Prototype Shipping Container Holds Plenty Of APeel

Service Detail from 3 Dimensional Services

Prototype Shipping Container Holds Plenty Of APeel-Image

21st Century packing, shipping and display container goes from CAD file to injection molded prototype parts in 2 ½ weeks…providing extra protection with less handling

What does a 500 pound gorilla eat? Anything he wants and plenty of it…and if he likes bananas don't get him riled by serving up bruised and damaged goods. And, while the danger might not be as imminent as an irritated gorilla, consumers shopping at food and produce stores will pass over damaged bananas, resulting in lost revenue and unrecoverable costs for harvesting, shipping and distribution of the fruit.

One company, however, is looking to make a difference. From its Orlando, Florida location, CHEP International, Inc., has developed a new design for a container that, since the first sailing vessels carried bananas back from the tropics, will revolutionize the shipping and handling of the fruit. The new, plastic "banana box" will replace the wood-and-wire crates, that have been in use for years. The box will provide a multi-purpose container. It is lightweight for carrying into the plantations for packing the just picked fruit, strong enough to protect the bananas during transport and provide an attractive appearance that provides an appealing presentation for consumer purchase in retail outlets. The protection afforded by the high strength box is increased when considering that the fruit need only be handled twice from the tree to the home-once by the harvester, second by the consumer.

The design of the 15" wide by 24" long banana box becomes even more functional with the fact that, once empty, it collapses down from its original 8" height to approximately 1.5" high, saving on storage and delivery space. The box can then be cleaned and returned for the next cycle of harvesting, shipping and selling of the fruit. In addition to its strength achieved through the incorporation of contoured interior ribs that help protect the bananas, the ribs are also configured as a sort of 'nest' or pocket for the fruit. The nest keeps the bananas raised off the bottom and reduces the risk of bumping and bruising. Plus, a series of holes and slots, hundreds in all, through both the sides and bottom allows for drainage and air circulation. Slots are also included as hand grips for ease of carrying.

Revolutionary and practical handling equipment like the banana tote is nothing new to CHEP. Since 1946 when it was established by the Australian government as the Commonwealth Handling Equipment Pool and produced its first pallets, the organization has continued to design innovative tote boxes and containers and provide material pooling services that have helped industries worldwide be more efficient. Today, as a private corporation and part of Brambles Ltd., the firm is recognized as a world leader in material handling systems. As was the practice for more than half a century of expertise and past successes, the CHEP project team needed to verify the banana tote concept for both manufacturability and use intent. They needed to build prototypes, and they needed them fast.

To produce the prototypes, CHEP called on Urgent Plastic Services of Rochester Hills, MI, specialists in the rapid prototyping of plastic injection molded components. Rapid prototyping, utilizing a broad range of manufacturing technologies and new, advanced materials, can produce injection molded prototypes in 50 to 75% of the time typically required when conventional prototyping methods are used. What's more, cost for tooling and molds is dramatically reduced in most applications because the company has developed several proprietary methods for molding plastics without the need for "hard" tooling.

Steve Kelly, sales engineer at Urgent Plastic Services says, "To begin the project, we were furnished CAD-generated files of the three different components that make up the tote (the bottom, two identical sides, and two identical ends). We put these files in turn on our CAD workstations where we could review for manufacturability. This step is especially critical for injection molded components since pattern and mold construction can play a significant role in final product characteristics, material usage and economics. From this review, we can also make suggestions for part design modifications and develop the most efficient tooling that will enhance its manufacturing intent."

After approval of any changes, each drawing file was translated by a CAM-type program and downloaded to one of the company's three stereolithography apparatus (SLA). Using the dimensional CAD file, the SLA creates a solid model of the part. The SLA employs a laser beam, programmed to travel and duplicate the cross sectional dimensions of the part, to cure a light-sensitive liquid polymer. Successive layers, again following the component outline, are added until the entire part is complete. In this way, model parts were created in hours and to precise, design dimensions, instead of days or weeks that machining or sculpting may have required.

The SLA-produced models served a two-fold purpose: First, as solid models they could be checked for assembly clearances and fits plus provide a "hands-on" review by CHEP engineers of each part's appearance, including capacity by loading with banana stalks and bunches; and second, they provided Urgent Plastic Services with the positive patterns required for the next step in the prototype process-the construction of the parts' molds and patterns.

Because of the complex contours of the ridges and ribs, plus the number of ventilation and weight-saving holes as well as the carrying handles, the tooling design was complicated…but construction was made easier and faster through the use of the SLA models. Using a liquid silicone, Urgent Plastic Services' pattern makers poured the material over and around the models, then allowed the silicone to cure. The silicone provides the right amount of rigidity to hold part tolerances while being flexible enough to remove the molded part without incurring damage to the part and mold.

The resulting cured silicone "tooling" was then loaded into one of Urgent Plastic Services' in-house injection molding machines where prototype components were molded using a reaction injection molding process. The RIM operation pumped a two-part resin and hardener polyurethane material into the patterns under low pressure. Given time to harden, the prototypes were formed, then easily removed from the rigid-yet-pliable silicone tooling. The special polyurethane formula selected cures quickly and closely reflected the strengths and characteristics the polypropylene material that is intended for the production of the final product. UPS uses a unique metered-mix system for the two-part urethanes, a process which precisely blends the components in the molds to achieve the desired properties for each "shot".

In addition to the time advantages this step provided, it also saved considerable dollar investments since no hard tooling had to be fabricated while allowing the necessary preliminary testing to take place.

From initial feasibility discussions to the delivery of finished prototype parts, Urgent Plastic Services was able to complete the job in under three weeks. And, thanks to the relatively low cost of tooling, plus the fast turn around, project budgets and timelines were kept on the smart track…no angry gorillas or consumers.

Urgent Plastic Services' capabilities include an in-house mold and pattern shop, a carbide machining and grinding center for the production of EDM tooling, an array of ram and wire EDM systems, plus CNC and manual machining centers and milling machines. The prototype facility has its own injection molding department, with machine capacities from 75 tons to 1500 tons. In addition to the stereolithography systems, the firm also has both laminated object and selective laser sintering 3-D modeling systems. The company is a sister company of 3-Dimensional Services which provides rapid prototyping of metal components fabricated through machining, stamping, cast and molding processes.