Archive for April 2018

Upstream Quality Factors: Wire

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.

We have covered a number of topics directly related to crimp quality. Such as Headroom, wire to crimp process sensitivity. Also Crimp Tool Setup Variability. Using tools such as Crimp Cross Section Analysis and Crimp Monitors to validate and monitor crimp quality.

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:

  • Wire Stranding
    • Dimensions and Material.
    • Wire Twist.
    • Strand Count.
  • 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.

Non-Concentric Wire

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.