(from Lexus Press Release) LFA NÜRBURGRING PACKAGE
In celebration of the LFA’s third, class-winning outing at the 2010 Nürburgring 24h race, Lexus has created the Nürburgring package for those customers who prefer their car to be a little more track-focused.
Limited to just 50 units within the total vehicle production run, the Nürburgring package is planned for the second year of LFA production, in 2012.
To improve track driving even further, the aerodynamic performance of the LFA with the Nürburgring package will be modified through revisions and additions to several key carbon fibre reinforced plastic components. Combining to offer improved high speed downforce, these modifications include a larger front spoiler, fin-type side spoilers, canard fin, and a fixed rear wing.
Maximum power will be boosted by 10PS to over 570PS. This will ensure that the LFA maintains its acceleration time of 0-100km/h in just 3.7 seconds and a 325km/h maximum speed, despite the additional drag created by increased downforce. The gear shift time will be 0.15 seconds.
In terms of handling modifications, the Nürburgring package LFA will include a sports tuned suspension, a vehicle height reduction of 10mm, exclusive mesh-type wheels and dedicated, high-grip tyres.
Available only in Matte Black, Black, White or Orange, the Nürburgring package—equipped LFA’s exterior will be complimented by a choice of three interior colour schemes —Black and Red, Black and Purple, and all Black. All feature a carbon fibre centre console and door trims, whilst the carbon fibre bucket seats will be trimmed in Alcantara*.
LFA customers specifying the Nürburgring package will be offered individual instruction on the Nordschleife by one of the Nürburgring chief instructors, and will also receive a one year pass for Nordschleife driving.
CARBON FIBRE REINFORCED PLASTIC (CFRP) PARTS MANUFACTURING
With a total of 175 employees involved in Carbon Fibre Reinforced Plastic parts manufacturing, vehicle assembly and painting, the ultra-high performance LFA will be produced at the rate of just one unit per day.
Combining exceptional strength and rigidity with significant reductions in weight, Carbon Fibre Reinforced Plastic (CFRP) accounts for some 65% of the LFA’s body structure weight. This represents a weight reduction of approximately 100kg, over an all-aluminium structure.
With a strong focus on future development, Lexus is producing and assembling CFRP components in-house. Compared to steel or aluminium, CFRP production is time consuming, and the LFA project serves as an important research test-bed for the development of new, automated CFRP production processes which will be used in the manufacture of future Toyota and Lexus products.
Based on the shape, role and required properties of each component, three different CFRP composite technology manufacturing processes have been adopted:
• Pre-preg – an industry-standard composite sheet material made of carbon fibre pre-impregnated with epoxy resin
• Resin Transfer Moulding (RTM) – dry sheet fabrication with epoxy resin injected into the mould
• Carbon fibre – Sheet Moulding Compound (C-SMC)
Within each of these three processes, Lexus engineers established two main goals; the development of new production processes to increase productivity, and the development of new quality control technology.
Combining exceptional strength and rigidity with significant reductions in weight, Carbon Fibre Reinforced Plastic (CFRP) accounts for some 65% of the LFA’s body structure weight. This represents a weight reduction of approximately 100kg, over an all-aluminium structure.
With a strong focus on future development, Lexus is producing and assembling CFRP components in-house. Compared to steel or aluminium, CFRP production is time consuming, and the LFA project serves as an important research test-bed for the development of new, automated CFRP production processes which will be used in the manufacture of future Toyota and Lexus products.
Based on the shape, role and required properties of each component, three different CFRP composite technology manufacturing processes have been adopted:
• Pre-preg – an industry-standard composite sheet material made of carbon fibre pre-impregnated with epoxy resin
• Resin Transfer Moulding (RTM) – dry sheet fabrication with epoxy resin injected into the mould
• Carbon fibre – Sheet Moulding Compound (C-SMC)
Within each of these three processes, Lexus engineers established two main goals; the development of new production processes to increase productivity, and the development of new quality control technology.
To counter this, Lexus has developed a new injection and compression method which not only reduces the resin filling time by some 80%, but also allows large components to be produced in one piece. As a result, the number of subsequent process stages and adhesive bonding processes is also significantly reduced, greatly improving productivity.
To date, conventional weaving machines have been used only to create simple, straightforward shapes in CFRP. Newly developed Lexus weaving technologies now allow for the automated creation of complex, 3D profiles with variable thicknesses, differing cross-sections and curved shapes.
For instance, in the production of the LFA roof rails, fibres are woven round a core, two layers at a time. In this case, the weaving of 12 layers achieves the necessary thickness. Once weaving is completed, the core is removed, leaving a hollow roof rail.
The production of the front crash boxes requires a different technique, in which a fibre placement machine arranges the fibres into a fabric mat, before a 3D stitching machine inserts further fibres through the thickness of the mat. Trimming and bending brings the fabric to its final shape.
Not only does the new 3D weaving technology reduce material volume by up to 50% and increase component strength, it also, through automation, paves the way for the increased productivity necessary for future larger volume production.
Productivity has been further improved through a new, two-stage fabrication process in which the sheet is first moulded under 1,000 tonne pressure for an hour, and then baked at 1,850°C for four hours to cure. The sheet’s removal from the mould before baking relieves a potential production bottleneck at the 1,000 tonne press, and has been the focus of much development for future production.
To date, conventional weaving machines have been used only to create simple, straightforward shapes in CFRP. Newly developed Lexus weaving technologies now allow for the automated creation of complex, 3D profiles with variable thicknesses, differing cross-sections and curved shapes.
For instance, in the production of the LFA roof rails, fibres are woven round a core, two layers at a time. In this case, the weaving of 12 layers achieves the necessary thickness. Once weaving is completed, the core is removed, leaving a hollow roof rail.
The production of the front crash boxes requires a different technique, in which a fibre placement machine arranges the fibres into a fabric mat, before a 3D stitching machine inserts further fibres through the thickness of the mat. Trimming and bending brings the fabric to its final shape.
Not only does the new 3D weaving technology reduce material volume by up to 50% and increase component strength, it also, through automation, paves the way for the increased productivity necessary for future larger volume production.
Productivity has been further improved through a new, two-stage fabrication process in which the sheet is first moulded under 1,000 tonne pressure for an hour, and then baked at 1,850°C for four hours to cure. The sheet’s removal from the mould before baking relieves a potential production bottleneck at the 1,000 tonne press, and has been the focus of much development for future production.
CARBON FIBRE – SHEET MOULDING COMPOUND (C-SMC)
C-SMC is used for the fabrication of upper body components and frames with complicated shapes.
Unlike Pre-preg and RTM, which uses continuous strands of woven carbon fibre, C-SMC incorporates fibres uniformly dispersed with random orientation. Because no part pre-forming is necessary, productivity is vastly improved, and cycle and labour times are reduced by a minimum of 95% over those of Pre-preg.
QUALITY CONTROL TECHNOLOGY FOR ADHESIVE BONDING
The assembly line consists of five consecutive processes, all of which have been digitally validated. For the first four steps –sub assembly, under body, small aluminium parts and main body— adhesive bonding is used. Final assembly of the aluminium parts is by mechanical fastening. This is the first time that Lexus has employed adhesive bonding for main body assembly, necessitating new quality control technologies.
Adhesive bonding consists of five processes – pre-treatment, adhesive application, assembly, curing and inspection, and Lexus has established quality control technology for each of these steps:
CFRP pre-treatment involves the abrasion of the surface with a water jet containing alumina particles, to remove the de-moulding agent and optimise the surface roughness for bonding. Quality checks involve the measurement of abrasion depth and surface roughness by profilometer, and a 100% visual inspection of wettability for all parts.
Automated adhesive application accuracy is ensured by optimised nozzle geometry, position, angle and velocity. After application, a laser is used to make a 100% inspection of adhesive thickness.
During assembly and curing, the accuracy of the adhesive bond gap is crucial. At the beginning of each assembly process, all components are fitted together in a jig, without adhesive, to verify the gap distance. The curing process is checked using a lap shear test, and the lap shear test pieces are processed together with the body to ensure similar curing conditions.
Flash thermography is then used as a quality audit for adhesive bonded joints. The body surface is first heated by flash, and then an infrared camera records the thermal image of the body. The adhesive is highlighted in yellow on screen, with any defect clearly visible. Ultra-sonic evaluation techniques are also used for quality auditing at this stage.
The final adhesive bonding inspection involves a 100% check for body stiffness. Using 100kg weights and micrometers, both the left and right hand side of the body are simultaneously checked for displacement within acceptable tolerances before the body is shipped to the final assembly line.
