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  • #10000
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    MMC60 Round Flexure Switch – 60 mm

     

     

    Overview

    This is a cost-effective, 3D printable accessibility switch. The switch has a 60 mm (2.5 inch) round activation surface and uses a standard 3.5 mm cable. The switch is 40 mm in height. Using the specified switch, the activation force is about 3.4 N (325-350 gf). The cost in parts is approximately $10 in hardware and 3D printing materials.

    Usage

    The switch is activated by applying pressure on the top surface. This switch can be connected to any standard AT interface, and can also be used with the Xbox Adaptive Controller. The switch can be used on a flat surface or mounted using the 1/4″-20 UNC connection on the bottom.

    The top button / activation surface is attached to the base by threading it on. This makes it easy to change tops to change color, labels, etc.

    Capabilities Needed

    Soldering, 3D Printing

    Time to Complete

    3.5 print hours + 30 assembly minutes

    Cost to Build

    Approximately $2 worth of filament + $6.11 of parts

    Creative Commons License

    attribution-sharealike-4-0-international

    Images

    switch-parts Interior-switch Flexure Switch

     

    Project Page

    https://makersmakingchange.com/project/round-flexure-switch-60mm/ 5

    Updates

    2021-Jun-16: Based on some work by  @marchache1717, we’ve added a 3D printable pin for securing the switch.

    #10001

    If you’ve made one of these and the top is sitting at a slight angle, take a look at the flexure. If there’s any kind of unevenness in the flexure it most likely won’t sit straight. Reprinting the flexure will likely sort it out.

    The button still works if the top’s a bit squint, though.

    #10002

    Further user feedback

    * If the top becomes unscrewed, the ¼”-20 nut can fall out easily. A small slip of paper folded a couple of times and wedged behind the nut will stop it falling out. Blue threadlock (the kind that’s reworkable with hand tools) may stop this unscrewing in the first place.

    * If you’re short of ¼”-20 nuts (as might happen if one fell out and got lost, as above), you can 3d print a spacer from this OpenSCAD code:

    in=25.4;
    linear_extrude(height=7 * in/32)scale(2/sqrt(3))difference() {
    circle(d=7 * in/16);
    circle(d=in/4);
    }

    This has the width and height of a ¼”-20 nut, but should slip over the screw thread easily.

    #10003

    Here’s our current list of possible / probable design changes. We’ll revise/review/prioritize once we get some more user feedback. If there is a Maker keen on taking on some of these changes, please let us know by responding below.

    1. Optimize the design of the flexure to improve durability (it may start to deform after ~10K activations, requiring greater travel to activate the switch).

    2. Add additional support/screw/etc to prevent switch holder and jack from moving / rotating.

    3. The screw bosses that support the switch holder should be reinforced (i.e. with webs) so they are less likely to shear off.

    4. Adjust screw hole sizing in base. Prints in PLA by outside printers were a little too tight, requiring bigger screwdrivers and more torque.

    5. Find a better method of mounting switch rather than somewhat challenging to source wooden dowel.

    6. Redesign button top to minimize or remove the need for support material or make it easier to remove.

    7. Add a design element to the button top to prevent the nut from falling out.

    8. Consider metric hardware, or a metric version, as the imperial 1/4″-20 UNC may be hard to source outside North America.

    9. Investigate whether there is an easier to source option for the #4 screws.

    10. Investigate ways to reduce the overall height.

    11. Investigate ways to center the mounting nut. (Could be separate mounting adapter, for example.)

    12. Redesign the button top to reduce the gap between button top and base.

    #10004

    More user feedback:

    “The positives are that it’s seems very durable, the action on the activation plate is great (activating on all points of the top surface, as well as hitting it on the side of the plate. I like having a separate cable that plugs into a surface mounted jack. It makes for less fuss with cable repairs.

    The potential negatives are the mounting nut being off center on the bottom? Though that may not really be too big a deal.

    And I can also see where some clients with developmental delay might persevere on trying to pry off the top plate, there is enough of a gap where it could be tempting for them.”

    #10005

    More user feedback:

    “The Makers Making Change [MMC60] Button, shown in Figure 4, is approximately 4 cm high and
    requires less force to activate than a traditional Jelly Bean or Buddy Button switch. A Big Buddy Button
    requires approximately 5 oz of force and about 2 mm of downward movement to activate, standing at
    1.5 cm high. A Jellybean Switch requires approximately 3.5 oz of force and about 2 mm of downward
    movement to activate, standing at 2 cm high. It is advantageous that the [MMC60] switch
    requires less force and is bigger than these other switch options, as it could be activated by individuals
    with less strength and control of their movements. The switch is easily mounted via Velcro, however its
    height may limit positioning on flat surface for individuals with smaller hands. As shown in Figure 4, the
    hand is raised off the table. Making shorter versions of this switch available as options would solve this.

    ![MMC60-Fig4|342×311](upload://w0JKVdXyF0n7KMgGGpHYbaAwxOR.jpeg)

    The surface is nicely smoothed and feels pleasing to the touch. The top blue disc may benefit from
    adding a more gradual curve to the edge in order to limit pressure on the user’s hand (or other access
    site) though this is not necessarily an essential change to make.

    The switch provides nice auditory and tactile feedback. When pressing down on the switch, a “click”
    sound can be heard and pressure can be felt when the button pushes down. This feedback occurs
    regardless of the angle of activation provided.

    As shown in Figure 5, activation of the [MMC60] on the edge, rather than centrally presents a
    potential concern for durability. There is 4 mm of distance between switch’s blue top surface and the
    bottom’s black mount. If an excessive amount of force is applied over multiple trials, this could
    eventually wear down the switch’s central attachment.

    ![MMC60-Fig5|690×354](upload://9U3cY76S7aVSndBo7c7li1vcKlv.jpeg)

    #10006

    In case you missed the [post](https://www.instagram.com/p/B4TNKzUpoQa) on social media, we made a festive version of the Round Flexure Switch for Halloween.
    ![RFS_Halloween_Sm|500×500,75%](upload://8zfVeNbTEaHlysv8DPXL3JMWGay.jpeg)

    Since the top is threaded on, it’s easy to print a different top and swap it out. In this case, we printed an entire switch in orange filament, and added a custom two-color top. (We used two models and a manual filament change – I’ll create instructions detailing how that can be done.)

    Different colored tops can be useful for adapted gaming as well. We have used them to match the colors of the X/Y/A/B buttons on a standard Xbox Controller when used with the Xbox Adaptive Controller.

    One challenge is that it is hard to control the rotational orientation of the top relative the base. You can get around this a little bit by changing how the nut is oriented in the top (there are three options).

    As @SRv mentioned above, the nut can fall out and possibly get lost when swapping the top. There is also a chance a user may inadvertently cause the top to unscrew through normal use (or purposefully try to do so.)

    This leads to several possible improvements to the top:
    – alter the design so a differently sized / colored / textured top can be swapped easily, but will remain securely in place during use
    – reduce the likelihood of the nut falling out and getting lost
    – enable a user to adjust the rotation of the swappable top relative to the base
    – alter the design so the top portion could have a different shape or texture (currently it needs to be essentially flat since that surface is in contact with the print bed), ideally without requiring lots of support material

    #10007

    Based on the results of some fatigue testing, we recommend changing the default print parameters for the flexure component. The original specification was two use two shells / perimeters for all parts. Flexure components printed with 4 shells / perimeters lasted much longer than those printed with two.

    #10008

    If you’re having difficulty sourcing some of the parts, here are alternatives from Digikey:

    * **Switch**: SS-01GLP Omron Electronics Inc-EMC Div — https://www.digikey.ca/short/zj7zc8
    * **Audio socket**: 35RAPC2AV Switchcraft Inc. | Connectors, Interconnects | DigiKey — https://www.digikey.ca/en/products/detail/switchcraft-inc/35RAPC2AV/772080

    (Digikey Canada are out of stock with the spec items and are on 12+ week delivery)

    The switch I listed includes a lever which will have to be removed. This is easily done by gently squeezing it from the sides with needle-nose pliers

    #10009

    Thanks for the tip @SRv :+1::+1:

    #10010

    @MMC_Chad Hi! Would you be able to share the Fusion 360 file for this project?

    #10011

    Hey @loretodalt. I’ve published the design on Thigiverse and included the Fusion files as well: https://www.thingiverse.com/thing:4643859

    Let me know if you have any questions or problems.

    #10012

    Got it @MMC_Jake! I totally missed that file from my last download. Thanks so much!!!

    #10013

    Note to self: need to double check the listed activation force on this switch 325 grams-force seems very high. One version I tested was closer to 80 grams force, though it may have an older style of flexure.

    #10014

    One of the pain points on this design is the pins inserted to secure the switch. Some 2 mm wooden dowels from a local dollar store fit well, but these have been hard to source elsewhere. Alternatives have included bamboo skewers, toothpicks, and coffee stir sticks.

    ![Switch Pins|649×454, 50%](upload://KT38HpIhiLHYodSa1BtSAWhBLE.png)

    If someone has a good idea for another option, or an alternative way to secure the switch, that would be very helpful. The switch mount was intended to be a modular component, so there is some leeway for changes that won’t impact the entire design.

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