An Introduction to Shrink Wrap Machinery

The benefits of shrink wrap are well known. Covers for computer equipment, food processing, and retail packaging are often made from these materials, because their plastic-like qualities protect the contents from unwanted contaminants. From a cleaner work environment to a more visually appealing product presentation, shrink wrap is satisfyingly versatile. Although shrink wrap is particularly attractive for the use of computer equipment, shrink wrap can be found in other production facilities and in retail packaging.

In 1951, Walter J. Henninger Jr., Bernard G. Mallon and Robert N. Davis received a patent for the electronic specialty machine (EFM) that was to become the founding EFM System that was to become the founding company of TRW Automotive Systems and later TRW Incorporated.[1] With a focus on high speed operation, this machine also came equipped with a compact electrical panel that would go on to become standard equipment on all of their machines. This patent is still in use today as it helped to set the foundation for what would become TRW Automotive Systems.

TRW Automotive Systems of Troy, Michigan was the first company to commercialize a high-speed shrink wrap machine. TRW Automotive Systems is currently part of the Northrop Grumman Corporation.

Shrink wrap machines are typically used in one of two ways: open-die shrink wrap and closed-die shrink wrap. Open-die shrink wrap machines use a single heater located at the end of unit that heats up to high temperatures to melt the film around product. This type of machine requires two operators (one on each side of the machine). The second operator is usually responsible for opening the film to make the size adjustments necessary in the wrapping process. In this type of machine, one operator is usually the only person that does any kind of quality control (QC) on the product. Open-die machines are commonly used for roll film but are also in use for web wrap/long wrap/rapid wrap jobs as well.

Closed-die shrink wrap machines also have a single heater at one end of the machine and an often times one or more heaters around the circumference of the machine to extend over all sides of product at once. This type of machine runs faster than its open-die counterpart and does not require two operators. Both machines operate in a similar fashion, with the difference being in the type of heat source used. The second operator can typically perform QC on the wrapped product immediately after being wrapped.

In "The Art of Shrink Wrap Machinery" by Richard C. Leake, Jr. and James E. Santel, the shrink wrap machinery market is reported to be valued at $500 million in 2007 and is expected to grow to $640 million by 2012. The U.S. is the largest consumer of shrink wrap machinery, followed by: Germany, France, China and Italy.

In addition to its standard use as a covering for waste material and product, shrink wrap has been adapted for basic safety applications (for running blades of industrial equipment), protective storage functions, packaging uses (such as boxes and cartons) and customized applications (to show off product in retail stores). An American company employing about 50 people produces over 7 million meters of film each year using thirty-two high speed machines. Before the advent of shrink wrap machines, alternative methods of film application included the use of hand tools, heat guns and blow dryers.

According to an article by J. Freedman, in "Industrial Lubricant Technology", shrink wrap is the fastest growing packaging material in U.S. industrial environments.[2] The purpose of packaging is to protect products during shipping and handling, to protect people from potentially dangerous products, to provide information about product contents or directions for use and maintenance, and to satisfy regulatory requirements on hazardous materials.

In a study conducted by E. Gerard & Associates at the U.S. Department of Energy in 1999, shrink wrap was found to be the most cost-effective way to ship hazardous material. Shrink wrap is approximately three times more efficient than other packaging options, such as paperboard cartons and aluminum foil.

Shrink wrap has been used in small quantities for the protection of tools and equipment during shipment but has now been successfully adapted for large scale use as a protective packaging material.

Shrink wrap can also be used in other ways. For example it can be made into a protective cover for items such as poker chips or even small electronic parts.

Shrink wrap machines have several components. The motor mechanism is the most important part of a shrink wrap machine and as such, the motor capabilities should be carefully considered when purchasing a shrink wrap machine. Most shrink wrap machines today are powered by three phase motors. A three phase AC motor is preferable to a 50/60Hz AC motor, as it reduces line loss to almost zero, which means that no additional line capacitance is developed between the two halves of the coil windings in a three-phase system. This can lead to higher power output with less power losses. The original TRW Automotive Systems was using this type of motor for its open-die heaters.

Heaters are typically used on open-die shrink wrap machines while they are not needed in closed-die shrink wrap machines. Heaters can be made with different types of heating elements such as elements that use oil or electrical heat, the design of the heating element is an important aspect when determining which machine to purchase. The heating element should have electrical characteristics of high resistance and low power consumption. Carbon steel is a popular material for heaters because it makes them highly resistive to thermal wear, long lasting and cost effective to manufacture.

In addition to heaters and motors, shrinking film is also an important part of the machine in order to create enough heat and pressure around product to evenly shrink the film around product. A good quality shrink films should be made with polyolefin resins and have good thermal stability, high resistance to oxygen and solvents, not to be affected by the adhesive used with the film, possess good tensile strength, be flexible and tear resistant to help with the conformability of the film.

Shrink wrap film is produced in different thicknesses depending on the type of material being wrapped. For example, corrugated cardboard needs a thinner type of film than a thicker plastic or metal product. Film's thickness is inscribed into its code number, for example 1/4" shrink wrap would indicate that the film is .250" thick.

Conclusion

The most efficient shrink wrap machine boils down to its motor and heating elements. The type and quality of the motor determines whether a desirable high speed can be achieved with the desired price. Many factors, such as packaging size and product weight, might influence which machine is an effective choice for a particular product, however the importance of high performance motors has been clearly demonstrated.

References

https://www.youtube.com/watch?v=YKlOiGdN0g8 https://www.youtube.com/watch?v=QsCgE2uIeR4 http://www.mtsalloysllc.