Architecture is the type of body built — two door sedan, four door sedan, station wagon, minivan, convertible, etc.
Architecture does not refer to specific parts sharing, but the second grouping of two letters in the body code (not used in the VIN) specifies specific trim levels, which are groups of parts.
A platform only define the space required to assemble the parts and nothing more.
A chassis is only the structural parts that attach the suspension, brakes, powertrain, steering, fuel, and ride control systems to the body. — Bob Sheaves
Flexible manufacturing is, in its essence, the capability of making different vehicles on the same assembly line without long delays to change tooling. In practice, it is now possible to make completely different vehicles on the same line with no delays to change between vehicles.
The way this works is by extensive use of robots and computers; the robots have tooling or spot welders on the end of their "arms" and when a new vehicle comes down the line, they can quickly swap to different tooling or welders, and apply their arms in different ways. This also works in the paint shops, where robot arms are programmed to act differently depending on the vehicle that shows up.
This requires more flexible robots with computerized programming and networked communications, which is one reason why flex manufacturing was not practiced much in the 1990s (when cars were assembled almost entirely by hand, flex manufacturing was also possible and was moderately common, but it could easily lead to quality gaffes, where the wrong parts were applied — e.g. Dodge labels to Plymouth cars or mismatched right and left side mirrors).
In addition to network communication, barcodes or RFID (radio frequency identification) tags can be used to tell the machines what model is coming down the line.
The primary requirement for using flexible manufacturing is the ability for different vehicles to use the same carriers (or having multiple carrier types); as bluecon wrote, there are usually four points where the carriers carry the body until tires are installed, and the vehicles is put onto a flat track. If these points are carried over from body style to body style and there is enough clearance in the carrier (or in the case of welding, you have the jigs and end tooling for the part) you can produce many different models and styles.
Bob Sheaves noted that platforms are defined as common dimensions between various “top hats” and “architectures” (collections of hard parts), so that various completely different vehicles can be built within the same physical space allotted to the vehicle carriers.
rapidtrans wrote: “You have to see a flexible body shop in operation to truly appreciate the advantage over the old style body shop. You do away with those large fixtures or jigs that could only assemble one part/vehicle each. With flex manufacturing a robot can be programmed to assemble and or weld say a Caliber quarter panel followed immediately by a Compass quarter panel then a Patriot quarter panel. One robot can hold the part while a second welds the piece even if the part is in motion. You can build completely different vehicles sharing the same architecture, one after another, with just a programming change. Robots are strong enough now to handle an entire body at full reach.
“When the new model changes, the software is simulated and then downloaded to the plant-floor robots with no need for expensive fixture rework or replacement.
We can do robot motion simulation without ever seeing the actual part/vehicle in the flesh. The CAD files are used to assemble the vehicle on my computer and run the simulation at my desk.”
Stratuscaster noted some of the advantages:
Techs and Workers
Dodge cars, 1914-2015
At the 2016 SAE World Congress
All Mopar Car and Truck News
Chrysler 300 Letter Cars
The Engine Cleanup Committee