From RepRap
Jump to: navigation, search

Cartesian Assembly (Electrical)

Now you've got your robot looking all Cartesian, it's time to install the electronics and get it wired (you need to have completed the mechanical assembly first.

Bill of Materials (BOM)

The BOM is on a separate page to reduce the amount of scrolling you need to do (Alt + Tab will quickly switch windows for you). It covers both mechanical and electrical sub-assemblies.

Installing the electronics

You will need to have completed the electronics section of the How to build it page.


For each axis you will need to install an opto-endstop so that each axis can find its home position. These endstops comprise of an opto-switch and a flag to trigger it.

Before installing the flags, glue some kitchen foil over the end (the opto-switch uses an infra red beam - the polymer flag on its own is unlikely to be opaque for this wavelength).

Bolt the PCB onto the bracket using the M3 caps, washers on the bracket side.


You can now clamp the assembly to a Ø 8 mm bar by passing the M5 cap through the end of the bracket.

++ X axis opto-endstop

Fit the opto-switch as shown.


The opto-flag for the X axis is part of the three-element assembly shown below. It is bolted with two M5 x 30 caps.


Adjust the position of the opto-flag so that it slots neatly into the opto-switch, and tighten the bolts.

Y axis opto-endstop

Fit the opto-switch as shown.


Fit the opto-flag using an M5 x 15 cap as shown.


Adjust the position of the opto-flag so that it slots neatly into the opto-switch, and tighten the bolts.

Z axis opto-endstop

Mount the opto-flag as shown. Fit the opto-switch as shown.


Adjust the position of the opto-flag so that it slots neatly into the opto-switch, and tighten the bolts.

Mounting the PCBs

The PCBs will be installed as shown. I am finding it difficult to make this section exciting. Explaining that opto-section has fizzled my enthusiasm, but take heart dear friends, we're getting closer...!


Begin with the Extruder PCB and X stepper PCB, using M3 x 15 caps, onto the points shown in the above picture. Note that you will have to detach the extruder PCB from the extruder to do this. It is designed to mount on the extruder so they can form a complete unit for testing, but, once both are in the machine, it is much neater if the extruder PCB is mounted on the carriage, not on the extruder itself. On the carriage it's not in the way of extruder adjustments and re-fills.

Take care your washers don't short circuit any of the wiring on the PCB. If in doubt (in this case) leave the washer out.

The comms board, Z stepper and Y stepper boards need to be attached to the frame using the PCB mounts as shown, using M3 x 25 caps.


Ensure the Y stepper board does not interfere with the X stepper board (i.e. move the X axis all the way over to the Y stepper motor side when installing the remaining boards).


And now it's up to you to wire the thing. I think the most help this section can be is to point out a few things which helped me keep things tidy, but really, the wiring diagrams in SVN are completely subject to your own artistic interpretation.

Power cabling

I used speaker wire which works a treat, plus it's speaker wire which everybody can get their hands on! The connectors specified for the PCBs will take a cable with up to ~42 strands. 42 strands is possible, but once you've soldered the end off, you need square it in the vice which is a waste of everybody's time. I used medium grade speaker wire (13 strands) which fitted easily and that took the current fine.

Signal cabling

A roll of multi-coloured ribbon cable is all you need. The multi-colours will keep you from going insane and chewing your legs off when the tracing wires, and the ribbon togetherness looks dead cool for the opto-switches.

Also make up two single strands with connectors on the end that will fit on the transmit and receive contacts of the Controller PCBs and the Power and Comms PCB. You will use these to gradually connect in the controllers and to test them one by one.

Wiring Notes

Here's a photo of how mine ended up, with some pointers.


A. Use the gap in the PCB mounts to funnel wires where possible. Otherwise use tie wraps to keep the wire bundles next the frame.

B. Use this diagonal (or its opposite) as a trunk route for all wires going up (including the z-opto wires).

C. For the wires to reach the x-axis, they need to leave the frame at this point, dangling up to the x-axis. When measuring out the cable length make sure the x-axis is docked at its extreme position, as shown in the pic (up against the y-motor).

D. When meeting the x axis the cable should trail up and through the triangular hole in the x axis motor bracket. At this point they should be secured to the motor bracket with a cable tie so they can't be yanked out of the PCB during general x-axis movement.

E. See the section below for a simple way to bridge the cables from the x motor bracket to the carriage.

F. When you're all wired up, run the x-axis back and forth, kinking the dangling cable in such a way that the cable doesn't catch on the PCB.

Bridging to the carriage

A length of build filament can act as a flexible bridge for the power and comms wires from the x motor bracket to the carriage. You will only need to run one power cable over to the carriage. It will be split between the extruders when it meets the carriage.

The filament can be anchored by replacing one of the rear motor bolts with an M5 x 40 cap and strapping it with cable ties.


This can then be bent over and locked to the carriage between the y-belt and the carriage rib, as shown below.



CONGRATULATIONS!!! Now you can put whiskey on the shopping list.

Thanks for completing the instructions. Remember, if you have any feedback, the links are in the 'notes to editors section'. ||-)


Always switch off the power before you change any wiring or connections.

Make sure you've got all the power connections the right way round.

Make sure you've got all the power connections the right way round.

Make sure you've got all the power connections the right way round.

Also, check that the optos are wired the right way.

Unplug (for now) all the transmit and receive wires to the controller boards. Leave the RS232 cable disconnected. Thus the only wiring going round the machine that is connected is the power and the motor-synchronization line.

Make sure you've got all the power connections the right way round. Again.

Switch on the 12v power. The LEDs on each board should light up. Switch off the power. There, I told you to make sure you've got all the power connections the right way round!

Connect the RS232 cable from the computer to the Power/Comms board, and connect the wire in the machine that goes from the transmit on that board to the receive on the Z-axis stepper. Use one of your flying leads to connect the transmit on the Z-axis stepper back to receive on the Power/Comms board. That way the Z-axis stepper is the only controller in the token ring.

Switch on the 12v power. Check that all the LEDs are still alight.

Run the stepper exerciser from the Java control program. All but the Z-axis should be greyed out. Drop the speed slider to about 200, and move the position slider a small distance to the right. The Z-axis should lower.

Adjust the flag that trips the Z-axis opto end-stop so that the build platform will stop well below the extruder nozzle. Select home from the stepper exerciser window. The platform should rise and stop when the opto-switch is tripped.

Gradually adjust the flag to bring the platform nearer and nearer the nozzle, but take care not to overshoot. (The Step - option in the stepper exerciser window is useful for this.) Get the platform to stop about 1 mm below the nozzle.

Stop the program and switch off the power.

Now take off the loop back from the Z-axis to the comms board, and instead route the signal to the Y-axis board using your installed wiring. Use the loop to come back from Y to the comms board as before.

Now you should be able to drive both Z and Y from the stepper exerciser program.

Do the same to get X working.

Finally put the extruder in the loop. Test that all three axes are still working, then close the stepper exerciser program and open the extruder exerciser program.

Check that you can turn on the heater - set it to about 80oC (assuming you're using CAPA polymer).

Lower the extruder speed using the slider. When the extruder is up to temperature turn it on. Increase the speed until it just turns. It should begin to extrude after a few seconds delay.

-- Main.EdSells - 24 May 2007