Nissan saves costs with plastic hot air staking

By working closely with Phasa Developments of Bishop Stortford, Le Profil was able to demonstrate that a switch to plastic hot air staking assembly would save costs for Nissan

The need to gain a competitive advantage by manufacturing products faster, better and more cost-effectively than ever before is driving companies throughout the manufacturing sector to continuously re-evaluate their working practices.

Nowhere is this more true than in the automotive supply chain, where OEMs are demanding year-on-year cost reductions from vendors, while imposing exacting standards of product quality and in-service reliability.

Such pressures not only challenge conventional methods, but also provide the catalyst for the revision of complete process specifications - providing the benefits can be fully justified! The assembly of windscreen demister vents for Nissan Almera vehicles by automotive plastics specialist, Le Profil, is a case in point.

The units, which are moulded in mating halves, are subject to rigorous quality control procedures, including dimensional checks, joint strength, twisting and leakage tests - all with a zero acceptable failure rate.

Total integrity of the assembly's fixing is vital, as the vents must be able to tolerate extremes of operating temperature - from well below freezing to more than 50C.

In order to meet these criteria, Nissan specified ultrasonic welding as the preferred manufacturing option.

However, by working closely with Phasa Developments of Bishop Stortford, the UK pioneer of plastic hot air staking assembly, Le Profil was able to demonstrate that a switch to this fastening method would not only meet all manufacturing criteria, but also provide increased throughput at substantially lower costs.

Plastic hot air staking uses the principle of directing air at between 150 and 400C on to pre-moulded pegs, ribs or collars - to bring them to their plastic state for re-shaping, clamping and subsequently cooling into new forms.

It is widely employed for the production of simple rivet heads, but is equally suitable for the retention of bearings, securing threaded inserts or pre-loading seals.

Accrington-based Le Profil already had three earlier generation Phasa machines on site when they won the Nissan Almera contract.

According to Production Engineer, Brian Gee: "These provided us with a good idea of the system's capabilities.

However, we wanted to see how far the process had been developed since our previous purchases.

"Phasa's engineers were quick to respond to our requirements and, through their long experience of supplying motor industry customers, were very pro-active in recommending the optimum solution for our needs." "From an early stage in discussions, it became clear that in terms of capital expenditure, hot air staking would be far more cost-effective than ultrasonic welding," Gee continued.

"However, this had to be backed by the ability to produce assemblies that would consistently meet Nissan's stringent quality standards.

"Through a series of demonstrations, backed by pilot batches of production components, Phasa provided the Nissan engineers with all the evidence they needed to amend the process specifications." Further benefits of the Phasa process in comparison with other fastening methods include its ease of operation - enabling the use of semi-skilled labour - as well as its precise control of process parameters, for fast and consistent results.

Indeed, capability studies conducted in conjunction with the Faculty of Engineering at the University of Hertfordshire have demonstrated that hot air staking will regularly produce Cpk values in excess of 2.0, the equivalent of fewer than one reject per million operations.

As a result, two Phasa type 20/40 E machines were specified by Le Profil - for the same cost as a single equivalent ultrasonic welding system! According to Phasa Developments' John Neugebauer, "20/40 machines are an ideal choice for high volume automotive industry applications.

They accommodate products up to 850 mm wide and 300 mm deep and can produce over 50 fixings in a single cycle.

They are also supplied with light guards as standard to provide operators with an open and accessible working area - a feature endorsed through the system's rapid acceptance by Le Profil's workforce." The equipment's ease of access provides rapid and simple loading, while improving visibility for component location and in-process inspection.

The 20/40E also features a heavy duty frame to provide the additional strength required for its larger processing area and the increased force applied by the unit's uprated forming heads.

Interchangeable The two machines at Le Profil incorporate rapidly installed, interchangeable tooling to accommodate both left and right hand drive model variants.

In addition, production flexibility is enhanced by mounting each of the machines on wheeled bases so that they can be moved easily between production lines.

In operation, mating halves of the air vents are located by hand into purpose designed fixtures mounted in the Phasa equipment.

During the automatic cycle, eleven stakes are produced to ensure the high strength, vibration and tamper resistant assemblies required.

A further advantage of the Phasa equipment is its ability to operate satisfactorily using dry, non-lubricated air - a growing trend within industry.

In Le Profil's case, this not only provides a health and safety benefit, but also eliminates the risk of surface contamination to components caused by oil vapour in the atmosphere.

Summing up, Brian Gee concluded: "In order to achieve our production, quality and cost targets, we needed equipment that would work straight away - with minimal commissioning - from the moment it arrived on our shop floor.

With the Phasa machines, that's exactly what we've got.

"Clearly, what used to be a good system ten years ago, has simply got better!".

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