SAP PP AND FINITE CAPACITY SCHEDULING
The
finite capacity scheduling is not available in SAP-PP module: firms must use
the SAP product
In
this document, some attempts to obtain finite capacity scheduling inside SAP
R/3 are shown: they are based on enhancements or/and custom
programs.
These
models are tested with simple cases and the results are shown below in the
linked files (red underlined words) and youtube links.
Two cases are examined:
1. finite capacity scheduling
2. family capacity scheduling
Finite capacity scheduling
This model is useful in this
case:
·
single work center usage: it means that for each material to be produced many work centers are
used and for each of them a detailed scheduling is performed. Then, many jobs
are allocated to each work center: it’s very important to sort them to obtain
an optimal sequence based on some criteria: capacity load, minimum setup,
delivery delay, makespan, critical path method, ecc. It’s very useful also in
case of bottlenecks.
A presentation of this model is available in
pdf format.
Next
2 pictures show an example of planned order scheduling.
For
a complete demo about this model
you can see the following video
http://www.youtube.com/watch?v=Qq6v0qS4NrA
or
download finite capacity document .
Example
1. The next 2 screens show 2 planned orders of identical materials: one is
scheduled with finite capacity logic, the other with infinite capacity logic.
It’s
evident that in the first case the phases’ dates are discontinued, whereas in
the second one they have not jumps, because there is not capacity control on
work centers.
More
details of this model are shown in the file linked above.
Family capacity scheduling
This model is useful in these cases:
·
production line usage : it means that materials of the same family are produced in sequence.
When it starts with material “A”, it will pass to next material “B” only when
all the quantity of material “A”, required in the actual period, is produced.
Also setup between materials is relevant for scheduling.
·
large material variousness : in this case is very difficult to plan material by material: it’s
very easier to plan the family quantity/capacity for each period. It’s also
typical the usage of configurable products.
·
preventive family planning: for all the families are assigned the maximum quantity that can be
produced in a certain slot (day, week, month, etc) and the slot edges. In this
way it’s created a sequence in which there is a rotation between the families:
it can be done manually or simulating different situations based on historical
requirements. Once a plan is done, during the availability check (in sales
orders) is important to verify, in case of material must be produced, the
capacity level of the own family: it allows to provide correct date (slot edge)
and quantity allocated to the requirement
(for an example you can see
http://www.youtube.com/watch?v=kAGo2cgNNeg
.
This
model, discussed above, is described in a presentation.
Next
2 pictures describe an example of family capacity check.
For
a complete demo about this model, containing SAP screens download family capacity planning document .
If
product families are based on characteristics values combination, download configurable
products document .
Example
2. Plans of families famiglia-a and famiglia-b.
In
the next picture there is an example of matfam1’s requirement allocation based
on family plan (in the example the family is “famiglia-a”, which matfam1
belongs). It’s a sales order screen, during the availability check.
More
details are shown in the documents linked above (red underlined words).
Both
models have a SAP custom WHAT-IF tool for simulate different situation
and choose the optimal one.
1)
In finite capacity check, there is a set of abap functions and programs that
allows :
-
to schedule each
single planned order with finite capacity criteria
-
to simulate the planned
order sequence and optimize it by production indicators, calculated with finite
capacity scheduling, as work center load, delay, cpm dates, etc.
2) In family planning, there is a set of abap
functions and programs that allows:
-
to
simulate and optimize the preventive family plan by different criteria: stock
average level, sales forecast, critical raw materials, etc.
-
to
distribuite the sales requirements within the family capacity during their
creation phase
-
to
optimize the work center allocation and the planned order sequence, by custom
criteria (setup time between materials, delay, work center priority, etc.).
It’s an open model based on parametric
functions that can be modified (using custom tables) and linked by its own
necessity.
Example of job sequence
About
the finite capacity scheduling is shown an easy problem of optimal sequence of
the jobs, to better understand how a what-if tool can help.
In
the picture below is shown a possible sequence of the jobs.
It
can be seen that:
1.
there is a big wait-time
(before first phase) for almost all work centers, first of all M4
2.
the makespan for complete
production is 21 days.
After
a What-if optimization, it can be found a new sequence: it’s shown in the next
picture.
In this new
sequence, it is evident that the makespan is reduced of 5 days (now is 17) and
the load has been improved. In practical situations, when there are much more
work centers and orders, with What-If tool become easier to find optimal
solutions.
For more informations
or a remote SAP demo (15-20 min), using Teamviewer, write to
eng. Vietri: michele.vietri@gmail.com. We can provide remote
consulting service at very competitive price about SAP R/3 modules (SD, MM, PP,
ecc.) or technical issues (Idoc, custom tools, ecc.), as handbook for your specific implementation, analysis for
improve and manage the processes with SAP and so on.
For an example about this custom model you can see
http://www.youtube.com/watch?v=kAGo2cgNNeg
Bibliography
1.
M.L. Valenzuela Luna; R.Z. Rios
Mercado - Comparando metodos heuristicos para secuenciar tareas en lineas de
flujo Ingenierias, octubre-diciembre 2004 Vol.VII, n° 25
2.
J.M.Framinan; R. Leinsten;
C. Rajendran - Different initial sequences for the heuristic of Nawaz, Enscore
and Ham to minimize the makespan, idletime or flowtime in the static
permutation flowshop sequencing problem – Int. J. Prod. Res. , 2003, vol.41,
n°1, 121-148
3. A. Agnetis - Introduzione ai
problemi di scheduling, 2000
4.
G. Schmidt - Scheduling with
limited machine availability, European Journal of operational Research 121
(2000) 1-15
5.
M. Solimanpur, P. Vrat, R.
Shankar, A heuristic to minimize makespan of cell scheduling problem – Int. J.
Production Economics 88 (2004), pp. 231-241
6.
M. Selim Akturk, G. R.
Wilson, A hierarchical model for the cell loading problem of cellular
manifacturing system, Int. J. Prod. Res. 1998, Vol.36 n° 7, pp. 2005-2023
7.
Mohammad Z. Meybodi -
Integrating production activity control into a hierarchical production-planning
model IJOPM 15,5 – may 1994
8.
Mark S. Fox -
Constraint-guided scheduling – A short history of research at CMU – Computers
in industry 14 (1990) , 79-88
9.
D.Little, K.Porter,
P.C.Jarvis, J.G.Kenworthy - MRPII and stand alone finite schedulers: the
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Links
http://journalsonline.tandf.co.uk/app/home
http://www.bilkent.edu.tr/~akturk/ie573.htm
http://www.informs.org/InformsArchive/Papers.html
http://hera.rz.hu-berlin.de/speps//contents00.html
http://portal.acm.org/citation.cfm?doid=331697.332335