Don’t want to end up with melted cables in your 3D printer? Want it to be reliable, too? Then wire it up properly! Learn how in this video.
This video is sponsored by Alephobjects, Inc! Learn more about their Lulzbot line of open-source 3D printers here
How to wire your 3D printer!
So the iTopie i3 is almost done, and what typically takes the longest is wiring everything up properly. Now, i know that part is not fun, it’s not rewarding, at least not for me, and it’s like this huge threshold between having a machine that looks finished, you know, with all the parts mounted and ready to go; and a machine that actually works. But at the wiring stage, you are actually setting the foundation for a machine that works reliably and is open for future modifications without it ending up as a total hackjob. So today i want to give you a rundown of what wiring to use, how to manage it properly and how to connect everything up.
And i need to start out with a disclaimer, basically, as always, use some common sense. I can give you the basics of “good practices”, but ultimately, you’ll be responsible for how you set everything up. Cables can overheat and potentially catch fire if they are sized improperly or wear out due to improper strain relief. This guide can help you avoid the most common mistakes, but please don’t sue me if you make one that i didn’t cover. Alright? Let’s go.
Let’s start out with what cables to use, first of what wire gauge to use for the various functions in your 3D printer. So there’s basically three tiers of components you’ll see. There’s sensors, fans and motors, which use practically no current, then hotend heaters, with a 12V heater drawing close to 4A, and a heated bed, typically around 12A. So what i like to use for, let’s call it tier 1, is ethernet cable, for a few reasons. First off, it’s cheap. Unshielded Cat5 cable is all you typically need and it’s like 20ct per meter. And that gives you 8 wires, twisted in pairs, which is great for what we’re doing because not only are they nicely bundled up, having them twisted keeps any electromagnetic interference in check. The one thing you should keep in mind, though, is that you want to get the flexible version and not the one with solid wires, more on that in a second. Even the cheaper 26-gauge wires, or 0.13mm², are rated for around two amps, which is plenty for a fan or sensor, and just barely enough for a stepper motor. The way you should use the twisted pairs is to have one wire carrying the current to the component and the other taking it back. So in case of a fan, that’s positive and negative, for a motor, that would be the two connections from each coil, which are the black and green as well as the red and blue wires. For an endstop, signal and ground, and for a thermistor, obviously the leads of that. What’s also nice about ethernet cable is that, because it has those two layers of insulation, it tends to keep its wires in a larger radius compared to individual wires, which is good for keeping them from wearing out due to the repetitive bending motion you’ll see when printing. There are two factors that decide how well a cable is suited to being repetitively bent, one is the insulation, in this case plain PVC, not ideal, but usually good enough, silicone would be better, but is much more expensive. And the other factor is the makeup of the copper conductor. You can obviously get solid-core and stranded wire, and when you bend them both in the same radius, the surface of the solid wire is going to stretch and compress much more than each individual surface of each strand. Solid wire is perfect for bending it into shape and then leaving it, but stretching and compressing cooper too many times will break it. So the finer the strands, the more suitable a wire is for being moved around. Now, again, the Ethernet cable i’m using is reasonably fine-stranded, but an even better choice would be specifically-made cables that have extra fine strands, especially when you need them to repeatedly bend around tight radii, which i’ll show you later on how to avoid.
Ok, so second tier components, heaters. Now i also use Ethernet cable here, but a single conductor is not enough for a 12V, 40W heater, so i usually use two wires and a total of two pairs here. Now, you don’t just want to use one pair for positive and the other for negative, you actually want to the plain wires together for one phase and the striped ones for the other, that way you have the forward current twisted to the return current. If you want to use a single wire instead, you’ll need something around a 22-gauge or 0.75mm² wire. Since the heater typically isn’t on for extended periods at a time, but instead pulsed, you do have some leeway there.
Now, for tier three, the heated bed, you’ll need something a bit more massive than that. And for a typical PCB heater, I’d actually recommend using a thicker wire than needed to minimize losses in the wire itself, as that will take away much more of the available heating power from the bed than you’d expect. As such, at least something around 12-gauge or 2.5 to 4mm² is what i’d recommend using. What usually fits that bill is speaker wire because wannabe “audiophiles” will completely oversize their wiring several order of magnitude to get that last bit of “crispness” out of their speakers. But just make sure the wire is, again, fine enough, and actually copper, as the cheaper copper-clad-aluminum wires will break way more easily under stress and fail over time in most connectors. Another good alternative is silicone wire, as used in electric RC cars, it’s a good bit more expensive, but is actually a perfect match for the job.
Now, next up, how do you route those cables to your components? What i actually see people doing is checking at which spot the cables need to be the longest and then just cutting them to that length. Which isn’t really ideal, what you’ll get is this caterpillar effect and the cable might end up going anywhere. A better way to handle it would be to create an anchor point somewhere in the middle of the axis and routing the cables there in a half-loop, so that you’ll never get the cables completely stretched straight at any point. Of course, how you can route them is going to depend on your exact printer, but in any case, having them in any sort of loop or half-loop is always going to be easier on the wires and easier to manage. Now, you still want to make sure the wires don’t end up kinking or flexing in the same spot over and over, so you still need to take care that the point where the cable is fixed to the moving and standing parts has some sort of support – this can be a bit of filament or simply the wire’s insulation itself. You just want to keep it supported at the most critical spots.
Now, to really get it not only looking a bit more nicely, but also out of the way and bundled together more tightly, there are two more options: Nylon mesh sleeving and drag chains. Drag chains are great, but they can be a bit tricky to use right, so let’s start out with Nylon sleeving: You can get it in all sorts of sizes, and it keeps your wires out of sight, bundled together and somewhat supports them at the same time. By the way, it’s the same stuff as used by computer enthusiasts and power supply manufacturers.
Your other option are drag chains, and on the iTopie we actually used both. So a drag chain is made to used like this, not like this. Its job is basically to keep the wire in a precisely defined position and to keep the bending radius constant. Though the problem is, if you want to use a drag chain, you have to plan for it, because typically you aren’t going to have the proper surfaces to mount it to to get that rolling motion. They come in two version, one opens up to let you just drop in your wiring, the other stays closed and you’ll need to push the wires through by hand, which might be a tight fit if you have any sort of connector on their end.
What’s also important to keep in mind with them is to only use a zip tie for the wires on one end, not both, or you might end up stretching, compressing and breaking the wires as the drag chain moves, so always leave a bit of slack on one end before anchoring it down again.
Now what i like to use for keeping the wires exactly where i want them are these little stick-on anchors, again, they’re really inexpensive, links in the video description, by the way, and they give you spots to zip-tie any wires to without having to drill holes or zip-tie around any larger components. You can also get them with a reusable twisty thing already attached, but those don’t hold the wires down as tightly, which can be ok for a lot of places.
Now, connectors are easy to overlook. If you’ve got cables that already have all the connectors on them, you’re good to go, but it’s not too hard to add your own, either. And i’m not going to go into full detail on how to use these tools, i think there are plenty of videos on Youtube already, but i can show you what to use. I’ve personally settled on two types of connectors, as they are compatible to what is typically used on controller boards and are easy to crimp yourself. The first type are what are called Dupont connectors, they are 1/10th of an inch pitch crimp connectors, they don’t have any keying and they will pretty much universally fit any other 1/10 inch connector, whether it’s these white types, as used for computer fans or the more complex, locking types as seen on some boards. Oh, and you can use male or female pins with them, so you can really easily craft extensions or disconnect points. All of these use the same crimping tool to get the contacts attached to the wire, and are all rated for about 2 to 3 amps, which is perfect for all those tier one consumers including motors. Now, for tier two, heaters, simply using two pins in a connector is valid, but you’re not going to find any board that has that sort of a connection. So what i like to use for hotend and bed heaters instead are these larger crimp connectors, again they’re a family of connectors that span anything from male and female blade connectors, wire end crimps or spade terminals for attaching to a power supply. These will carry as much current as the wire you crimp them to.
Now, both of these crimping tools are great to have and they make properly wiring a 3D printer or anything else just so much easier. I paid about 20 buck for each one, with a big set of connectors, and that was totally worth it.
So one last tip i want to give: Make wiring plans and label your cables. It’s super easy to do, just write down which wires in which cables you’re using for what functionality, and since they are color coded, you know exactly where to look. And even the simplest plans can help you out a ton should you ever want to modify anything or have to look for an issue down the road.
This video is sponsored by Aleph Objects, Inc., a Free Software, Libre Innovation, and Open Source Hardware company headquartered in Loveland, Colorado, USA and makers of LulzBot desktop 3D printers.
Watch my reviews of both LulzBot 3D printers here and check the links in video description for more info on the machines straight from Aleph Objects.
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Music is Jahzzar – Seas of Mars, licensed CC-BY-SA
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