The weld booths are robotised to ensure consistency; and Honda claims its NSX chassis are welded to within 0.1mm accuracy. That means that, unlike other supercars Honda declines to mention by name, no post-welding machining is necessary; say, around the suspension components. The way the NSX spaceframe comes out of the booth is the way it's built.
Here’s a completed welded spaceframe. A carbonfibre floor and roof panel is yet to go on. This is all aluminum bar the A-pillars, which are steel. That complicates things - it means they have to be bolted rather than welded in place, and they are coated to resist corrosion. Honda took a late decision to use steel because it couldn’t get good enough forward visibility with aluminium A-pillars, which have to be wider to provide the same strength.
To make sure each body has been assembled to within tolerances, more than 2700 points of data from 500 different locations on the body can be measured by this coordinate measuring machine. This static one in the middle of the factory is accurate to within of 30 microns - less than the width of a human hair. Honda also has two portable ones that can take to the factory floor, measuring to within an accuracy of 50 microns.
Once checked, the bodies are off to be dipped before they're coated and painted. There are six tanks like this, none of which look like ones you'd want to fall into. It's a pretty industrial-looking process - the noisiest in the factory - but Honda claims most of the liquid is recycled.
Most of the NSX’s body panels are painted by robot, with around four gallons of paint - in up to 11 coats - making it onto the body. Some bits are painted by hand, such as the front grilles, which arrive finished as black plastic, but are then painted black again, mysteriously.
While the body is being painted, the hand assembly of each chassis begins, in the kind of order you might expect. Electronics and hardware first, with the interior coming towards the end.
Every nut and bolt is tightened to a pre-set torque by a wrench that's wired up to a computer. So if anything goes wrong in future, Honda will know where, when, and to what torque setting anything was tightened; and whether other cars might be affected in the same way. Even so, every bolt into aluminium is hand-threaded for the first few turns, to make sure there’s no cross threading in what is delicate (for a metal) material.
The NSX’s engine is also built in the US, but not in the same plant as the car. It’s a similarly labour-intensive process though, which culminates in each 3.5-litre, twin-turbocharged V6 sitting on a test rig undergoing a 45-minute test/running-in cycle.
Honda uses as few robots as possible in the assembly area: in fact, there’s just one, used to apply sealant. Even here, where the body is dropped towards the engine, and then the engine is raised on a table for the last few inches, the process is controlled by hand. There’s only 3-4mm of clearance either side of the motor, and it takes 62 minutes to install the engine in the chassis.