Replicator 2X Cura definition - slightly tweaked for my printer, which is running Sailfish

makerbot_rep2x_1st.def.json

{
    "id": "makerbot_rep2x_1st",
    "version": 2,
    "name": "Rep2X Right Extruder",
    "inherits": "fdmextruder",
    "metadata": {
        "machine": "makerbot_replicator_2x",
        "position": "0"
    },

    "overrides": {
        "extruder_nr": {
            "default_value": 0,
            "maximum_value": "1"
        },
        "machine_nozzle_offset_x": { "default_value": 0.0 },
        "machine_nozzle_offset_y": { "default_value": 0.0 },

        "machine_extruder_start_pos_abs": { "default_value": true },
        "machine_extruder_start_pos_x": { "value": "prime_tower_position_x" },
        "machine_extruder_start_pos_y": { "value": "prime_tower_position_y" },
        "machine_extruder_end_pos_abs": { "default_value": true },
        "machine_extruder_end_pos_x": { "value": "prime_tower_position_x" },
        "machine_extruder_end_pos_y": { "value": "prime_tower_position_y" }
    }
}

makerbot_rep2x_2nd.def.json

{
    "id": "makerbot_rep2x_2nd",
    "version": 2,
    "name": "Rep2X Left Extruder",
    "inherits": "fdmextruder",
    "metadata": {
        "machine": "makerbot_replicator_2x",
        "position": "1"
    },

    "overrides": {
        "extruder_nr": {
            "default_value": 1,
            "maximum_value": "1"
        },
        "machine_nozzle_offset_x": { "default_value": 0.0 },
        "machine_nozzle_offset_y": { "default_value": 0.0 },

        "machine_extruder_start_pos_abs": { "default_value": true },
        "machine_extruder_start_pos_x": { "value": "prime_tower_position_x" },
        "machine_extruder_start_pos_y": { "value": "prime_tower_position_y" },
        "machine_extruder_end_pos_abs": { "default_value": true },
        "machine_extruder_end_pos_x": { "value": "prime_tower_position_x" },
        "machine_extruder_end_pos_y": { "value": "prime_tower_position_y" }
    }
}

makerbot_replicator_2x.def.json

{
    "id": "makerbot_replicator_2x",
    "version": 2,
    "name": "MakerBot Replicator 2X",
    "inherits": "fdmprinter",
    "metadata": {
        "visible": true,
        "author": "TheUltimakerCommunity",
        "manufacturer": "MakerBot",
        "category": "Other",
        "file_formats": "application/x3g",
        "platform_offset": [ 0, 0, 0 ],
        "has_materials": true,
        "preferred_material": "*generic_abs_175*",
        "machine_extruder_trains": {
            "0": "makerbot_rep2x_1st",
            "1": "makerbot_rep2x_2nd"
        },
        "supported_actions": [ "MachineSettingsAction" ],
        "supports_usb_connection": true,
        "machine_x3g_variant": "r2x"
    },
    "overrides": {
        "machine_name": { "default_value": "MakerBot Replicator 2X" },
        "machine_gcode_flavor": {
            "default_value": "Makerbot"
        },
        "machine_acceleration": {
            "default_value": 3000
        },
        "machine_width": {
            "default_value": 246
        },
        "machine_depth": {
            "default_value": 152
        },
        "machine_height": {
            "default_value": 155
        },
        "gantry_height": {
            "default_value": 60,
            "comment": "This needs to be filled in"
        },
        "machine_nozzle_head_distance": {
            "default_value": 3,
            "comment": "This needs to be filled in"
        },
        "machine_heat_zone_length": {
            "default_value": 16,
            "comment": "This needs to be filled in"
        },
        "machine_heated_bed": {
            "default_value": true
        },
        "machine_max_feedrate_x": {
            "default_value": 300
        },
        "machine_max_feedrate_y": {
            "default_value": 300
        },
        "machine_max_feedrate_z": {
            "default_value": 19.5
        },
        "machine_max_feedrate_e": {
            "default_value": 26
        },
        "machine_center_is_zero": { "default_value": true },
        "machine_extruder_count": {
            "default_value": 2
        },
        "machine_start_gcode": {
            "default_value": "; -- START GCODE Rep2x -- \n; begin print\nM136 ;(enable build)\nM73 P0 ;(set build percentage to zero)\n; homing\nG162 X Y F2000 ;(home XY axes maximum, standard feedrate 2000 mm/min)\nG161 Z F900 ;(home Z axis minimum, standard feedrate 900 mm/min)\nG92 X0 Y0 Z-5 A0 B0 ;(set Z to -5)\nG1 Z0.0 F900 ;(move Z to '0', standard feedrate 900 mm/min)\nG161 Z F100 ;(home Z axis minimum, standard feedrate 100 mm/min)\nM132 X Y Z A B ;(Recall stored home offsets for XYZAB axis)\n; set start position\nG92 X152 Y72 Z0 A0 B0 ;(set zero for X and Y)\nG1 X-112 Y-73 Z150 F3300.0 ;(move to waiting position, standard feedrate 3300 mm/min)\nG130 X20 Y20 A20 B20 ;(Lower stepper Vrefs while heating)\n; heat platform\nM109 S{material_bed_temperature} T0 ;(Set build platform temperature in degrees Celsuis)\nM134 T0 ;(Wait for platform to heat up)\n; EXTRUDER HEAT BEGIN\nM135 T0 ;(Set the extruder as the current Extruder)\nM104 S{material_print_temperature} T0 ;(Set extruder temperature in degrees Celsius)\nM133 T0 ;(Wait for extruder to heat up)\n; end start sequence\nG130 X127 Y127 A127 B127 ;(Set Stepper motor Vref to defaults)\n; initial purge\nG92 A0 ;zero the extruded length\n; -- END OF START GCODE --"
        },

        "machine_end_gcode": {
            "default_value": "; -- END GCODE -- \n; end position\nM18 A B ;(Turn off A and B Steppers)\nG1 Z{machine_height} F900 ;(Move Z to machine_height, feedrate 900 mm/min)\nG162 X Y F2000 ; (Home Z Axis Maximum, feedrate 2000 mm/min)\nM18 X Y Z ;(Turn off steppers after a build)\n; cool bed\nM140 S0 T0 ;(Cool Bed)\n; cool extruders\nM104 S0 T0 ;(Cool Right extruder)\n; end print\nM73 P100 ;(end  build progress)\nM70 P5 ;(We <3 Making Things!)\nM72 P1 ;( Play Ta-Da song )\nM137 ;(build end notification)"
        },
        "retraction_amount": {
            "default_value": 2
        },
        "retraction_speed": {
            "default_value": 25
        },
        "material_diameter": { "default_value": 1.75 },
        "default_material_print_temperature": { "default_value": 230 },
        "material_print_temperature_layer_0": { "default_value": 0 },
        "material_initial_print_temperature": {
            "enabled": false,
            "value": "max(-273.15, material_print_temperature)",
            "default_value": "max(-273.15, material_print_temperature)"
        },
        "material_final_print_temperature": {
            "enabled": false,
            "value": "max(-273.15, material_print_temperature)",
            "default_value": "max(-273.15, material_print_temperature)"
        },
        "material_bed_temperature": {
            "default_value": 120,
            "maximum_value_warning": "150"
        },
        "material_bed_temperature_layer_0": {
            "default_value": "material_bed_temperature",
            "maximum_value_warning": "150",
            "enabled": false
        },
        "speed_print": { "default_value": 100 },
        "speed_travel": {
            "default_value": 175
        },
        "speed_layer_0": {
            "value": "speed_print * 30 / 90"
        },
        "acceleration_enabled": { "enabled": false },
        "jerk_enabled": { "enabled": false },
        "adhesion_type": { "default_value": "raft" },
        "raft_margin": { "default_value": 3 }
    }
}

Hi.
This sounds exactly what I want.
But being a complete newcomer to Cura, how do I actually load it in to Cura 3.1?

I'm using a print profile that is virtually identical to yours. I'm having an issue where the left extruder is extremely misaligned (it is printing half off the left side of the build plate). Have you experienced similar issues with your print profile?

You might have different values in your EEPROM. There's a dual-extrusion calibration process you can go through with the firmware.

My full cura configs are here, but I haven't used Cura in a while. https://github.com/rpavlik/cura-rep2x

I use PrusaSlicer now, and regularly use the left extruder (though rarely dual-extrude, I mostly just keep PLA+ in the left, PETG in the right) - configs are here https://github.com/rpavlik/Rep2x-GCodeSnippets-PrusaSlicer

Thanks for the reply. I have used Makerbot's now deprecated dual extruder software and it prints well aligned, so I'm assuming the EEPROM calibration is fine. Maybe this will be what gets me to try out PrusaSlicer.

it may also be a firmware difference - whether you're using a newer sailfish or not. At least in newer sailfish, the eeprom value meaning changes. Both my extruder offsets are approximately 0. I upgraded to a newer sailfish very shortly after getting my machine, so I've never really tested any of these configs on their old outdated firmware.