A new digital approach to leather cutting is establishing greater levels of equipment reliability and material throughput making it a more viable option for the volume production of car interior elements
Normally any visible blemish on an automotive component is a reason for instant rejection. But there is one circumstance in which that is not always the case and in which scratches, for example, may simply be cut out and other visual irregularities even treated as indicators of product authenticity. The material in question is leather, used for all aspects of car interiors. Nevertheless some blemishes will be too blatant and will have to be removed which, given both the cost of leather and the fact that in such a natural material their distribution will be random, poses a genuine technical challenge in ensuring maximum material utilisation.
Digital approach now a viable optionFrench company Lectra, based just outside Bordeaux has developed the equipment to meet this challenge, and as senior vice-president automotive sales Javier Garcia observes, the level of technology that the company provides has undergone a step change in the last five years. Since the company introduced its Versalis digital leather cutting system, Garcia says it has established levels of equipment reliability, uptime, material throughput rates and utilisation that make a digital approach a viable option for the volume production of leather car interior elements.
The essential capability of the system is in recognising the areas of an individual hide that need to be removed and then programming itself to do that using a blade system that is manoeuvred above the hide in a mobile gantry. The point, though, is that the system achieves performance levels significantly greater than its previous generation digital counterpart. Garcia says, for instance, that it can sustain a 98% level of total possible uptime and at least a 25% increase in productivity.
The alternative to this approach is to cut the imperfections out of a hide by physically placing small, sharp-edged dies over localised areas of the hide and then pushing them through the material by applying a force to them from above by some sort of press – an industrial version of a manual cookie-cutter. In fact, says Garcia, that sort of methodology is still the one that is predominantly employed throughout the global automotive industry. He estimates that probably 90% by volume of the leather used in cars worldwide is still produced this way.
For the most part actual leather cutting is not an OEM activity but one carried out at either Tier 1 level by vehicle interior system suppliers or at Tier 2 level by leather material suppliers.
For the most part actual leather cutting is not an OEM activity but one carried out by suppliers of interior or materials
OEM adopts cutting technologyNevertheless one OEM that has adopted digital technology from Lectra as both a prototype design and manufacturing tool is Volvo Cars in Sweden. Johanna Bergström, who leads the in-house team responsible for upholstery design, confirms the details. She says that Volvo started to evaluate the technology in 2007 and after approval for purchase was granted later that year moved over to the use of digital techniques in the area in 2008. As such it is now using Lectra's Design Concept and Diamino 'marker-making' systems – the latter being a 'what-if' system to evaluate cutting strategies before they are implemented in order to maximise material utilisation – as well as physical cutting systems with the latter confined for the moment at least to prototyping work.
The essential technical capability that the Volvo team derives from its use of the various systems, says Bergström, is that it can take 3D information gathered from further upstream in the company and then easily and quickly turn it in “2D patterns”. In more general terms, she continues, this means that the Lectra kit is fed with the “design proposal” – the seat geometry and proposed material – and can generate an output that comprises a number of important items of knowledge. On the latter count she cites as examples “print visibility, material usage and cutting efficiency”. Those items of information, she continues are then put together with further data concerning the material itself and manufacturing procedures – she mentions purchasing cost per metre, labour rates and mark-up rates for instance – to generate the complete body of figures that can then be input to the “cost calculation sheet” so that the team can then, as she simply puts it, “find out the cost of it.”
According to Bergström this means that company can generate key business benefits for itself before a supplier is even sourced. That capability derives in part, she confirms, from the fact that relevant design data such as seat geometries generated in the company's Catia 3D design software can be fed directly into the Lectra systems. Nevertheless the two areas of operation are quite distinct with the procedures carried out with the Lectra system more closely allied with manufacturing than design. “The design department is the part of the organisation that creates the shape of the seat and the engineering department are the ones using the Lectra systems,” she confirms.
Bergström indicates that in terms of calculating material usage the company is now effectively autonomous. “We don't need to go outside and ask suppliers,” she explains. “Instead we can make our own cost-based design choices,” though she stresses that does not necessarily mean the lowest cost option but “the one that is best suited for us at a cost that is affordable.” Moreover those cost projections are extremely reliable. “The security of genuinely knowing costs is very important,” she states. In addition she indicates that the relevant lead-times are now “just a few weeks”, which she observes, “really is quite short” in comparison with the norm for costing procedures. The fundamental factor underpinning all these quantifiable gains, though, is perhaps something that is more intangible even if it is perceptible. “Using these systems has given us the opportunity to understand the main drivers of our material utilisation,” she explains.
But Bergström also makes it plain that a major aspect of Volvo's use of the technology lies in its impact on relations with suppliers. Some of them, she states, are also users of the Lectra technology, though that is not the case in all instances and in any case direct communication of digital data to identical proprietary software systems is not necessary. “There are programs available today that can convert files between different systems,” she states.Ironically one of the ways the technology impacts on supplier relations is to reduce them or more accurately to reduce the need for Volvo to question them to gain information it can now generate in-house. “We don't need to waste the time of our Tier 1 and Tier 2 companies asking them questions,” she says.
As such, says Bergstrom, Volvo is definitely intent on expanding it use of the technology. She identifies two ways in particular. The first is to extend the scope of its application beyond just seating to encompass “whole vehicle interiors”. The second is to exploit further the potential for autonomy the technology offers by bringing the advantages of integrated design, costing and production in-house. “We have looked at the possibility of doing CNC cutting ourselves,” she confirms though she does not suggest any sort of timetable.
Challenges for tier suppliersMeanwhile at the beginning of the automotive supply chain Gruppo Mastrotto has been supplying automotive leather for more than 20 years, according to Dr Alberto Silvagni, automotive general manager. In 2010 the company initiated a new industrial and commercial strategy in order to become a more relevant player in this market. “We are now working with more than 50 OEM and Tier 1 companies in the supply of leather and cut parts for seats, steering wheels covers, interiors accessories like headrest and armrests,” Dr Silvagni confirms. It is, he observes, a highly demanding sector to serve with “quality, flexibility, reliability and international footprint” the key requirements Gruppo Mastrotto has to fulfil.
Though Dr Silvagni cannot identify customers he says that they include “one premium European OEM and a large Japanese OEM and also one steering wheels producer”. He says that the material range involved ranges from split leather, embossed corrected grain to nappa free chrome. “With some of them we are supplying around 20% of their needs,” he adds. “Italy is the main production hub, but we are also supplying automotive customers from Tunisia and Mexico for cut parts and Indonesia for both leather and cut parts.”
As a part of its expansion strategy the company started to adopt digital cutting technology from Lectra in 2014. “Flexibility in answer to customer demand was the first driver and then optimisation of leather utilisation,” Dr Silvagni explains. Nevertheless more is involved than just production efficiency. Indeed Dr Silvagni stresses how the technology facilitates interaction between Gruppo Mastrotto and its OEM and Tier 1 customers in the earliest stages of a contract. “The benefit in front of the customer is reactivity in prototype development and management of engineering change,” he states.
Meanwhile for Gruppo Mastrotto the benefits of this technological transition are “speed in response to design change and reduction of the risk of obsolescence during design change in development as well as in mass production.” As such, states Dr Silvagni, “we are going to proceed, depending to the customer strategy evolution, with priority on digital cutting.”