Page 32 - MetalForming November 2017

Curved Flanges No Problem for This Punch Press
flanging challenge: implementation of a new 20-metric-ton Strippit PX punch press from LVD, boasting 3 in. of punch-die clearance for optimum forming capabilities, equipped with a custom Wilson Tool Opti-Bend tool designed to flange curved profiles. A rotating cam in the die bends the mate- rial during the punching stroke, sim- ulating the cycling of a press brake without marking the sheet. Wilson Tool modified the rocker to, in concert with the way in which the sheet indexes in the press, create the curved flange.
Of note: The H34 temper on the alu- minum stock means that the material is strain hardened, and then stabilized, to a strength that is roughly halfway between annealed (O) and full-hard (H38). That gives it good workability, in addition to good corrosion resist- ance, high fatigue strength and good weldability.
LVD markets the Strippit PX press, installed at the New York Mills plant in January 2017, for punching, bending and tapping. It boasts, in addition to the added bending capacity, a 20-sta- tion tool carousel; maximum hit
rate is 505 hits/min. at a
1-in. pitch. Nominal
workpiece capacity on
the machine is 60 by 120
in. However, to accom-
modate larger sheet sizes
and to avoid drooping of the relatively thin work, LVD worked with the facility to equip
the machine with an additional 40 in. of table length.
Accuracy on the Rise
“Flanging these parts manually used
to require one ded- icated machine operator working 25 to 30 hr./week, per-
forming a two-step process,” Pederson explains. “Now that we’ve automated the process and spared that operator the challenging ergonomic conditions, we’ve also noted dramatically improved part quality, dimensional accuracy and repeatability.”
Pederson says that bend-angle tol- erances now are ±1.5 deg., improved considerably from as much as a 3-deg. variance before. The shop uses two sets of the custom Opti-Bend tooling for flanging—one to form a 77-deg. angle, the other to set a 90-deg. flange.
“Flange height also is more consis- tently held as well,” Pederson adds. “Dimensional tolerances are now with- in ±0.010 in., compared to as much as 1⁄16 in. before. The improved accuracy
and repeatability of the bend angle and flange height improves fitup in the boat when the technicians go to rivet them in place, and also results in a flatter, more level floor.”
Laser on the Way
In one week’s time, the Strippit PX press turns out 2000 of the structural supports, in a variety of sizes and shapes to fit the contour of the boats—about 600 different part numbers in all. When we spoke with Pederson, the press, in addition to flanging the parts, also was being used to nibble the part peripheries. The master plan is to use a new 8000-W fiber-laser cutting machine, an LVD model expected to hit the shop floor early in 2018, to cut the blanks.
“That will free up some time on the punching machine,” says Pederson, “which is at near-capacity right now.”
MF
Each boat manufactured at the Brunswick factory includes five or six of these supports, fabricated from 0.063- and 0.080-in.-thick Type 5052-H34 alu-
minum. Flanging the parts manually using a 1940s-vintage machine created inconsistent results (bottom part) and was
not a very ergonomically sound job. Forming the parts on a punch press with a custom upforming tool automated the work and led to much more consistent part quality (top).
30 MetalForming/November 2017
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To automate the forming operation performed on the bulkheads, the plant invested in a new Strippit PX punching machine from LVD. The blanks (shown here still in the sheet- metal nest) are flanged in the press using a custom Wilson Tool Opti-Bend upforming tool (inset).