Overview of the Scheduling Tool
A scheduling tool was created in Microsoft Excel with the aid of Visual Basic for Applications. The tool allows initial solutions to be created and then improved. The solutions are constructed using the processing schedules that are given to the contracted catchers. The processing schedule specifies the order in which the farms are to be visited. The order cannot be changed as it reflects plant and bio security requirements. The solutions consist of the following information:
∑ Which trucks go to which farms and in what order
∑ How many modules the trucks are to take to each farm
∑ Which farms the van visits and in what order
Once the vehicles have been assigned to farms, the timing of the schedule is then estimated. This produces an Excel spreadsheet for every truck and van available, informing the user of every point in time that an event takes place. Events include the following:
∑ Truck/van arrival at the plant and farms
∑ Truck/van departure from the plant and farms
∑ When the trucks begins filling with full/clean modules
Figure 2 displays part of the timing sheet for truck 1. Truck 1 was not assigned to the 'Farm 1' and so the first farm that truck 1 visits is 'Farm 2'. Truck 1 visits a total of three farms and finishes its shift at 10:56 a.m..
|Farm||Demand||Trip number||Modules delivered/ picked up||Catching gang start||Catching gang depart||Farm arrival||Start catching||Farm departure||Plant arrival||Plant start unloading||Plant departure|
|Farm 2||11||1||11||3||3||2:13 a.m.||2:20 a.m.||3:24 a.m.||3:38 a.m.||3:38 a.m.||4:17 a.m.|
|Farm 3||22||1||22||3||3||4:27 a.m.||4:34 a.m.||7:14 a.m.||7:24 a.m.||7:24 a.m.||8:13 a.m.|
|Farm 4||35||1||22||8||8||8:25 a.m.||9:27 a.m.||10:15 a.m.||10:27 a.m.||10:27 a.m.||10:56 a.m.|
2. The timing of truck 1ís schedule
The event times make it possible to calculate the number of clean module stock outs at the plant and the amount of downtime that the trucks and van sustain throughout a shift. These are used to measure the performance of the schedules.