Newport News Shipbuilding Plate Handling System

The Plate Handling System began as a study to see how computers could be used to improve the handling of steel plate at the shipyard.  During this period, under mandate from the Navy, the company was exploring innovative avenues of improving their manufacturing processes.  A team of people from various departments was assembled, with myself representing the Computer Aided Design and Manufacturing department.  Previously computers were used primarily as a drawing tool, but the time was right to exploit their potential further.  With such vague requirements, we set off to make a thorough understanding of how steel plate was used in the shipyard.  In the first three months we interviewed people at all levels in the plate handling yard, from senior management to inventory clerks to crane operators and fabricators.  Surprisingly, the shipyard was quite unique in their methods of handling plate.  For one thing, the sizes of the plates was unusual.  Intended for use on aircraft carriers and submarines, the plates could be up to twenty-five feet by fifty feet, with thicknesses sometimes exceeding four inches. That makes for a very heavy plate! There was also a wide variety of types of steel, aluminum and other materials. Steel was by far the most common material used in the domain of this study, both in it's quantity and because aluminum couldn't be handled by the magnetic cranes.  Because of chemical interactions, some plates cannot be allowed to come into contact with other plates.  The shipyard is also unlike most other business in that they do not actually own the plate in their inventory; the Navy does.  The Navy is given a list of plate necessary for the construction of a specific phase of a certain vessel, and they buy the steel and provide it to the shipyard. This detail, the contract number of the buy and the ship the plate was intended for, becomes a portion of the part number assigned to the plate. Further, traceability requirements on each plate is extreme.  Ever since the loss of the submarine Thresher, each plate is identified by lot from the foundry pour, and follows downstream to each part made from that plate. The identification flows upstream as well, so that if a part ever fails on any ship, the Navy can identify the steel plate it came from, and all other steel plates made in that pour, and all the parts made from all those plates.  In this way inspections and repairs can be made proactively on any ships that may be at risk.

The plate yard consisted of several workshops where plates were cut to size and shape, tagged appropriately, and sent off to other departments for further manufacture.  Surrounding these workshops were the stacks, where dozens or hundreds of plates would lie on top of each other, perhaps to twenty feet high.  Cranes, either tracked or on gantry rails, would straddle the stacks to acquire a targeted plate and deliver it to the staging area.  The weight of these stacks is so great that occasionally plates would be "lost," driven into the summer softened asphalt by their overburden and then held too tightly for the crane to lift.  The way the yard normally operated was as follows: a work order would be received calling for a particular plate by it's part number would be received by the plate handling yard.  the database of plate would be referenced.  The stack it was stored in would be identified, as well as it's position within the stack.  At the time, this database was a series of small boxes holding index cards, on which were written the data about the plate they represented, one card per plate.  A retrieval order would be generated that scheduled a particular crane to acquire the plate, and said where to deliver it to. When the time came, the crane operator would go to that stack, lift the first plate, and see if it was the plate targeted.  If not, he would deposit that plate on a staging area and go back to the stack for another plate. If that was not the designated plate, it would also be deposited on the staging platform on top of the other plate.  This would continue, the operator "tearing down" the stack, until the exact designated plate was acquired.  This would be dropped off at the destination area, and the operator would then go back to the staging area, acquire the top plate from that stack, and put it back on it's home stack.  This would be repeated until all plates from the staging stack was restored to it's home stack, in an operation known as "rebuilding."  This is how the inventory was maintained.

Clearly, that involves a lot of plate movement, especially unnecessary when an identical plate was available closer to the top of the stack, even if it wasn't the exact one purchased for that contracted vessel.  We proposed keeping the database on computer, associated with the contracts database.  This computerized database could be searched to find the exact specified plate, as well as a plate which was physically identical to the desired plate that was closest to the top of any stack.  If two stacks had suitable plates equally close to the top, the stack closest to the delivery area would be selected.  The computer could then exchange these plates (the audit trail required "buying" the highest plate from whatever contract owned it and "selling" the original plate to that other contract--a trivial activity for the computer). The crane would then be scheduled, and only a much smaller amount of the stack would have to be torn down and rebuilt.  We estimated that this change alone could save the plate yard almost 40% of their budget.

In addition, we proposed using bar code scanners to identify the plate.  We suggested two types of labeling for the scan codes; one using Mylar adhesive labels on the side of the plates, and the other painted large on the top sides of the plate, using a type of reflective paint similar to the way white lines down the highway are painted. We identified a turnkey camera system (hardware and software) that could read those bar codes from the crane operator's cabin from twenty feet above the plate, even in the moderate fog that was not uncommon in Southeastern Virginia.  We expected this top barcode to have a lifespan of eight weeks before abrasion from overlying plates made it unreadable (longer if plate teardowns were reduced as we proposed), and at that point it could be repainted from the side label.

We also examined the use of computer software to calculate the nesting loft for each plate.  This means that when several smaller shapes have to be cut from a single plate, what is the optimum placement so that as much plate is left over as possible.  This is actually an NP-hard problem, one for which there is no theoretically best algorithm.  However, which a best solution cannot be proven, pretty good solutions aren't hard to come up with, especially for a person with experience. We surveyed the state of the art in nesting software, and were disappointed compared with the results claimed by the plate yard for their people. We recommended that this task continued to be done manually, with another survey done in five years.  Similar results were obtained for the storage of leftover plate, which could be of irregular size and shape.

At this point, we presented our findings to management.  When I left the shipyard a year later, after completing the Pipe Cutting Robot project, the status of this proposal was still undecided.  I believe the main problem here was tat union rules did not allow any workers to be eliminated or displaced due to automation. Since plate handling was not a bottleneck to production, and since the Shipyard did not invest in it's inventory, immediate changes could not be justified. This was also a problem on the Pipe Cutting Robot project, but since that area required much higher numbers of laborers, normal attrition allowed more room to bring in advanced equipment without violating the union contract