Click here to go to our main page on semi-rigid coax
Click here to go to our main page on coax
New for February 2022. Semi-rigid cables are used in test equipment, for connecting "black boxes", and in many other commercial and military applications. Let's take a look at some videos of how they are made.
Bending semi-rigid cables
Let's start with some bending background. Bender Bending Rodríguez, of "Futurama" fame, was built in 2996 at Fábrica Robótica De La Madre in Tijuana, México. He attended Mars University and was a member of Epsilon Rho Rho (ERR) fraternity. At one time he held a job bending structural steel for suicide booths. Despite his many talents, he would be likely to be hauled into Human Resources if he worked at any of today's billion-dollar microwave industry companies, for his insensitivity... You have to admit, he would be a good guy to have a beer with after work.
Semi-rigid cables can be formed using programmable, automated benders, or by hand using suitable equipment. The important thing is to not kink the cable, and not to violate manufacturer's limits on minimum bend radii. Here we present a short video of an automated cable bender. Winton is the company that makes this equipment (and this video, thanks!) The wheel that the cable is bent against is called a mandrel. The other part that bends the tube is called a wiper; both can be referred to as "die". The tube must be fully supported around its outside, otherwise kinks and bulges will result. Therefore, the mandrel and wiper die are profiled to exact fit of the cable radius. There is a third die, called the clamping die, that holds the material stock while the bending takes place.
Automated cable bender, by Winton
A note from Captain Safety: use of any automated machine requires propert training, with the main lesson being keep your hands and hair the hell away from the equipment when it is running.
Here is a very "PowerPoor" sketch of mandrel and wiper dies, with a semi-rigid coax in its grip. The mandrel die is usually a wheel, so it is profiled the same all the way around. The wiper typically does not need to rotate so it is profiled only on the surface where it is close to the mandrel.
Mandrel and wiper die
For today's English language lesson, when you are talling about a "die" in the machine shop, its plural is "dies". When you are talking about a "die" in a casino or in a wafer fab, its plural is "dice". Honestly it is not that big of a deal, people often say "dies" when they mean "dice". It is certainly not worth stopping a meeting to correct your boss!
Here is a hand-bending setup, unfortunately labeled "ridged"... Note the difference between the words "rigid" and "ridged". We are talking about rigidity here, not potato chips.... We are not sure if the bending jig is a home-built set-up or something that you can buy. Whatever you do, if you want to make good bends in semi-rigid cable, make sure you have the proper tools. For example, don't try to bend 086 cable in a 141 die!
Bending semi-rigid cables by rfshop1
Connector attachment
To make a useful cable you need to attach appropriate connectors on both ends. This is typically done with resistance soldering, like in the video below. This video is from rfshop1, they have some other laboratory content you might want to check out. Editor's note... the cable in the video appears to be conformable, not semi-rigid... you can tell by the braided jacket (semi-rigid cable is solid). Conformable cables are the subject for another day!
Resistance soldering 141 cable into DIN 7/16 connector