Although less popular these days, wire-wrap is still a very relevant, easily reversible solder-free way to assemble (prototype) systems using wire-wrap wire and a wire-wrap tool. This latter tool can be either a hand or powered tool, but all it has to do is retain the stripped wire, fit around the wire-wrapping post and create a snug, oxidation-proof metal-metal contact fit. For the very common 30 AWG (0.25 mm) wire-wrap wire, the Jonard Tools (OK Industries) WSU-30M wire-strip-unwrap tool is pretty much the popular standard. It allows you to strip off insulation, wrap and unwrap connections all with one tool, but the question is whether you can just 3D print a wrap-unwrap tool that’s about as good?
First a note about cost, as although the genuine WSU-30M has risen in cost over the years, it can still be obtained for around $50 from retails like Mouser, while clones of varying quality can be obtained for around $15 from your favorite e-tailer website. From experience, these clones have quite sloppy tolerance, and provide a baseline of where a wrapping tool becomes unusable, as they require some modding to be reliable.
Taking a quick look at the wire-wrap tools available on Thingiverrse, we can see basically two categories: one which goes for minimally viable, with just a cylinder that has a hole poked on the side for the stripped wire to fit through, as these versions by [JLSA_Portfolio], [paulgeneres], [orionids] and [cmellano]. The WSU-30M and similar tools have a channel on the side that the stripped wire is fed into, to prevent it from getting tangled up and snagging. On the clone units this channel often has to be taped off to prevent the wire from escaping and demonstrating why retaining the wire prior to wrapping is a good idea.
This leads us to three examples of a 3D printed wire-wrap tool with such a wire channel: by [KidSwidden] (based on a Radio Shack unit, apparently), another by [DieKatzchen] and an interesting variation by [4sStylZ]. Naturally, the problem with such fine features is that tolerance matter a lot, with an 0.2 mm nozzle (for FDM printers) recommended, and the use of an SLA printer probably a good idea. It’s also hard to say what kind of wire-wrap connection you are going to get, as there are actually two variants: regular and modified.
The starting guide to wire-wrapping by Sparkfun uses the WSU-30M, which as the name suggests uses modified wire-wrap, which means that part of the wire insulation is wrapped around the bottom of the post, for extra mechanical stability, effectively like strain-relief. A lot of such essential details are covered in this [Nuts and Volts] article which provides an invaluable starting guide to wire-wrapping, including detecting bad wraps.
Naturally, the 3D printed tools will not include a stripper for the wire insulation, so you will have to provide this yourself (PSA: using your teeth is not recommended), and none of these 3D models include an unwrap tool, which may or may not be an issue for you, as careful unwrapping allows you to reuse the wire, which can be useful while debugging or reworking a board.
Top image: completed wire-wrap on a post. (Credit: Sparkfun)
