The target function in the form of the formula (1) ensures that in the operational
research procedure there will be found a solution which ascribe manufacturing operations
to the machines in a way that will guarantee the highest minimal exceeding
of the capacity or the lowest maximum reserve of the capacity. The limitation (2) assures
that every operation in the production series is carried out only once on a given
machine. The symbol si denotes the index of the product manufactured in series i,
while cjksi denotes the time of the manufacturing operation j production of the halffinished
or finished product si on the machine k. In the situation when half-finished
or finished product cannot be manufactured on a given machine, the parameter cjksi has got value 0. Suggested formof limitation (2) assures that on the left side of the limitation
the variables, which match the possible operations to be carried out – number
of the operation, a machine and a product, are only taken into consideration.
The limitation (3) joins the utilization of production capacity with the variable
zmax. The available working time of the machine in the period when the plan is carried
out was denoted by the symbol Dk whereas hAk
stands for the short changeover
of the machine k. Limitations (4) and (5) are bank limitations for the decisionalmaking
variables. As it can be observed, in the suggested model, only times of short
changeovers were considered. Initial verification of this model has some positive results.
After generating the task which contained the real number of production series,
it was possible to solve it in a short period of time (less than 1 second) by means of
a simple software like lp solve. Moreover, the analysis carried out by planners proved
the greater accuracy than, used before, total number of manufactured products. As
a part of further research a second version of the model was established. This for mulation, apart from the assurance that the plan will be fulfilled (if it’s possible),
minimizes the times of changeovers, including long and short changeovers. In the
model denoted by the formulas (6)–(12) three groups of decision-making variables
xijk, zmax and ypjk were used. The first two have got the same interpretation as in the
earlier formulation, whereas the variable denoted as ypjk is a binary variable which
has got the value 1 if the operation j of manufacturing the product p is carried out on
the machine k. As opposed to the variable xijk which corresponds to ascribing the
operation of a specific production series to the machine, the variable ypjk allows us to
tell if, at least, one operation j of a production series of half-finished or finished product
p is manufactured on the machine k. Carrying out the operation of a production
series of half-finished or finished product requires to perform a long changeover