3 Fundamentals of press design

Organization of stamping plants
batch size [pcs.]
10,000
8,000
6,000
4,000
2,000
6,400
production cycle: ABCABD
production cycle of 50 hours
A
9,000
part cycle A
6,200
4,800
B C A B D
6 12 18 24 30 36 42 48 56
part A: 7 p/min
part B: 10 p/min
part C: 8 p/min
part A: 11 p/min
inventory of finished parts
in the intermediate storage
for part A
daily working hours:
15 hours
time [hours]
10 min die change after each batch
Fig. 4.9.5 Load schedule and parts inventory for production on a large-panel transfer press
time per part. Die changes and setting of new dies takes place within
press stops between production, whereby the die changing time plays
an important role (cf. Sect. 3.4).
Production must be resumed once the storage drops to the defined
safety inventory level, generally one day’s production. If we take type A,
for example, this level would be reached at 6,200 pieces, while for type
B the corresponding figure is 2,800 pieces. The 5,000 or 3,000 parts produced,
less the parts used during manufacture, must last until the next
planned production period – around 14 resp. 22 hours later. When compiling
the load schedule, a fine balance must be drawn: On the one hand
the production period for a batch size has to guarantee sufficient time
for set-up of the die set for the next part. At the same time, however,
excessively large batch sizes violate the principle of just-in-time production
in terms of capital costs for work-in-process and costs for intermediate
storage of finished parts.
8,800
Metal Forming Handbook / Schuler (c) Springer-Verlag Berlin Heidelberg 1998
6,400
3,300
397
A