There’s an ongoing push toward lighter, smaller, thinner and more environmentally friendly wire and cable insulation in the auto industry. This affects cutting, stripping, crimping and other wire processing applications.

There’s an ongoing push toward lighter, smaller, thinner and more environmentally friendly wire and cable insulation in the auto industry. ASSEMBLY Magazine recently asked Gustavo Garcia-Cota, crimping product manager at Schleuniger Inc., to discuss how insulation affects stripping, cutting, crimping and other wire processing applications.

ASSEMBLY: How has wiring insulation changed in the past 5-10 years?

Garcia-Cota: I've seen a definite change toward thinner and more resistant insulation. While the insulation gets thinner, it also needs to be more resistant to heat and abrasion due to less material protecting the copper. This trend is driven by the need to save weight and space for better gas mileage; aggressive price reduction policies by automotive OEMs; the need to accommodate more data; power-thirsty devices; and more safety devices.

I've also seen an unfortunate change toward a worse quality cable in terms of tolerances and concentric dimensions. I see this problem arising from increasing pressure to buy cheaper wire, due to increasing copper cost.

ASSEMBLY: What are the latest trends in wire and cable insulation?

Garcia-Cota: There’s a trend in the direction of thinner walls and stronger materials, in addition to insulation that produces less contaminants when burned. Also, more compounds are being use with the purpose of retarding flame and combustion. This is especially important in safety-sensitive equipment like marine applications.

ASSEMBLY: What types of new materials are being used for insulation today?

Garcia-Cota: Cross-linked polyethylene insulation continues to be widely used in automotive applications. Also, polytetrafluoroethylene (PFTE) insulated wire provides resistance to very high temperatures and abrasion. It can be used in under-the-hood applications, such as engine valve covers. Ultra-thin polyvinylchloride is also increasing in use, in addition to halogen-free materials that provide better protection using less contaminants.

ASSEMBLY: Do these new types of materials present any wire processing challenges?

Garcia-Cota: These materials present mostly problems in cutting, stripping, feeding, marking and correctly positioning at the crimping applicator in automatic applications.

Feeding and Cutting-On smaller wire and less flexible insulation, most of the wire memory comes from the insulation. This is difficult to straighten, even using two sets of wire straighteners. If the wire comes in reels, it becomes even worse, making it difficult to feed, position and cut.

Stripping-Since the materials are getting thinner, there is less material for the blades to grab on the slug and separate from the wire. The way-back function and special radius blades help in solving this issue but it does add some process time and set up time to use the correct radius blades for the correct wire. Also, because of lower quality cable with larger tolerances, the insulation is less uniform. The blades need to get closer to the strands, which creates a higher potential to cut or damage the strands.

Marking-The use of PFTE and other Teflon insulations makes it very difficult to mark wires in a high-speed process. Ink jet does not provide enough adhesion. Hot stamp is slow, not very controllable and not suited for automatic legend transfer to the machine. Laser is still too expensive, slow and does not provide enough contrast for some colors.

Crimping-Higher scrap rates are produced, because the wire memory with this type of insulation is more difficult to position correctly and uniformly over the terminal. Crimp force monitors also detect positioning problems.

ASSEMBLY: Does smaller wire present big insulation challenges?

Garcia-Cota: There can be problems marking and identifying cable. It’s difficult to do it with ink jet, because the [markings] are too big for such small wire OD. Several harness manufacturing problems occur with this very small wire as well. For instance, it is very difficult for wire harness assemblers to identify the color coding on the wire. Also, at the time of inserting the wire in the connector, the smaller pitch in the connector and the flimsy wire makes it very difficult for the operator. This affects productivity, quality and cost.

ASSEMBLY: What future wiring trends may affect insulation?

Garcia-Cota: I believe we’ll continue to see a need for smaller copper content, higher data and communication, lower weight and higher voltage, which will continue to drive development of new insulation types.