When PediaVision, inventor of the Spot vision screener, approached Mack to manufacture its new, wireless, handheld vision screening device, the original design included a multi-component optical frame that served as the support structure for all internal components.
Initially, the frame design included:
- seven machined plastic components
- 14 screws
- 12 pins
- 15 minutes of assembly time.
This design was labor intensive and used relatively expensive material and manufacturing methods. The challenge? Cut cost.
Turn the seven-piece, machined assembly into a single, one-cavity, molded part.
First, Mack looked at molding each of the seven components separately. This plan would have produced a savings, but the upfront tooling costs would have been prohibitive.
Tom Revane, Mack tool design engineer, had another thought—mold the part as one piece. “He looked at it in a different light and set a new paradigm for the product.” says Scott Rishell, Mack program manager on the account.
Mack presented the idea for the single molded frame to PediaVision. “They loved the idea and began redesigning the part right away,” adds Rishell. The redesign was a collaborative effort, with Mack addressing design for manufacturability and PediaVision focusing on optimum performance of the device. “It was definitely a two-way street,” says Rishell.
Specifying the Material
To move from a machined plastic part to an injection molded part, the design team had to reconsider the material. “Just by the nature of the labyrinth that this geometry creates, a standard injection process would require a relatively high injection pressure to adequately pack the part,” explains Rishell. The high injection pressure can stress the material, causing the part to distort and warp when it comes out of the mold. For a product like Spot, minimizing warp and distortion is critical, as incorrect angles and excess light in the frame could cause the device to capture data inaccurately.
The Mack team began looking into materials that would provide structural durability with lower injection pressures, finally settling on structurally foamed polyphenylene oxide (PPO). “Structural foam allows the part to fill and pack out evenly, which results in less internal stress and, therefore, less part distortion,” says Rishell.
1 piece, 80% cost reduction
|Individual Component Design||One-piece Design|
|7 molded plastic components||1 molded plastic component
|5-6 molding tools||1 molding tool|
|12 pins||0 pins|
|15-minute assembly||<1 minute assembly + molding cycle|
By consolidating parts and specifying a new material, PediaVision has enjoyed a return on its tool investment in just six months. The consolidation cut tooling costs in half, reduced part cost by 80 percent, and trimmed assembly time by 10 percent, meeting PediaVision’s cost goal, as well as all product specifications.
Contact: Scott Rishell, Design Engineer
Tom Revane, Tool Design Engineer
Anastasia Satterthwaite, Program Manager
PediaVision (Lake Mary, Fla.) is a leading developer of vision technology and inventor of the award-winning “spot” – a new generation of user-friendly vision assessment technology that transcends age, developmental capacity and mobility. Spot is a fast, portable, easy-to-use binocular vision screener with wireless communication capabilities designed to screen for refractive error, which can be associated with several ophthalmological issues in patients of all ages. Welch Allyn, Inc. (Skaneateles Falls, N.Y.), a leading medical diagnostic device company that delivers pragmatic innovation at the point of care, announced the acquisition of certain assets of PediaVision Holdings, LLC, on June 3, 2014.