Ruggedizing the HMI Display of an E-Cigarette


Challenge

We received a request for information from a customer regarding a consumer product that was experiencing failures in the field. The device, a high-end E-cigarette, had an excessive number of field-returns where customers complained the OLED display was no longer functional.

They also complained that their current supplier was unable to confirm the exact failure mode and root cause, leaving the customer dissatisfied and with few options. They asked us to review the design, failures, and try to draw some conclusions on how to remedy the project. The challenge was to determine the root cause of the failed user interface OLED display and implement a solution.


Solution

The customer provided additional design details along with samples with the failed OLED displays. We confirmed that the E-cigarette user interface was not working properly, specifically the OLED displays were not functional. After further review we determined that the failure mode was physical damage to the display. The next step was for us to study the use case and attempt to duplicate the failure.

We began with drop testing from heights of 1 ft, 2 ft, and 3 ft. In multiple drop orientations we confirmed the OLED displays were being damaged by their consumers’ rough handling. Specifically, drops that landed on the face of the OLED display caused ~80% of the device malfunctions.

  • HMI Display of an E-Cigarette
  • HMI Display of an E-Cigarette Ruggedized Bumper

The fix was easy, ruggedize the E-cigarette housing to survive mechanical shock and impacts on the OLED display surface.


Result

The proposed redesign featured a modification to the housing adding a thin profile 60 durometer (Shore A scale) overmolded lip around the perimeter of the OLED display that acts as a bumper. This bumper is approximately 4 mm tall and 2.5 mm wide and when dropped on its face, helps reduce the impact load on the OLED display like a shock absorber, protecting the screen.

By using tabulated mechanical material properties, the impact force and resultant compression of the bumper can be calculated. We estimated that when dropped from a height of 3 ft, the bumper will compress less than 0.1 mm during the impact event, which is well within the material’s allowable compression range.

Simulation and analysis can only predict performance, and the best way to confirm the results is to test. Accordingly, drop testing was reperformed and the overmolded lip significantly improved the results of drop testing.


High Reliability Human-Machine Interface Solutions
Celebrating 70 Years of Manufacturing Excellence
America's Oldest. A History of Innovation.

Over the past 70 years, the electronics manufacturing industry has changed dramatically as the industry continues to adapt to evolving demands and technology. Epec is at the forefront of innovation, with the expertise and agility to move at the speed of today’s businesses. At Epec, the customer comes first, and everything we do must be put through that filter. Whether it is developing e-commerce platforms to make it easier to work with us or creating a new product introduction (NPI) process that helps our customers get to market faster, we must focus on building the new. By doing that every day, and by always making the customer our top priority, we plan on being here for another 70 years and then some.

Learn more about our 70 year story →





Celebrating 70 Years - Epec Engineered Technologies