Highly Flexible Cable

We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm.  The arm swings through up to a 90 degree angle with most often a 60 degree angle.  

I know there are special cords that provide for this sort of flexing.  They use cables to connect to printer heads in 3D printers and laser cutting devices.  What do they use. 

-- 

  Rick C.

  - Get 1,000 miles of free Supercharging
  - Tesla referral code - https://ts.la/richard11209

On 2020-08-08, Ricketty C <gnuarm.deletethisbit@gmail.com> wrote:
> We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm.  The arm swings through up to a 90 degree angle with most often a 60 degree angle.  
>
> I know there are special cords that provide for this sort of
>flexing.  They use cables to connect to printer heads in 3D printers
>and laser cutting devices.  What do they use.

Mostly they use easily replacable cables

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

-- 
  Jasen.

On Saturday, August 8, 2020 at 11:02:09 AM UTC+10, Ricketty C wrote:
> We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm. The arm swings through up to a 90 degree angle with most often a 60 degree angle. 
> 
> I know there are special cords that provide for this sort of flexing. They use cables to connect to printer heads in 3D printers and laser cutting devices. What do they use. 

If it is just flexing one direction, balanced flexible printed circuits work 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 dimensions 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 about it's central plane - having the copper layer stretch as well as bend lead to early failure.

-- 
Bill Sloman, Sydney

On Friday, August 7, 2020 at 6:02:09 PM UTC-7, Ricketty C wrote:
> We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm.  The arm swings through up to a 90 degree angle with most often a 60 degree angle.  


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.

On 08/08/2020 05:07, Jasen Betts wrote:
> Mostly they use easily replacable cables
> 
> Hard drives, ink jet, and impact printers use flat flexible pcb.

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: https://www.seventransistorlabs.com/

"Ricketty C" <gnuarm.deletethisbit@gmail.com> wrote in message 
news:c6032dc3-db6a-4763-abd7-b798d8ba7e80o@googlegroups.com...
> We are going to need a highly flexible cable on this vent project if we 
> mount a switch on the motor arm.  The arm swings through up to a 90 degree 
> angle with most often a 60 degree angle.
>
> I know there are special cords that provide for this sort of flexing. 
> They use cables to connect to printer heads in 3D printers and laser 
> cutting devices.  What do they use.
>
> -- 
>
>  Rick C.
>
>  - Get 1,000 miles of free Supercharging
>  - Tesla referral code - https://ts.la/richard11209 

On Friday, August 7, 2020 at 9:02:09 PM UTC-4, Ricketty C wrote:
> We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm.  The arm swings through up to a 90 degree angle with most often a 60 degree angle.  
> 
> I know there are special cords that provide for this sort of flexing.  They use cables to connect to printer heads in 3D printers and laser cutting devices.  What do they use. 
> 
> -- 
> 
>   Rick C.
> 
>   - Get 1,000 miles of free Supercharging
>   - Tesla referral code - https://ts.la/richard11209

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.

On Saturday, August 8, 2020 at 6:55:24 AM UTC-4, Tim Williams wrote:
> 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.

What is special about neoprene?  

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

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 reach 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 specific position of the arm.  There are various failure modes that can be detected 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 sensed via a "feeler" arm with a pivot point on the main arm translating contact with the bag to a point at the center of rotation.  Then the switch can be at a fixed position at the center of rotation without the flexible cable.  But that seems to be a bit much to ask the mechanical engineer to figure out.  Sounds to me like something fun to design. 

-- 

  Rick C.

  + Get 1,000 miles of free Supercharging
  + Tesla referral code - https://ts.la/richard11209

On 8/8/2020 7:46 AM, Ricketty C wrote:
> On Saturday, August 8, 2020 at 6:55:24 AM UTC-4, Tim Williams wrote:
>> 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.
> 
> What is special about neoprene?

https://en.wikipedia.org/wiki/Neoprene


> I figured there would be someone selling cable specifically intended for this sort of use.  I wasn't able to find anything with any particular specifications.
> 
> 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 reach 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 specific position of the arm.  There are various failure modes that can be detected 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 sensed via a "feeler" arm with a pivot point on the main arm translating contact with the bag to a point at the center of rotation.  Then the switch can be at a fixed position at the center of rotation without the flexible cable.  But that seems to be a bit much to ask the mechanical engineer to figure out.  Sounds to me like something fun to design.
> 

On 08/08/2020 02:02, Ricketty C wrote:
> We are going to need a highly flexible cable on this vent project if we mount a switch on the motor arm.  The arm swings through up to a 90 degree angle with most often a 60 degree angle.
> 
> I know there are special cords that provide for this sort of flexing.  They use cables to connect to printer heads in 3D printers and laser cutting devices.  What do they use.
> 
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.

http://www.lk-tinsel-wire.com/

http://atagcables.co.uk/tinsel-wire.html

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