Inteva’s Closing Systems has a strong tradition in the design and manufacture of latching systems and door systems. Continuing just-auto interviews with leading door system manufacturers, Matthew Beecham talked with William Hanna, vice president and executive director of Inteva Products’ Closure Systems business about trends in car door design and build.

just-auto: As more and more electromechanically-performed car functions – such as power windows, electric windows and door locks - are transferred into the electronic module, in what ways has this trend affected your door module designs? 

William Hanna: The great thing about door modules is that they are flexible enough to accommodate most elements as long as the design goal is clear during the early stages of the development process.  If a customer prefers an ECM in their door, the door module is designed in such a manner to accommodate its packaging.  If the door module is constructed mostly in composite materials, opportunities would be examined to integrate ECM features into the door module carrier, eliminating fasteners and reducing cost and variation in the system.  Our motors can be developed to include higher levels of electronics to accommodate any electronic requirements associated with raising and lowering windows, such as express up/down and anti-pinch features. 

However, one of the largest impacts electronics has had on door module design is in the manner in which we “protect” those electronics from the environment. The environment inside a door is harsh. Components are exposed to extreme heat, dust, salt, water, air currents, etc. The key to effective door module design is giving consideration to protecting those electronics from potentially destructive elements.  This is one of the reasons that led to the development of the wet/dry side door module, a door module that seals to the door sheet metal thereby providing a perfectly dry side on which environment sensitive components can be packaged.  The wet/dry side door module is the most prevalent in the industry today.

As we understand it, there are basically two different architectures for an electric door system: centralised and decentralised. A centralised system normally has one centre module that controls and drives every load in all doors. Meanwhile, the decentralised system has multiple ECUs for different door functions. What trends do you see in respect of the decisions to use centralised and decentralised architectures and how does that affect the way in which you package and build door modules? 

The trends vary dependant on the customer and region. From a door module perspective it is simply a matter of providing packaging space in the wet or dry side of the door. The real technologies reside in the electromechanical components that react to the power and signal distribution. There are advantages and disadvantaged to any electrical architecture but Inteva is building a technical base to accommodate whatever is defined by OEMs across the globe.

To what extent are composite materials – including natural materials - being used (or could be used) in doors? 

Composite materials are being used extensively inside of doors, and have been for many years.  In the mid-1990s Inteva introduced a groundbreaking development and implementation of the SuperPlug, a plastic door module that eliminated 60 components from within the door. The SuperPlug module is currently considered a top product and will be inducted into the Hall of Fame this year by the Society of Plastics Engineering for its contributions to composite material utilisation in doors.

Inteva also experiments with different recycled materials to create new developments. Composite material products and processes dominate a door’s Bill of Materials in today’s vehicles since technological advancements in composite materials offer structurally sound and energy absorbing alternatives to traditional steel components. 

With an increased emphasis on improved emissions, mass reduction, and cost savings, composite materials offer OEMs the ability to meet their objectives.  Composite materials are enablers for improved quality as many features and components can now be integrated in ways that are impossible using traditional metal components, thereby reducing system variation and improving overall performance of your door’s subsystems.

Natural materials have their place in the market as well, although at the moment are not as typical or popular as composite materials.  Natural materials such as wood fibre can be incorporated into trim products but usually are not structurally sound enough to be used in door module applications.

Over the past few years, there have been many arguments ‘for’ and ‘against’ the use of plastic over steel carriers.  Where are we now in terms of the steel versus plastic carrier debate?  How do you see the prospects for fitment of plastic carriers? 

When the SuperPlug, was introduced, there were OEMs who could not imagine plastic as a replacement for steel. Today, plastic door modules are commonplace because of the advances made in plastic material formulations, technological advances in manufacturing processes of plastic materials, in the design standards developed for designing in plastic, and for the analytical tools developed to assist the engineering community and developing components in plastic. 

At Inteva, our thought process begins with plastic as the mainstream design intent. This is because of plastic’s numerous advantages vs. steel. Advantages include:

  • Mass savings
  • Integration of components
     - Reduced parts (inventory)
     - Reduced freight costs
     - Reduced system variation
     - Reduced component cost
     - Reduced tooling cost
     - Reduced number of fasteners
  • Increased value add of the carrier plate
     - Can now be used as an integral component of the interior theme of a vehicle as it can also provide a class A surface
  • Less reliance on grease and other lubricants
  • Easier serviceability
  • Improved sound quality. 

There must be a fine balance between providing a door which improves side-crash safety yet reduces overall vehicle weight.  Could you provide an example of how Inteva has contributed toward both? 

Inteva has offered many different technologies that have contributed to improving side-crash safety while reducing overall vehicle weight.  The SuperPlug was an all composite door module that utilised a gas assist injection moulding process allowing for the carrier plate to be designed with hollow, yet structural tubes that had designed-in-stress points to manage energy absorption and a more controlled breakage event.  The hybrid door module, introduced by Inteva in the early 2000’s on a commercial truck application, utilised a simple constant section roll-formed steel beam with over-moulded plastic features.  The beam provided the required structure strength while the plastic over-mould provided the advantages of moulding in brackets, eliminating fasteners, and reducing overall weight. 

Advances in material formulation of composite materials have offered increased structural integrity of plastic parts without sacrificing mass.  Design standards have been developed to the point where ribs and fillets can be strategically placed to increase strength performance.  Plastic can also be easily moulded around structural components to offer increased side impact countermeasures.  Finally, energy absorption features can be designed into plastic components to improve crashworthiness of a vehicle’s door.

Inteva has built unique technical capabilities in polymer and composite development. One of the company’s latest developments is extrusion compression moulding with in-line compounding. Inteva is currently applying this technique to cross car beam components and is testing the development for other parts. The technology allows selective control fibre of placement which tailors the product to the structural needs of the application. The process allows for transition from thin to thick sections with accurate dimensional control and can even insert mould steel members if necessary. This new technology offers tremendous performance and flexibility.