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Thread: Pros/cons methods holding delicate parts in panels

  1. #1
    Associate Engineer
    Join Date
    Jul 2021

    Pros/cons methods holding delicate parts in panels

    I am looking for qualitative understandings that will help me chose the approach i use to hold a delicate
    Electronic part in a thick polymeric panel

    In this specific instance
    the delicate electronic part is a capacitive switch with internal electronics. The mfr is Schurter. The mfr does not make internal construction available

    The panel is delrin about 6 mm thick

    The task of the holding method is to minimize
    The ability of the capacitive switch to rotate
    And move longitudinally( move in and out of the panel hole) Under use and ambient conditions.
    Ambient conditions are a relatively stable office environment

    I see only two fundamental solutions to be evaluated.

    Switch held in place by longitudinal tension
    And switch held by radial compressive forces

    Example of longitudinal tension is revealed by a flanged threaded switch. The flange prevents the capacitive sensor on the panel surface exposed to the user From being pulled through the panel by a nut threaded on the switch and pushing against the
    Panel surface not seen by the user.

    Rotation is resisted by friction of the flange against the exterior panel surface. The force is normal so the entire longitudinal tension force is totally applied in creating the friction. The area, while not a factor in calculating friction, is minimal.

    In snd out movement is more complicated because
    The panel is composed of Delrin approximately 6 mm thick. Delrin is not likely to change in dimension
    Due to humidity or temperature fluctuations that take place internal to an office in which this switch is used. But i am surmising the delrin might creep over time under compressive Loading.(i need to look that up)

    The second method of holding the switch is with a radial compressive load.

    That force is generated by a sleeve placed between
    The panel hole and the switch threaded body.
    It is slightly longer than the panel
    Thus acting somewhat like a compression limiter.
    The force of a nut is applied to the compression limiter which passes the force to the switch flange
    Thus the delrin does not see any compressive force
    Unless the compression limiter is made slighlty smaller than the panel thickness.

    In this design, however, the sleeve is slightly larger than the panel thickness but the sleeve
    Is compressible in two ways. The material can compress and the sleeve shape can change shape if there is a slight clearance between switch and panel. If a nut on the switch applies tension on the switch (compression on the sleeve) the sleeve applies a radial force on the switch body exposed to the sleeve.

    I dont know how to think in order to evaluate this approach, i do appreciate that getting the sleeve to be the right length and thickness would be tricky. But it seems the radial force is applied to significantly more area And hence the anti-torque feature could be superior to the pure tension approach

    I am guessing, with no real understanding that the switch�s resistance to longitudinal movement might
    Be superior in a relative sense. Meaning, it might move very small movements (mil or two) but elastically snd hence return to the switch�s original longitudinal position

    I welcome all insights and criticisms. I am here to learn

  2. #2
    Principle Engineer Cragyon's Avatar
    Join Date
    Feb 2013
    Newark, NJ
    Not to derail this thread but what does the manufacturer have to say or recommend for mounting?

    Are there install examples for similar or exact applications?

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