Creating secure electrical connections is critical for the safe and reliable operation of electrical systems and equipment. Properly crimping wires and terminals ensures low resistance, durability, and prevents failures that can cause damage or unsafe conditions. This comprehensive guide covers everything needed to crimp wires and terminals correctly.
Overview: The Importance of Proper Wire and Terminal Crimping
Crimping may seem like a trivial task, but improper crimping accounts for an astonishing number of electrical failures. Loose connections have high resistance leading to overheating, arcing faults, and intermittent operation. In severe cases, unsafe crimping can even start fires. Taking the time to crimp wires and terminals properly avoids these risks and creates superior, long-lasting electrical connections.
What is Crimping?
Crimping is the process of firmly joining a wire and terminal together using a mechanical compression tool. The crimping tool applies extreme pressure which deforms the terminal so it grips the wire tightly forming a secure connection. This connection method allows wires to be easily terminated without soldering or screw terminals.
Crimped wires and terminal
Why Proper Crimping is Crucial
Incorrect wire crimping can lead to a variety of problems:
- Loose connections - Without sufficiently grasping the wires, loose crimped terminals will have high resistance leading to voltage drops and overheating under load. Loose connections can increase resistance 10-100 times normal.
- Intermittent contacts - Vibration or tension on poorly crimped wires can cause momentary contact losses leading to dropped signals or erratic behavior.
- Early failure - Insufficient crimping force results in terminals working loose over time. Electrical arcing and heating accelerate terminal loosening.
- Shock/fire hazard - Loose high current connections generate significant heat levels that can melt wire insulation, damage equipment, cause electrical shocks, and even start fires.
Proper wire crimping is especially critical for high vibration environments like vehicles or industrial machinery where wires are subject to continual movement. Taking steps to crimp wires correctly will deliver reliable, long-lasting wire terminations.
Required Tools and Materials
Achieving quality wire crimps requires having the right crimping tools and components. Selecting unsuitable wires, terminals, or tools is a recipe for disappointment.
Essential Crimping Tools
Manual Crimping Pliers
Manual crimping pliers like the Ferrule Crimping Tool Kit provide the precision and "feel" for making high quality crimps on smaller gauge wires and terminals. Quality crimping pliers will have precision machined jaws to ensure even crimping pressure.
Automatic Crimping Pliers
Automatic crimping pliers use ratchet mechanisms to provide consistent crimping pressure while reducing hand fatigue for high volume electrical work. They are an excellent choice for large wiring projects.
Choosing correctly sized pliers with jaws for the terminal size being used ensures proper crimp dimensions. Obtain a separate set of crimping pliers for substantially different wire or terminal sizes.
Types of Wires and Terminals
Wire Selection
Using wire that is undersized for the current load can overheat the wire possibly leading to insulation damage or fire. Be sure to select wire gauge suitable for the expected electrical current and conditions. Stranded copper wire allows flexibility whereas solid core wire withstands vibration better. Consider the environment and wire bending requirements.
Terminal Selection
Match the wire terminal size and type to the gauge and number of wire strands being crimped:
Closed barrel terminals grip individual wire strands. Open barrel terminals capture all strands.
Closed barrel terminals are best for single solid core wire while open barrel terminals suit multi-strand wires. Using closed barrels on stranded wires may result in lost or damaged wire strands. Select terminals sized for the wire gauge with a barrel long enough to fully insert the trimmed wire.
Insulated vs Non-Insulated Terminals
Insulated terminals provide protection against inadvertent contacts with exposed conductors. Use insulated terminals for closely packed wire terminations or where risk of short circuit exists. Non-insulated terminals more readily dissipate heat.
Matching wire size, strand type, and terminal style helps achieve solid, long-lasting crimp connections.
Steps to Properly Crimp Wires and Terminals
Follow these key steps when crimping to avoid common mistakes:
Step 1: Strip the Wire
Using a dedicated wire stripping tool, remove just enough insulation so that the bare wire will be fully inserted into the terminal.
Err on the side of longer wire strips - a little bare wire exposed from a properly crimped terminal causes no harm. But excessive trimming risks cutting wire strands and reduces contact area inside the terminal. Avoid nicking or cutting wire stands when stripping insulation.
Step 2: Select the Right Terminal
Choose a terminal where the wire gauge matches the terminal size. The barrel must be large enough to accommodate the width of wire being inserted fully.
Slide heat shrink tubing over the wire now if using. Position it far enough away to avoid interfering with the actual crimp.
Step 3: Crimp the Wire
With the stripped wire fully inserted into the terminal barrel, use the crimping tool to compress the terminal firmly around the wire.
Avoid applying multiple partial crimps to reposition the wire. This work hardens the terminal metal reducing its grip. Apply full crimp pressure in one smooth motion. The crimped area should show evenly compressed indentations from the tool's teeth.
Inspecting and Testing the Crimped Connection
After crimping inspection and testing ensures quality:
Visual Inspection
Closely examine both the wire insulation and crimped terminal for:
- Wire stranding - There should be no loose wire strands. All strands must be fully captured in the terminal.
- Insulation clearance - No wire insulation should be pinched inside the crimp.
- Terminal deformation - The terminal should be evenly compressed with no gaps between crimp jaws.
- Crimp tightness - Attempts to twist or turn the wire in the terminal should fail. There should be no looseness.
- Right tool - Imprints in the terminal match the crimping tool used. Other tool jaw marks indicate improper equipment.
Any evidence of poor crimping requires reworking the connection.
Tug Test
After visual inspection, check crimp tightness by gently pulling on the wire while avoiding bending stresses near the terminal. Properly crimped connections will not come loose or separate from this mild pulling force. Retest questionable crimps after re-crimping.
Common Crimping Mistakes and How to Avoid Them
Improper technique leads to crimping faults:
Using the Wrong Tool
A mismatch between wire size and crimping tool results in malformed terminals and loose connections. For quality crimps, the tool jaws must match the terminal size. Investing in multiple crimping pliers for different wire and terminal sizes lowers the risk of using the wrong tools.
Mismatching Wire Size with Terminal
Even with properly sized crimping pliers, undersized terminals incapable of fully enclosing wire strands lead to compromised connections. Always choose terminals rated for the wire gauge being used.
Incomplete Crimp
Applying insufficient crimping force is a common issue with manual crimping tools. Incomplete terminal compression demonstrates itself through loose connections and crimp deformities. Use automatic ratchet crimpers or double check manual crimp quality via tug tests.
Conclusion
Producing robust and reliable wire terminations relies on using quality terminals and tools matched to wire gauge along with proper stripping, crimping, and inspection practices. Workers in experienced in crimping would benefit from additional training and reviewing crimp quality standards for their application. Paying attention to the little details goes a long way toward eliminating electrical problems.
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