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We are manufacturing electronic instrumentation which comes in a machined aluminium case. We have full flexibilty on design of the case. I need to design some form of strain relief for the single cable, which has a diameter of 6mm. The case needs to be sealed to IP67. I have in mind some sort of glue but not sure what is the best thing to use here - we intend to produce tens of units, so needs to be repeatable and relatively easy to manufacture. What would be recommended here? Thank you

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    \$\begingroup\$ Make sure you think about longevity. If the glue breaks down in 10 years, and the cable starts to pull through and come off the board, your customers will be sad if the device is expensive. \$\endgroup\$ – Glenn Willen Mar 19 at 17:38
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    \$\begingroup\$ Hire a mechanical engineer with expertise in design for manufacture. It's that simple. Non-experts will at best get a sub-optimal solution, and at worst will get something that's faulty and/or dangerous. Much also depends on what's inside that 6mm cable, because acceptable risks at 1V and 1KV are very different. If this is supposed to be professional quality and you don't have the skills, get a professional. The upfront cost of hiring a contractor for a couple of weeks is way less than anything else. \$\endgroup\$ – Graham Mar 19 at 19:07
  • \$\begingroup\$ You used to be able to get a rubber grommet that fit tightly around the cable and which, when fed from the inside, would pull tightly into the hole in the case. Dunno if these are still readily available. \$\endgroup\$ – Hot Licks Mar 19 at 22:18
  • \$\begingroup\$ Bear in mind that moisture can enter inside the cable between the wires if the remote end allows it. Not very quickly, but maybe asking the cable manufacturer about that could lead to improved long-term reliablility of your product for little extra outlay. \$\endgroup\$ – Andrew Morton Mar 19 at 22:43
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You can use a cable gland. For your use case:

  1. Select a cable gland which can hold a 6mm cable. These glands can either be made up of metal or nylon, like the "RS PRO PG 7 Cable Gland" or "HellermannTyton NGM M12 Cable Gland". At any rate, these should provide strain relief and at least IP67 rating -- you turn the gland with the cable passing through and the rubber or nylon material inside squeezes on the cable.
  2. You need to drill a hole larger than 6mm to accomodate the gland. The specific size depends on the gland that you'll be using.
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  • \$\begingroup\$ I didn't know the word for these! Cable Gland makes a lot of sense! \$\endgroup\$ – Marcus Müller Mar 19 at 8:26
  • \$\begingroup\$ You provided the right part though! :) \$\endgroup\$ – Carla H. Mar 19 at 8:35
  • \$\begingroup\$ Cable Grip or Cord Grip is another name for this type of part, by the way. \$\endgroup\$ – Nick Alexeev Mar 19 at 22:28
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You could just buy a grommet that fulfills your sealing requirements, and fits into a larger hole, and solve the strain relief issue on the outside, e.g. by a screw-on clamp thing.

However, standard way: Sealing Grommet/Strain relief to fasten into a hole:

https://www.digikey.com/en/products/detail/phoenix-contact/1411126/5188735

strain relief with seal

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  • \$\begingroup\$ And they come in metal \$\endgroup\$ – Damien Mar 19 at 8:44
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You don't mention anything about what type of cable this is but for most even vaguely common types of cables, you should be able to use a panel-mount connector. The connector provides strain relief, and you can get them already certified to IP67. A few random examples:

Most companies that manufacture connectors have entire product lines that are ruggedized and already tested against various standards. Installing a connector in a cutout is less manufacturing work than running a cable through a hole and trying to seal the opening with glue or epoxy, plus you don't have to worry about the seal breaking loose over time as the cable gets jostled around. It also makes the device overall easier to package and transport since the cable can be disconnected and stored separately, and discourages harmful practices like winding the cable tightly around the device for storage.

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