JML
Headphoneus Supremus
RE: headband sliders & screws (lessons from pocket clips on folding pocket knives)
Metal screws inserted into plastic are not an ideal long-term fixing solution for anything, especially if the screws and threads are extremely tiny. If the sliders into which the screws go aren't metal, then one solution - at production or afterwards - would be to use threaded metal inserts into which the screws go (or an internal metal plate inside or behind the plastic, into which the screws attach). These are possible solutions for iBasso to implement at production, with upgraded replacement parts available..
Threaded metal inserts are usually brass or steel, with internal machine threads to receive the screw and external coarse threads to go into the substrate (mechanically attached and/or secured with adhesive to extra strength). If the screws threaded into plastic loosen repeatedly, that's because the screw threads are cutting away the plastic, increasing the diameter of the hole and removing the plastic that the threads "grasp." Larger diameter screws used as a substitute for smaller ones can cause other problems because the increased diameter stresses the plastic, especially if the hole in the plastic was smaller than the unthreaded shank of the new screw. Overtorquing screws at the production end, or afterwards, is probably the cause of the loosening parts. It would not take much force to start to degrade the plastic into which the threads cut.
So a possible solution for users - apart from replacing the assembly - would be to fill the old holes and then drill/tap them for threads that match the screw shank and threads. Thick gap-filling cyanoacrylate glue might work, but it has to be the non-fogging type, compatible with the plastic substrate, and mixed with finely-ground pieces of plastic that match the substrate. A better solution might be to use high-quality metal-filled epoxy to fill the hole, and then drill and tap for the fixing screw, or to fill the hole with epoxy and use an oiled screw so the epoxy doesn't adhere to the screw, with a clamp to hold the parts together until the epoxy sets.
But the cost of repair (tools and materials), plus time and risk of making things worse probably exceeds the cost of replacement parts!
Metal screws inserted into plastic are not an ideal long-term fixing solution for anything, especially if the screws and threads are extremely tiny. If the sliders into which the screws go aren't metal, then one solution - at production or afterwards - would be to use threaded metal inserts into which the screws go (or an internal metal plate inside or behind the plastic, into which the screws attach). These are possible solutions for iBasso to implement at production, with upgraded replacement parts available..
Threaded metal inserts are usually brass or steel, with internal machine threads to receive the screw and external coarse threads to go into the substrate (mechanically attached and/or secured with adhesive to extra strength). If the screws threaded into plastic loosen repeatedly, that's because the screw threads are cutting away the plastic, increasing the diameter of the hole and removing the plastic that the threads "grasp." Larger diameter screws used as a substitute for smaller ones can cause other problems because the increased diameter stresses the plastic, especially if the hole in the plastic was smaller than the unthreaded shank of the new screw. Overtorquing screws at the production end, or afterwards, is probably the cause of the loosening parts. It would not take much force to start to degrade the plastic into which the threads cut.
So a possible solution for users - apart from replacing the assembly - would be to fill the old holes and then drill/tap them for threads that match the screw shank and threads. Thick gap-filling cyanoacrylate glue might work, but it has to be the non-fogging type, compatible with the plastic substrate, and mixed with finely-ground pieces of plastic that match the substrate. A better solution might be to use high-quality metal-filled epoxy to fill the hole, and then drill and tap for the fixing screw, or to fill the hole with epoxy and use an oiled screw so the epoxy doesn't adhere to the screw, with a clamp to hold the parts together until the epoxy sets.
But the cost of repair (tools and materials), plus time and risk of making things worse probably exceeds the cost of replacement parts!
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