Workbee CNC (COMS00003) Broken controller

[Pakue95]

The controller of the Workbee CNC has been having some issues lately with:

• loosing configurations (Workbee CNC: Wrong settings #303)
• randomly stopping during jobs

Which seems to boil down to a faulty controller board.

The best course of action IMO is to replace the controller board + the CNCjs Pi with a single Duet board, as that can serve a web based UI standalone.

Possible boards:

• Duet3 6HC (250€)
• Duet3 5+ mini Wifi/Ethernet (150€)
• Duet2 Wifi/Ethernet

I'd go with one the Duet3 Ethernet boards as they are still in active feature development in RRF and can be hooked up to a Pi in case somebody wants to implement a gamepad controller. The 5+ mini has a little lower stepper current than the current controller (1.4A vs 1.75A RMS).

@reogaro and @Blacksheep70 agreed to tackle the conversion project and will send me a BOM once a plan has been made.

ToDo so far:

• rewire drag chains to allow the controller board to be mounted on the table instead of the X-axis
• install controller board in dust proof box
• configure controller board
• update Wiki docu for the new controller board

Optionals:

• @reogaro suggested getting a display (PanelDue) for the CNC
  • alternatively @Johannes09 offered a wall mount android tablet that can also run the web controller

[Blacksheep70]

@reogaro : Let me know if you have a task to complete

[reogaro]

Today, the planning has advanced further.

Motherboard: The workbee uses MT-2303HS280AW NEMA23 stepper motors which take up to 2.8A phase current, which would require a Duet 3 6HC to drive to their full potential. We should get that. And we're installing it on the X axis beam (read wiring section for why), but in an enclosure. Details on the enclosure aren't set yet, I am looking into it.

Wiring: Johannes has donated some 4-wire drag chain cables (6x 4m AWM E43868 20379 80C 30V VW-1 probably 0,14mm^2). Since these cables are quite thin, we can't move the controller off the X axis. Longer cables, same thickness -> more voltage drop, and we're quite close to the edge (back-of-the napkin math suggests more than 10% losses already), but mounting the motherboard on the X carriage will shorten the wire runs just enough to make them viable.

Endstops: There has been some discussion about adding positive and negative endstops, inductive endstops, and more. I'm making a call and putting a endstop to this discussion, if only to make that pun. We're keeping the current clicky switches, but will rearrange them to home to X- Y- instead of X+ Y+ to simplify the wire runs.

Crimping: It seems like the motors are using JST SM plugs. I will donate a set and lend my crimping tool. The Duet board uses Molex KK 254 plugs, maybe @Pakue95 has the plugs and crimping pliers required for that?

Tablet: Johannes has offered to donate his industrial tablet for the project. No PanelDUE required. Thank you!

Helpers: Jannek and Lennard have also offered to help, which is very much appreciated.

Drag Chains: We're gonna flip the Y Axis drag chain by 180° to have it end on the front of the machine. This will include designing a new mounting bracket, I'll do that.

Updated ToDo so far:

• Acquire Duet 3 6HC @Pakue95
• Acquire touch interface @Johannes09
• Solve Molex crimping problem
• Find a dustproof mainboard mounting solution, or build one (I'm on it)
• Once the parts arrive, we can schedule a date to start working

[Pakue95]

I've got a crimping tool that works for the Molex KK 254 plugs, so that shouldn't be an issue.

I'd honestly avoid using cables with such small diameter for running the steppers. Given that drag-chain Ölflex with 0.75mm2 costs 1.10€/m (maybe shielded would be even better) I'd say that that's an unnecessary compromise. I'd rather have the controller board fixed to the table which avoids running an ethernet cable through the Y-chain and makes access to the controller board easier.

The 0.14mm2 cables can still be used to run the end stops if we want to safe a little on buying cables.

Here is a case option for a duet 3 6hc: https://www.reichelt.de/alugehaeuse-1550-w-222-x-146-x-105-mm-aluminium-1550wh-p221425.html

[Pakue95]

The crimping connectors and boards are available now. I've ordered the 0.75mm2 cable (12m) but will order some more to be sure it is enough).
I've also gone ahead and ordered the aluminium case.