Crimping
Under crimping is meant a joining process in which two components by plastic deformation are bonded together, for example by crimping , pinching, crimping or folding. A crimp connection can only be released to a limited extent and can only be replaced with a suitable tool in the event of repairs.
application
A common area of application for crimping is making electrical connections. It is used here in particular to create a homogeneous, difficult-to-detach connection between the conductor and the connecting element, which ensures a high level of electrical and mechanical safety. It is an alternative to other connections such as soldering or welding . Crimp connections are mainly used in the production of large series, where the assembly of the individual strands takes place in chord.
The connecting element is a plug or a socket. If, for example, it is not possible to lay a pre-assembled cable with plugs, the individual cable can be routed to the destination and a permanent electrical connection can be established there (e.g. by crimping) at the end of the cable.
With the help of crimping pliers, the wires of a cable and plug or a wire end ferrule are positively connected. When pressing, the force for the plastic deformation of the conductor or connecting element usually acts via a toggle lever , because manual force is too weak for a permanent deformation process. In industrial use, stop presses or automatic cable assembly machines are used. For this purpose, the crimp connectors are available as machine-processed tapes to ensure high productivity.
This type of connection has become established, particularly in the field of HF electronics and telecommunications , since, in addition to connection security, it also makes handling considerably easier. The connection is made by pressure , with crimping dies precisely matched to the connection part and conductor cross-section causing a precisely specified deformation of the connection element and conductor. This process is carried out with the help of special crimping pliers. The tool and the pressing force of the crimping pliers must be precisely adapted to the crimp connection.
There are crimp connections with and without strain relief, whereby the connections with strain relief also deform them. The strain relief rests on the insulation of the cable and is not squeezed to the same extent as the wire crimp. The strain relief must be firm enough that the insulation does not slip out from under the insulation crimp by bending it several times by 45 °. However, it must not be so strong that it breaks through the insulation and even injures individual strands.
When crimping is performed correctly, a gas-tight connection is created. The deformation of the crimp sleeve and the finely stranded cable creates a structure that is largely sealed off from oxygen and thus largely protected from corrosion on the inside .
Assembly of a cable lug
Pull-off forces and conductor cross-sections for cable lugs according to IEC 60352-2
| Conductor cross-section | Tensile force / N | |
|---|---|---|
| mm² | AWG | |
| 0.05 | 30th | 6th |
| 0.08 | 28 | 11 |
| 0.12 | 26th | 15th |
| 0.14 | 18th | |
| 0.22 | 24 | 28 |
| 0.25 | 32 | |
| 0.32 | 22nd | 40 |
| 0.5 | 20th | 60 |
| 0.75 | 85 | |
| 0.82 | 18th | 90 |
| 1 | 108 | |
| 1.3 | 16 | 135 |
| 1.5 | 150 | |
| 2.1 | 14th | 200 |
| 2.5 | 230 | |
| 3.3 | 12 | 275 |
| 4th | 310 | |
| 5.3 | 10 | 355 |
| 6th | 360 | |
| 8.4 | 8th | 370 |
| 10 | 380 | |
Sources of error
If insufficient force is applied during crimping or if the wrong crimping tool is used, cables will be crimped insufficiently or incorrectly. As a result of the faulty contact, the contact resistance between the line and the sleeve increases due to corrosion on the individual strands. There is also the risk that an incompletely crimped cable can be pulled out of the crimp barrel.
The crimp connection must also not be pressed too hard. If the pressure is too strong or the crimping tool is too small, the cross-sections of solid and finely stranded cables can be impermissibly reduced. Furthermore, if the pressing force is extremely exceeded with fine-stranded cables, there is a risk that individual conductors could be sheared off. As a result, the current-carrying capacity of the connection decreases inadmissibly due to the reduced cross-section. In addition, the sleeve of the crimp connector can become unusable if it is cracked or broken.
Errors can arise during the stripping process. If no tools are used for stripping, the quality depends considerably on the skill and experience of the user. In addition to an incorrect length of the conductor, DIN IEC 60352 Part 2 points out the following typical stripping errors:
- Insulation was not properly separated.
- Remnants of the conductor insulation are on the stripped conductor.
- Remaining conductor insulation was damaged by the stripping tool.
- Single wires were damaged or cut off by the stripping tool.
- Individual wires were subsequently twisted too much.
- Individual wires are no longer twisted.
Other uses of crimping
- Attachment of rings or identification plates in livestock farming ( ear tag )
- When sealing freight containers with security tags and sealing pliers .
- When printing a sample in a certificate.
- For sealing laboratory vessels (samples, etc.).
- For closing containers with a spray head (e.g. perfume bottles).
- In the food sector, as no adhesives are required ( Maultaschen etc.).
- When making ammunition . The sleeve is crimped around the bullet.
- When cold forming metallic semi-finished products (e.g. pipes , sleeves , profiles )
- In cosmetics : Hair is "crimped" in a wavy manner with the help of a crimper. Here the individual hairs are pressed together.
- In the manufacture of nuts. The nut body is deformed during crimping and is therefore self-locking.
- When connecting water or heating pipes
- When attaching the plastic water tanks to the end plates of the aluminum networks of car water coolers .
Special versions of crimping pliers are used for most of these applications.
Norms
- DIN EN 60352-2: 2006-11 Solderless connections - Part 2: Crimp connections - General requirements, test methods and application notes (IEC 60352-2: 2006); German version EN 60352-2: 2014-04
See also
Web links
- Crimp the RJ-45 connector (German, illustrated)