I recently ran out of white wire and needed to order some more. You would think that wire would be the simplest electronic component to shop for -- just choose the color, thickness (wire gauge), and flexibility (stranded vs solid). However, when I went to place my order, I discovered that I needed to put a little more thought into my choice: What type of insulation material?
Polyvinyl chloride (PVC) is the standard wire insulation. It is inexpensive and widely available. However, it tends to melt and pull back from the end being soldered.
PVC insulation (the yellow wire) melted and retracted
On the other end of the price scale, silicone rubber has a wonderful grippy texture and flexibility, but poor abrasion resistance. Silicone rubber coated wire is difficult to find in a full selection of colors and diameters.
Another type of insulation is Tetrafluoroetheylene (FEP, TFE, PTFE, Teflon). Its primary feature is that it has a wide temperature range. PTFE is more expensive than PVC and is not as widely stocked from hobby sources. But, it does not tend to melt and pull back as much during soldering, has excellent chemical resistance, and will not become brittle in the cold.
Little did I know, but all these years I’ve been fortunate to use PTFE insulated wires. When I worked at Motorola, they were closing down the manufacturing floors at the headquarters. Amongst other things, they threw away spools and spools of PTFE wiring, which I retrieved from the dumpster. (I’d like to think I did the environment a favor.)
On a few occasions, I’ve purchased cheap wire and figured I must have gotten a bad batch, because the insulation would burn or pull back during soldering. Nope - I had just become accustomed to the good stuff.
To replace my stock, I ordered 150 feet of 26 AWG white PTFE wire for $22, which is 15 cents a foot. The seller, Skycraft Parts & Surplus, delivered promptly, but the wire was not on a spool (wire reel) and the shape was a little weird. No big deal. This gives me a chance to print a spool on a 3D printer.
Wire delivered as a pentagon
I based my Tinkercad 3D model off a spool from Jameco. I stayed true to the width and height, however, I chose a wider diameter interior so that wire would have less of a curve when despooled. Also, I choose a thicker wall thickness for all dimensions, because 3D printed ABS tends to be brittle and it needs a little more of a frame than molded parts.
3D printed spool with wire
The interior of the spool features a triangular notch to hold one end of the wire during spooling. (The triangle is a feature present on the Jameco spool.).
Triangle notch for holding end of wire
The spool consists of two parts, because otherwise 3D printing the top would have required extra supports to prevent sagging.
3D printed spool with top
The pieces stay connected just by pressing them snuggly together. Super glue can be used if desired.
3D printed spool with both ends in place
The bed on my printer is large enough to print both parts at the same time. I feel that this may have significantly slowed down the printing process as the print head wasted travel time. All in all, I was surprised at how long this took to print, even on the low-quality setting.
Printing an orange spool on the Flashforge
Now that we have a spool of high quality wire, is there a better way to hold wire during soldering?