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Adding Keypads and Cables to Your Injection-Molded Enclosure - Q&A

Epec Engineered Technologies
Written by Epec Engineered Technologies
Posted on August 23, 2023 at 8:44 AM

At the conclusion of our webinar, Adding Keypads and Cables to Your Injection-Molded Enclosure, we had several questions submitted to our presenter, Steven J. Goodman, User Interface & Cable Assembly Product Manager at Epec. We have compiled these questions into a readable format on our blog.

Q&A From Our Live Webinar

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Question: What's your electrical test plan look like for these types of productions?

Answer: For our electrical test plan, there are two ways to approach this. One way is there are basic wiring and continuity tests that we can perform, most of which are just using a multimeter and our test technician is probing specific points in the circuit. These are standard IPC-620 level tests where we're checking continuity across various wires and components. We're making sure that everything is electrically wired to the approved schematic. We do this on every product. But some of our customers will require a hi-pot, insulation resistance, or some other higher complexity test that can be done with automated test apparatus.

Some customers have displays, touchscreens, or embedded systems that need to be tested. Or there is software that needs to be flashed onto local memory within the device. Sometimes testing is more complex than just turning a switch on and off. To answer the question of what a test plan looks like, some of our projects require a complete functional test largely defined by our customers. Epec can also help develop a full acceptance test plan to make sure all electrical systems are operating as planned. Overall, this largely depends on what's involved in the box build and what our customers need for system requirements.

Question: Do you recommend drop testing, and when do you need to perform this test?

Answer: Yes, absolutely. We recommend drop testing. There are formal shipping and handling tests that can be done- some of which are derived from ISTA standards. But the goal here is to simulate real-world abuse. And this is more than just kicking a box off the loading dock. This is using the product, plugging it in, unplugging it, dropping it while installed, dropping it while uninstalled. etc. Dropping it from a table 10 times and seeing what happens, dropping it on all corners, and then documenting the results. Our suggestion here is not to overcomplicate drop testing, but it is important to get some type of real-world data on this. Gain feedback from stakeholders regarding the expectations in terms of drop testing performance and requirements and take action with a 3rd party test lab or as needed to satisfy program objectives.

Question: Can you color match the plastic to a powder-coated aluminum, and what's that process look like?

Answer: Yes, absolutely. We can color-match any of the thermoplastics or silicone elastomers that we mold. Typically, Epec defines these colors as a Pantone color or an RGB color. We need a repeatable way to define the color that’s obviously more than red or blue. The challenge is that if you colorize or print the same Pantone color on a sheet of powder-coated aluminum and then do that on an ABS- polycarbonate blend, and again do that with a silicone elastomer keypad, you could have three different perceived colors, even though all three are using the same Pantone.

And what's important here is that the actual medium you're colorizing has very slight tendencies to look a certain way when colorized. If color matching is a concern and you have different materials like a powder-coated aluminum next to a silicone elastomer keypad, there are two ways we can approach it. One would be to get an actual Pantone color that your team, your marketing team, and other stakeholders are good with, or two, give us literally a swatch or a coupon, and we will take that and color match the material directly to that pigmentation.

Giving us a color-match coupon may be the best way to go and get the exact color-match specs needed. The problem is we’re going to need to hang on to that color match coupon indefinitely, and with each batch do a color match to the “golden sample” to make sure our colorization is dialed in.

Question: We are using a NEMA 5-15, like the one you showed in the slides. Can you make those with custom strain relief and how long does that take?

Answer: A NEMA 5-15 is a pretty standard connector scheme, typically used in the wall outlet you plug in at your house to charge whatever electronic device you have. Whether it’s your phone, a stereo, or a television, the NEMA 5-15 is a standard household electrical plug here in North America. We have existing overmold hard tooling for NEMA 5-15 and other related plugs and receptacles. These existing tools are typically free to use when building an overmold. But if custom strain relief is needed, we can help design and build a customized version in just a few weeks.

To be successful we want to understand what the specific type of customization is, or if it's something that we need to go and make a whole new dedicated tool. If the strain relief customization is something where we can just modify an existing tool, this can be much faster and less expensive. Since the latter can be just a few days and a couple hundred dollars instead of four weeks and thousands of dollars, we always recommend using standard tooling designs wherever possible at the least as a starting point.

Question: What's your choice for bolts and screws for a removable lid, and what if we want to ultrasonic weld the lid?

Answer: So, for bolts and screws, it comes down to if the designer wants the lid to be removable and by whom? If this is a product that’s not intended to be field serviceable, a more permanent attachment method like an ultrasonic weld is appropriate to attach the lid. Or we can use an adhesive or an RTV sealant to help affix the lid onto the body. Additionally, one may require that the lid cannot be removed whatsoever, and removal of the lid could be an indication that the design is tamperproof.

This could be a lid that must be removed to access batteries or a debug port. If your requirement is that a technician will need access to the inners of the housing, then we would recommend a cap head or a panhead-type bolt with a mating heli-coil insert that's pressed into the enclosure. Dodge inserts are a common name for those types of inserts that are set within the walls of the enclosure. The primary reason for choosing a set of bolts and threaded inserts is that these are fasteners that can be installed and removed repeatedly. Our goal is to try to dial in the best type of fastener and then study how the threads are going to engage the other side of the enclosure.

If cost is an extreme concern, we don't always need to add heli-coils. They're not typically a cost driver, but if the price is critical, we could use a thread-formed fastener and then design the mating plastic part in a way to make sure that the faster interferes with the material there and that the thread-formed features on the fastener can go and engage the material and cut into the material and basically self-tap itself making a hole there.

Topics: User Interfaces, Cable Assemblies

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