connectors for auto-insertion on cnc machine

Currents and voltages? kickback spikes? Magnetic dirt? ...

Joe

Industrial lego - 24vdc, low power and sensing, twisted pair (cat5). The machine mostly does wood, with occasional plastic or aluminum. No steel. The machine itself is fairly precise and I have an idea for holding the tool-plus-connector in the right spot for insertion, so the tolerance isn't terrible. It just isn't zero ;-)

The reason[*] for this project is I want a touch probe, but I don't want to worry about batteries or forgetting to hook up the cable. There may be other uses in the future but they'd be in the same category.

Here's the video that inspired me:

pass on pogo pins, and I don't see how those allow for misalignment

"Blind mating" was the term I needed. The hirose look overcomplicated for what I want. I found some other blind mating connectors at digikey, but they look like sawdust traps:

Typical pogo-pin interface is a pointed pin resting on a flat plate, so misalignment is accommodated. All gold-plated machined brass.

Mil-Max stuff is usually very good. I'd dig deeper, maybe find a sample to inspect.

Won't handle dirt and fragile too.

Joe

but you'd have to come up with some floating mount to account for misalignment, the hirose has it build in, specs say +/- 0.5mm

A lifetime ago, we used a ZIF-ish connector pair to allow for a "memory cartridge" to be inserted into an instrument "effortlessly" to reduce the risk of requiring any sort of force to mate the connectors DAMAGING the connectors and rendering the machine inoperative.

Our implementation effectively ran the processor bus out to the pins (buffered, of course) so it had loads of conductors (30?).

The (each!) pins, IIRC, were composed of groups of rigid strands of gold plated conductors that "meshed" with an equivalent number of strands in the opposing "pin(s)". Imagine two pieces of Litz wire (for each conductor) "interpentrating" each other.

The connectors were costly but lasted forever -- mechanically and electrically. (the device in question was several kilobucks in

My concern would be for the cleanliness of your environment; I wouldn't know the types of particulate matter that could become embedded (??) in those little meshes.

OTOH, our connector was up-facing so anything that was dropped in its vacinity would find its way onto those "pins". It was in a medical environment so liquid reagents were perpetually present yet we didn't have problems, there.

You might also consider mechanizing the mating of the connectors as you likely have "programmed" the head to move to the "pick up tool" location.

We had a device with a 600 (not a typo) coaxial pin connector that used a motor driven screw mechanism to physically pull the two connectors together (mere mortals wouldn't be able to do it, let alone *align* the pins without damaging any of them as the connector had a ~1 sq ft mating surface).

Note that the electrical connection might be able to just be electromagnetically "reinforced" (flat conductor faces) given that the "tool head" has already been accommodated in your design (?).

A lot, of course, depends on what is passing through those contact pairs... current, voltage, "content". Can you reduce the number of conductors (power, gnd, bidir data) my putting an MCU on the toolhead?

To be clear, in light of my followup on this, there was no "mechanization" of the interface; you simply DROPPED the cartridge onto the connector and the connection was made. No "second step" to secure it as required in the case of ZIF sockets for DIPS, flex cable, CPU sockets, etc.

As such, something else would have had to ensure the two devices remained in contact (gravity, in our case; whatever mechanical interlock holds your tool head in place in yours)

My plan was to make a custom tool fork (it holds the tool holder) with a tapered slot in it for the "arm" of the connector. The arm would have a matching geometry, so when the machine moves Y- to insert the tool into the fork, it also slots the arm into the tapered slots and mostly locks it in place. At that point, the Z motion of the cnc is enough to mate/unmate the connectors. Or destroy them.

The side of the connector that moves with the tool would have some wiggle allowance which should be enough to allow the connectors to line up, I just need the connectors to want to line up.

I could reduce it to four, I suppose - power, ground, sense, and probe. Nothing excessive. I chose eight because I put extra cat5's in the cable run when I built it ;-)

To be ATTRACTED to each other! (see below)

What about repurposing a "magnetic PHONE connector" (no idea what they are called -- USB connector that magnetically couples to its mate when brought in close proximity.

Sawdust and vibration, that's why. I really wanted a wiping contact along with the air jets to make sure it made a good reliable connection. I've already broken enough things due to forgetting to connect probe cabled, I don't need the machine doing the forgetting for me ;-)

The video I posted used pogo pins, which could be combined with magnets and/or a printed funnel. The oscilloscope connector could hold itself together with the force of its wiping contacts.

as one example.

(Be wary, some only support two conductors -- "charging cables")

But, why can't the machine VERIFY the connection (by "talking/listening" to whatever is on the other side)?

This doesn't help with the vibration (but, the magnetic example I posted may have enough attraction force to address that). Air jets to clean it same as any other connector.

If you want a wiping action, then it will tend to require more force (friction).

Wireless power via induction or light (depends how much power you need) and data optical or inductive or radio.

The 'oscilloscope connector' seems to be an Amphenol Micro Ribbon. There was a more robust similar family called Blue Ribbon.

I have no idea if they are still being available.

I'm assigning one pin to be "device connected" but the device isn't smart. Basically, it's a switch, either on or off. The only way to really *test* the device is to touch something, but if it doesn't trigger, it's likely to just break off if the machine doesn't stop in time.

I've got a big servo motor driving it down. I have enough force. I probably have too much, hence wanting something that self-aligns the last bit so the motor doesn't just destroy the connector.

Bingo! I wonder if there's a modern equivalent...

(now I wonder if, with today's technology, I could just print one... what are those metal bits made of again? :)

I found a few on eBay that weren't stupidly expensive, and ordered them before they vanished. Hopefully they work the way I want ;-)

Thanks!

Centronics connectors (used on old printers) work the same way, and may be easier to find, especially if you have a bunch of old kit lying around. ;) (GPIB is another approach.)

I pal around with folks who put optical instruments on train cars. The only way to keep the window clean is to delete it and blow compressed air continuously out of the hole. Some nice solenoid-valve version of that might be the ticket, for a one-off.

Cheers

Phil Hobbs