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.
Networking Process Equipment.
Data Collection and Reporting.
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.
Terminal Crimp Quality is one of the most, if not the most critical factors in a wire assembly. Your wire assembly has many connection points and most have a connector to facilitate this connection. It only takes one bad connection to render an entire electrical assembly in-operable.
The wire to terminal crimp is made up of several elements. Each element has it’s own process capability. The crimp itself has physical factors which comprise an acceptable electrical connection and mechanical strength. These are repeatable factors which can be validated and monitored.
Two measurements are used most in almost all wire harness factories: Conductor Crimp Height and Pull Test.
Conductor Crimp Width is also an important factor when considering overall crimp quality. But how does it fit in with the measurements above?
Crimp Tools are engineered and produced to form a terminal around a wire. Each crimp tool set (Conductor and Insulation punch and anvil) have a profile which produce the desired crimp shape. The wire and terminal are pressed together to assure the conductor strands are deformed at a proper compression ratio while achieving acceptable mechanical strength.
A terminal typically has a few wire sizes that can be crimped without compromising electrical integrity or mechanical strength. The crimp applicator has a dial that sets the conductor and insulation crimp height to the rated wire size.
The Conductor Crimp Width is not adjustable and is the same for all wire sizes within a terminal’s wire range. On top of the dial described above, crimp height is further adjustable to a limited extent by the shut height adjustment on the press.
Over time, tools wear. And as those tools wear, the ability to maintain the required physical measurements (height and width) are compromised. Although small adjustments in shut height can compensate for tool wear, the tool width is fixed. And the sides of the crimp tool profile will wear to the point where the crimp height to width ratio is not met. And following is a reduction in crimp compression.
Maintaining Conductor Crimp Height and Width is critical to assuring the proper conductor compression. Replacing tooling before the crimp height and width are compromised is very important. Despite the tendency to defer to the economics of tool costs and use tooling past their ability to maintain the proper measurements. Deferring to the latter raises the risk of crimp failure in the field.
Measuring conductor crimp width should be a parameter that maintenance tracks to determine when tools should be replaced. Conductor Crimp Width is measured using a dial caliper or Blade Micrometer.
A well equipped factory includes well maintained and capable processing equipment. An equipped factory should also include validation and monitoring tools to assure repeatable quality. But even the best processing tools and quality tools are completely worthless without adequate worker training. Training for the equipment and tools but also the quality standards and measurements. For the crimp process, Crimping Solutions by WireProcess Specialties provides end to end support for the terminal crimp process. Visit Crimping Solutions or Connect to WireProcess to get started.
We are living in an age where communication between people is real time and instant. Now you can communicate across the globe with anyone, at any time just by picking up your favorite device.
Machines are also capable of talking to one another. What once was science fiction, is now a reality. Phrases such as IOT (Internet of Things) and AI (Artificial Intelligence) are a regular part of our vocabulary. We still have a long way to go before the Smart Factory becomes a reality across all industries. But the pieces are now available to create the factory of today and tomorrow. But like all areas of development in a company, laying out the integration starts with the right plan. And all plans require the right knowledge and the right people to ensure successful launch and operation. So where do you start? You always start with the Why.
Why Should You Network your Processes?
We are living in an area of extreme complexity. So much complexity, the average person cannot deal with the breadth of details required. So our ultimate goal should be to create simplicity out of complexity.
Our ultimate goal should be to create simplicity out of complexity.
Most tasks have some repeatable components to them. Components that can be automated so the main task can be completed with more efficiency.
Every process has its human element. When workers process their assigned task, two things can occur: errors and simple bias. Removing as many points where errors can occur is a critical factor in network and automation. Considering the following points:
Selecting raw materials and processing tools. Have the right tools and materials have been selected?
Are the processing instructions clearly laid out?
Is Quality data available and as important, is it the current revision?
When a process has been in place for many years, workers become comfortable with that process. So much that bias can enter in. In the case of product quality, who makes a decision what is an acceptable quality component? Who decides whether to place the component in the good or reject pile? And how can you be assured that the rejects are not placed as part of good production?
Removing simple bias and reducing causes of error are reasons for Network Integration.
What about process tool capability? You depend on machines to process your materials into a quality component. These machines require routine maintenance and parts replacement. Some considerations:
Are your machines capable of repeatable processing? Is there a process in place to ensure process capability?
What is the life span of consumable tools (cutters, punches, forming tools etc.). Do you have a process in place to replace consumable tools to ensure process capability?
Do you have a system to enforce routine machine maintenance and consumable tool replacement?
All of these factors are why you need to consider Network Integration. Let’s consider the critical factors in your planning and integration process.
Identifying the Processes to Integrate.
Integrating as many factory processes is important. Most processes are different so a common system of communication between machine processes is key,
In the case of a typical wire harness factory, here are a few examples of processing systems:
Bench Top Terminal Crimp Machines.
Ultrasonic Welders (Wire Splice and Terminal to Wire Welders). Telsonic TS3 pictured below.
Automated Wire Processing Machines.
A common system of communication between machine processes is key.
Your factory will not only have different processes being used, often you have machines of the same processing type from different vendors. When you introduce a new vendor solution, you don’t simply throw out what you have used in the past. So in reality, you can have older process machines operating next to newer technology from the same and often different companies.
Competing companies may have their own solution. But does that solution talk to machines from other companies? Communication Systems must cover all machines whether they are older legacy systems or newer systems from different vendors.
Platform independence is critical.
Connecting Processing Machines and Quality Validation/Monitoring Systems.
You should be considering networking not just your processing machines for communicating process instructions and collecting valuable processing data .But also connecting quality validation and monitoring processes. In the case of Wire Harness Processing and the critical process of terminal crimping:
Blade Micrometers or Calipers (Conductor Crimp Width and Insulation Crimp).
Crimp Cross Section Analysis.
Crimp Force Monitoring.
C&S MPN100 Network for Benchtop Crimp Presses
These and other tools are important to ensure production starts with a validated process. And to monitor the production process for good output and to remove defects from the production stream.
Let’s face it, you don’t have all the answers. That’s why you need external support. Selecting the right companies to partner with is an important first step. Companies who are able to consider your unique requirements. Companies that have highly knowledgeable and experienced personnel to provide guidance. Along the full journey of your plan.
We have written about Crimp Force Monitors (CFM) many times over the past few years. The Crimp Force Monitor is a critical tool that provides real time monitoring of the crimp process.
Crimp Monitors can detect quality issues with upstream processes such as wire. Also Crimp Monitors provide valuable information on equipment conditions and variability in Crimp Tool Setup.
In this article we are going to discuss some of the important considerations for implementing a Crimp Monitoring Program. Whether it is on an automated cutter like the Megomat 600 or a benchtop crimp press, getting started properly will better ensure a successful implementation.
The first and most important point when implementing a CFM program is to understand what CFM’s are not.
Crimp Force Monitors do not solve your crimping problems. They will bring quality problems to the surface, problems you might not know actually exist. Awareness of issues in crimping is the first step to a consistent and repeatable crimp process. It is common when using Crimp Monitors for the first time to blame the Monitor when a crimp application experiences frequent CFM alarms.
Crimp Monitors do not solve your crimping problems, that is your job.
Culture Change. Consider this fact: things will be different after implementation. How you approached crimp quality before will change. This is a whole company effort not just the domain of a few quality people. Workers on the plant floor will need to be trained. Attitudes will need to change. Consistency is king. No more adapting to make it work, CFM’s require consistency in order to separate process noise (external variables) with the consistent factors and you need to work to eliminate those variables.
No Crimp Set up is identical. Treating all crimp application as equal will lead to problems. Wire/Terminal match, crimp tool shape and condition are variables that differ from application to application. Some are naturally more sensitive than others.
Understanding the five elements of a crimp. A typical terminal crimp is comprised of five elements: Wire, Terminal, Operator, Applicator and Crimp Press. The match between the wire and terminal is critical. Mismatched terminals and wire can cause piece to piece variation due to the movement of the wire in the terminal during the crimp process. Crimp presses that are not maintained with loose ram movement and worn ram adapters/base plates is also a source of piece to piece variation.
Constantly improving the process. Identifying problem applications and prioritizing them for process improvement is important. Employing analysis tools can help to uncover core issues that cause inconsistencies. Cross Section Analysis is an essential part of quality improvement efforts. Headroom Analysis identifies the sensitivity of the crimp process based on the force to crimp the terminal with and without the wire. The C&S CFM-Lite includes built in Headroom Analysis.
Creating a repeatable validation process. Validating your crimp process is a critical step. Considerations:
The right terminal and wire for the circuits being produced.
The right applicator tooling and just as important, well maintained and production ready tooling.
A Crimp Press that provides repeatable shut height and crimp force. Maintained and free of debris.
Calibrated Measuring Tools including:
Crimp Height Micrometers (Conductor Crimp Height)
Blade Micrometers (Conductor Width and Insulation Height and Width).
Quality Parameters. Who makes the decisions? Crimp Monitors use tolerances which are applied around a teach-in value (average of test pieces measured prior to production). These tolerances can be adjusted to suit each crimp application. Which can make the measurement of crimp force more or less sensitive. Access to the tolerance setting can be open or restricted.
When tolerance setting is left open, there is a risk of un-trained workers making adjustments that can allow for defective crimps to pass undetected. This can create a behavior we call the CFM Cycle.
Avoid the CFM Cycle. Restrict access to the tolerance setting to trained personnel. Address problem applications with analysis tools such as Headroom and Cross Section.
Summary. Creating an implementation process at the start prevents problems on the factory floor and with Crimp Quality.
A wire harness has a few basic qualities, critical to performance and longevity of the device it is installed into. Low electrical resistance through the harness reduces heat and improves overall electrical performance. But as important is the ease of installation and the effect installation may have on electrical performance.
As we consider the critical elements of wire harness assembly and in particular the wire to terminal crimp process, a number of variables can make or break the performance of the most important aspect of a wire harness. Bend Angle is one of those variables which is receiving more scrutiny as we work to improve overall wire harness quality.
So what is Bend Angle?
Bend Angle is the condition caused by the crimping of the terminal. The pressure on the terminal from the press (and crimp applicator) causes the terminal to extrude outward. Extrusion is a natural occurrence of material (wire and terminal) being formed under pressure. The terminal actually can lengthen slightly during the crimp process. But excessive pressure can also cause the terminal to bend upward, in the shape of a banana. The banana shape is a measured attribute which is called Bend Angle.
So why is Bend Angle critical to the wire harness? It is important for two primary reasons.
First in the fit and function of terminals loaded into a multi-wire connector. When terminals are not straight, there can be mis-alignment between the pin and receptacle. On it’s own, one matching terminal pair can be harder to mate when the terminals are fixed in a housing. Consider the compounding effect of inserting multiple (unmatched) mating pairs in a housing. This can cause installation issues for the customer who is installing the wire harness.
Second is the potential of high electrical resistance at the mating point between the two terminals. We work to reduce electrical resistance of the terminal crimp by the proper crimp and crimp tool design along with a wire range rated for the crimp. Even with close attention to the proper wire/terminal match and recommended crimp height, high resistance can occur at the mating point.
It should be noted that bend angle is not as a factor with terminals that are not encased in a connector. More ‘forgiveness” in installing terminals that are not forced to mate in a confined space.
Reducing Bend Angle.
As mentioned extrusion during the crimp process is normal and some bend angle can occur. But ultimately reducing bend angle is important. Let’s consider some of the factors that can cause bend angle.
Crimp Height Too Low.
Worn Crimp Tools.
The Wrong Crimp Tools.
The Wrong wire size for the terminal.
Not only can these issues cause bend angle, they can also affect the electrical performance of the crimp.
Measuring Bend Angle and Parallelism.
There are actually two possible measurements: Bend Angle and Parallelism.
Bend Angle is measured from the top surface of the conductor crimp to the terminal body. Bend Angle can be measured from the top and side as pictured.
Bend Angle Side View
Bend Angle Top View.
Parallelism is a “go/no go” measurement. Parallelism ensures all points are within a tolerance window in relation to a datum point. In the case of a terminal, measuring parallelism of both the insulation and wire crimp is possible. The datum line is placed on the conductor body and a set of parallel lines are placed on the wire and insulation crimps. The wire and insulation crimp must be enclosed within the parallel lines.
Bend Angle and Parallelism dimensions are established by the terminal supplier. And by the customer when supplier dimensions are not available
Bend Angle is an emerging issue which is expected to be introduced into crimp standards such as USCAR-21. Regardless the existence of a mandated standard of not, the condition exists for multi pin/receptacle connectors. If high connector insertion or electrical resistance are an issue, perhaps evaluating bend angle is a variable that could be checked.
Need to measure Bend Angle? We are prepared to help. Whether in house capability or ad hoc requirements, we can supply your own solution or provide this as a service through Crimp Quality Solutions. Connect Your Way to WPS to find out more.
Pull Testing, measuring the Tensile Test of a wire to terminal crimp has been a measurement of quality since the advent of pressing a wire to a terminal for electrical assembly.
Pull Test Methods have varied from weights, fish scales, portable and benchtop manual and motorized digital. I have even heard stories of an acceptable pull test being performed by pulling the terminal by the teeth. A dentist’s nightmare.
Given today’s demands for higher reliability and failure rate approaching zero, how does the Pull Test process fit in with the other testing methods being deployed? Are you even performing pull tests properly? This article will answer these questions and more as we put Pull Testing Into Perspective.
Pull Testing Defined.
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.
Considering a cross section of quality standards, typical process parameters for pull test include:
Disengaging the insulation support so the pull force reading is based on the wire crimp alone.
Pull at a constant rate of 50 to 250mm/minute.
Wire should be taut prior to applying pull force. Remove slack from the wire.
But Pull Test is not the whole picture.
Pull testing is not a measurement of electrical performance. A quality crimp includes a secure mechanical crimp with low electrical resistance. Low electrical resistance comes from a crimp with a wire under compression. Terminal suppliers validate crimps by optimizing the crimp barrel size to match the wire. Crimp tool profile is also a critical factor. Using the proper crimp tool profile, the wire and terminal are compressed together. Pull and electrical resistance reading are made and the recommended conductor crimp height is established and published. It is the responsibility of the end user to follow the crimp guidelines in order to assure an optimum performing crimp. Which includes conductor crimp height as a primary measurement with mechanical pull test as a secondary standard.
A few facts to consider:
Pull test and electrical resistance measurements rarely follow in tandem. Typically pull strength peaks before electrical resistance. Therefore it is possible to meet a minimal pull test while not optimizing electrical resistance. There will always be a compromise between Electrical Resistance and Pull Test.
Pay careful attention to how the wire separated from the terminal. This is an indication of the wire compression. Strands completely broken at the wire crimp indicate over compression. Conversely strands which completely pull out of the wire crimp still in a round shape indicate severe under-compression. Crimps with good compression should primarily break outside of the wire crimp.
Depending on Mechanical Strength as your primary crimp quality measurement leaves you open for premature crimp failure. And the consequences can be wide ranging. Even a single failure can be costly. Large scale recalls (not uncommon today) can cripple even a large company.
Assumptions may be a tool used in financial forecasting in absence of actual facts but is hardly a good practice to apply to actions around product quality.
This is the conclusion of our series on Objective Evidence as it applies to the terminal crimp process.
Objective Evidence is an important concept to ensure actions from decisions are causing positive results. To review from part one:
Objective Evidence defined: “Information based on facts that can be proved through analysis, observation and other such means of research.” Source: BusinessDictionary.com.
In this article we explore the production and process monitoring of the terminal crimp process. Ensuring the pre-production validation process continues into production and controls that are in place, effectively reduce the chances of non-conforming assemblies leaving the production facility.
Assuming everything is working simply because you implemented a new monitoring process can lead to unacceptable outcomes. From material rework locally and goods returned from a customer to product recalls. Non conforming (or poorly performing) materials that are introduced into the supply stream can be costly, in monetary and non-monetary ways.
The ability to effectively monitor crimping using a Crimp Monitor (CFM) is affected by a number of factors. The terminal/wire match is one factor, considering Headroom which can influence the sensitivity of crimp monitoring. Equipment condition is another.
Duplicate an crimp error like strands missing. Determine if the threshold of the crimp defect detection is acceptable based on your requirements.
Strand Missing from Crimp
Crimp Monitors provide real time monitoring of the crimp process and as stated above the sensitivity of the monitoring process is affected by each element of the crimp process. The wrong tolerance setting whether set too high intentionally or by mistake increases the risk of introducing non-conforming crimps into your product.
Visual and Physical Measurements.
Take a batch of processed wires and fan them out. Check wire position in the crimp to ensure insulation is not in the wire crimp, the bell mouth and brush positions are correct. Measure wire crimp height and pull test and confirm they meet the manufacturer’s specs.
Crimp Height and Pull Test
Operator Bias: Removing Subjectivity from the Crimp Process.
Let’s face it. After a long period of time, operators and set up people can form their own bias towards quality. Left unchecked, this bias can be a problem in improving process quality. And be a process variation itself.
Lock down the validation and monitoring process. Connect your bench and automated crimp machines into a network. Process parameters do not change over time and should be stored in a central database. Create a process where validation of process parameters is required before machines are released for production. Then monitor the process to ensure ongoing conformity to the validated process parameters.
C&S MPN-100 Network
The stakes are never higher than they are today. Exposure to liability from non-conforming products can be reduced by following a repeatable process.
Crimp Quality Solutions is end to end support for the terminal crimp process. Connect with WPS to get started.
Companies make countless decisions each and every day. Micro decisions affecting short term operations and macro decisions affecting the company’s big picture over the long term. Whether micro or macro, good business decisions are made using factual information. And those decisions are generally based on objective analysis and free of subjective influence.
In this series, we are going to uncover questions which can be used in an assessment of a quality system for terminal crimping.
Objective evidence is a term which applies to a wide range of situations and are a basis for an effective decision. The audit process irregardless of what is being audited use objective evidence.
Objective Evidence defined: “Information based on facts that can be proved through analysis, observation and other such means of research.” Source: BusinessDictionary.com.
Part one will deal with questions surrounding the validation and pre-production process. Part two will cover the production and process monitoring. Here are some questions to consider.
Are the right materials picked and introduced into production?
Surprisingly, the introduction of the wrong materials into the production stream is a cause of defects and rework. Hopefully caught before leaving the facility, a major issue if caught by the customer. Is your system set up to eliminate the possibility of employee error when picking materials for production?
Applicator Set Up.
Has the applicator been prepared for production?
Was the applicator inspected after the last production run?
Are the tooling capable of producing crimps that meet quality specifications?
Applicator installation is a variable in production set up.
The recipe or defined measurements for crimp validation include wire crimp height, crimp width, pull test and visual factors. Pull test alone exposes you to the potential of crimps with high electrical resistance. Wire Crimp Height is the primary method terminal suppliers specify to measure crimp quality.
Remember it is not enough to ask good questions. Acting on the answers to those questions are critical in managing a system of people, processing equipment and process monitoring tools.
Part two will focus on questions to ask during processing.
A wire termination is a very simple process: take a wire and terminal, force them together using a range of crimping tools and voila, a crimped wire.
A quality crimp is altogether different. Not so much in the crimp process, it is is somewhat the same. But ensuring the wire performs well over the life of the product and the process to assemble that wire with repeatable quality requires specialized knowledge. And application of that knowledge to the crimp process. This is very critical in electrical assembly today with the cost of failure (rejects, re-work, loss of customer confidence, liability) being so high. Which is precisely why we publish this technical blog: to arm you with the knowledge and processing tools needed.
In this post, we are going to move “upstream” and consider the effect of the wire itself to the crimp process. Considering the elements of the wire and the effect on process variation. Also the process (cut and strip) to prepare the wire for crimping.
Reviewing and controlling all factors in the crimp process makes for more consistent results. And a level higher sensitivity to allow for a CFM to pick up small differences in the crimp process.
It all starts with quality wire. Consistent and repeatable material is critical to consistent crimp quality. And by extension, the ability of a crimp monitor to detect other defects related to the wire to terminal crimp process. Lot by lot and supplier to supplier consistency is important. Some of the factors in process variation:
Dimensions and Material.
Insulation dimensions and material.
Wire Concentricity. Concentric wire allows for closer stripping of the insulation and ultimately better strip quality. Non-Concentric wire means the strip blades must be positioned farther away from the wire stranding to ensure the wire is not contacted by the blades, causing nicks and scrapes to the strands. Plus strip quality if affected.
It continues with consistent processing methods. Wire Cut and Strip methods contribute to crimp quality in a positive or negative manner. Today’s technology motorized processing machines handle wire in a precision far better than previous generation machines. But they are far from infallible. In addition no matter how precise they are, external forces can introduce process variation that can affect the crimp process. Here are primary variables in wire cut and strip processing:
Strip Length. Length variation can be random or consistently high or low. Random strip length variation can be affected by the back pressure from the wire source. Consistently high or low strip lengths are typically programming errors from the process setup. Strip length variation can come from the processing equipment itself but is more of a rare condition than the conditions mentioned above.
Strip length variation whether random or consistent directly affects crimp quality. The conditions are the same whether an operator presents the wire to a “wire stop” in the terminal applicator or a swing arm on an automatic cutter presents the wire to the applicator. A strip length that is too short presents a high insulation condition where insulation is embedded in the wire crimp. Low insulation means the insulation is partly or completely out of the insulation barrel.
Example of Normal Crimp Curve
Example of Crimp with High Insulation
Strip Quality. A few conditions can affect strip quality:
Wire Concentricity. See above.
Blade Type or condition. Dull blades can cause residual insulation to enter the wire crimp. Universal V blades are good for most applications. But in some cases, no matter how much the blade setup is tweaked, the strip quality is not good. This could be due to the wire type. An alternate blade profile might be a better option. Such as a radius V style which cuts around the full periphery of the insulation.
Dirty Wire. This condition does not show up in a visual condition or as an error condition with a crimp monitor. It can affect the electrical properties of the wire. High electrical resistance is possible where contamination is severe. Contamination can be oxidation from wire that has been stored for a long time. In addition, residual oils or chemicals used in the wire production can be present.
Awareness of processing variables is critical. Applying this knowledge is even more critical. Employee training is important and could be considered one of your last lines of defense in detecting crimp defects. Good validation and monitoring tools are invaluable to assist in process control and improvement. Especially when your production depends on automation systems with high production rates. A lot of wires can be produced that are not possible to detect fast enough by a human.
Automate your setup validation to improve production efficiency and reduce the chance of setup error from the wrong information.
Crimp Quality Solutions is your end to end support for the terminal crimp process. We have the tools in your drive to take your crimp process to the next level. Do you have Crimp Monitors installed but do not use them? You are in the CFM Cycle. Crimp Performance Optimization is our solution to reactivate the crimp monitors to monitor your crimp process. Connect with WPS.
A terminal crimp as simple as it appears, involves several inputs. Wire, terminal, crimp tooling, the crimp press and operator (bench) or automated machine are all factors which can directly affect crimp quality and ultimately the performance and longevity of the product the wiring is installed in.
Headroom analysis is a valuable indicator of Crimp Sensitivity. Headroom isolates the wire and terminal and the match between the two.
Headroom is the difference in peak force between crimping the terminal with and without the wire. Headroom is typically expressed as a percentage. For example headroom of 85% means the wire represents 15% of the total peak force of the wire and terminal. The higher the headroom percentage, the more sensitive the crimp is for detecting small defects such as strands missing in the crimp. Conversely, the lower the percentage of headroom, the less sensitive the crimp process is.
What Can affect Headroom?
The terminal crimp size in relationship to the wire size is the main factor in overall headroom. If the majority of force is used to form the terminal only, then there is very little margin to add the force of the wire.
It is important to note that a wire of the same gauge but different strand count/strand thickness measure similar area. So headroom percentages are similar. But the strand count and individual strand thickness can affect the amount of strands a Crimp Monitor (CFM) can detect that are missing from the crimp. Here a few examples of headroom with different wire sizes and strand counts.
Crimp with Wire
Crimp without Wire
7 Strand Wire: Average Peak Force (wire and terminal) is 6.78 (kn). Average Peak Force (Terminal Only) is 3.82 (kn). Headroom is: 6.78 – 3.82/6.78 = 43.7%.
Each Strand represents 6.24% of the wire portion of the crimp. Using a +,- 3% CFM tolerance, this means the CFM can detect one or more strands missing.
19 Strand Wire: Average Peak Force (wire and terminal) is 10.9 (kn). Average Peak Force (Terminal Only) is 7.36 (kn). Headroom is: 10.9 – 7.36/10.9 = 32.5%.
Each Strand represents 1.71% of the wire portion of the crimp. Using a +,- 3% CFM tolerance, this means the CFM can detect two or more strands missing.
26 Strand Wire: Average Peak Force (wire and terminal) is 4.52 (kn). Average Peak Force (Terminal Only) is 2.70 (kn). Headroom is: 4.52 – 2.7/4.52 = 40.3%.
Each Strand represents 1.55% of the wire portion of the crimp. Using a +,- 3% CFM tolerance, this means the CFM can detect three or more strands missing. And randomly detect two strands.
These are three examples of headroom calculations. Each application will be different depending on the terminal crimp profile and wire.
It should be noted that the ability of a CFM to detect small variations is greatly affected by the capability of each input in the crimp process. What may appear to be a “false reading” on a CFM is actually variation observed by the CFM compared to the reference samples. For example, Press Shut Height or Crimp Force can cause variation when all other inputs are in control. So in some cases, it may not be possible to reduce the CFM tolerance to a lower percentage due to variation in one or more process inputs.
The terminal design can affect headroom. The overall crimp profile is affected by the end use of the terminal. In some cases the terminal may require a thicker base material and that can translate into more material mass being crimped. Making headroom less sensitive.
Headroom is one tool used to Optimize Crimp Performance. The CFM-Lite CFM for Bench Presses is from C&S Technologies. This is a powerful tool for not only monitoring the crimp process but helping to troubleshoot crimp applications. Headroom analysis is a part of the CFM-Lite platform.
Crimp Performance Optimization is part of Crimp Quality Solutions, end to end support for the terminal crimp process. For more information on how we can support your crimp process or the CFM-Lite, Connect Your Way to WPS.