Duet Generation 3 upgrade and TCT show part 2.

Following on from a previous post, I’ve made further progress on changing over to the new Duet Generation 3. Progress has been slow up until now because it have been waiting for the hardware to arrive. The expansion boards which are prototype boards, arrived on Monday 19th so I have now been able to fit them and wire them up. As I write this (Wednesday 28th August) I am awaiting the main board which should arrive in the post today.

I bought a Raspberry Pi 4 and I printed this back plate which will hold that and the Duet main board.

I have fitted fans to blow cooling air onto the back of both the RPi and the Duet main board. They may not be necessary but it is a lot easier to fit them now than at a later date. The fans won’t be all that efficient because the cavity between the aluminium plate is only the 20mm deep. The smaller fan behind the RPi is 10mm thick and the larger one is 15mm thick which was the thin thinnest that I could find at the time.

The Duet team sent me a 7inch touch screen. This isn’t something that I would normally bother with as my printer sits very close to my PC and I prefer to use the web interface. But it is something that the Duet team wanted to be able to demonstrate at the TCT show so I printed a case and mounted it on my printer in such a way that it won’t obscure the view of the other components.

It simply hooks over the top rail so it can easily be removed. I connects to the RPi via HDMI and USB.

I need to point out that at this juncture, I know absolutely nothing about single board computers so setting up the RPi will be a big learning curve for me. But I have become friends with a German chap called Manuel Coenen who goes by the user name of “wilriker” on the Duet forums, and he has been a huge help. He has also agreed to configure the RPi remotely so that I can concentrate on all the other things that I have to get done before the TCT show. Thanks again Manuel.

This is a picture of one of the mounts/cases that I printed for the expansion boards.

For the TCT show, these cases will be open so that people can view the boards. I may eventually fit covers. I haven’t made provision for any sort of forced cooling because the expansion boards will only be used for relatively low current stepper motors. So cooling will be by natural convection. The boards sit on printed stand off pillars which gives a gap of about 10mm behind them. The sides and top are double thickness with a 1mm gap between. I’ve fitted some very fine stainless steel mesh in this gap to prevent any debris from falling inside which could potentially cause a short circuit. Here is a close up of how that works…….

…..and this is what the 3 boards look like when mounted.

This is the third expansion board fitted and wired up apart from the CAN cable. Again, this will eventually have a cover but for the TCT show, it will be open. It is mounted on the back of the extrusion so the wires don’t protrude more than a few millimetres outside the printer frame.

I like to use nylon braid to cover the cables and then I fit printed labels covered with clear heat shrink to the ends before fitting the connectors. The labels identify both “what and where”. So for example “XY Beta” then “Board 3 Drive 0”. This is especially important on the other expansion boards because they are mounted on the “UV” extruder carriage so many of the cables that connect to the lower “XY” gantry have to be disconnected whenever I take the printer apart for transportation.

Here are the other two expansion boards fitted to the extruder gantry and almost fully wired up. This first picture is in their normal closed position.

The boards are held top and bottom using thumb bolts which can be easily undone to allow the boards to hinge. The next picture shows the top bolts removed and the boards hinged at the bottom to allow easy access to the connectors for when the printer is taken apart or reassembled.

The next picture shows the lower thumb screws removed and the boards hinged at the top to allow access to the 6 extruders for loading filament or other maintenance.

Here is a side view of the gantry with the boards in their normal closed position.

I would have liked to use slightly short CAN cables and did in fact buy a network tool kit and some cable to make my own to the lengths required. But, the CAN cables to the extruders need to be able to withstand constant flexing as the carriage moves around. Which means using multi core cable, and after many attempts I gave up on trying to fit 4 highly flexible but small conductors into an RJ11 plug. Solid core I can manage but I ran out of patience with the multi core cable. So on the advise of David Crocker form Duet, I bought ready made high speed ADSL 2 cables of the nearest lengths I needed, which are bit too long for the neatest of installations.

Apart form that, I reasonably happy with how it has turned out so far. Fitting 6 extruders and two expansion boards to a moving carriage was never going to be easy. Especially when it is necessary to be able to access those extruders.

That really is all I have time for now because the postman has delivered a parcel which looks like it will be the Duet main board. As I will be on holiday near the beginning of September, I have less than two weeks left before the TCT show.

Oh one final picture

This is some of the old wiring, cable chain, and trunking that was taken out and which is no longer needed now that I don’t have to run all the cables back to a central point.

Ian

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