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+ | | | | | |\ /| \-------------------------|
Coil A (a pair) is made up of the top two wires. Coil B (another pair) is the bottom two wires. For more information on finding the pairs on your motor, see the Stepper wiring page. Swapping the +/- of one pair changes direction, or swapping the two pairs with each other changes direction. (Or swapping the +/- of each pair AND swapping the two pairs changes the direction, which is why with a 4x1 connector you can just turn over the cable to switch directions. This approach however sets a standard for which wires need to be which, so you don't have to worry about motor directions when swapping out extruders.
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.
