CTL Line Upgrade Improves Quality and Productivity

Problem:

A steel service center operates a mid-1970ís vintage 60" x .028"-.120" x 150 FPM hump table-positive stop type cut-to-length line that was unable to hold length and squareness tolerances that its customers were demanding. In addition, the old sheet stacker was producing sloppy, staggered sheet packs that were becoming unacceptable to its customers. Something had to be done in order to maintain existing sheet and blank accounts; either purchase a new CTL line for around $1 million, or if possible, upgrade the existing CTL.

Solution:

Coiltech was commissioned to upgrade the existing CTL line to produce tight tolerance sheets and blanks, increase productivity, and produce "solid block" finished packages.

The existing entry end equipment was saved, as was the leveler, shear, and measuring table runout belt conveyor. The old hump table, positive stop, and sheet stacker were discarded in favor of a new Precision Electronic Roll Feed and a new Sheet Stacker and Weigh Station.

Development:

The new equipment delivery schedule was established, and new CTL line engineering drawings were prepared. About a week before the new equipment was due to arrive, the old CTL line was de-commissioned to begin preparations for the new line arrangement. The entry equipment through the leveler was left untouched, remaining in existing locations, while the old hump table, shear, measuring table, and stacker were removed. A shallow 20' long looping pit was installed after the leveler, as was a new concrete footing for the old shear. The new Servo Feed with the associated looping pit carryover tables and loop quadrants was installed along with the old shear and measuring table. Finally, the new Sheet Stacker with its elevating table and integral scale was installed after the old measuring table was in place. The upgraded CTL line was ready to run as a Precision Electronic Roll Feed Blanking Line. Down time was about 2-1/2 weeks.

Results:

Precision Electronic Roll Feed

The upgraded line was prepared to produce sheets and blanks to precision length and diagonal tolerances, and was able to stack those sheets and blanks into solid block packages. Productivity nearly doubled that of the old line because; (1) the Servo Feed allows the leveler to run at a constant speed rather than losing speed in its former slow down-positive stop cycle; (2) new lengths are set-up by key pad operator input rather than trial and error re-positioning a positive stop; (3) pack weights are recorded before removal from the line, eliminating double handling; and (4) fresh pallets are power injected into the stacker, minimizing time lost to unloading finished packs.

 

Automatic Sheet Stacker - Weigh Station

Allows Visual Sheet Inspection

Although the old measuring table belt conveyor could have been eliminated from the new arrangement by installing the new sheet stacker immediately behind the shear, the belt conveyor was re-installed because it allowed each and every cut sheet to be visually inspected for flatness and surface condition, and it allowed blanks to be easily removed from the line for length and squareness verification without interrupting production. Those operational benefits dictated the re-installation of the runout belt conveyor.

Cost:

The cost to upgrade the existing CTL line to produce close tolerance sheets and blanks was a small fraction of the cost of a new CTL line. The increased productivity assured a quick return on the investment, and the improved length and diagonal tolerances opened new markets and assured the retention of existing accounts.

Conclusions:

Late 1960ís through early 1980ís hump table-positive stop cut-to-length lines equipped with a corrective roller leveler are generally well maintained and normally produce an acceptably flat sheet. But because of the positive stop measuring system, they usually are deficient when it comes to 21st century length and diagonal tolerance demands and productivity. It is cost effective to upgrade those CTL lines by replacing the hump table-positive stop measurement system with a "state-of-the-art" electronic roll feed system. The new microprocessor based motion control electronics are operator friendly, extremely reliable, and incredibly accurate. As compared to "mechanical" type feed devices, the electronic roll feed occupies much less space and offers quicker set-up time, lower operating costs, significantly lower maintenance costs, and has a significantly longer operational life expectancy.

Solid Block Steel Packs

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Last modified: January 30, 2004