T3P3 Kossel Mini Kit - Release 2

Assembly Instructions

Chapter 17 - Wiring and related items

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Think3DPrint3D Ltd


1701 Wiring - Parts required


Arduino Mega clone

RAMPS board

No2 x 9mm Pozi pan woodscrews x 4


Hot-end wiring loom - 10 wire


Motor cable set

PanelOne LCD ribbon cables (can also be fitted later - see Chapter 22)


200m diameter x 4mm thick aluminium plate with 3M ™ Kapton adhesive heater pre-applied, complete with a MF58104F3950 thermistor taped to the centre of the aluminium plate.

NOTE: The aluminium heat-bed as supplied may have some minor surface imperfections and scratches. You may care to rub it down with very fine (600 or 800 grit) emery paper to remove these and provide the smoothest possible surface for contact with the print glass, if used, or for printing on directly. The picture shows the top surface of a prepared plate.

Fan Splitter Cable

See Section 1508

1702 Other Parts installed during wiring

For the heated bed  mount

12mm M3 plated brass M/F PCB standoffs x 3

M3 x 10 countersunk socket screws x 3

M3 penny washers x 3

M3 flat washers x 3

For the Z-probe retractor

Z-probe retractor peg

M3x30 socket capscrew


Aluminium tape

Approximately 800mm of self-adhesive aluminium foil tape for covering the cardboard heat insulator (see below

Cardboard insulator, pre-cut

185mm diameter cardboard insulator disc

1703 Hot-end wiring

Plug the wiring loom into the socket at the effector, and ziptie to the Bowden tube above and below the plug.

Route the cables along the PTFE Bowden tube, ziptied at intervals.

Fit a ziptie close to the extruder, then route the wiring loom down the side of the extruder motor, adding the Z-endstop cable and the extruder motor wires on the way.

Route the cables down the Z-tower,  zip-tieing at about 100mm above the bottom, and again at the bottom of the tower.

Feed the cable bundle between the Y-Z extrusions into the base of the printer.

Run the Y-endstop cable along the Y-Z channel and ziptie

Similarly run the X-endstop cable along the X-Z channel, and ziptie.

1705 Electronics installation

Make sure you take precautions not to build up electrostatic charge while handling the electronics - refer to the Introduction for more details.

Fit the Mega to the electronics bracket with 4 No 2 x 9mm Pozi pan self-tapping screws.

Make a loop in the USB lead to take up the spare length and plug it into the USB socket on the Mega.

Carefully fit the RAMPS onto the Mega, checking that all the mating pins are aligned. Push down firmly and progressively to seat it fully.  

Route the power lead past the USB cable and plug it into the RAMPS. The cables need to be bent to a tight radius to fit.


 1706 Motor wiring

Fit the motor cables to the X, Y and Z motors, ensuring the labels match up correctly. Make sure they go in fully.

1707 RAMPS wiring


If in any doubt about the wiring, consult the official RAMPS wiring instructions and diagram shown opposite. The diagram is from  http://reprap.org/wiki/RAMPS_1.4#Pre-Flight_Check (click on the wiring diagram at that link to enlarge).

Note that the diagram is for a conventional printer, not a delta, so shows 2 Z-motors. It also shows a second extruder, but we will connect a print cooling fan instead.


Start by  connecting the endstops. The RAMPS board has 6 three-pin headers labelled END STOPS at the top right corner of the board next to the 4-pin I2C header, which is not used. The endstop headers are, from left to right: X-min, X-Max, Y-min, Y-max, Z-min and Z-max. Only the outer (No 1 pin) and centre pin of each 3-pin header are used with mechanical endstops. As the Kossel has Maximum endstops only, the X-min and Y-min endstops are not used, and set closed with jumpers. The Z-min position is used for the Z-probe.

Begin with the Z-endstop on row 6, as shown. Be careful not to put it on the 4-pin I2C header by mistake.

Next the Probe on row 5

Followed by the Y-endstop on row 4.

Finish with the X-endstop on row 2

Connect the hot-end thermistor cable to the first pair of thermistor pins labelled T0.

Note: The label “E” for “Extruder” has been changed to “T” for “Thermistor”

Connect the X, Y, Z, and E motors as shown. There are 2 rows of pins for Z - you can use either.

Connect the hot-end to the + and- pins marked D10 on the RAMPS board. The hot-end wires are not polarised.

Connect the yellow-and-black wires for the second 40mm print cooling fan to the screw terminals D9 on the RAMPS. These are polarised! Connect the yellow wire with a red ferrule to the + terminal.

Fit the fan splitter cable to the 2-pin fan header and connect the hot end and electronics cooling fans to the splitter cable, observing polarity.

Fit the PanelOne LCD controller ribbon cables to AUX2 and AUX3 on the RAMPS board, and lead them out between the X-Y base extrusions.

Flatten motor cables by bending at 90 degrees just above the plugs, to maximize clearance below the heated bed.

The other wiring should also be pushed down alongside the RAMPS to maximise clearance under the heated bed. It is probably not worth  tidying it up properly until after testing, in case any adjustments and alterations need to be made. Final tidying up of wiring is covered in Chapter 21.

1710 Fit Heated Bed

First fit the heat-bed mounts. Drop an M3 nut into the nut launcher at the end of the X-Y channel …...  

... and slide it along to the centre of the channel.

Prepare a heat-bed standoff by fitting it with an M3 flat washer and M3 penny washer, …..

… fit it to the M3 nut in the channel, screw up loosely, centralise it on the extrusion, and screw up finger-tight.

Repeat for the X-Z and Y-Z channels to provide 3 mounting points for the heated bed.

Balance the heated bed temporarily on the X-motor, leaning against the X-tower, while connecting its wiring.

Connect the 2 heavy red heater element wires to screw terminals D8 on the RAMPS. Make sure you tighten these fully and firmly because of the large current they carry.

Plug the black thermistor wires onto the T1 thermistor pins - the center pair immediately next to the T0 hot-end thermistor pins.

Cover the insulating cardboard disk with the aluminium foil provided.

Note: On kits sent out before 3 February 2015, it may need to be modified slightly because the batch of Kapton heaters used before that date were intended for a smaller aluminium plate and have very short wires. If applicable, cut a wedge about 20mm deep by 10mm wide out of the foil-covered cardboard insulator.

Lay the insulator over the electronics (with the heated bed wires in the notch just made, if applicable). It should be a slight interference fit between the 3 standoffs and rest on the inner edges of the upper base extrusions.

Lay the heated bed on top of the standoffs and align the bolt holes. You may have to adjust the standoff positions slightly for correct alignment (they should still only be finger-tight). Insert the 3 M3 x10 countersunk retaining screws and do up loosely. Tighten the standoffs firmly, and finally screw the countersunk bolts in fully.

Now go on to the next Chapter