Hot Crimping or Wire Compacting? 8 Questions Answered

Manufacturers — especially those in the automotive sector — often use stranded wire for its flexibility, but it can present a challenge in making robust interconnects. While flexible and durable, stranded wire tends to fray and splay when pressed without confinement, which may create hazardous short circuits. Using hot wire crimping or wire compacting, manufacturers can create a single, solid electrical and mechanical connection for efficient energy distribution and robust performance by gathering and compacting the ends either directly or in a terminal sleeve. The resultant package provides lower resistance and a more robust connection.

Here are a few key questions and answers that explain hot crimping and wire compacting and review when and where each is best used.

What is the difference between hot crimping and wire compacting?

The shortest answer is that hot crimping uses a sleeve and compacting does not.

Hot crimping is a wire crimping manufacturing process that uses electrical current and mechanical force to form a robust electro-mechanical connection. A sleeve is placed on the end of the wires, which gathers them into a neat package. An electrical current is applied which both removes insulation and fuses the wires and sleeve into a single, connection-ready package.

Wire compacting also uses current and mechanical force to create a solid cuboid shape, but without the use of a sleeve so the wires must be stripped of any insulation before fusing. The resultant compacted wires form a solid welded volume that facilitates connections to other components.

Explain how hot crimping and wire compacting help manufacturers meet the stranded wire challenges they face

Manufacturers utilizing stranded wire face four primary challenges: contact resistance, mechanical stress load, product lifespan, and cost.

• Contact resistance — Mechanically crimped stranded wires have a higher resistance than compacted or hot crimped stranded wires, which generates heat at the interface that weakens cables over time. Hot crimping and wire compacting produce a connector that possesses reduced contact resistance, thus reducing the electrical system’s overall temperature.
• Mechanical stress load — Stresses due to vibrations can cause degradation or failure in conductivity. Hot crimping and wire compacting result in more robust connections, reducing potential problems due to mechanical stress load.
• Product lifespan — The cycle of localized heating and cooling of the weld joint causes minute expansion and contraction of the material, which ultimately reduces the part’s lifespan. Compacted joints offer reduced contact resistance, resulting in lower temperatures, less thermal cycling, and, ultimately, improved product lifespan.
• Cost — Hot crimping and wire compacting reduce the need for complicated assemblies that require additional processing steps, like organizing frayed wires. This also reduces cycle time and increases throughput, saving money.

How do manufacturers determine whether to select hot crimping or wire compacting for an application?

Key considerations for selecting a technology include material and process, insulation, connection size, and final product design.

• Material and process
  • Hot crimping
    • Ideal for joining standard magnet wires, high-frequency magnet wires (above 10 kHz), and uninsulated copper wires. Because the crimping process essentially encapsulates the wires, the material choice is more forgiving than wire compacting.
    • Ideal for applications where the cable elements are individually insulated, and that insulation needs to be removed to make a connection.
  • Wire compacting
    • Particularly well-suited for copper wire, with or without a tin or silver coating. It is also a good fit for twisted pairs and multiple sheathed cables. It is not well suited to aluminum because the thin oxide layer that naturally occurs on the aluminum inhibits strong welds.
    • Not suitable for copper wires with nickel plating or a nickel barrier layer; the different melting points of the base material and coating make it difficult to get stable process results.
    • Better suited to applications where the compacted connection requires direct contact to deliver current and the individual cable elements are not insulated.
  • Size
    • Hot crimping can be used for individual magnet wires as thin as 30 AWG (0.05 mm²) or a wire bundle as thick as 400 mm² (stranded or braided).
    • Wire compacting can handle a wide range of wire sizes, from 0.25 mm² (26 AWG) to 120 mm² (4/0).

What are some typical applications of each technology?

Hot crimping in electrical vehicle (EV) manufacturing is used for making high-current connections from the battery to the inverter as well as high-current connections from the inverter to the electrical motor internal components.

Wire compacting EV manufacturing applications include sensors (safety belts, temperature, etc.), electrical distribution from batteries, airbag initiators, and Y and T connections.

What other criteria should I consider when selecting between compacting or hot crimping?

Pay careful attention to part requirements (particularly weight), and such manufacturing criteria as throughput and available facilities.

What equipment is typically used for wire compacting and hot crimping?

Wire compacting typically uses an alternating current (AC) inverter or direct current (DC) inverter weld control and high-force weld head with bus cooling. Hot crimping usually features a DC inverter paired with a pincer weld head.

Contact your local AMADA WELD TECH sales representative for more information and a free sample evaluation.