Page 46 - MetalForming March 2012

Tooling Technology
Electronic
Gas-Spring
Pressure
Monitors
...bring processes under control for three completely unique applications: small-caliber bullet assembly, in-die resistance welding and deep drawing.
ATK to keep pace with the Army’s latest ammunition solution—the Enhanced Performance Round (EPR). The new bul- lets are “green” (lead-free), featuring a bismuth-tin copper-alloy core and steel penetrating tip.
Forming and assembling the new rounds in the Waterbury presses requires ATK to take production- process control to new heights. Its ongoing Green Ammo program even- tually will comprise a range of EPR sizes manufactured on 24 presses. To date the firm has completed upgrades to 12 BAMs for one of the EPR prod- ucts—the M855A1 5.56 x 45 bullet, which has been used in Afghanistan since the spring of 2010.
The rounds are manufactured on 12 Waterbury presses, each outfitted with 14-station dies. Bowl-fed copper- alloy cups that enter the die are drawn over several stations to become the bullet jacket. As the drawn cups move through the die, the penetrator gravity- feeds into the jacket. Trim stations fol- low, then an ogive sizing and assembly station, additional sizing stations and a final cannelure or knurl station. Press- es stroke at 60 hits/min.
Three different and unique appli- cations—in-die assembly, in-die welding and deep drawing—all paint the same picture, illustrating how digital nitrogen-gas pressure monitors can improve quality and productivity. First, consider the U.S. Army’s desire to build a better bullet, and the creative solution provided by its primary small- caliber supplier, Lake City Army Ammunition Plant, operated by Alliant Techsystems (ATK), Independence, MO. Lake City is the Army’s largest sup- plier of small-caliber ammunition, the lone survivor among a supply chain that once numbered a dozen different companies. In the last several years— and particularly since 9/11—ATK has seen its production volumes jump to 1.4 billion small-caliber rounds/yr., tripling its output since 2000.
Supporting the growth at Lake City is an ongoing $280 million manufactur- ing-equipment modernization program.
Each of the 12 Waterbury Farrel presses that have been upgraded at ATK for the Green Ammo program now boasts four pressure transmitters connected to nitrogen- gas springs, monitoring pressure at four critical die stations (shown here) used during bullet assembly.
“The design engineers that developed the process specified that we must closely monitor and track gas-spring forces in the die,” says ATK engineer John Segovia. “Insufficient force (from a leak in the nitrogen-gas supply sys- tem, for example) or over-pressurized gas springs trigger a press shutdown before out-of- specification bullets are fabricated.
“When we launched the program (early in 2008),” continues Segovia, “we installed electronic
44 MetalForming/March 2012
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BY BRAD F. KUVIN, EDITOR
The program includes updating several 1940s-vintage Waterbury Farrel deep- drawing presses, which ATK refers to as bullet-assembly machines (BAMs). Upgrades to the 30-ton presses will allow
load cells to meet this requirement— four load cells in each BAM. However, we quickly realized that the load cells were too complicated for our manu- facturing environment.”