Constraints (5) ensure that molds of type i are assigned only to compatible
positions of the preset setting adopted in each sub-period.
yips 6
X
j2J
lipjzjs 8i 2 N; p 2 P; s 2 S ð5Þ
Constraints (6) force that all positions of the setting adopted has a
type of mold assigned. These constraints guarantee in practice, that
all of the machine faces are full of molds, as expected commonly in
the molded pulp packaging industry.
X
i2N
X
p2P
yips ¼
X
j2J
mjzjs 8s 2 S ð6Þ
4.3. Constraints related to setup operations
Constraints (7) determine how many molds of type i are
attached or detached in each sub-period. Note that they depend
on the settings adopted in two consecutive sub-periods (s 1
and s) and on the mold assignments to each position in these
sub-periods. Observe that
P
p2Pk
yipsnpk
P
p2Pj
yipðs1Þ
npj > 0 means
that molds of type i are attached in s. In the same way, if this
expression is less than 0, it means that molds of type i are detached
in s, and in both of the cases Setup II occurs.
uis P
X
p2Pk
yipsnpk
X
p2Pj
yipðs1Þ
npj
bjks 8j; k 2 J; s 2 S; i 2 N
ð7Þ
See that (7) are non linear constraints, however they can be linearized,
without losing generality, by the sets of constraints (8) and
(9). Constraints (8) represent the case when molds of type i are
attached in s, which implies that the number of molds of this type
used in s by setting k is greater than the one used in s 1 by setting
j, if settings j and k are used in these sub-periods ðbjks ¼ 1Þ.