Quick release connector for TC

Discussion in 'Tool heads & ToolChanger' started by blarbles, Jan 21, 2020.

  1. blarbles

    blarbles Well-Known Member

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    I've been messing around with a quick release connector for the TC heads. I would like to be able to easily swap tools for a variety of reasons. The pictures below show what I have so far and are by no means a final design. I'm posting here to get some constructive feedback on the design.

    Connectors are 12 pin. The wires I have in the picture are just for testing fit. I bought these if you care which ones specifically:
    https://www.amazon.com/gp/product/B06XK9D14S/

    This will be designed to work with the Almost Direct Drive I designed (elsewhere in this topic). If it ends up being useful I will post the design to Thingiverse.

    2020-01-21 14.08.46.jpg 2020-01-21 14.08.21.jpg 2020-01-21 14.09.03.jpg
     
    Olle Wreede likes this.
  2. Paul Meyer

    Paul Meyer Well-Known Member

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    Very cool. What is holding down the tool? Are you just clamping down the two side tabs on the base with those two printed pieces? Did you design those pieces with recesses for the tabs?

    Ordered a set of the 12 pin and 16 pin to play with, thanks for the pointer!

    Paul
     
  3. blarbles

    blarbles Well-Known Member

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    Clamped on the tabs. It is not much plastic to hold onto, but it doesn't move or come out even if I try to break it.

    Inked2020-01-21 16.44.22_LI.jpg
     
  4. blarbles

    blarbles Well-Known Member

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    Getting closer.
    • Added brass threaded inserts
    • Adjusted dimensions to actually allow the motor to be installed (seemed important ;))
    • Many small tweaks
    2020-01-26 09.47.51.jpg 2020-01-26 09.45.53.jpg
     
  5. yngndrw

    yngndrw Well-Known Member

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    Some of the original tool changer pictures showed connectors (Molex Micro-Fit 3.0 I believe) but sadly for some reason they were dropped from the final version - I think it was a missed opportunity for the platform especially as it's designed as an experimental platform for new tools. I think with the upcoming Duet 3 it makes even more sense as you can have relatively few pins and, more importantly, only need one set of data pins for any type of tool. (Even for a dual pick and place head which might require three stepper motors)

    Do you know what the current rating for that connector is? I couldn't find any mention of it on Amazon. I think the Molex Micro-Fit 3.0 is a pretty good choice for this usage for the following reasons:
    • There's a proper panel-mount version
    • It's the same connector as E3D use for the heaters, so less types of crimps to buy
    • It's rated to 8.5A per pin, which is just over 200W at 24V
    • A molded cable is available which provides some strain relief, although the price of it is silly
    For the Duet 3 I'd probably have a double row connector with:
    • A fused 24V / 0V pair
    • A fused 5V / 0V pair
    • A CAN bus input pair
    • A CAN bus output pair
    For the Duet 2 your 12 pin connector looks just right for a normal tool, you may need some more pins for a dual thermistor supervolcano if you ever wanted that. Are you going to have a second set of connectors for the heater, thermistor, fan and motor so that you can swap them out individually or are you going to just remove / replace the pins if you need to swap one? What are you going to do for strain relief so that the moving wires don't snap off at the plug pins? I think some heatshrink around the base of each pin should do, as long as it doesn't prevent the pin from being clipped in.
     
  6. blarbles

    blarbles Well-Known Member

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    I cannot find it now, but before I bought I saw an eBay listing for these that said up to 15A per pin depending on cable. This seems a bit high, but my understanding for an 80w heater @24v is 3.5A max so I think what I bought is fine.

    I looked at the Molex connectors, but I did not see an all-in-one (12 pin) solution and they were significantly more expensive for something I was just experimenting with. Honestly I had trouble figuring out how to look for Molex options, but if you saw something that would be idea I wouldn't mind taking a look.

    Duet 3: I'll wait and see what other people come up with.

    Duet 2: You are right, I need exactly 12 pins to make it work. On the TC I probably won't go with a supervolcano. I will not have a second set of connectors because getting the pins out of the connector I bought is easy with a very small flathead screw driver. Anything I need to replace can be handled with that. Still thinking about strain relief.

     
  7. yngndrw

    yngndrw Well-Known Member

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    Oddly it looks like the Micro-Fit 3.0 connectors are rated differently depending on the standard, for IEC they are rated to 5A per pin. (120W @ 24V) Still plenty as you say, but something to watch out for.

    Here are the 12pin parts:
    https://www.molex.com/molex/products/datasheet.jsp?part=active/0430201200_CRIMP_HOUSINGS.xml
    https://www.molex.com/molex/products/datasheet.jsp?part=active/0430251200_CRIMP_HOUSINGS.xml

    And some Ebay multi-buy links, they are a little pricey (These are without pins) but it isn't too bad for the quantity:
    10x Sockets, £7.51: https://www.ebay.co.uk/itm/171948284132
    4x Plugs, £4.89: https://www.ebay.co.uk/itm/193313059343
     
  8. blarbles

    blarbles Well-Known Member

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    Thanks for the links. I went shopping at Digi-Key and bought some micro-fit 3.0 connectors with pins to play with. I was never really sure what I was getting when I browsed before since they put "image may not be representative of product" everywhere. Also some things I would choose said "minimum purchase 12,000". Thanks for pointing me in the right direction.

    I even got a tool for releasing micro-fit 3.0 pins after install.

     
  9. yngndrw

    yngndrw Well-Known Member

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    Digi-Key aren't the best for pictures of their products and sometimes don't even bother to upload the relevant datasheets which is annoying, but they do stock an amazing range.

    Often the items with silly purchasing amounts have another listing with a standard purchasing amount, often sold in different packaging and at a slightly higher cost so it often helps to search on the part number if you know it. (Although some things do just have the silly minimum amount)

    The releasing tool looks good but keep in mind that it is said to destroy the pin you're removing so you'll need to re-crimp afterwards. Make sure you leave some slack on your thermistor / heater / fan wires so that you can re-do them.

    Sadly it looks like the overmolded cables only go upto 10 pins, although the 8 pin version would be great for the Duet 3 tool board.

    It's worth noting that they have a temperature rating of 105C. Not an issue unless you have a heated build volume and even then you can probably go over this.
     
  10. blarbles

    blarbles Well-Known Member

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    I'll make my own overmold(ish) cable. I've started work on modeling parts for the Molex Micro Fit 3.0 plugs.

    Screen Shot 2020-01-29 at 1.33.09 PM.png Screen Shot 2020-01-29 at 1.54.25 PM.png Screen Shot 2020-01-29 at 1.54.56 PM.png
     
  11. yngndrw

    yngndrw Well-Known Member

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    That looks great, especially if it was in TPU.

    You might want to terminate the metal strip at the plug rather that on the tool so that it's easier to remove without tools - the strip could extend through into a slot on the tool for extra support but I think it should only be clamped on the plug.
     
  12. John Meacham

    John Meacham Well-Known Member

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    The TAZ seems to have a 13 pin very robust toolhead connector. However I can't figure out what they actually are or if they are inexpensive. In any case, micro-fit 3.0 seems pretty good to me. It would be nice to include an uncommited GPIO pin or two capable of driving servos. As that would break out pretty much all of the duet's functionality for tools to use.

    https://ohai.lulzbot.com/media/uploads/Connect_Extruder_Harness_01.JPG.600x0_q85.jpg

    I don't think you need an explicit CAN bus output because the base can just wire them all in parallel. They don't need to be chained, it is just a convienient way to provide the ability to add multiple nodes without adding a bunch of ports to your main board. stubs splitting off with no termination can be up to a meter long at the highest baud rates supported.

    I guess ideally for duet 3, I'd like to see CAN plus a few general purpose IO pins, that can be used for tool interrupt and enumeration to allow the board to determine which CAN device is in each slot or for when you don't need a full tool board they can be used to drive servos, trigger an endstop or maybe speak slow i2c which will be suitable for simple toolheads and experimentation.
     
  13. blarbles

    blarbles Well-Known Member

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    My concern with attaching the metal strip to the plug and not the tool base is with a lot of movement that the print head will go through it may be enough to start to degrade the molex pins and cause a short. Releasing the metal strip would just involve unscrewing the grub holding it.

     
  14. Paul Meyer

    Paul Meyer Well-Known Member

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    One off the wall thought:
    That metal strip would make a nice conductor! Use it as ground for the heating element and save one pin!

    (just kidding, it'll get so much stress/vibration/wiggling I would never trust it to stay connected. You'd need another metal strip to give strain relief to the first metal strip....)
     
  15. dc42

    dc42 Well-Known Member

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    Where did you get the "a meter long at the highest baud rates supported" bit from? With 1m stub cables, i think you might have issues with reflections, due to lack of termination of the stubs.
     
  16. John Meacham

    John Meacham Well-Known Member

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    A meter is still only 4-5ns delay, the reflection should have plenty of the time to bounce back and hit the termination before causing an issue. I admit I don't have a duet 3 to play with so could be missing something obvious about how you are using it and mostly have experience with rs-485 but over a range of a few feet across the print bed, I think it should be fine by an order of magnitude. Unless you are running at some crazy high speed. Here is a reference with some calculations.

    https://www.onsemi.com/pub/Collateral/AND8376-D.PDF
     
  17. blarbles

    blarbles Well-Known Member

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    Well... I'm giving up on the Molex MicroFit 3.0 connectors. They have way too much slop in the connection and with all the print head moves I don't see it lasting long before a short. I am going back to the original connectors I bought as they connect with no slop and were designed for connecting trailer hitch lights so designed to handle some movement.

    I will add the STL if anyone is interested in continue to pursue the Molex style connectors.

    2020-02-02 12.33.56.jpg 2020-02-02 12.33.38.jpg 2020-02-02 12.34.11.jpg
     

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  18. yngndrw

    yngndrw Well-Known Member

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    Oh that's a shame, I thought they would have been fine especially with the metal strip as I'd seen connectors like that on the early tool changer pictures. Sorry for leading you down that path!
     
  19. dc42

    dc42 Well-Known Member

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    We use Wurth Electronics clones of 6-pin Microfit 3.0 on the Duet3D Smart effector. They have no slop at all, and we have no complaints from users about them failing.

    @blarbles, were you using actual Molex Microfit connectors with locking hooks, or something else?
     
  20. blarbles

    blarbles Well-Known Member

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    I used actual Molex brand these exact models:
    https://www.molex.com/molex/products/part-detail/crimp_housings/0430201200
    https://www.molex.com/molex/products/part-detail/crimp_housings/0430251200

    I'm not sure if the rocking clip in the above connector that connects the two is what you are referring to as locking hook or not.

    When connected and I lightly flexed the connection it moved more than I thought was acceptable. I base this on seeing similar connectors short on 3D printers that used them for the hotend and bed cable to mainboard and someone did not properly zip tie the cable to reduce flex.

    I think the Molex Microfit would be fine if I used a lot of support with zip ties and tape to ensure the two connectors didn't flex much, but that kind of defeats the point of having a connector. Right now my design would mean unscrewing the grub screw holding the metal strip and disconnecting the two connectors - I'm not sure the Molex can hold up with that setup.

    Looking at the Duet3D Smart Effector: The Molex connection there would see less stress than my setup since the cables appear to be connected to other cable bundles and most importantly the Bowden tube.

    I would love for someone to prove me wrong since the Micro Fit is smaller and lighter.

     

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