Page 16 - MetalForming January/February 2022
P. 16

 Tooling by Design
By Peter Ulintz
Considerations for Transfer-Die Design
   Progressive Die
Fig. 1
 Coil-Fed Transfer Fig. 2
 Blank-Fed Transfer Fig. 3
 Stock Width (in.)
 20.50
 19.60
 27.00
  Progression (in.)
  6.125
  5.750
  10.55
 Thickness (in.)
 0.100
 0.100
 0.100
  Gross Blank Weight (lb.)
   4.163
   3.980
   4.045
 Weight Differential (lb.)
---
0.183
0.118
  Savings @ $0.85/lb.
   ---
   $0.156
   $0.100
 Annual Savings (200,000 units)
---
$31,200
$20,000
  5-yr. Savings
  ---
  $156,000
  $100,000
   With few exceptions, transfer dies are designed much like the dies used for individual and tandem press-line operations. Important differences include main- taining all dies to a common pass line and shut height; incorporating guide pins, heel blocks and set blocks unto the upper die shoe to avoid interfer- ence with transfer rail movement; and providing clearance in lower die sec- tions for transfer fingers to pick up and place parts.
Transfer-Die Advantages
As compared to dies for other types of stamping operations, transfer dies can eliminate secondary operations, decrease labor costs and increase mate- rial utilization. Improving material uti- lization can produce significant cost savings, especially when running thick or expensive materials.
Transfer dies, not restricted by the progression of the part, can be designed to match part requirements without sacrificing material use. They enable more robust and easier-to- install form and trim punches, improv- ing die life and serviceability.
Progressive dies, able to produce multiple parts/stroke with potentially
Peter Ulintz has worked in the metal stamping and tool and die industry since 1978. His back- ground includes tool and die making, tool engi- neering, process design, engineering manage- ment and advanced product development. As an educator and technical
presenter, Peter speaks at PMA national seminars, regional roundtables, international conferences, and college and university programs. He also pro- vides onsite training and consultations to the met- alforming industry.
Peter Ulintz
Technical Director, PMA pulintz@pma.org
high material utilization and operable at relatively high speeds, often provide the best solution for high-volume pro- duction. However, tooling may be complex with corresponding manu- facturing risks and higher maintenance costs.
Transfer dies can be mounted in the same press and use the same feedline as progressive dies, with parts trans- ported from station to station mechan- ically rather than via carrier ribbons attached to the coil. Die construction tends to be less complex than progres- sive dies and provides more flexibility for rotating parts, with raw material blank- or coil-fed into the die.
Other reasons for considering a transfer die: possible elimination of offline or secondary operations; less die maintenance due to ease of serv- iceability and adjustment; and better process control and part quality—all acting to keep an existing transfer sys- tem busy. Note that part size dictates the use of a transfer die—part volume excludes the use of manual-load dies, with part rotation or tipping required
to account for burr direction or difficult access that cannot be accomplished in a progressive die.
Getting Started
The first step: Create a strip layout for a progressive die and a flow chart for a transfer die. A flow chart shows the work to be performed in each station. Next, consider how the blank will load into the transfer die. Possi- ble methods: coil feed, coil transfer, zig-zag feed or blank destacker. Com- pare the material use for several methods and calculate the cost dif- ference (see the accompanying table and figures).
Analyze the part drawing’s geomet- ric dimensions and tolerances to verify necessary control and adjustments required in each die to meet specifi- cations, and change the layouts if nec- essary. In some instances, the ability to control critical product features and make simpler in-process adjustments provides the compelling reason for building a transfer die.
Another design consideration: cam
  14 MetalForming/January-February 2022
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