Motivated by the Hackaday circuit sculpture contest, I had the ambition to create circuit sculptures. Not just one or two, I wanted to be proficient enough to make it part of my repertoire of fabrication skills. And as the old adage says: "Practice makes Perfect."
If I want to create lots of practice sculptures, I need a source of wire for these practice projects. Buying straight metal rods from the local hobby shop will get expensive quickly. Buying a spool of wire is a lot cheaper, but they are not straight.
Hence the motivation for this project: a holder for a spool of wire that can straighten the wire as it comes off the spool.
My wire straightener project was focused on simplicity and reliability. There are no mechanical adjustments for different gauge wires or to correct for a 3D printer's dimensional accuracy (or lack thereof.) Every adjustment had to be made in CAD by changing the relevant dimensions and printing a test unit. This requires more work up front, but once all the dimensions are dialed in, the single piece tool will never fall apart and will never need readjustment.
It also means the raw STL files generated by Onshape for my printer would probably not work properly for anyone else. For starters, it was tailored for my specific spool of 18 gauge copper wire. According to Google, 18 gauge translates to a diameter of 1.02mm. My calipers say my spool is 1.00 +/- 0.01 mm, slightly smaller than specified. It is then processed into G-Code by Simplify3D, my printing slicer. And finally that G-Code is translated into plastic by my printer, with all its individual quirks.
So while I was happy to share my Onshape CAD file, I resisted sharing the STL because it almost certainly would not work correctly and I don't want people to have a bad experience with my design. But people ask for it anyway, over and over.
I have since changed my mind on the topic of posting the STL. I will post the STL, but never by itself. I will also post information describing why the STL is probably not going to work, link to Onshape CAD, and what people need to do to make their own. I foresee the following possibilities:
People who don't read the instructions will print the file as-is:
If it works for them - great!
If it doesn't:
Abandon with "This design is stupid and it sucks." - Well, let's face it, I was not going to reach this audience anyway.
"Maybe I should go back and read the instructions."
People who read the instructions:
Successfully fine-tune parameters to successfully make their own straightener - great!
Tried to follow directions, but encountered problems and need help - I'm happy to help.
Unless I've failed to consider something horrible, these possibilities have more upsides than downsides, so let's try it. I'm going to share the STL files on this project page, and I've created a Thingiverse page for it as well.
Now that I’m warmed up to make circuit sculptures, it’s time for more practice. And for that practice, I’ll need wire and lots of it. Most of the projects I’ve seen are built from straight rods of brass that I could procure from the local hobby shop. However, I personally prefer the color of copper (though it will suffer from oxidation) and I can get copper wire fairly inexpensively in a large spool. But of course, that wire would need straightening.
Thus the next project: A holder for a spool of wire that includes a straightener. For reference on straightener, I looked at CNC wire bending machines of both the DIY variety and an industrial offering, both of which featured similar wire straightening mechanisms. Then I tried to replicate my own using my stock of cheap 608 bearings and metal 8mm shafts left from my Sawppy rover project.
Version 1 was a very simple base that laid out the five shafts in the arrangement I wanted. I neglected to consider wire behavior so they ended up getting caught under the bearing.
Version 2 addressed that issue by raising its working surface so wire would not get under bearings. However, a 3D printer has problem holding precise tolerances and so shaft holes had to be drilled out before the shafts would fit. This changed position enough that final bearing spacing didn’t work well.
Version 3 attempted to eliminate variability of shaft position by eliminating the shafts entirely – have bearings sit on 3D-printed posts. Unfortunately position errors were even worse!
After stopping and thinking about the problem, I thought perhaps I’m over-complicating the device. As an introduction, I’m only dealing with 18 AWG wire. This is fairly easy to bend so perhaps I don’t even need bearings – simple shapes might be enough. Hence version 4 replicated the round (but not rolling) surfaces in a wave
Version 5 tried to improve by having a second stage with different spacing. This is an improvement. A mild one, but an improvement nonetheless.
Version 6 integrated version 5 into a spool holder.
Since I’m not using bearings, friction is quite high. It would not be acceptable if I were trying to build a CNC wire bending machine (a potential future project) but for manual use it’ll do for now. Using a pair of pliers, I can grab and pull on the end to give me wire straight enough for the next few projects.
Onshape CAD file is publicly available here. Adjust dimensions to fit your 3D printer’s characteristics, then export to STL for printing.