance intensive requiring frequent lubrication with high temp grease and the occasional replacement of the roller covers. Stainless steel mesh or wire belts are the most durable, require the least maintenance and give an excellent result on most packages when running a polyolefin film. Polyethylene films will stick to metal belts and, for this reason, require the use of a Teflon or fiberglass mesh belt. When products are heavy or when many units will be on the tunnel belt at the same time, a positively (sprocket) driven plastic grid belt is required to avoid stalling and yet allowing good air flow to the package.
Proven shrink tunnels
Texwrap’s standard line of forced air tunnels have proven over years of use to be capable of producing excellent results with most packages. Digital temperature controls, high velocity fans, individual top and bottom controls for air direction, and variable speed conveyors all contribute to the precise control of the process to put the right amount of heat of the right places over the correct amount of time to produce outstanding shrink results.