Connector insertion and extraction forces in electrical wire harness design

The design of electrical wire harnesses is a critical process across automotive, aerospace, and medical equipment manufacturing. A key aspect of both design and manufacturing involves the connectors that provide the electrical path between components, assemblies, and subsystems. Getting connector force specifications right matters more than most people realize. Too much insertion force damages connectors and creates ergonomic problems on the line. Too little extraction force means connectors that come apart under vibration in the field. Neither outcome is acceptable (IEEE).

Why connector force validation matters

Connectors are an essential component of wire harnesses, providing the necessary electrical connections between different subsystems. The forces required to insert and extract these connectors from their mating parts must be carefully measured and controlled.

If the insertion force is too high, it can lead to assembly difficulties, potential damage to the connectors or the equipment, and increased manufacturing time and cost. If the extraction force is too low, it can result in loose connections that may cause intermittent signals or power losses, which are unacceptable in critical systems such as those found in aerospace or automotive applications. Current North American ergonomic regulations call for insertion force in automotive wire harness terminal connections to be no more than 75N, with indications that future regulations may tighten this further to 50N (Materion).

What is connector insertion force?

Connector insertion force refers to the amount of force required to join two connector halves or a connector to a mating component. This force is a crucial parameter in the design of connectors, as it affects both user experience and the longevity of the connector itself. The insertion force is composed of two main stages: the spreading stage, which is associated with higher force and responsible for the peak force, and the sliding stage (Samtec).

During the spreading stage, components within the connector are forced apart to accommodate the joining piece, leading to the peak force experienced. This is a result of both frictional and normal forces acting on the connector components. The sliding stage involves less force as the components slide into place to complete the connection.

If the insertion force is too high, excessive force may damage the connector pins or the housing, leading to poor contact and potential failure in the electrical circuit (IEEE). A high insertion force also increases the risk of repetitive strain injuries for workers who frequently engage in manual assembly, particularly in large-scale production environments. For EV battery connectors and other high-voltage terminals, the extraction force requirement is ≥150N. For sensors and low-voltage terminals, the minimum is 50N (ZGSM Wire Harness).

Why is connector extraction force important?

The extraction force, the force required to disengage the connector halves, is equally important. If the extraction force is too great, it risks damaging the connector during disassembly, leading to increased maintenance costs and downtime. A high extraction force can make repairs or upgrades difficult, as technicians may struggle to disconnect components without causing harm to the surrounding circuitry.

An extraction force that is too weak may lead to connectors becoming dislodged unintentionally. This is particularly hazardous in applications where connectors are exposed to external forces or vibrations, such as aerospace or automotive environments. Unintended disconnections can lead to catastrophic system failures. Failed Terminal Position Assurance devices caused 12% of connector recalls in 2024, underlining how seriously the industry takes retention force specifications (ZGSM Wire Harness, citing SAE J1742-2022).

How are these forces measured?

To measure insertion and extraction forces, a force test is conducted. This involves placing two pluggable electronic connectors in an initial position and setting force and torque gauge readings to zero. The connector is then inserted or extracted at a rate specified by the product specifications, and the peak forces are recorded. Standard test speed for most automotive connectors is 50mm/min, while precision connectors require speeds reduced to 12.7mm/min to obtain more accurate data (Vistar Electronics).

For repeatable testing, motorized testers such as the Mecmesin WTST series are used to ensure consistent pull force and speed. Customized mounting fixtures maintain correct alignment during the test (Wire Terminal Strength). The test is typically repeated across a minimum of 10 insertion and extraction cycles to evaluate terminal fatigue and performance degradation over time (Wire Harness Assembly).

When should these forces be considered?

The design and production processes for wire harnesses must consider insertion and extraction forces early. Contact resistance, which directly affects these forces, should be strictly controlled to ensure stability and reliability during the use of the connector. Waiting until the assembly phase to identify force problems is expensive. Catching them at the design stage, before tooling and components are committed, is where the real cost savings happen.

Where do environmental factors come into play?

Environmental protection is a key consideration. Connectors should be shielded from environmental factors such as moisture, dust, and extreme temperatures, which can affect both mechanical and electrical performance. For aerospace engine wiring harness connectors, the pull-out force must remain no less than 80% of the initial value at 125°C to ensure reliability under extreme temperatures. Under vibration testing per EN 61373 standard, instantaneous interruption time must be under 1 microsecond (Vistar Electronics).

Standards and guidelines

To ensure reliability and safety, the industry adheres to various standards. AS50881 covers aerospace wiring systems including connector force requirements. ISO 26262 addresses automotive safety across the lifecycle of electronic systems. MIL-STD-202G, designed for extreme environments, requires that the pull-out force attenuation rate of connectors under vibration not exceed 15% (Vistar Electronics). IEEE 315-1975 covers graphical symbols for diagrams. These standards provide guidelines on the acceptable range of insertion and extraction forces to ensure that connectors perform reliably under the expected operating conditions.

How are these forces optimized?

Optimization of these forces is driven by a combination of technology and market factors. Miniaturization and increasing pin counts require precise control over insertion and extraction forces, while market factors demand low-cost and durable solutions. The only practical means of reducing insertion force are to either decrease the coefficient of friction or decrease the initial normal force. Decreasing normal force without compensating elsewhere increases contact resistance and the risk of vibration-induced failure, so the design tradeoff requires careful analysis (Materion).

An example of this optimization process can be seen in a study where the insertion and extraction forces for a snap-fit were found to be 140N and 170N respectively. Through convergence and animation, a smooth insertion and extraction process was depicted, demonstrating the successful optimization of these forces.

The process of measuring connector forces

Selection of appropriate equipment. Specialized force gauges and test fixtures are required to measure insertion and extraction forces accurately. The equipment must be calibrated and maintained to provide reliable measurements.

Preparation of test samples. Connectors and their mating parts must be prepared according to the specifications of the wire harness design, ensuring they are clean and free from defects.

Conducting the test. The force gauge applies a steady force to insert or extract the connector, with the value recorded by the equipment. The test should be repeated several times to ensure consistency.

Data analysis. The recorded forces are analyzed to determine if they fall within the acceptable range as defined by the relevant industry standards. Statistical methods can be used to assess variability and predict performance in actual use.

Documentation and feedback. Detailed records of the testing process and results are maintained. If any connectors do not meet the required standards, the design or manufacturing process must be reviewed to identify and correct the cause.

Case examples

In the automotive industry, ISO 26262 mandates safety requirements throughout the lifecycle of automotive electronic systems. A manufacturer of vehicle wiring harnesses would use force measurement tests to ensure that connectors meet the standard's requirements, including specific insertion and extraction forces to prevent accidental disconnection due to vibrations or impacts.

In aerospace, AS50881 provides guidance on the design of aircraft wiring systems, including connector force requirements. A failure to meet these requirements could result in catastrophic failures due to loss of signal or power in critical flight systems.

Connector force specifications also feed directly into your quoting process. When a drawing calls out specific connector types with known force requirements, that affects material selection, assembly time, and testing requirements. All of those have a cost. Cableteque reads customer drawings and extracts connector specifications automatically, so nothing gets missed when you are building your BOM and labor estimate. See how it works.

Conclusion

Understanding and validating connector insertion and extraction forces is a vital part of the wire harness design and manufacturing process. Adherence to industry standards and rigorous testing ensure that connectors perform reliably, which is critical to the safety and functionality of the end product. By implementing a structured approach to measure these forces, manufacturers can minimize the risk of errors, reduce costs, and ensure the timely delivery of high-quality wire harnesses to their customers.

FAQ

What is connector insertion force in wire harness design?

Connector insertion force is the amount of force required to join two connector halves or a connector to a mating component. It is composed of a spreading stage, which produces the peak force, and a sliding stage where less force is required as the components move into place. Current North American ergonomic regulations require automotive wire harness terminal insertion forces to be no more than 75N.

What happens if connector extraction force is too low?

A connector with insufficient extraction force may become dislodged under vibration or mechanical stress. In automotive and aerospace applications this can cause intermittent signal loss or complete disconnection, which can be a serious safety risk. Failed Terminal Position Assurance devices caused 12% of connector recalls in 2024.

What standards govern connector insertion and extraction forces?

The key standards are AS50881 for aerospace wiring systems, ISO 26262 for automotive safety, MIL-STD-202G for military and extreme environment applications, and SAE J1742 for connector locking mechanisms. Each standard defines acceptable force ranges for the relevant application.

How are connector forces tested in wire harness manufacturing?

Testing uses calibrated force gauges and test fixtures. The standard test speed for most automotive connectors is 50mm/min. Tests are typically repeated across a minimum of 10 insertion and extraction cycles to evaluate terminal fatigue. Peak forces are recorded and compared against the relevant industry standard.

How does connector specification affect wire harness quoting?

Connector type and force specification affect material cost, assembly time, and testing requirements, all of which need to be reflected in your quote. Higher-force connectors typically require more assembly time and may need specialized tooling. Missing these details at the quoting stage leads to cost surprises in production.

References

"Connector Insertion and Extraction Forces." IEEE.

"Insertion Force: Spreading and Sliding Stage." Samtec.

"In Our Element: How Can Connector Insertion Force be Reduced." Materion.

"Automotive Wiring Harness Standards: Global Regulations, Design and Testing Guide." ZGSM Wire Harness.

"Connector Insertion and Extraction Force Testing Methods." Vistar Electronics, November 2025.

"Wire Harness Connector Insertion and Withdrawal Force Standard Guide." Wire Harness Assembly, October 2025.

"Connector Insertion and Withdrawal." Wire Terminal Strength.

"AS50881 Wiring Aerospace Vehicles." SAE International.

"ISO 26262 Road Vehicles Functional Safety." International Organization for Standardization.

"MIL-STD-202G Test Methods for Electronic and Electrical Component Parts." US Department of Defense.