At ATI, we are innovators that push the envelope in the world of thermoforming manufacturing. Our uniquely trained and specialized engineers can anticipate design problems and offer practical time and money saving solutions prior to product manufacturing. As case in point, our twin sheet thermoforming process, a relatively new process that most engineers and designers are unfamiliar with, became a pivotal answer to a client challenge in order to ensure the product could be manufactured – both effectively and aesthetically – without expensive retooling and retrofits.
Challenge
Sizewise, the parent company of Wheelchairs of Kansas, had contacted ATI to design and manufacture Headboards, Footboards and Side rails for bariatric therapeutic beds. Another key player, Samson Design in Boulder was retained to engineer and design a set of parts to be visually distinctive, strong, cleanable and house some functional components like electronics and monitoring devices.
ATI was faced with determining how these adjunct components could be constructed to be durable enough to handle various use and weight issues while also maintaining a high aesthetic quality. It also discerned four other complications prior to manufacturing that it had to resolve, which included resolving differing rates of thermal expansion between varying materials, positioning holes in steel weldment to plastic part, creating a countoured, radiused appearance that looked smooth and allowed easy cleanability and resolving draw-ratio issues for the Hand Control Docking Station. All of which needed to be accomplished within their budget.
Solution
Working with Samson Design and Sizewise, ATI chose to manufacture the Headboards, Footboards and Side rails using the twin sheet thermoforming process. This allowed them to insert mold aluminum or steel weldments inside the parts for added stiffness, strength, and encase them in a 2 part urethane foam to prevent rattling, provide additional strength and provide sound deadening while maintaining the desired aesthetics and ease of cleaning.
ATI also resolved the other issues discovered by their intuitive design for manufacture process. These include:
Resolve differing rates of thermal expansion between varying materials.
To insert mold aluminum and steel weldments in the various parts, ATI had to figure out how to accommodate the differing rates of thermal expansion that the aluminum and steel would have relative to the plastic. When plastic is molded, the sheets are at around 300°F and the weldments are at room temperature. If ATI did not adjust for the temperature differences, as the plastic would cool around the metal and would break or promote failure later on.
ATI accommodated this temperature difference by providing adequate clearance between the “legs” of the panels and interior features of the panels and the weldments. This then presented the challenge of how to hold the weldments in place during the forming process. To solve this, ATI used custom articulating “core-pulls” on the molds to hold the weldments in place which could then be retracted for de-molding.
ATI also had to develop a process to hold the weldments in place during the foaming process. It was done by incorporating centering fixtures into the foaming fixtures.
Lastly, ATI successfully developed a way for the steel weldment to fit together inside the side rail during the foaming process. This was crucial for the side rail to function.
Position holes in steel weldment to plastic part.
ATI had to locate the steel heel plate on the side rails precisely to the molded plastic so that it could mount properly to the bed frame. (See Siderail view #3). To do this, ATI developed the part’s geometry to allow registration with the foam fixture. The addition of the 2 part urethane foam inserted into the part positively locates the weldment in relation to the side rail.
Create a contoured, radiused appearance that looked smooth and allowed easy “cleanability.”
The client needed an aesthetically appealing look along with an easy to clean surface for the medical environment. The challenge in the twin sheet process is that the weld line between the two sheets protrudes outward, which cannot be removed without weakening the structure.
This requirement was satisfied by developing a concave weld trim (See Headboard view #1).
To prevent a weak weld, we developed a “heated pinch-line” in the mold. The purpose of this is to keep the sheet at weld temperature while the weldment is being inserted. ATI was able to use this novel approach, despite others belief that it is too difficult to be done in the thermoforming industry.
Resolve draw-ratio issues for Hand Control Docking Station.
(See Footboard view #2). The draw ratio presented in the areas for the internal electronics presented an issue. ATI modified the part design to allow robust material distribution in this region.
ATI assisted in material selection, sourcing a material that was tough, met the UL94V0 flame rating, and possessed anti-microbial properties.
ATI contributed to best practices in inventory control by limiting additional molded SKUs for the Siderail. The “level” feature, (See Siderail view #2) requires a molded feature that is only needed in two of the four Siderails. ATI decided to mold that feature into all the parts and cover it up on the parts that didn’t need it with the polycarbonate overlay. This reduced the number of molds required.
Results
Because of ATI’s extensive involvement in design phase, the product successfully rolled out without any field issues. Further, due to ATI’s design-for-manufacture process, all modifications and solutions were able to be delivered on-schedule and without any budget increases.
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