6 Extruder carriage upgrade

Unlike the Z axis upgrade which was done mostly for aesthetic reasons, this is something that really needed doing for a number of reasons.

Firstly, it had become a sorry state. Here is what I mean

While doing some other work on the printer I managed to lean rather heavily on the cable chain which broke away from it’s printed plastic mount. I had already taken off one of the extruders before I remembered to take pictures.

Also, like my other plastic motor mounts, heat from the motors had softened the plastic which had distorted where the belts fix to the carriage. Here is a picture which illustrates what I mean.

So I needed to remake the carriage in aluminium which would be stronger for the cable chain and not prone to distortion due to heat. But there are other two other reasons why it needed to be redesigned. Firstly. if I ever manage to get my own design hot end working, I’ll need 6 extruders rather than 5. Secondly, fairly soon I will be upgrading my electronics to Duet Generation 3 when it becomes available. I need to do this because currently I only have enough stepper drivers to be able to use either the 5 colour Diamond hot end, or the dynamic load balancing gantry but not both together. One other advantage of Duet 3 will be that expansion boards can be placed some distance away from the main board.

So the new design will take 6 extruders, plus two Duet 3 expansion boards. That will enable me to do away with that massive 30mm x 20mm cable chain and replace it with something like 10mm x 10mm or even 7mm x 7mm. At the last count, I have over 40 conductors going through that chain but with the new expansion boards, I will only need power and data plus maybe one or two other cables for my Z switch/probe and hot end mounted, separately switched LED “COB” light.

I’m quite pleased with how this turned out. I actually ended up with something that is 60 mm taller but 40 mm narrower in X and the same width in Y. That’s despite adding provision for an extra extruder and 2 Duet 3 expansion boards.

I did the design in OpenScad because that’s the only CAD package I know how to use at the moment. Then I set about making the parts on my mill. Here they all are.

These are the carriage plates assembled with the Open Builds wheels. I don’t normally fix the wheel “axels” at one end only but made an exception in this case because the plate is aluminium and positional accuracy isn’t too important for the extruder gantry, so if there is some “flex” it’ wont have any detrimental affects (I hope).

The extruders fix to separate plates which bolt onto the carriage.

As you can see, the extruders can be fitted either inside or outside the plates. This is to allow the most direct path for the Bowden tubes to whatever hot end configuration is used. Because the bolts that hold the extruder to the stepper motor are fitted from the front of the extruder, those extruders which are on the inside of the carriage would be impossible to fit or remove once the opposite extruders were in place. Hence the reason to use separate mounting plates. In this case, the extruders are configured for the Diamond 5 colour hot end which has 5 heat sinks arranged in a circular pattern. The plate on the left is the front plate. The Bowden tube from the upper extruder will run in front of the gantry rails. The tubes from two lower inner facing extruders will run between the front and rear gantry rails. The plate on the right has two extruders which will face outwards (the picture is reversed) and the tubes from these extruders will run behind the gantry rails.

Here is how it looks fully assembled

Obviously, there are only 5 extruders fitted at the moment. There are two sets of mounting holes for the upper extruders. This is to allow either left hand or right hand versions of the Bondtech BMGs to be fitted such that the outlet will always be centrally located between the two lower extruders.

The Duet 3 expansion boards will fit at either side. The plan is that they will be hinged at the top so that they can swing upwards to allow access to the inner facing extruders for loading filament or for any other reason. The hinge points are those rectangular bars that stick out at the top. Wherever possible. I added pairs of 3mm diameter holes for cable ties to secure wiring for the stepper motors and those cables which go down to the hot end gantry below.

Finally, this the beast mounted onto the machine.

There is no hot end fitted because I have to change all the Bowden tubes and lengthen the heater, fan and thermistor wires (for all 3 of my hot end assemblies). I’ve just kind of lashed up the wiring because it will all have to change once I get my hands on the new Duet 3 boards. I will be so glad to get rid of that huge cable chain and more importantly, the 40 plus wires that are inside it.

Finally, keen eyed readers will have noticed that I’ve improved access and visibility of the hot end and extruder gantries somewhat. You can see new triangular brackets that I made for the extruder gantry front extrusion which has now lost it’s centre section. I wouldn’t have chopped the main hot end gantry about like that but for the extruder gantry, positional accuracy isn’t so important. So a small amount of misalignment wouldn’t cause any problems as long as the gantry is fee to move.

It’s made a huge difference for when I’m working on the machine and will make shooting footage for my YouTube videos much easier. I’ll have to fit a temporary cross member whenever I to take the top section of the printer off, to prevent the legs which are normally bolted to the lower section from “splaying” outwards or inwards, but that’s not a problem.

In preparation for the new Duet 3 electronics, I’ve started to change all the mains wiring and moving my PSU etc. I’ll post those changes here in a week or so.

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