Waiting time before assembly

Few researchers have studied the impact of product structures on flow times, scheduling and due date management policies [41] [56]. For assembly jobs, delays in the system occur not only due to waiting in queues (due to busy resources), but also due to staging, i.e., waiting for the completion of other parts of the job before assembly. Fry et al. [41] study the impact of the following job parameters on the flow time total processing time (sum of all operation... 

The RTM process can be spht into four steps as depicted in Fig. 7.1. First a stack of dry reinforcements is assembled into a preform, often formed into the shape of the final part and held together with some form of binder or stitching. This preform is placed into the mould (Fig. 7.1(a)) and the mould is then closed to the desired final cavity thickness (Fig. 7.1(b)). After closing the mould, a liquid thermoset resin is injected into the preform through one or more inlet ports (Fig. 7.1(c)). Resin cute is then initiated and completed either by implementing a thermal cure cycle or by waiting the desired amount of time before demoulding the manufactured part (Fig. 7.1(d)). 

This applies only to water- or solvent-based adhesives that set by drying. After application on the substrates, water or solvents start to evaporate at the ambient air, and also to be absorbed by substrates if fliese are porous. The adhesive fliickens, becomes tacky or sticky and evenmally develops enough cohesion so that it becomes possible to assemble the parts without risk of parts moving or sliding. The waiting time is the time that the operator must wait before assembly in order to let some water or solvent evaporate and to develop enough tack (refer to definition in Section 2.2.2.13). 

The biggest impact on the supply of parts on time was clearly the way the incoming unserviceable turbines were treated. Previously, these units were fed into the process to balance the workload of the whole operation. This meant that turbines could wait several days in the fully assembled state before being disassembled. Although this workload buffer was effective in managing capacity, it caused a major delay in the supply chain dynamics. 

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