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Pillar Three: Measured and Mechanical Specifications.

In Part One of our series: The Four Pillars of a Terminal Crimp, we explored the five elements of a Terminal Crimp: Wire, Terminal, Crimp Tooling (Applicator), Crimp Press and Crimp Operator (bench press and automatic processing). We discussed the need for all elements to be in full statistical control. Any one element that is out of control can affect crimp quality.

In Part Two, we discussed visual specifications, the first of two core measurements of crimp quality.

Part three is the second group of core measurements. Measured and mechanical specifications include Conductor and Insulation Height and Width and Pull/Tensile Test. Also we will cover conductor compaction as part of measurement criteria that makes up the conductor crimp height and width criteria.

Conductor Crimp Measurements.

Conductor Crimp Measurements include Crimp Height and width. The measurement of crimp height is accomplished with crimp height micrometers that have a point on the spindle and a flat on the anvil. Place the point in the center of the bottom side of the crimp. The flat on the anvil bridges the crimp legs on the top of the crimp.

Conductor Crimp Height can be measured with calipers or blade micrometers.

Conductor Crimp Width and Height are defined by the terminal manufacturer and need to be followed to ensure acceptable electrical performance. Conductor Crimp Width is a good indicator of tool wear.

Insulation Height and Width can be measured with calipers or blade micrometers.

Pull/Tensile Test.

Pull Test is a destructive test designed to determine the mechanical strength of a terminal crimp. A good mechanical crimp assures the crimp can withstand the normal handling and installation process. Pull Test is not an accurate indicator of electrical performance. Conductor Crimp Height and Pull Test (in that order) are the primary set up validation and in process measurements. Crimp Height is performed with the insulation support disengaged. For information, see our article Pull Test Putting it into Perspective.

Conductor Compaction.

A crimped terminal with low electrical resistance must exhibit a few internal attributes:

1. All individual strands must be touching each other and compressed from their original round shape.
2. No air gaps.
3. Crimp Legs must only touch the conductor strands and not the sides or bottom of the crimp.
4. Crimp Legs must be locked together with no gap on the top of the crimp.

If the wire strands are not compressed, there is gaps in the crimp or the crimp legs contact the sides or bottom of the crimp, it is possible that the wire is too small for the crimp barrel.

Internal Crimp Characteristics are determined using Cross Section Analysis.

Visual and Measured Specifications are important factors in a quality crimp that provides good electrical performance. It is critical that all factors are validated prior to production and monitored in-process, Pillar Four will cover in process monitoring techniques and the technology used for in process monitoring.

WireProcess Specialties has over four decades of experience in crimping technologies and crimp quality. Crimp Quality Solutions provides a path to a higher quality standard.

Connect with WireProcess Specialties to get started.

Watch out for Pillar Four coming soon.

Pillar Two: Visual Specifications.

In Part One of our series: The Four Pillars of a Terminal Crimp, we explored the five elements of a Terminal Crimp: Wire, Terminal, Crimp Tooling (Applicator), Crimp Press and Crimp Operator (bench press and automatic processing). We discussed the need for all elements to be in full statistical control. Any one element that is out of control can affect crimp quality.

Visual Specifications are one of two core measurement types that assure a quality crimp from a mechanical and electrical performance perspective. We will cover the second core grouping in part three.

Visual Specifications provide an assurance the wire is crimped in the right position. An improperly positioned crimp can affect electrical and mechanical properties over the expected life of the electrical assembly. The position of the wire crimped to the terminal can also provide an indication of crimp tool set up. For open barrel style terminals, here are the visual specifications:

Brush: Brush is the end of conductor that protrudes out of the conductor barrel on the contact side. Brush must be present but not in a position that interferes with the working of the contact.

Bell Mouth: Bell Mouth is formed from the crimp tools and is designed to protect the conductor strands during the crimp process. Bell Mouth is acceptable on both sides of the conductor crimp but required on the insulation side of the crimp.

Insulation Position: Insulation and wire must be present in the area between the conductor and insulation crimp barrels. Insulation must not be present inside the conductor crimp. Equal wire and insulation is preferable.

Visual attributes are critical in the pre-production validation and in process inspection of a terminal crimp. These attributes are also used in the maintenance of applicator tooling.

Visual Images are part of DocuCrimp a snapshot of a terminal crimp at a point in time. DocuCrimp includes visual images, pull test force chart and Cross Section analysis.

Crimp Quality Solutions is our suite of services to support the Terminal Crimp process. WireProcess Specialties is committed to helping companies to produce the highest quality wire assemblies available. Let’s get started today.

Pillar One: Crimp Elements

The process of crimping a terminal to a wire seems simple enough. Take a connector and a crimp tool and press that terminal around a wire. Do you assume that as long as it is secure on the wire, it is a quality connection?

But is it a Quality Crimped Connection?

This is the first of a four part deep dive into the pillars of a Quality Terminal Crimp. This article will introduce Crimp Elements as the initial pillar.

A crimp is characterized by five elements: Wire, Terminal, Application Tooling, Crimping Press and Operator (or automated processing machine).

Wire.

The wire construction as well as the processing (cut and strip) quality are critical to crimp quality.

Wire Construction includes the wire OD, Insulation, Concentricity, Strand Count and Internal Wire Twist. Process variables include cut and strip quality, strip length (and strip length repeatability).

Terminal.

The terminal construction (material type and thickness) is important as is the proper wire/terminal match. We will dive deeper into the implications of a mis-matched wire in part 3 of this series.

Application Tooling.

An applicator is the heart of the mechanical part of the crimp process. Tooling rated for the terminal and wire match, the applicator set up and maintenance are all critical to a repeatable crimp process. A poorly maintained applicator can cause poor crimp results.

Crimp Press.

The crimp press is subject to thousands if not millions of crimps per year. Like the applicator, the press is subject to wear over time. Wear parts include the base plate and ram adaptors and moving components like the ram and crank shaft.

Keeping the press lubricated and checking for wear should be regularly scheduled. These tasks assure that the press provides repeatable press force and shut height.

Presses should also be calibrated annually. Using a digital press analyzer combines press calibration along with capability studies of press shut height and force. This provides evidence of press repeatability and allows maintenance to prioritize press maintenance.

Crimp Operator.

The operator of the crimp press has a critical role in crimp quality. The operator must inspect the wire to ensure there are no defects in the wire. Then the wire is crimped to the terminal and a visual inspection is needed. Training on machine operation and quality inspection is essential.

In the case of an automated machine, the operator is replaced by robotic arms that must be aligned to assure the wire is presented in the correct orientation (front to back and side to side).

Crimp Quality: The sum capability of all elements.

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Crimp Quality depends on all elements being in full statistical control. For example:

• Wire gauge is within rated specification of the terminal.
• Wire is stripped to the specified strip length with no nicks, strands or scrapes.
• Crimp Tooling is properly maintained and correctly set up.
• Crimp Press has been inspected for wear, lubricated, calibrated and capability studies show press shut height and force repeatability is within statistical limits.
• Operators and Maintenance are trained in the set up and operation of crimping equipment.

Pillar One represents the basic elements of crimping, their relationship to one another and the importance of all elements being in control. Crimp Quality Solutions is your source for training, crimp validation services and consulting on crimp quality. Watch for Part Two coming soon.

From WireProcess Specialties, providing solutions for wire harness assembly for over four decades.

The process of crimping a terminal to a wire is a time tested procedure used in the production of a wire harness. The physics behind a terminal crimp has been established for many decades.

Reliable terminal crimping is critical to electrical circuits that meet or exceed the performance expected from the electrical device that they power. It only takes one defective crimp to render a wire harness useless. And raise the risk of injury and/or damage to the device or operator using the device.

Although the physics of crimping is time tested, pre-production validation, in-process monitoring and quality documentation has evolved over the past number of years. Validation and Production Monitoring tools include Crimp Height Micrometers and a Pull Tester but have expanded to include:

• Crimp Force Monitoring.
• Crimp Cameras for automated cut, strip and crimp.
• Cross Section Analysis.
• Digital Imaging.
• Networking Process Equipment.
• Data Collection and Reporting.

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It is very important to use these tools to ensure repeatable crimping that meets the terminal supplier’s specifications. And to validate to the crimp specifications. Having a method to collect this information can provide the means to analyze and document the crimp process.

WireProcess Specialties is pleased to announce DocuCrimp. DocuCrimp is part of the suite of services provided through Crimp Quality Solutions. DocuCrimp is a single page report of a wire to terminal crimp and includes:

• Terminal and Wire Data.
• Top and Side View Images.
• Cross Section Image.
• Pull Test Results and a force chart.
• Data including: Conductor Crimp Height and Width and Conductor Compression. Results can be compared to crimp specs from the supplier (if available).

DocuCrimp is a snapshot of the terminal crimp based on the equipment setup, materials and assembly methods at a point in time. As these elements change so can the results so we recommend reporting to be done on a regular basis, based on the volume of crimps processed.

DocuCrimp is priced on a single report basis but can be packaged in multiple packs and annual contracts.

For more information, please click here to start the dialogue.

The Essential Guide to Wire Processing Automation provides a breakdown of the basic components of an automated wire processing machine for cut, strip and wire end process single conductor stranded wire. In edition this paper provides some of the typical options for pre and post processing as well as multi-tasking processes for the ends of the wire.

The 2017 edition includes a number of revisions to the First Edition from 2015. In addition, the resources section has new supporting articles on wire processing and crimping technology.

Subscribers of the WireProcess Connection, the newsletter of the WireProcess Global Community have access to this white paper which we deliver free of charge.

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