Ferrule

So what is a ferrule?Generally speaking, any type of strap or clip used to connect, reinforce or secure objects together.It’s a broad definition that covers everything from straps applied to the ends of shoelaces to keep them from unraveling, to sturdy metal clips used to connect wire ropes together.But in the world of wire, ferrules have a more specific definition and serve a very different purpose than ferrules used for purely mechanical applications.
A wire ferrule is a soft metal tube that is crimped to the end of a stranded wire to improve the connection characteristics of the wire.Most ferrules are made of copper, usually tinned.Ferrules are sized for a specific gauge of wire, both in diameter and length.However, the ferrule is more than a simple cylinder – it has a lip or flare on one end that collects and consolidates the single strand of wire when the ferrule is inserted.
The flare in most ferrules is not immediately apparent because it is usually wrapped in a tapered plastic cable entry sleeve.The sleeve acts as a transition between the wire insulation and the ferrule itself, and also serves to gather any loose strands into the lumen of the ferrule.Unlike more traditional crimp connections, the plastic sleeve of the ferrule is not compressed during installation.It remains intact around the insulation and provides some degree of strain relief after installation by moving the bend radius of the wire away from the end of the insulation.Most ferrule sleeves are color-coded for wire size in the DIN 46228 standard, which, confusingly, has two different codes, French and German, in square millimeters for the same cross-sectional area.
If the ferrule sounds more of a European thing than an American thing, that’s for good reason.In order to obtain CE certification, electrical equipment must terminate stranded wires into screw or spring terminals with ferrules.There is no such regulation in the US, so the use of ferrules in US devices is not common.But ferrules have specific advantages that are hard to deny, and their adoption seems to be spreading because they make good engineering sense.
To understand how, clamp a short piece of insulated stranded wire of any gauge.Stranded wire is flexible, which is one of the reasons why stranded wire is used instead of solid wire in mobile applications and the potential for vibration.But it’s still somewhat stiff, in part because the insulation wraps the conductor’s strands, keeping them in close contact and keeping the individual strands twisted or laid out.Now peel off a little of the insulation from one end.You’ll notice that in most cases the laying of the strands is at least partially disturbed – they unravel a little.Strip more of the insulation and the strands get more and more separated.Remove all insulation and the conductors will lose all structural integrity and fall into individual strands.
This is the basic problem that ferrules solve: After stripping, they maintain a tight bond between the strands in the conductor and allow the connection to conduct its full rated current.Without ferrules, stripped strands compressed in screw terminals tend to splay, reducing the number of single strands that make firm contact with the terminal.This termination has a much higher resistance than a proper ferrule connection.The performance of stranded wire with ferrules is much better than without ferrules.Source: Weidmüller Interface GmbH & Co. KG
Ferrule connections do more than just reduce resistance, though.As with other crimp connections, the wire strands within a properly applied ferrule are subjected to tremendous pressure, stretching axially and deforming radially in the process.Tensile action tends to destroy and displace surface oxidation on the strands, while radial compression tends to remove air spaces between strands.These tend to make crimped connections better at resisting oxidation than uncrimped wires, increasing the life of the connection.
So are hoops the way to go for family gamers?Overall, I would say yes.Ferrules have clear advantages over normal stranded wire, and in high current applications I would stick to using them with screw terminals, or anywhere in the shield where stress is relieved.Plus, they give projects a clean, professional look, so I tend to include them in my stranded wire connections even if the application isn’t critical.Of course, tooling the ferrules is not without cost, but at $30 for a kit with various ferrules and proper ratcheting crimping tools, that’s not bad.
“The stranded wire is flexible, which is one of the reasons for using stranded wire instead of solid wire in mobile applications and the potential for vibration.”
Don’t have a link to the talk you posted a few weeks ago about connecting pipe organs and using ferrules?That video made me fall in love with the ferrules and now I am in love with them.
Phoenix Contact makes a great tool that includes magazines (like guns) preloaded with ferrules of various sizes that slide into the tool.
A used Weidmuller PZ 4 usually sells on eBay for around $30.Quality tool with replaceable dies.They will use wire sizes from 12 to 21 AWG.
For most connectors, cheap crimping tools from china/ebay will do you a very good job.- For Ferullas, simple 4 prongs are enough (6 prongs are technically better, but with 4 prongs you get a nice square, which allows you to fit slightly oversized wires in the PCB screw terminals) with It is more suitable to use 6 claws in AC installations with round terminals.– For blade connectors, you can use a kit with replaceable jaws, like China Paron, you get a crimper with 4 jaws and a thin wire stripper in a nice bag – JST connectors – especially fine pitch connectors are a story in themselves, you need a narrow tool to be able to do anything decent with them, like an engineer 09 or a proper one from JST, but they are ($400+) – —IDC (implied displacement connector) can be done easily without tools.But you can simplify the tool by using simple pliers with 2 flats.
– Most name brand connector making tools are expensive, but some have tools specifically for connectors that are more affordable (TE connections)
– When you move to semi-batch production of 50+ pieces, also consider dirty cables, services provided by Dirty PCB https://hackaday.com/2017/06/25/dirty-now-does-cables/ and provide information on popular connections More instructions on the pile are at this link http://dangerousprototypes.com/blog/2017/06/22/dirty-cables-whats-in-that-pile/
It is always good to consider the type of material when designing the connection system (gold is not always the best fit), the voltage developed between the two metals can create a joint that is not suitable for long term installation https://blog.samtec.com/ Post / dissimilar metal in mating connector /
If you want to understand the basic mechanics of connector crimping, check out this hackaday article about it https://hackaday.com/2017/02/09/good-in-a-pinch-the-physics-of-crimped-connections /spoiler crimp = cold solder
If you want to really get into the details, there is a very good book by Wurth elektronik http://www.we-online.com/web/en/electronic_components/produkte_pb/fachbuecher/Trilogie_der_Steckverbinder.php
Bonus: If you master all of the above, you can work without problems in any major industry, and there is a certain aesthetic to crimping connectors properly
Knipex ref 97 72 180 Pliers.Paid about 25 euros to crimp about 300 cable ends with them, and I’ll be using them a lot next week to rewire the electronics in the CNC router.However, instead of buying the cheapest ferrule, buy a branded ferrule (like Schneider).
Pressmaster MCT frame and correct plug-in thingie (die).The frame is about $70, the mold is about $50, give or take.This is the best thing I found after reading eevblog and trying it.It does molex kk connectors and all sorts of stuff, just buy the right mold insert.pressmaster is sold under many names, so find it by the photo and see what other names it has listed for you.
This is where it was renamed.wiha nothing to do with this, but a huge markup!Best to avoid this; get any name you can find on the MCT to save you money.The molds are all the same, no brand on them, just pressmaster (as far as I can see; I have about 3 or 4 molds for all my needs).
https://www.amazon.com/gp/product/B00H950AK4/ is what I use at home.It’s much cheaper, but seems to be the same one sold by ferrulesdirect.com (the vendor we use where I work).
Always use tools, especially crimpers, with care.Something that looks the same from a low-res picture on your computer could mean the mold is pretty bad between the Amazon version and the version sold by a reputable supplier.The dies are the most important part: if they are not carefully designed and manufactured, you cannot rely 100% on the quality of your crimp, which defeats all the purpose of using ferrules.
Unior 514 and gedore 8133 are great for quick crimping if you don’t want to carry a lot of tools in your bag.In the workshop, it is best to have special tools.At work we have gedore and knipex which have worked fine for the past 7 years.
How about tinning the ends of the strands?How does this compare to ferrules?It also removes oxidation and eliminates air spaces around the strands.
I’ve always thought this was a bad idea, since solder is actually pretty high resistance relatively.
It works, but without arguably the most important mechanical strain relief.I’ve seen too many tinned wire ends that break easily at the transition between the tinned and non-tinned sections.
To make matters worse, the end of the solder provides a stress point that makes it easier to break
To make matters worse, solder is malleable and inelastic, so even if the screw is tightened, any mechanical deformation will cause the connection to become microscopically loose.
To make matters worse, the end of the solder provides a stress point that makes it easier to break
If I recall correctly, it makes the part of the wire at the end of the solder more likely to break.So you’ll have a nice sturdy tip, but the wire will break faster.
yes.Solder can wick wire into insulation and become a weak point for fatigue.
A few months ago, NASA’s soldering bible made it clear that don’t let the solder rise 1-2mm in front of the wire insulation.When the wire needs to be connected to the mowing equipment, what you do is use Litze wire (just cheaper, not the individually insulated strand type) because it is loosely wound from hundreds of filaments.Then you have a wire that is flexible enough not to break.
Litz wire, as the name suggests, is a bundle of individually insulated wires.There is no “cheap version” of uninsulated strands, as that defeats the purpose of litz wire.You just need high strand count or “super flexible” wire.However, it doesn’t do much for weak spots created by welding.
That’s not even a reason why you shouldn’t solder wires in screw terminals anyway.If so, it’s fine as long as the wires don’t bend or vibrate near the terminals.The problem is that solder is prone to creep (“cold flow”).It deforms over time, the joint loses compression, and then you have a loose connection and all you need.
not good.It creates a weak point immediately after the solder joint, and over-bending the cable can damage the cable at that precise point.Sleeves (ferrules) with plastic ends are easier on the cable even if you pull hard on the cable.
Tin is not really a solid, but will deform over time.As a result, connections that were tightened during installation can loosen over time.loose connection -> higher resistance -> higher temperature -> less solid tin -> looser connection…you know what’s going on
Also, the tin can run into the insulation and form a hard spot somewhere away from the terminal – if you’re unlucky, this is where the single strands of wire start to break, causing invisible defects.
The main problem, in addition to the fact that tin or conventional tin+lead mixtures are too soft, tin “cold flow” out of the screw through thermal cycling and stress, sooner or later creates considerable contact resistance.
The third reason I’ve heard against soldering is that the solder is too soft and over time the screw connections will loosen.
Cold flow under pressure is the same reason that old aluminum power cords are so dangerous.Over time, connections become loose, resistance rises + poor connections can cause arcing.
I never like to find it on site.Solder is hard and smooth, so the terminal block doesn’t compress and hold onto it like softer stranded copper.Ferrule crimpers put serrations on the crimp, so it grips better than solder.
Tinned wire for screw terminals is a bad idea because even at room temperature the solder will shift slightly under pressure and as the temperature is cycled, will flow out of the joint reducing the contact area and increasing the resistance, thus heating up, resulting in a positive feedback effect.
Tin plating is softer than bare copper.As a result, screws can lose over time faster than ferrules or lugs.
I know that in Europe, stranded wires are usually tinned before many devices fail or burn, and crimping is now a problem.
Causes a problem with stress relief…usually breaks completely where the solder ends, as it allows for very sharp bends (soldered wires are hard, non-soldered wires are not….
I would never suggest soldering wire.Especially if there is vibration or even movement, your cable can break in a short time.