Today we will take a look at the design process, rules, expectations, and guidelines that should be followed when designing injection molded parts.
Si-Tech knows that rules are in place for a reason, which is why we follow these rules, recommendations and protocols for the creation of all our keypad designs. These rules govern everything from decorating to coatings to color matching – all important considerations when designing a silicone component or keypad.
You have to take a lot of factors into consideration in regards to how the tooling will be crafted, to be sure, but also how it will impact production standards and timelines.
1. Our 7 Fundamentals
We are proud to follow stringent industry standards that help us create and develop your design. As such, we follow these seven fundamentals:
- Between a bezel and a key, the clearance can’t be less than 0.012”.
- The min. radius allowed is 0.010”. We don’t recommend using anything smaller than 0.020” when it comes to deeper pockets or cavities.
- Recommended air channel geometry is 0.080” –0.125” wide by 0.010” –0.013” deep.
- The mat of a keypad should have a min. thickness of 0.040”. When the mat is too thin, this can negatively impact the force profile you’re going for.
- A keypad’s maximum thickness can’t be more than 0.150”.
- Keys taller than 0.200” must have a minimum draft of 1°; anything taller than 0.500” must have a min. draft of 2°.
- Tear plugs are necessary in openings within the silicone part, removable by tweezers or by hand. With a smaller opening, it’s more challenging to remove the plug.
2. Backlighting Requirements
Backlighting is a necessary feature on many keypads because it helps the viewer to see each key in dark or dim conditions. LED lighting is used via a printed circuit board to achieve this effect, whereby a LED insert or clear window displays the light.
LED light pipes, displays and windows must follow these design recommendations:
- The insert molded silicone light pipe should be a min. of 0.060”.
- In regards to the feature window opening, the max undercut depth should be 0.250”.
- Between the edge of a silicone window or light pipe, and opening or keypad, the min. distance should be 0.030”.
- An insert molded window’s min. thickness should be 0.030”.
- For molded silicone light pipes, the min. height is 0.030”.
3. Shrink & Tolerance Guidelines
It’s not uncommon for injection molded silicone components to shrink down a bit after demolding. But just how much they shrink will depend on molding temperatures and the materials used. Components and keypads usually shrink between two and three percent, adjusted from the molded size.
Due to this variable shrinkage for silicone parts, liquid silicone rubber components have to keep up with a certain standard tolerance for sizes of all kinds.
We take standards very seriously here at Si-Tech, whether that involves backlighting or component design. The rules we follow ensure the best possible end product for our clients.
Contact Si-Tech
Curious to know more about our process, as well as the keypad design recommendations and rules process we follow? Just contact us today at 757-887-8488.
