The mark 3 assembly line. The three similar-looking protruding racks are for the conveyor belt mechanism, the other two are for the brick and plate positioners, and the horizontally-mounted gears are on the top of the press.
The mark 3 assembly line. The three similar-looking protruding racks are for the conveyor belt mechanism, the other two are for the brick and plate positioners, and the horizontally-mounted gears are on the top of the press.
The mark 3 assembly line was controlled by the Technic Control Lab, visible in the overview photo above. It was never entirely finished, but if complete it would have been able to build 6 small modules (different from the previous assembly lines - my school, where I built it, had no 2x6 plates nor any 2x2 wheel plates, so the product was as in the photo below) before needing to be reloaded with raw parts.
The different stages in the production of a module by the assembly line. At the back are the two individual parts and the module in which they are eventually put together (very simple, I know); at the front, from left to right, are a spacer pallet (in between each of the usable pallets to avoid the sticking-out plates of the modules fouling each other), an empty ordinary pallet, a pallet with a brick in position and a pallet with a completed module. The different colours of the smooth plates on the bottom of the pallet do not mean anything!
The conveyor belt took the place of the advancer in previous versions of the assembly line, in that it moved the partially-completed product through the different stages of the process. However, instead of only being able to handle one model at a time the conveyor belt consisted of a number of pallets (I forget how many), onto which parts could be placed, and mechanisms for cycling them through the various stations on tracks made from smooth bricks. In each corner they were pushed along by a rack-and-pinion system as far as needed - in one corner this was only one pallet's worth of space, while in the other three it was the entire length of the side.
The worm-driven rack-and-pinion pusher from one corner of the assembly line; the black and grey bricks are the smooth bricks on which the pallets slide.
The brick store loaded a single 2x4 brick out of a magazine of 6 onto the appropriate position on a pallet using another rack-and-pinion with a rotation sensor attached for position feedback/knowing how many bricks there were left.
The magazine of 6 2x4 bricks and the worm-driven rack-and-pinion to load them onto a pallet (which would be to their immediate right).
The plate store worked in a very similar manner to the brick store to load a single 2x8 plate out of a magazine of 6 onto the positioner using another rack-and-pinion with a rotation sensor attached for position feedback/knowing how many plates there were left.
The positioner laid the plate in the right place on top of the brick, without applying any force to push them together. Like in the Mark 2 assembly line it was essentially a pair of 1x2 smooth bricks that supported the ends of the plate and could be moved up and down. When up it was in line with the plate store to have another plate loaded onto it; when down, on the other hand, the smooth plates were below the level of the top of the brick on the pallet so the 2x8 plate was carried away as the pallet moved on.
The positioner, consisting of the pair of 1x2 smooth plates just in front of the topmost black 2x8 plate (which is the last in the plate store - the grey brick at the bottom left is part of the motor that moved the plates, but the rest of the plate store is not shown in this picture) and the frame that links them to the two racks at the top of the picture. Not a very good shot, but this mechanism was fairly complex and enclosed in guide rails so I was not able to show it in a straightforward manner.
The press used the same screw-thread technique and light-sensor feedback as the Mark 2 assembly line, though with a very large gear on top to connect the two screws instead of the chain used before.
If the line had ever become operational, the completed modules would have been separated from their pallets as they were pushed along the final stretch of the conveyor belt by a pick-off ramp of slope bricks that caught the overhanging ends of the plate.
Since the hardware was never finished, the control programme was not completed either; nonetheless, if you are interested you can download it in Lego Control Lab format.
This shows the complete assembly line from above - the conveyor belt would run anticlockwise, taking the pallets in sequence to the brick store (top left of the central rectangle of smooth brick "track"), plate store and positioner (the rest of the left side of the rectangle), press (bottom right corner) and the pick-off ramp (right side of the rectangle) before returning to the start.