Synchronizing Schedules for Transportation

Read this article. It discusses synchronizing transportation schedules. Because the logistics segment of the cycle is a large-scale effort, the waiting and queues are magnified. How many different modes of transportation do you think are required to make a product from raw material to the customer's hand?

3. Single Machine Assembly Scheduling Problem

3.1 Forward Synchronized Scheduling Heuristic (FSSH)

Normally in practice, the schedules constructed use dispatching rules and follow a forward dispatch method. Forward approach schedules jobs in a given sequence one by one, starting from the first job, to achieve feasible and compact schedules. The approach usually generates non-delay schedules.  A non-delay schedule is one in which no machine is kept idle at any time when at least one job is waiting for processing. Longest Processing Time (LPT) rule is selected as the dispatching rule. LPT minimizes total earliness in single machine scheduling in the situation of no tardiness for jobs. Since there may be split orders in allocation, the sequence determined by LPT rule may be adjusted to combine the split orders to facilitate assembly manufacturing while maintaining the transportation schedule of the split orders. 

The general scheme for FSSH is: 

Step 1: Group orders that are allocated to the same flight, and sequence the order groups by the rule of earliest flight departure time first.

Step 2:  Use LPT rule to sequence the orders within the each group. 

Step 3: Assembly batching of split orders (ABSO): This step is used to combine the split orders in a batch for assembly so that split orders in transportation can be treated as a whole order in assembly. This step is applied only in the situation when an order is split and allocated to two adjacent flights. The split orders are processed in sequence by scheduling them as last order for the first flight and first order for the second flight. This is to facilitate the assembly processing of an order. 

Step 4: Calculate each order's release time by forward dispatch method starting from the first order to the last order. The first order's release time equals zero. The release time of succeeding orders are obtained by adding the assembly processing time of their preceding orders

Step 5:  Compute the AWT between assembly and transportation. 

The number of order groups in the planning period, corresponds to the number of flights that transport orders to the customer destinations, is determined by the transportation allocation model. Each order group consists of set of orders and they have same assembly due-date.