As the printer ages, the constant motion of the print head wears out the conductors inside the cable. Creating all sorts of fun debugging scenarios.
Is there such a thing as a bundled cable, with all the necessary wires, for the stepper motor (in the case of direct drives), hot end, thermistor, etc... and when one of the conductors wear out just replace the whole bundle?
People have used parallel port cables (DB25) for a while. They are cheap enough and have enough pins for most uses.
Obviously you will need to use multiple pins for the power hungry devices (heater, stepper motor). Parallel cables often use 28 AWG (0.08 mm^2) wires, which carry up to 1.5 A @ 30 °C temperature rise over ambient. It's quite a lot, so better stick to about 0.8 A/wire, which means one pin or better two are enough for each wire of the stepper motor. A 12 V/50 W heater draws 4.2 A and will likely need 5 pins per each wire, to be safe while a 24 V/50 W heater could work with two.
See some ratings here.
You can also use Ethernet cables, they are even cheaper and more widely available, but each cable has only 8 of them. The advantage is that they are usually 23-24 AWG (0.21-0.26 mm^2), unless you look for slim or flat cables, 30-32 AWG, so the heater will need fewer wires. However, they are all twisted pairs therefore you may be forced to use more wires than you need: for example, you may have an accelerometer which uses four data wires: TX, RX, clock, enable. You cannot twist RX and TX to avoid interference, and also clock should not be twisted with either RX or TX. You may need to be creative (TX/GND, RX/VCC, clocl/enable), but in general it's uncommon.
The many manufacturers create the printer configuration in nearly as many ways as there are models of printers. I've seen flat flexible cables used in a manner akin to cable chains, which allows the ribbon to roll back on itself in the return movement. Minimal flexing at the end connectors and an acceptable radius on the bend. My BCN3D Sigma R16 has a ribbon cable from a fixed location out to the head, which travels in both x and y direction preventing a roll-back/cable chain type of configuration but also maximizes the radius of the bend.
If you are considering a DIY printer build, your options are open, but if you have an existing unnamed printer, your modification has to remain within the constraints of the manufacturer.
Have you thought of using a ribbon cable? I have/ have had similar issues with a large print area CoreXY. I'm not sure if the ribbon cable can handle the motor current or heater current but pairing up wires may help. One other issue you may have is electrical interference if you have bed leveling that uses a servo command.
I'm going to try a ribbon cable on my next print head rewire.
You may be able to find replacement wiring harnesses from a good manufacturer that supplies replacement parts for its printers, or possibly a 3rd party replacement for very popular printers, but there is no standard for length, number and types of conductors, gauge of wire, and types of connectors for the ends.
For connectors, many 3D printers have settled on “JST” headers on the ends. There are several types and pitches that aren’t compatible so identification is important when finding a replacement. Here is a good resource on identifying the connector: http://www.mattmillman.com/info/crimpconnectors/common-jst-connector-types/ An alternative to finding the correct pre assembled wiring harness (not out of the question with the explosion of 3D printers and CNC machines) is salvaging the original plastic header and crimping new connectors on new wires. This sadly requires a special crimping tool, but it is a worthwhile purchase if you do electronics.
If the 3D printer uses a ribbon cable, it isn’t terribly hard to replace those, if they use the rectangular IDC connectors at the ends. You can cut the cable to length and punch down the connector in a vise.
Whatever the connector or type of cable, for the wire, the finer the strands of copper the better, as far as resisting breakage from constant movement. One good source of salvaged fine stranded wire is the cabling in wall warts (so long as 2 conductor works for you, say for a heat bed).
As others have noted, the bend radius of the wire has a lot to do with its longevity. Sharp kinks will do the harness in, especially at the printhead end. Strain relief is key, as is not nicking the wire where it is stripped. Most cables, in general electronics, seem to break at the ends.
In shopping for a printer, it’d be good to check the cabling doesn’t pull directly on the connectors when it moves, doesn’t kink it, especially if it has DIY mods done to the print head. For printers you already own, check the strain relief. Other than that, wait for it to break, rather than ripping it out just because you’re worried it may break. It isn’t hard to diagnose with the continuity tester on a multi-meter. In a repair you can always leave the old broken wires in there and add a couple new ones. Pay attention to wire gauge, as others have pointed out- fans, thermistors, other sensors can be small, hotends and steppers larger, heatbed largest.
