At the 17th Annual Electrical Wire Processing Technology Expo, Terry Curtis President of WireProcess Specialties presented the seminar “How Do You Inspect Your Crimps?”. This seminar was presented as a teamwork effort between WireProcess and our Global Technology Partner: Crimping and Stamping Technologies.
The seminar was presented to a capacity crowd at the Expo. This speaks into the need for more information on crimp validation techniques. Crimp Quality is a topic we as a company are passionate about.
Terry started the discussion by stating ” it only takes one bad crimp”. It only takes one miss-applied crimp to render a wire harness defective. There are a range of implications from repair of the affected harness to in house sorting of larger batches of harnesses. Certainly the customer relationship can be affected with legal liability a possibilities in severe cases. Can you company afford the risk?
A Quality Crimp: It All Starts Here.
A quality crimp starts with fundamental crimp specs, typically established by the terminal supplier. This includes the physical geometry of the crimp section, visual attributes and measurement standards. An emerging specification (bend angle and parallelism) which affects the mating of connectors was presented.
An excerpt of a comprehensive study into crimp compression as it affects electrical resistance was shared to illustrate the co-relationship between compression and electrical resistance and the effect compression has on mechanical crimp strength (Pull Test).
The take away from this section was the terminal suppliers based on their design and testing of crimp geometry produce a “Recipe” to follow. The end user’s task is to “Follow the Recipe”.
Apply the Recipe.
Pre-Production validation involves taking the “Recipe” and ensuring the specifications are met. Prior to production start. Required measurements, methods and the proper measurement tools were discussed. Visual inspection was also covered as well as a few tips on how to spot a wire under compression in a terminal were uncovered.
The shape of the terminal, measured through Cross Section Analysis shows how the crimp tools form the terminal and the distribution and compression of wire strands. A good indicator of crimp to crimp consistency and a factor in “false CFM readings” (which are not really false at all).
Validation alone is not sufficient to assure the quality will be maintained through the production run. Factors which can affect quality during the production run were discussed. Also stressed was tools which are used in the validation process are also used to measure crimp quality during production.
A Crimp Monitor (CFM) is an essential tool in process monitoring. The CFM provides 100% real time monitoring of crimp force and detection of typical crimp defects.
The CFM Cycle, a topic introduced in our 2016 seminar outlines what can happen when constant alarms from a CFM are not investigated for their cause and CFM tolerances are opened up to stop the CFM alarms.
Applicator and Press Capability and Maintenance.
Applicators and Crimp presses are the two critical processing tools for the crimp process. Maintaining this equipment to ensure they provide statistically repeatable crimp performance.
Ensuring the Applicator crimp tools are within the manufacturer’s specifications is the most critical attributes of an applicator. Also important are feed and cut off system and general wear of the applicator body and feed track.
The press is the common factor and sees more wear and tear than an applicator which is removed after production. Assuring the shut height is calibrated is one factor. But statistically repeatable shut height and crimp force is required to assure consistency during production. Press Analysis is a very important aspect of equipment maintenance.
As illustrated below, a repeatable press (Shut Height and Press Force) equals smaller tolerances with the CFM which means the CFM’s ability to detect smaller defects is increased. The converse is true when a press is not repeatable. This equation also can apply to the Applicator.
A validated crimp indicates the recipe is followed, and production monitoring assures the process stays within the validated tolerances during production. But what about your plant personnel? What happens when all of the materials and processing tools converge for production?
- How can you be assured that the right materials and tooling are used? And what about validation specifications. Are they followed?
- What about material and tooling changes, how do wire and terminal changes as well as applicator maintenance affect the initial validation?
Networked production equipment and measurement is a way to assure the right materials and tooling are deployed. Also measurements attributes are validated and re-validation occurs when process parameters change.
Any quality initiative lives and dies with Management support. Management needs to be actively involved in assuring resources are acquired and deployed, personnel are trained, systems are created and they measure the overall improvement of quality. Cooperation between functional areas (production, quality, set up and maintenance) are ensured.
How Do You Inspect Your Crimps? A fundamental understanding of crimp development and validation techniques is an important first step. Production Monitoring ensures validation specs are maintained through the Production cycle. Using the right tools for both Validation and Monitoring is very critical. Maintaining production equipment is also critical to assure consistent piece to piece results. Networking ties it all together and removes some of the routine decision making from plant floor personnel. Quality Improvement programs live and die with Management support.