Extruder Pluggable Wiring Convention

Please note this is a proposal so far.

This page is here to document a proposed wiring convention to enable interchangeable extruders. The idea is that if you have a convention for your plug interface, you could readily swap out your entire extruder and replace it with another one without much effort at all. One of the key ideas behind this is to leverage existing affordable connectors that are suited to pulling the current that an extruder uses. The existing PCI-e power cabling standard can be leveraged. One can cheaply order an extension cable such as [[1]] from many sources, cut it in half and splice the wires into it between your microcontroller and your extruder, thermistor, and extruder motor. This prevents people from having to crimp these cables themselves, saving labor, and the need for a crimping tool. These plugs are very easily detachable, yet lock into each other to keep them securely connected as the extruder moves. They also are keyed so that you don't accidentally plug in the wrong component in, or plug it in the wrong direction when swapping extruders. The above PCI-e power cable has two 4-pin plugs called 41 and 42. We propose using 41 for the thermistor and heater and 42 for the extruder stepper motor. The exact wiring is as follows:

F41 (female) - reprap side - thermistor & heater F42 (female) - reprap side - stepper motor

M41 (male) - extruder side - thermistor & heater M42 (male) - extruder side - stepper motor

LOOKING AT WHITE FEMALE F41 (Heater & Thermistor)

   |-------------------------|
   |            |            |
   |   Heater   |   Heater   |
   |            |            |
   |            |\          /|
   |------------+------------|
   |            |            |
   | Thermistor | Thermistor |
   |            |            |
   |\          /|            |
   \-------------------------|

LOOKING AT WHITE FEMALE F42 (Stepper Motor) (RR = RepRap ribbon cable, Mtr = Stepper Motor wires)

   |-------------------------|
   |            |            |
   | Motor A-   | Motor A+   |
   |            |            |
   |\          /|            |
   |------------+------------|
   |            |            |
   | Motor B-   | Motor B+   |
   |            |            |
   |            |\          /|
   \-------------------------|

This wiring idea was first used by jkeegan and devzero in their repraps. We've posted it in the hopes that others might find it useful. If more people adopt this convention, it will enable folks to swap out components in their repraps more easily. This is especially useful as the idea of using different tooling heads on a reprap moves forwards.

Thanks for trying to standardise things. Virtually all RepRap electronics use 4 pins in a row for the motor connectors, previously Molex KK156 types (4 mm pin spacing), now Molex KK100 types (2.54 mm pin spacing). Is there an urgent reason to change that or is it just the first thing you found at newegg? About all the RepRap shops should have proper cables available. --Traumflug 09:48, 28 October 2012 (UTC)

The idea is that you still use whatever connections you need for your electronics (standard headers, etc), but that connects to the white female part of this locking, secure, and standard connection. Then your extruders all have connections to the black male side (I have an additional chocolate block between my hot-end wiring and the corresponding black male connector, with the stepper motor soldered straight to its black connector as that almost never needs changing. Also note that this allows you to swap extruders that require different motor directions (such as Wade's vs Greg's) with ease, as you just wire the black connector appropriately for the extruder it is connected to. Here is a video I recorded a year ago on the subject, but haven't uploaded until now (I threw it into iMovie too to add this URL to the end): RepRap Extruder Connector Standard - Jkeegan 14:20, 28 October 2012 (UTC)

This wasn't just the first cable I could find off of newegg. Obviously on the endpoints you want a KK100/KK156, but for a middle-connector to enable hot swapping, you want the locking mechanism to prevent the connector from falling out during normal operation, and you want the keying so you don't accidentally plug it in the wrong way. For the extruder, you also want to make sure that the gauge of the wires and connectors can handle the amperage for safety reasons. This meets all of these criteria. - devzero 23:33, 29 October 2012 (EST)

I see. So this page isn't about stepper wiring, but about stepper extension cables. A few additional notes:

• Connectors on the electronics board have a locking and keying mechanism, too. I'm aware some electronics sellers are too cheap for that, but a good choice in electronics helps here.
• "Hot swapping" motors is a bad idea. Unplugging a motor (DC or stepper, doesn't matter) while being powered up injects very high voltages into the stepper driver circuitry, similar to how a coil driven spark plug works. Quite some stepper drivers had to die due to (accidental) hot swapping.
• Every seller should provide cablings long enough, so extension cables aren't needed.

That said, I appreciate your writing. Even when discussing it.

--Traumflug 10:33, 30 October 2012 (UTC)

I still think the essence of this convention is being missed here, so at the risk of being redundant let me try to elaborate. (By the way this discussion should probably be moved to the discussion page for this page, which I'll try to remember to do later today).

• Everyone has a long set of cables going from their RepRap to their extruder. With the advent of removable carriages, it's desirable to easily be able to disconnect an extruder for service. This provides a break near the extruder side of that (so it can be unclipped near the extruder).
• Agreed 100%, no one should be swapping things out while the power is on. This is all about maintenance.
• This convention allows you to have a spare extruder with you, and swap it out, without even looking at your motherboard or the connections on it. Those spare extruders can even be of different types (with different motor directions), since the junction point has an agreed-upon stepper wiring convention. So when you wire up the black male side of that middle locking interconnecting clip on your extruder when building it initially, you make sure the stepper will rotate the correct direction for that extruder. (Wade's and Greg's rotate differently. Trying out Greg's caused me to worry about having to keep track of which motor direction I was using each time I swapped extruders. This convention fixed that).
• The reason that the locking mattered here (more than it does on the motherboard) is the constant motion and vibrations associate with being connected to a moving x/z axis. Adrian's original suggestions had regular headers being used on the extruder - these proved unreliable (for me anyway) during movement due to strain on the connection.
• The reason that the keying mattered in the interconnect cable was to make it easy to disconnect and reconnect without concerning one's self with electronics at all. There's no chance of accidentally connecting the motor leads to the heater/thermistor instead, nor the heater to the thermistor, nor any chance of *unintentionally* changing motor direction.

Right back at ya - I too appreciate this discussion! :) Like I said I'll move this all to the discussion page later today if someone doesn't beat me to it - easier on a computer than on a phone. - Jkeegan 11:48, 30 October 2012 (UTC)