How Advanced Plasma Cutting Is Replacing the Drill Line

The productivity of structural steel fabrication is closely dependent on the path the workpiece navigates as it goes from raw materials inventory to eventual loading on a truck going to the job site. Every time the workpiece is "touched" adds delay and cost to the final finished beam, channel or angle.

A structural element with a dozen or so bolt holes and cut to length has really very few "touches". However, many structural sections are quite a bit more complicated than that.

For example, complete fabrication recently done on an 96" W16x31 structural beam involved 35 unique operations

All those operations involve a lot of "touching." But they also involve just a lot of time actually making the cuts. Or do they? Better question: Do they have to?

In the first case, the "high touch" path is a predominantly manual approach. The workpiece has to be measured and marked, then cut off on the bandsaw. Afterward, there is plenty of "manual" drilling (that is, non-CNC, as opposed to really manual) and quite a bit of thermal (torch) cutting to make the copes and flange flush cuts, in addition to hammer stamping to make the nine character piece marks. The total time involved to perform these various tasks was estimated to be 120 minutes - 2 hours. However because of the shuttling involved and the time in queue at different stations, the elapsed time would cover at least two shifts - typically two days at most shops.

Next, a more modern and automated approach was followed to fabricate the section. This involved cutting the piece on the bandsaw, then moving it to a CNC drill line to drill the bolt holes and 3 slots. The better beam drill lines can probe the beam to determine location and dimensions, then drill the holes according to instructions determined by specialized software that reads standard detail drawing files. The remaining features have to be measured and marked on the beam before cutting begins. Then cutting is done by coping torch, plate thermal burning machine, and stamping the various piecemark letters. The estimated time for this path is 82 minutes. Again, when figuring in the time needed to shuttle the workpiece between stations and time waiting in queue at those stations, the total clock time stretches out to consume most of an 8 hour shift.

Lastly the section was actually fabricated using a new approach. Every single feature is produced on a single machine - a robotic plasma cutting system. Employing this approach, there is no use for any measuring or marking at all. The sensor tip probes the workpiece for location and geometry, then follows its own calculated cutting instructions it generates from engineering drawings of the workpiece downloaded into the operator control from programs like TEKLA, SD/2,StruCAD and others.

The plasma machine starts cutting on the section and stops when it's done... 10 minutes and 13 seconds later. All thirty seven features are fabricated in this time and the workpiece is completed. No time is lost to moving the piece or waiting, so the time from start-to-finish isn't a day, or a shift or even an hour... it's merely the time of a standard coffee break.

This technology has the potential to revolutionize the economics of structural steel fabrication. While it doesn't impact the basic cost of materials, it can give fabricators so many more inventory turns on that material, so significant working capital is no longer tied up in steel. It cuts labor costs, eliminating most material handling and operator requirements. It lowers overhead and capital costs, because a single plasma system replaces up to 5 traditional machines or workstations, which frees up floorspace and investment capital.

Structural fabricators are an enterprising and tenacious bunch. They'll take the shortest path they can find to reduced total cost and achieve lean manufacturing. They are discovering that path very well may run through this new technology robotic plasma cutting system for structural steel fabrication.|



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