Strain relief - worn wire - Page 1
Forum section: electronics / general

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 27, 2022, 03:07:13 pm
content: I am replacing all the cables in this ultrasound head (my daughter's beauty parlor/don't ask) as the insulation, shield and one wire have broken in one cable and all the cables are stiff presumably from heat near the ultrasound head.Was wondering whether anyone has any idea how I could improve the strain relief/lessen the wearing of the cable(s).Let me explain the photos:Photo 1 - Here we see the ultrasound head with top shellremoved and the cable which is broken (arrow points just afterit's strain relief). The break occurs somewhere just afterwhat I named as the "coupling" as it couples the top and middleshell. This cable as well as four other cables and thepolyurethane pipe pass through the flexible plastic conduitwhich is strengthened/supported with steel wire as can beseen on the photo. These cables/pipe pass tightly through theconduit i.e. little space for movement. The plastic tie near end of the conduitI presume both helps a little so there is less motion of thecables and stops the conduit from moving back throughthe coupling.Photo 2 - Here we can see the break in cable and theflexible spring like support for the whole cable (samesupport is at other end)There are traces of some type of grease along thewires presumably for pulling the cables/tube through(not looking forward to this) and maybe to lessen wearin case of any movement.What is strange to me is that although I see a slight wear on theconduit at exit from coupling, I don't see / feel any abrasivesurface and the wires are quite tight in there not being ableto move - what could cause such a break in the cable and is there anywise I could do to avoid or reduce reccurence ?

author: mastershake
author_rank: Frequent Contributor
timestamp: January 28, 2022, 02:36:32 am
content: this happens to my wife's clippers as a dog groomer the cords do this all the time from just tons of use. i like to use different sizes of heat shrink. so what i mean is i start with a 1" piece over where the most tension is, then a 2" piece over that and further down. then a 4" piece over that etc if needed. then it gets sandwiched between the case layers with a knot at the top keeping it from pulling out. this is a bit different situation. but this lasts for usually 2-3 years of daily use before i have to fix it again (she uses them 8 hours a day every day). there has to be movement normally for a break like that to happen even if small. either the wire or maybe the sleeve moving. the wire tie is prob there to prevent it from pulling out of the "coupling" its possible its chafing on the grey sleeve. another thing you can try as long as this doesnt get to warm you can try to fill the grey tube with silicone or hot glue once you pull the wife through to keep the wire off the edge. i wish i could explain it better. tough without having it in hand. could be a number of ways to skin the cat if you will.

author: vjekobalas
author_rank: Regular Contributor
timestamp: January 28, 2022, 06:40:19 am
content: Could you please clarify:The heat shrink is placed over the tension area as per my attached sketchand is it not heat shrunk/why (I presume the string is needed only for this reason) ?