Latching magnetic tool changer
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Thanks all for the kind remarks.
@Martin1454 I've dug out some pics of my changer's latching mechanism.
I CNC'd the rather elaborate brass guides, but it turns out that they are almost completely superfluous because of the way the magnets keep the head aligned even when not fully attached. Without the guides you would just need a stop to prevent the pawl from moving above horizontal when the head is docked. The shape of the pawls could easily be filed by hand.
You can look at my cad files on Onshape if you like but they are a complete mess.
I can't take credit for the magnetic kinematic mounts. They were based partly on commercial versions used in optical systems (such as these: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1546) and partly on material from an engineering book that I have which was published in 1934 and has two chapters on kinematics! It seems there is nothing new in mechanics!@1ri The sturdy frame is just aluminium angle welded together, and is a nice cheap way to make a strong frame. It probably would have been easier/better to bolt the sections together, but I had just bought a new welder that I wanted to play with
@fma Your idea sound good. Gear mechs are fun. The four heads shown in my video are unplugable, and I have just made a version which carries a Bondtech BMG extruder so that I can print flexible material. I haven't properly tested it yet, but it looks like it will work ok.
@bearer Ha ha
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ingenious. would love to have one!
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@pawprinter said in Latching magnetic tool changer:
You can look at my cad files on Onshape if you like ...
I think that's a very good system and would like to build it. Would you please provide the cad data?
Unfortunately I can not find the oneshape link.
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I think this is here: https://cad.onshape.com/documents/ee78eeb0f6b8aaf2d8eaeb6f/w/dcf1bccd45c5fcc6fbba5f9c/e/701e92f83c58894a4886d70a
Do you have to pull hard to disconnect the magnets?
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@fma said in Latching magnetic tool changer:
I think this is here: https://cad.onshape.com/documents/ee78eeb0f6b8aaf2d8eaeb6f/w/dcf1bccd45c5fcc6fbba5f9c/e/701e92f83c58894a4886d70a
Do you have to pull hard to disconnect the magnets?
Thanks for the link, but i have no account and the link leads me to a login page.
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Mmm, I though it was possible to see designs even when not logged on (a recent feature); I may be wrong.
I suggest you create an account, it's free. Create a dummy one, just to see public designs (there are thousands) if you don't plan to use Onshape...
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Yeah, sorry, I have enabled link sharing now so you should be able to view without an Onshape account.
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@pawprinter said in Latching magnetic tool changer:
Yeah, sorry, I have enabled link sharing now ...
Thanks
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@fma said in Latching magnetic tool changer:
Do you have to pull hard to disconnect the magnets?
Not once the plates have been angled apart by the wedging action of the latch. There is still some pull which is easily overcome. I was surprised how far the magnet's attraction is effective, but once the plates are split they are easy to separate fully. The remaining attraction is actually helpful to keep the heads aligned properly. Obviously there is a balance between the strength of the magnets and the size/angle of the wedged latches. I found it quite easily by trial and error.
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I see. Clever design!
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Here are some more heads that I've made for my latching tool changer.
Two are water cooled: One for a standard hot end, and one to fit a volcano. It turns out that water cooling is fantastic, and much less fuss than I thought it would be.
The other head is sporting a Bondtech BMG fitted for printing flexibles. It is a bit experimental to see if the magnetic mount can take the weight. So far it has worked very well, but it's perhaps not the most elegant solution. However, it was very simple to adapt the Bondtech in this way, and I get the advantage of a well proven feeder.
When you can easily swap heads over, it starts to get very versatile, but can be a configuration nightmare!
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Very nice work!
I'm thinking to make a system to be able to swap hotends but keep the extruder on the carriage. Or at least, just the motor, and use a quick shaft coupling...
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@fma Thanks. Yes, your idea would make a lot of sense. I might wait to see what you do, before I re-design mine.
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Don't hold your breath, as I need to re-design all my CoreXY gantry to be able to implement a tool changer
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@fma Ha ha - Yeah, I know how it is!!
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@pawPrinter Have you seen any issues with the magnets causing interference with the stepper motor driving the Bondtech extruder? I want to make a version of a magnetic parking extruder system on a Prusa style machine, but am concerned about the electromagnet interfering with the operation of the stepper motor.
almost an engineer
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A magnet does not generate electromagnetic interference, as it is a pure static magnetic field.
It can influence a stepper motor in 2 ways:
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if the stepper and the magnet move relatively of each other (Foucault currents, Faraday effect...). But you need to move them fast to have an effect!
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if the static field is high enough to reduce/cancel the magnetic field of the stepper. Unless the magnet is very big and touches the stepper, it should not happen.
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As @fma implies, the chances of magnets interfering with stepper drivers is very small. However, strong magnets can prevent brushless fans from working, and even weak magnets can affect a BLTouch.
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@fma @dc42 Thanks for the info! I'll probably have the Bondtech/Titan in between the electromagnet and the stepper motor just to be safe. I'm planning on using a small M3 screw, spring and printed flag with an optical endstop switch (and homing without the electromagnets on) so there shouldn't be any issues there as might happen with a BLTouch.
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@red-sand-robot No, I've not noticed any problems with the Bondtech being affected by the magnets (which are permanent magnets in my case, not electromagnets - I found electromagnets a bit heavy).
Interestingly, I have had one occasion when a fan didn't start up properly. I didn't think much of it at the time, because fans can be annoying, but it could have been related to the magnets as @dc42 predicts.
