The magazine of Friedhelm Loh Group

The magazine of Friedhelm Loh Group

Plastics for the automotive industry
Experience – Platics

Plastic in the car convinces

Cooperation. The plastics manufacturer LKH supplies a global automotive specialist with locking systems. Its plastic parts are installed in almost all locks. The expansion of deliveries across national borders is taking this collaboration to a whole new level.

Text Meinolf Droege ––– Photography

The door closes. It clicks. The motor hums. The tyres start moving. The car glides along the road, accelerating, overtaking and leaving a smile on the driver’s face. Every driving enthusiast gets the same thrill from speed. Anyone who wants to enjoy their vehicle for the long term has to secure it against break-ins and theft. There’s a reason every journey starts and ends with the door – more specifically, its locking system. There’s only one thing more annoying to a driver than a car that won’t start – and that’s a car that won’t open.

Reliable servant behind the scenes

Locking systems are precise, invisible assemblies that have to serve the user over many years, even in adverse conditions. They are only noticeable when the doors cannot be opened or closed by approaching with a keyless system, by pushing a button on a remote control or with a ­mechanical key. The negative impact such problems have on the car manufacturer as a brand is immense. What does this say to the driver about the quality of the car if problems arise before they’ve even taken a seat.

What the driver usually achieves with the simple push of a button prompts a great deal of effort behind the scenes. Complex systems consisting of mechanical and electrical components and installed in usually very limited space ensure that doors and boot lids can be locked and unlocked reliably in a fraction of a second. Even in the harshest sub-zero temperatures of the Scandinavian winter, after hours exposed to the blazing heat of the southern European summer, or in the extreme humidity of certain Asian regions, car doors need to offer immediate access.

Plastics driving innovation

Plastics play a major role in the ongoing development of locking systems. Integrating many functions into just a few components makes it possible to produce very compact and easily assembled solutions. Lubrication, corrosion and noise issues are easier to keep under control. There is constant desire to keep on reducing weight, particularly in the automotive industry.

As a medium-sized supplier, how has LKH been able to tick all the boxes so far? Thomas Prause, Head of Sales at LKH, attributes this to a combination of skills. “On the one hand, our injection moulding processes can be relied upon to achieve the very low tolerances that are usually required. On the other hand, we have extensive experience with production-integrated, automated 100% inspections, which we also use here.” Flexibility is also a very high priority. “For instance, in the case of one special lock in particular, our expertise in designing and constructing injection moulds produced a solution where three ‘standard tools’ create eight multiples of 14 different parts per shot. Our employees require no more than 30 minutes’ retooling time to switch from one standard part to the next.” This allows LKH to respond quickly and highly efficiently to modified supply requests instead of amassing larger ­storage quantities.


The lock plateacts as a cover and contributes greatly to the lock’s stability, which is why it is usually made out of Pocan.

The lock cover protects the enclosure from external influences. It is screwed onto the lock plate.

The lock enclosure contains all the moving components and the bearing. For optimum rigidity and thermal stability, it is usually made out of the thermoplastic polyoxymethylene. The movable plastic parts produced by LKH include the clips, interior lock levers, switching nuts and drivers.

The panelling of the car door is where the lock sits. It consists of three main components – the lock plate, cover and enclosure.

In order to reliably meet customers’ tolerance specifications, LKH developed an indirectly operating, integrated test device, which measures weight rather than ­geometric values such as length, width or sink marks. For example, the interior lock lever, weighing only five grams, is manufactured out of 30% glass-fibre-reinforced polybutylene terephthalate using the eight-in-one injection moulding tool. A robot takes each batch of eight parts from the tool and places them all on the conveyor belt of a precision scale, which checks the overall weight against the setpoint and the pre-set tolerance limits of just ±0.3 grams for all eight parts combined. Weight that deviates from these values is an indicator that process parameters were not adhered to or that there are problems with the materials, resulting in potentially faulty components. In this case, the conveyor belt drops the parts into a reject bin. If the scale registers several of these “faulty shots”, production is interrupted. At the same time, the scale counts the parts and ensures that all packaging units contain exactly the right quantity. To achieve redundancy and thus even greater reliability, production is carried out on two systems with identical injection moulding and testing technology.

Moreover, many of LKH’s injection moulding tools contain state-of-the-art temperature and pressure sensors that will flag up any deviation from the process parameters in any one of the moulds known in the industry as the “nest”. Trends in the recorded values inform the staff well in advance of any maintenance work that will be required. And should a rogue shot occur out of the blue, the parts in question are immediately removed automatically.

Flexibility right up to the loading ramp

However, security and flexibility don’t end with the products and production. LKH delivers quality-assured parts directly to some sites, without overstocking. The company’s own consignment stocks enable it to supply products to several continents – reliably and on time.

Despite numerous international assembly locations and opportunities for worldwide sourcing, more and more customers are turning to LKH as their supplier – but this is nowhere near as surprising as it might seem. LKH is clearly extremely adept at meeting customers’ high expectations in terms of the quality of both products and delivery. This ultimately ensures that all kinds of motorists, driving anything from premium cars to vans, benefit from high-quality locking systems that do their job reliably and conveniently behind the scenes for a vehicle’s entire life cycle – however adverse the conditions.

One question remains to be answered: Why does LKH use different colours for certain components? It’s not as if they will be visible later on. LKH’s expertise and attention to process quality can even be seen in small details such as these. This little trick prevents mistakes during the later assembly stages of the lock, as the components are then immediately visible.

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