That's too bad, they would be a great improvement over the ones in the images you have so far. Maybe altering the direction of the film would make it easier for you to do rather than placing it flat in the backing plate, it could have mulit tiered angled areas for each row and improve the look and utility and still be able to be closed with the method you have chosen, or another method of sealing the unit might be your answer. Heat staking is superior to ultrasonic welding today and might allow you to improve your product if you chose to upgrade to more modern equipment.We wouldn't be able to ultrasonic-weld the lenses to the backing plate if there were LEDs placed closer to the edges.
Historically, plastic assembly projects have always relied on the most reliable, repeatable, and consistent method of joining plastic parts available to them. Half a century ago, this meant using ultrasonic welding tools which at the time seemed like a sci-fi welding solution of unlimited potential.
Heat staking machines, on the other hand, were largely seen as inconsistent machines best used for installing metal inserts in to plastic bosses or housings. However, the forward march of technology continues unabated, and heat staking has taken strides in new directions beyond what ultrasonic welding machines are capable of.
One of the most obvious reasons for this is that heat and plastic technology has advanced a great deal since the 1970s. New polymers respond more precisely to heat, which is more accurately controlled by modern temperature controls and more advanced thermal head systems – our entire industry’s understanding of plastic thermodynamics has vastly increased.
So why isn’t heat staking a more popular plastic assembly method today? The truth is, it is, but only for companies who share a demonstrated commitment to adopting modern approaches and – importantly – phasing out obsolete production methods.