Replacing broken standoffs (not very electronic, i know) - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: March 21, 2018, 09:13:12 pm
content: Hi guys, please forgive me for this request which is probably more mechanical engineering than EE.I have a device i am repairing which i am very familiar with, i am fixed these for people dozens of times. The only relevant info you guys need to know to help me, is that the PCB with all the buttons for user input is a rubber mat with conductive dots that press onto a board with traces printed. The rubber mat is held down with screws sandwiched between the top plastic case and button PCB.This is a new problem ive never ran into before, about half of the plastic standoffs built into the front half of the case are snapped off. I thought about filling the ones that were broken with epoxy and screwing back into them, but i do not want to do something that is irreversible or will cause further damage.Is there some kind of metal standoff I can buy that measures about half a centimeter tall and glue/epoxy them to the plastic front i was thinking. I dont' want to use screws that will pierce the plastic, since it's not very thick and the screw tips would then be poking out at the user's fingers....Thanks in advance for any help on this.

author: Nusa
author_rank: Super Contributor
timestamp: March 21, 2018, 09:33:24 pm
content: To answer the question you asked, google "5mm standoff".Metal is usually not the best material choice for gluing. Consider just buying some plastic or wood dowel of suitable diameter and just cutting bits off in the required length to glue in place.

author: Mp3
author_rank: Frequent Contributor
timestamp: March 21, 2018, 09:45:10 pm
content: Quote from: Nusa on March 21, 2018, 09:33:24 pmHehe, i hadn't thought to use plastic to replace plastic!Thanks for that!It is so obvious i didn't think of it after having my mind of IC's all day

author: RyanT
author_rank: Contributor
timestamp: March 21, 2018, 09:46:00 pm
content: Pictures would help. Sometimes there are more elegant fixes you can do depending on the construction.As for standoffs, yes, of course you can get almost any ID, OD, length, and M/F threads you want in plastic, brass, or a range of other materials. Digi-Key'sBoard Spacers and Standoffssection would give you some idea, or you could try some local shops. If you get plastic standoffs that are a bit too long, a few seconds with a piece of sandpaper would shave them down to size. Same goes for metal standoffs, though you'll probably want to break out the power sander and a coarser grit sandpaper to hog off material. More easily done if you attach the standoff to a scrap piece of material first, so you have something to hold on to. A bit of epoxy will bond them to the chassis.With resin/epoxy, you can indeed fill the broken standoffs as you suggested. If you pour it and leave it sit well past its curing time, you can drill a smaller diameter hole in it and then send in a self-tapper similar to drilling plastic, and the screw can be removed normally later as long as the epoxy was cured when it went in. You can mix a bit of dye in with the epoxy to color match it to the original chassis, and if the whole thing is done with a bit of care, it will be hard to spot your fix on casual inspection.Edit: Forgot to conclude, I'd certainly go with option A (using pre-fab standoffs) if possible, as it is less work and gives the cleanest result. B is good if you either don't have time to wait for parts or you're in the middle of nowhere with a drill, 2-part epoxy, and a broken bit of kit.

author: kosine
author_rank: Regular Contributor
timestamp: March 22, 2018, 04:23:36 pm
content: Polycaprolactone :https://en.wikipedia.org/wiki/Polycaprolactone#Hobbyist_and_prototypingVery useful for ad hoc repairs, and widely available if you search for some of the trade names. Melts in hot water (60-80C) or with a hair dryer / hor air gun. Fully reworkable, easy to cut, file, drill etc.(And if you ever need something more rubbery and flexible, ethylene vinyl acetate (EVA) is available in low melting point grades, but it's not so easy to source.)

author: Teledog
author_rank: Regular Contributor
timestamp: March 23, 2018, 03:03:56 am
content: Weeell.. a lot of plastic chassis' are ABS..If you happen to have a friend with a 3D printer..there's lots of .stl files for standoffs on Thingiverse. (or create your own) Printed in ABS, of course.Flatten the broken area, dab on some MEK & place on the new ABS standoff (let it set minimum of 2 hrs..better 24 hrs)