Main > frePPLe Tutorial > Constraints: Not enough time...
The current plan has no constraints, and the results are identical to a classic MRP explosion of the demand. In this section we'll see how frePPLe handles lead time constraints in the plan.
- Update the due date of the demand to be January 5th, i.e. a few days after the current date.
In the previous section the current date of plan was configured with the parameter currentdate and is currently set to January 1st 2009. - Create a constrained plan.
The demand can't be satisfied at its due date.
FrePPLe creates a plan that delivers the demand at its earliest possible delivery date. - Review the results
- Problem report
A problem report is available to highlight infeasibilities and constraints in the plan. The user doesn't need to browse through all entities one by one, but his attention is immediately pulled towards the issues.
In our current plan we see the late delivery as a problem, together with some problems about excess inventory. The excess inventory is caused by the minimum purchase quantity we defined on the purchasing operations. - Demand plan report
In the problem report, click on the demand name and select "plan". The demand plan report allows you to see at a glance which operation caused the delay: clearly the purchasing of the .
Notice also that there are 3 "make fabric @ factory 1" operations planned in parallel to minimize the delivery delay.
Observe also how the "Purchase ink @ factory 1" operation is planned just-in-time for the make operations. The availability of both components "ink" and "thread" is coordinated. - Why short or late?
In the problem report, click on the demand name and select "why short or late?". The constraint report will identify the reasons why the demand was not satisfied in time.
- Problem report
- Create an unconstrained plan.
FrePPLe also allow creating a plan that deliberately ignores some constraints, which can be very useful to highlight and summarize the demand and supply inbalances.
In our simple model, the unconstrained mode will plan operations to be performed in the past. The problems about the excess inventory remain. - Review the results
- Problem report
The problem report doesn't report any late demands, but operations in the past. - Demand plan report
The Gantt shows us the operations planned in the past. - Why short or late?
Since the demand is met on time in this plan this report is empty for our demand.
- Problem report
- Exercises
- Our demand had a quantity of 100, and we also specified a minimum shipment of 100. This indicates that we don't allow partial shipments of the demand, i.e. an "all-or-nothing" delivery policy.
Try reducing (or removing) the minimum shipment quantity and recreate the constrained plan.
What is the earliest day you can ship anything to your customer?
Does the unconstrained plan change? - Assume that our factories have a frozen manufacturing plan of 3 weeks. This means that we can't freely plan additional "make fabric @ factory 1" operations in the first 3 weeks of the horizon.
Update the model with this contraint (hint: field 'fence' on the operation), recreate the constrained plan and see how this impacts the results.
(This exercise isn't completely realistic: we'll normally load the frozen manufacturing plan in frePPLe as well, such that the planned production can also be used to satisfy demands.) - In the constrained plan we noticed 3 parallel make operations.
Why are there 3? Can you change the model to have a different number of parallel operations?
- Our demand had a quantity of 100, and we also specified a minimum shipment of 100. This indicates that we don't allow partial shipments of the demand, i.e. an "all-or-nothing" delivery policy.