Tool Changer and the wiring Issue



  • Hey guys,

    I recently built a CoreXY printer with a built volume of 500x500x500mm. You can find information about the project here:
    CoreBot

    I want to use the E3D tool changer in the printer as soon as possible. At this built Volume a may have some problems with wiring each direct drive tool head (E3D Titan + V6). I'd need 12 wires per tool (2 Fans, Extruder Motor, Thermistor, Heater Cartidge).

    Right now I have "manual swappable" tools for which I have to disconnect and reconnect an MPX6 pin plug, the NEMA17 connector and an XT60 plug. With the "automatic" tool change mechanism that will not work anymore - obviously.

    Is it possible to use Pogo Pins for tool changing? In this way I can run 1 set of wires to a drag chain to the x-carriage and the wires will be changed automatically during the tool change.
    Any suggestions, expirience or sources about that?

    Pogo Pins

    Other Problems:

    A) With this "setup" I need to hot-swap the extruder motor. Is it possible to do so with using i.E. "M18 E0" or will this kill the stepper drivers over time?
    B) I'd need to control & monitor the heater / thermistor / fan of the tools which are "parked". I'd do this with an additional set of pogo pins just for these parts in the parking dock. Or are there any other solutions to this?
    C) I want to attach the wires directly to the pogo pins. Are there any pins with that I can do this? All I have found are through hole or SMD ones.

    Greets
    Max


  • administrators

    First, be aware that the use of pogo pins on a tool changing 3D printer has been patented. In the UK at least, this does not stop you using that arrangement for your personal non-commercial purposes. But it does stop anyone else from selling kits etc. that are designed to do that.

    It's safe to use pogo pins for everything except the stepper motor. The danger of using pogo pins for the stepper motor connections is that disconnecting stepper motors from the driver while they are energised is likely to damage the driver. So there would need to be a very reliable software interlock to make sure that the driver is disabled when the pogo pins connect and disconnect. The M18 E0 command disables the driver output mosfets, so in principle it would do the job.

    If the heater and the 2 fans use the same supply voltage, you can use a common positive wire for all three. That can be used to reduce the number of wires or pins you need to 10.

    For Duet 3 we'll be making a Smart Tool board that needs just 2 power wires and a 2-pin CAN bus connector. It will control the extruder motor, heater and fans itself; so on worries about disconnecting the motor. We're not currently planning to make it hot-swappable via pogo pins, but we might if we can work around the patent.

    The only pogo pins I have used are through-hole types. Perhaps you could mount them in a piece of perfboard if you drill out the holes to the required size.



  • Thanks for pointing out the patent. I was not aware of this. Never the less I'll at least try this for my personal use.

    Using a common wire for VCC is a really good idea - I have not thought about this yet.

    Would the "smart tool board" in that be some sort of "small pcb" that attaches to the tool head itself? This would actually help quite a lot with "my" problem. Any timeline on when the board will be available? Obviously I will not need it until E3D starts to sell the tool changer itself...but I want to have it 🙂

    One of my ideas was to mount the Stepper driver for the extruder motor on the back of the stepper itself. This would at least mitigate the risk of burning the driver when the pogo pins have contact issues.

    In the meantime I might experiment with pogo pins just to get the hang of it.

    Thanks for your help & great work.



  • @macnite said in Tool Changer and the wiring Issue:

    Hey guys,

    I recently built a CoreXY printer with a built volume of 500x500x500mm. You can find information about the project here:
    CoreBot

    How is this different from a Hypercube Evo? Just curious..


  • administrators

    @macnite said in Tool Changer and the wiring Issue:

    Would the "smart tool board" in that be some sort of "small pcb" that attaches to the tool head itself? This would actually help quite a lot with "my" problem. Any timeline on when the board will be available? Obviously I will not need it until E3D starts to sell the tool changer itself...but I want to have it

    Yes, that's the idea. We've not started designing it yet because we are waiting to find out what facilities our OEMs need on it; but it will be basically a cut-down version of the prototype Duet 3 expansion board that we exhibited at TCT, with support for just one stepper motor and one heater instead of three. So the design and firmware should be straightforward. We won't be able to make it as inexpensive as we would like because it will need a CAN-FD capable MCU on board, CAN transceiver, 5V regulator etc. We may use a lower-current stepper motor driver on it such as the TMC5130, on the grounds that extruders don't normally need very fast or powerful motors.



  • @chanders
    Mostly in using a different motion system in the xy-gantry (MGN rails instead of smooth rods). The smooth rods were way to flimsy at this size.

    @dc42
    That sounds really great. I was expeting a kind-of hefty price tag for this. But IMHO it's better to do something with high quality parts and design instead of doing it bad multiple times.



  • I've been using pogo pins successfully on a tool changer for the part cooling fan. Yes, personal use, but I thought that's the sort of thing pogo pins were meant for.
    I just press standard through hole pins into a tiny print on the head, after soldering wires onto them. They contact with a pair of small brass turnings held similarly on the carriage. I can't remember the current rating of the pins (and my brass fitting make the data sheet irrelevant for me anyway. It only measured about 0.1ohm, but no doubt you could source a proper matching gold plated contact plate, I didn't look very hard), but they are 5mm long, 2mm dia IIRC. It does make it nice and tidy, and well worth a try



  • Thanks - that might help me.

    I just ordered a few pogo pins and contact pads from china (I could not find any pads for THT installation anywhere in europe).

    The pins I ordered have a current rating of 1 Amp. I'll just have to look out how "stable" the connection between the carriage and the tool head is 🙂

    You can find out more about my pogo-pin-solution here at step 9.

    Greets
    Max


 

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