|
|
|
|
|
|
Our Enterprise-Wide Manufacturing
Data System performs MRP. Why do I need a separate planning or scheduling solution?
|
|
|
|
|
|
As discussed below, MRP is NOT scheduling. In the best of worlds, MRP would work
out all of the operational details to have the most accurate estimate of capacity,
and an exact determination of the time at which raw materials must be available.
Enterprise Wide Manufacturing Data Systems do not perform this detailed calculation,
because planning or scheduling to maximize capacity in the presence of finite resources
is mathematically a very complex problem.
You need an optimized planning/scheduling solution to precisely know the capability
of your business, and to have the power to determine how to improve that capability.
High level MRP based planning models simply are not capable of doing so.
top
|
|
|
|
|
|
What benefits can I expect
to obtain by implementing a Planning/Scheduling solution from Applied Optimization?
|
|
|
|
|
|
For a summary of benefits, click here.
top
|
|
|
|
|
|
What is a Schedule?
|
|
|
|
|
|
A schedule is an assignment of tasks for given resources (equipment or personnel),
at given times.
top
|
|
|
|
|
|
What is the difference between
scheduling and planning?
|
|
|
|
|
|
Planning and scheduling both refer to the allocation of resources to meet product
demands subject to process constraints. By convention, planning addresses a medium
to long time scale of months to a few years, while scheduling addresses a shorter
time scale of days to weeks.
top
|
|
|
|
|
|
What is a Feasible Plan or
Schedule?
|
|
|
|
|
|
A feasible schedule is one that satisfies manufacturing constraints, including material
balances, hard demands, inventory and resource limitations and user defined criteria
such as campaign length and minimum run length. A schedule is not feasible if even
a single constraint is violated.
top
|
|
|
|
|
|
What is an Optimal Plan or
Schedule?
|
|
|
|
|
|
An optimal Plan or schedule is one that is feasible and has the best possible performance
with respect to a desired performance criterion. Common performance criteria are
maximizing profit, or minimizing production costs.
top
|
|
|
|
|
|
What is MRP?
|
|
|
|
|
|
Basically, MRP is a calculation method geared toward determining how much of which
raw materials are required and roughly when they should be ordered to fulfill a
set of product orders. MRP generally consists of four steps: 1. Bill of Materials
Explosion - looking backward from each product, determine which intermediates and
raw materials are required, and in what quantities. 2. Netting - compare the above
quantities against current inventory. 3. Lot Sizing - determine how the needed materials
will be purchased or produced. 4. Start Date Determination - based on cycle time
information, determine when each order should start production.
top
|
|
|
|
|
|
Is MRP the same as Scheduling?
|
|
|
|
|
|
No. MRP, depending on the implementation, usually generates rough plans of which
tasks will be done during a given planning horizon. However, the exact sequence
of carrying out the plan, including the allocation of finite resources among the
potentially many products, is not generated. Since MRP does not typically analyze
the details of carrying out its plan, the feasibility of the plan is not necessarily
guaranteed. In particular, capacity may actually be overestimated by an MRP system,
which can result in unrealistic production goals.
top
|
|
|
|
|
|
Why should I be interested
in a scheduling or planning solution?
|
|
|
|
|
|
To optimize process operations in order to improve customer service, lower production
costs, reduce inventory and/or increase capacity. Another reason is to make the
scheduling and planning process transparent, replicable, and institutionalized.
top
|
|
|
|
|
|
What are the most important
factors to look for in a scheduling and planning tool?
|
|
|
|
|
|
Effectiveness, extensibility, ease of use and cost. Other factors to consider are
support and database integration.
top
|
|
|
|
|
|
What kinds of products are
available in the planning and scheduling arena?
|
|
|
|
|
|
Products are available costing anywhere from a few hundred dollars to hundreds of
thousands of dollars. The less expensive products essentially replace a pencil and
paper and allow manual construction of a Gantt Chart on a computer screen. The more
expensive products contain algorithms to automatically generate plans and schedules.
It should be noted that there is enormous variability in the capabilities of algorithms
in high end packages. You should insist that an expensive tool be demonstrated on
their process or one of similar complexity and structure.
top
|
|
|
|
|
|
What is the total cost of
ownership for a scheduling and planning tool?
|
|
|
|
|
|
It is the sum of the software cost, consulting fees, and indirect costs attributable
to training, database integration, and maintenance of underlying models.
top
|
|
|
|
|
|
How can a non-expert distinguish
between the many products and companies servicing the growing scheduling and planning
market?
|
|
|
|
|
|
While there are a lot of products, services, and features in the market, the prospective
client need not entirely base their choices on sales literature and sales representative
claims. Asking for a demonstration is one way to assess how a product will perform
in your application. Nothing is better than watching a system work on the real data.
top
|
|
|
|
|
|
Why have optimization and
mathematical programming based approaches not been used in the past for scheduling
and planning applications?
|
|
|
|
|
|
Essentially, the huge number of equations and variables implied by industrial scale
problems has been too large for the past combinations of solution algorithms, computer
memory and processor speeds. The dramatic increase in computer memory and speed
has finally reached the point where more sophisticated mathematical programming
based approaches are tenable.
top
|
|
|
|
|
|
Is there evidence that Optimization
and Mathematical Programming Technology will become dominant in the scheduling and
planning area?
|
|
|
|
|
|
Many companies that offer scheduling and planning tools also offer tools that are
geared for supply chain applications. Notice that these tools are almost always
based on linear programming approaches and sometimes use mixed integer linear programs
with a small number of integer variables. Given the number of similarities between
supply chain and more detailed scheduling and planning applications, one would expect
that mathematical programming would also be successful on the more detailed scheduling
problems. The predominant reason that mathematical programming is not applied is
that translating the successful solution methods from the supply chain to the more
detailed level requires a significant skill base and investment of time on the part
of a vendor.
top
|
|
|
|
|
|
What is the mathematical programming
approach for solving scheduling and planning problems?
|
|
|
|
|
|
The mathematical programming approach translates all of the decisions that must
be made in a scheduling and planning problem into a set of variables whose values
determine all the features of a solution. The physical constraints of the problem
such as material balances, resource limitations, hard demand requirements and forced
equipment outages are written in the form of equations using the variables. The
goal guiding the solution of the scheduling and planning problem is supplied as
an objective function which also uses the variables. Once defined from problem data,
the mathematical program can be solved to determine feasibility and, in some cases,
optimal solutions to the scheduling and planning problem.
top
|
|
|
|
|
|
Our Enterprise-Wide Manufacturing
Data System performs planning and scheduling, why would I want to invest in yet
another software system?
|
|
|
|
|
|
The expertise of Data System vendors resides in Database and Transaction Systems,
not planning and scheduling. If your Data System is capable of planning or scheduling,
it may not be fully capable of generating operationally feasible schedules. Furthermore,
if scheduling is not the main product focus of the vendor, its growth path is not
assured. You may not have access to advanced capabilities such as cost optimization
or improved capacity utilization as the scheduling software industry expands the
technology envelope. If you perform production scheduling with less capable methods,
you concede a valuable competitive advantage. The best way to remain competitive
is to assemble a system composed of best-of-breed software for each aspect of your
business. Before committing to the scheduling engine included in your Data System
software, verify that it is capable of handling your real process constraints and
that it can generate usable schedules.
top
|
|
|
|
|
|
How do I integrate data and
maintain its integrity when using multiple software systems?
|
|
|
|
|
|
Data integrity must be assured for each client of the data, whether the client is
a human or a software package. As such, the responsibility for data integrity must
be placed on the central repository. Other tools can operate on data and even cross-check
data integrity. Although it is essential that software components communicate, the
important factor to keep in mind is that projects succeed primarily because each
component excels at performing its designed task.
top
|
|
|
|
|
|
How can I perform valuable
"What if?" studies and maintain data integrity?
|
|
|
|
|
|
Historically, plans and schedules have been generated for operations and the factory
floor. Today, business changes are demanding more. In order to answer, "What if?"
questions, data must be modified off-line. Clearly, it is impractical to make an
entire copy of the Enterprise Wide data for each experiment. Rather, applications
can extract a subset of data pertinent to the "What if?" and operate locally on
that data. The central repository is left correct and intact.
top