Q: How do I identify ‘resources’ that are constrained?
A: Any machine / work center / human with utilization consistently more than 80% in the preceding 3 months is constrained. Here is when you start talking ‘Optimization’.
If your resource utilization is consistently less than 66.7%, you can live with basic planning like in MRP. (think golden ratio)
Constrained simply means you are struggling to meet immediate demand with AVAILABLE capacity.
Q: How do I know my bottleneck resource then?
A: You won’t. They keep changing. Visual inspection is the only way. But checking a resource as ‘bottleneck’ (because you think it is), simply means that your scheduling heuristics will schedule operations in a manner that ‘overloads’ bottle neck resources. In SAP these heuristics are e.g. SAP003 – Fix Bottleneck Resources, SAP005 – Schedule bottleneck first but the result of this scheduling can be anyone’s guess. Someone needs to analyze and take a call. The start date or due date can both get delayed for certain orders. Some resources may be left idle most of the time and then that can become constrained in next shift.
Multiple resources can be marked as bottlenecks but no more than 5% of resources should be bottlenecks.
Q: Can a resource be a bottleneck and technically not be constrained?
A: Yes. this can happen because of unexpected downtimes, idle times, non-availability of material being transformed at that resource makes it a bottleneck but not really a constrained resource.
Analogy – Think of long queues at immigration counters. Some officers in some shifts are slow by habit or go for breaks too often. It isn’t constrained by design, but he is the bottleneck responsible for queues. ‘The ‘counter’ is not constrained by design. (it is another matter that they should completely automate this immigration nuisance and get rid of these ugly immigration officers)
Bottleneck simply means something is slowing ‘work’ on that resource. Long queues, bad staffing, bad sequencing.
Q: Are production managers intellectually so endowed to analyze scheduling results and heuristics at such level of detail? Does he know which heuristics to use?
A: A smart production manager knows the Value at Risk – The economic consequence of delaying certain orders or operations and cost of not doing something of little economic consequence. …”kitney ka maal hai” .. Kitney aadmi theey”
What’s the point?
Before embarking on projects involving detailed scheduling, make sure the consultants know the consequences of their advisory. Industry know how. Customer Service Rules. The do-ability, the transfer of know-how, a set of rules on which heuristic to use and when.
