Page 37 - MetalForming January 2012

The Science of Forming
Rejection patterns noted from time logs
1) All rejections from one coil of steel
2) Rejections immediately after lunch break, shift change or long down time
3) All rejections on midnight shift 4) All rejections after die transition 5) All rejections after die was
tweaked
6) One or two rejects throughout
the run
Logical Root Cause
A) Ground-down draw bead
B) Did not have a “Bernie” book
C) Substitute press operator
D) Spot buy of steel (at great price) E) Drop in die temperature
F) System on edge of deformation cliff (An obvious question: What is a
“Bernie” book? Bernie was the super- visor of die transition at a large Tier One stamping plant. All die transitions were done on the third shift. Bernie’s book contained all of the die and press- line settings for every die set in the home press line. Included were allow- able blank thicknesses, blank gauge settings, lubricant type and thickness, press shut heights, tonnage-monitor values and other key variables. Wher- ever possible, complete settings also were recorded for the assigned backup press line if the home press line was unavailable. The book was written in pencil to allow the insertion of revised numbers if the die was modified or the press underwent maintenance. If Bernie went on vacation or was sick, the book was always available in his office for others to use. The plant’s first required troubleshooting instruction: “If you do not know exactly what changed, then return all settings back to the transition settings in Bernie’s book.” The very last instruction: “Now you may pick up the grinder, with the permission of the shift manager.” No mention was made about about average values; only extensive raw data was needed to run an excel- lent press shop.) MF
Stamping and Forming
High Strength Steel? Use high performance tool steels to reduce part costs
The use of high strength steel sheet presents new challenges for tooling. Tool life is shortened dramatically when using standard tool steels like A2 and D2. We have developed a wide range of steels to address these concerns, manufactured in our own mills and stocked in our own facilities.
UDDEHOLM CALDIETM - Extremely crack resistant. Readily weldable. Coatable. Cost effective. Replace your A2 requirements.
BOHLER K340 ISODUR® - More chip resistant than D2, and capable of higher strength and better stability during high pressure stamping and forming.
UDDEHOLM VANADIS 4 EXTRA® - PM steel optimized for long run tooling where thicker, high strength, or more adherent work materials are used.
BOHLER S693 MICROCLEAN® - High carbon PM M4 high speed steel for use where mixed failure modes of abrasive and adhesive wear are present.
BOHLER K294 MICROCLEAN® - PM A11 tool steel with extremely high abrasive wear resistance, with improved chipping resistance over other A11 types.
UDDEHOLM VANCRON 40 - New generation PM tool steel with excellent galling resistance, ideal under severe conditions where surface coated tool steels are required.
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MetalForming/January 2012 35
Answers: 1-D, 2-E, 3-C, 4-B, 5-A, 6-F