Highly Flexible Cable

Mostly they use easily replacable cables

Hard drives, ink jet, and impact printers use flat flexible pcb.

ount a switch on the motor arm. The arm swings through up to a 90 degree an gle with most often a 60 degree angle.

y use cables to connect to printer heads in 3D printers and laser cutting d evices. What do they use.

If it is just flexing one direction, balanced flexible printed circuits wor k fine, HP used them in their X-Y plotters, and it got written up in the HP journal as having lasted for 10 million excursions when tested. In two dim ensions you'd need it to twist and bend, but if you stay within the elastic range you should be fine. The flexi did seem to need to be symmetrical abo ut it's central plane - having the copper layer stretch as well as bend lea d to early failure.

If it's a hinge flex, can you use a hinge pin which is a tube? Then the cable flex is just a small amount of torsion on a protected length, if you thread the cable through that tube.

Display hinges often have a few wraps of a flexible circuit cable around the hinge pin. Those wraps slightly expand and compress in diameter, but don't kink at the hinge angle.

Using reversible cables is also a good way to extend their lifetime. It applies to lawn movers ,electric guitars and even firemen hoses.:-)

Right, flat flex cables are nice, for simple in-plane bending motion like you get in a linear axis. If more current (or better signal quality?) or more complicated motion is required, or just more signals in a smaller cross section, go with multiconductor cable, high strand count, neoprene jacket.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

Others have mentioned flat cable. I notice the more flexible cables use wire that has multiple strands of finer wire to give it more flexibility. If a strand or two breaks there are many more remaining to make up for it.

oss

What is special about neoprene?

I figured there would be someone selling cable specifically intended for th is sort of use. I wasn't able to find anything with any particular specifi cations.

This use only requires the cable to bend around a single axis. No torsion is required. We have a pretty fair length to work in. In fact, the motor is on the other side of the bag from the control board, so if we use a flex cable we likely would either need something two or three feet long to reac h or would need a local attachment point connected to the control board by a separate cable.

This is all about not wanting to add a $20 position encoder to sense the sp ecific position of the arm. There are various failure modes that can be de tected by knowing when the arm is expected to contact the bag vs. when air starts to flow (which we are sensing). So either know where the arm is via a position encoder, or put a contact sensor on the arm.

I also drew up a simple diagram showing how contact with the bag could be s ensed via a "feeler" arm with a pivot point on the main arm translating con tact with the bag to a point at the center of rotation. Then the switch ca n be at a fixed position at the center of rotation without the flexible cab le. But that seems to be a bit much to ask the mechanical engineer to figu re out. Sounds to me like something fun to design.

In the days when we had phones with cords they used tinsel (copper tape wound round cotton or other fibre). I couldn't find anyone (easily) just selling 2 or 4 core stuff on reels.

A long time ago we made military telephone handsets which used neoprene sheathed tinsel curly cables - only necessary for wide temperature range

- I'm sure PVC will do you for ventilator temperature range.

MK

I'm guessing the switch is detecting a position rather than switching significant current.

So you don't /need/ copper. Steel will flex without fatiguing, think guitar string.

mount a switch on the motor arm. The arm swings through up to a 90 degree angle with most often a 60 degree angle.

They use cables to connect to printer heads in 3D printers and laser cuttin g devices. What do they use.

I believe some headphone cables are also steel for the same reason

Give

I looked for phone curly cords but didn't find much in the off the shelf department. Kinda obsolete these days I guess.

I'm leaning toward a 12" or longer flat flex cable but that will require an interface board and other cable to reach the control board. I think it would also require some sort of clamp so the stress isn't on the connectors. PITA

A wire cable is probably a better choice but finding one with a rated lifetime is the problem. But it looks like we can use a continuous flex control cable and live rich, full lives.

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Thanks. I think the problem is this is a well established matter and you n eed to have particular knowledge of what works and what doesn't. I don't s ee any guides anywhere on specifics of this sort of design. The data I fin d on the cables is a bit shy of the info needed to know what will work and what won't.

Heck, the listing in McMaster seems to be a single company and doesn't even say what the stranding is in the conductors.

Well, yes. You everyday inkjet printer has a long ribbon cable leading from the main board to the print head. For example:

A key issue besides the basic electrical and mechanical ones is "bend radius". The design, during motion, should keep the cable from making ny tight bends. The ribbon cable maker, I expect, would specify this radius.

Cheers, Rich S.

Well, yes. Your everyday inkjet printer has a long ribbon cable leading from the main board to the print head. For example:

A key issue besides the basic electrical and mechanical ones is "bend radius". The design, during motion, should keep the cable from making any "tight" bends. The ribbon cable maker, I expect, would specify this radius. In the inkjets I've seen, the ribbon cable is not held down so the flexing can occur over a long portion of it length - which I suppose, evens out the stresses.

Cheers, Rich S.

Well, yes. You everyday inkjet printer has a long ribbon cable leading from the main board to the print head.

For example:

It might be worth a look inside any inkjet model, just to get the idea.

A key issue besides the basic electrical and mechanical ones is "bend radius".

The design, during motion, should keep the cable from making any tight bends. The ribbon cable maker, I expect, would specify this radius.

In the inkjets that I've worked with, the majority of the ribbon cable is not secured -- it flexes over much of its length, so the radius stays large enough, so the stresses are minized and get spread out.

Cheers, Rich S.

mount a switch on the motor arm. The arm swings through up to a 90 degree angle with most often a 60 degree angle.

They use cables to connect to printer heads in 3D printers and laser cuttin g devices. What do they use.

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ius". The design, during motion, should keep the cable from making any "tig ht" bends.

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that's a FFC,

not a ribbon cable,

I believe one of the 3D printers used a ribbon cable and it didn't last ver y long

On Saturday, August 8, 2020 at 7:15:50 PM UTC, Lasse Langwadt Christensen w rote:

we mount a switch on the motor arm. The arm swings through up to a 90 degr ee angle with most often a 60 degree angle.

They use cables to connect to printer heads in 3D printers and laser cutt ing devices. What do they use.

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adius". The design, during motion, should keep the cable from making any "t ight" bends.

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Indeed! Thank you, Lasse.