T3P3 Kossel Mini Kit

Assembly Instructions

Chapter 17 - Wiring and related items

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Think3DPrint3D Ltd


1701A Wiring - Parts required  (printers without heated bed)


Arduino Mega clone

RAMPS board

No2 x 9mm Pozi pan woodscrews x 4


Hot-end wiring loom

Note: On kits sent out after 05 July 2014, the label “E” has been changed to “T”

Second fan cable - for E3D V6 hot-end option only

Motor cable set

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

1701B Wiring - Parts required  (printers with heated bed)

Electronics,  Hot-end wiring loom,  Second fan cable (for E3D V6 hot-end option only), Motor cable set and PanelOne LCD ribbon cables as in 1701A above.


178mm 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

1702A Other Parts installed during wiring (printers without heated bed)

For the printbed mount

Glass tabs x 3

M3 x12 socket capscrews x 3

M3 x12mm OD penny washers x 3

M3 full nuts x 3 (not shown)

For the Z-probe retractor

M3 x 20 socket capscrew

M3 full nuts x 3 (1 not shown)

M3 x 12mm OD penny washer

1702B Other Parts installed during wiring (printers with heated bed)

For the heated bed  mount

Heated bed mounts x 3

M3 x18 socket capscrews x 3

M3 x14 countersunk socket setscrews x 3

M3 full nuts x 3 (not shown)

For the Z-probe retractor

Z-probe retractor peg

M3x30 socket capscrew

NOTE: The height of the pillar can be increased if necessary by using the M3x12 penny washers supplied in all kits but only used to attach the mirror glass print bed if a heated bed is not fitted.


Aluminium tape

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

Cardboard insulator, prepared

Cut a 165mm diameter cardboard insulator disc from a piece of scrap double walled corrugated cardboard (like the box your Kossel kit was shipped in). If you only have very thin corrugated cardboard (<2mm) then you can use two layers, however only bother with aluminium tape on the layer next to the bed.)

Cover the top only with the aluminium foil tape provided.

1703 Hot-end wiring Stage 1

NOTE: The pictures show wiring for a J-head hot-end but the procedure for V6 is generally the same.

Plug the wiring loom into the socket at the effector.

If you have a V6 hot-end, then plug the red-and-black 40mm fan wires into the yellow-and-black fan cable as well, matching black to black and red to yellow.

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

When nearly at the extruder, add the Z-endstop cable and ziptie together around the Bowden tube

Route the cables down the side of the extruder motor, adding the motor cables to the bundle, zip-tieing at intervals, and at the bottom of the tower.

1704A Fit Glass tabs and Z-probe retractor (printers without heated bed)

Before routing the the cables the rest of the way to the electronics, you need to fit the printed support tabs for the glass printbed and the Z-probe retractor.

Drop an M3 nut into the fitting hole at one end of each base frame top channel.

Slide it along to the centre of the channel.

Fit an M3 x 12 capscrew with M3 penny washer to each glass tab.

Fit the tab assemblies to the nuts and tighten.

Assemble the Z-probe retractor from the M3 x 20 capscrew, penny washer and 2 nuts.

Drop an M3 nut into the fitting hole at the left-hand end of the X-Z base frame top channel, slide it along about 80mm towards the centre, and fit the retractor assembly. (this picture was taken at a later stage so ignore the print plate)

1704B Fit Heatbed mounts and Z-probe retractor (printers with heated bed)

Before routing the the cables the rest of the way to the electronics, you need to fit the printed heatbed mounts and the Z-probe retractor peg.

Drop an M3 nut into the fitting hole at one end of each base frame top channel.

Slide it along to the centre of the channel.

Fit an M3 x 18 capscrew to each heated bed mount, fit the mounts to the nuts and tighten.

Drop an M3 nut into the fitting hole at the left-hand end of the X-Z base frame top channel, and slide it along about 80mm towards the centre. Fit the retractor peg with the M3 x 30 capscrew.

1705 Hot-end wiring Stage 2

Ziptie the extruder/hotend/endstop cables at the base of the Z-tower and divide the cables and routing the hot-end cooling fan, z-probe, thermistor and Z-endstop cables along the Y-Z channel. Ziptie in place and route into the base of the printer.

Route the motor and hotend resistor cables (and V6 hot-end second cooling fan wires, if applicable) along the X-Z channel - these can only go as far as the Z-probe retractor.  Ziptie in place and route into the base of the printer.

Similarly route the Y-endstop cable along the Y-Z channel, ….

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

1706 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. (Picture shows heated-bed power lead)


 1707 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.

1708 RAMPS wiring

Bring all the loose wires together around the RAMPS board.


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 and a heated print-bed - just ignore the second extruder (and the heated print bed if you don’t have one).


If you don’t have a heated print-bed, connect the hot-end fan wires to the 2-pin header next to the yellow fuses.


If you have a heated print bed, 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.

Next connect 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 hotend thermistor cable to the first pair of thermistor pins labelled T0.

Note: On kits sent out after 05 July 2014, 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 hotend to the + and- pins marked D10 on the RAMPS board. The hotend wires are not polarised.

If you have a V6 hot-end then 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.

Optional: Fit the PanelOne LCD controller ribbon cables to AUX2 and AUX3 on the RAMPS board. You can either do this now or when installing the LCD in Chapter 22.

This concludes the basic wiring for printers without heated bed.  It will be tidied up later, after commissioning, once it is all confirmed as working.

If you have a heated bed, continue to the end of this Chapter.

1710 Fit Heated Bed

Balance the heated bed temporarily against the X-tower while connecting the wiring.

Attach 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.

Flatten the wiring over and around the RAMPS, and gently fold the yellow fuses away from the power plug as far as they will go, to provide clearance for the insulation under the heated bed.

Guide the heat-bed power and thermistor cables out of the way and fit the cardboard insulator to the bottom tabs on the heatbed mounts. It is not fixed in any way, but just rests loose on the tabs.

Centre the heat-bed mounts  at 120mm along the extrusions but do not tighten yet. Fit the heat-bed to its mounts, aligning the countersunk holes in the aluminium plate with the tapped holes in the mounts. You may have to move the mounts slightly to get them to line up, but try to keep them central on the extrusions. Once accurately aligned, tighten the M3 socket capscrews to hold the mounts in place.

NOTE: You will probably want to defer the final step of screwing the heatbed down onto its mounts until after you have tested the electronics, though it is given here for completeness.

Fit the M3x14 countersunk screws and tighten up  until you feel the printbed firmly in contact with the mounts. Do not overtighten as you may strip the threads tapped into the printed parts.