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84 SMT Magazine • September 2017 mate that the total required labor would be 110 hours. Set-up, programming, etc., and balanc- ing against available capacity is discussed in the next section. In our example above it is not important whether you use actual minutes or tenths of an hour. It is important that whatever meth- od you decide to go with that it is consistent and applied equally across all assemblies be- fore the data goes into the system. All the oper- ators using the system should also understand the "rules" as well before misinterpreting 1.1 for minutes vs. hours. It is easy to see in the example above how much time can also be accumulating in what may be considered "non-key" process steps. If you were to only count the SMT time and post- wave time in the example and were only track- ing this in your labor estimates, you would be missing 19 minutes' worth of labor required for every one of those 100 units. This would amount to 32 hours' worth of labor or roughly one man-week. That is also why it is important to identify and capture any work center that the product is likely to pass through. Consideration should be given to the fact that many work centers have significantly low- er cycle times than others, particularly the ma- chine-driven work centers. Careful consider- ation needs to be given to the buildup of in- ventory queues around constraint operations and its working capital impact related to the lot sizes quoted. The notion to run a work cen- ter as much as and fast as you can create seri- ous inventory issues. The goal is for product to flow and avoid the buildup of excess invento- ry queues in front of constraint work centers as much as you can. Focus your efforts in sched- uling the constraint work center and base your production releases on the ability of these con- straints to process parts further down the pro- duction flow. Products will not move any fast- er than the constraint work center therefore it does not matter how fast you run previous work centers, product will just sit waiting for the pacemaker. 7. All available resources are identified in each work center. To complete the other half of your CP mod- el, you will now need to identify the "available" resources in each work center. Depending on the type of model you are running, these will either be labor hours, machine hours or com- puter hours. (Other variables may apply.) If you are estimating the available labor hours simply begin by taking a head count in each work center. First, note the "fixed" labor— the labor that does not float in and out of that work cell to work on other assignments. These should also be the resources that are available to apply labor to the product not supervisory head - count unless they are a "working" supervisor. Once you have identified all the fixed or sta- ble labor, estimate the net "heads" for those re- sources that move in an out of that work center. For instance, if you have two people that spend half of their day in that work center then you would add an incremental "1" for your available headcount. Total the two amounts, the fixed and variable resources. You will then need to discount this amount somewhere between 10- 20% depending on your estimated time spent on set-up, programming, material transit time, tooling set-up, operator fatigue, break times, unplanned stoppage, sick time, vacation time, meeting times, clean up times, line set-up, etc. This discount will vary depending on how you can overlap or utilize your time wisely. IMPLEMENTING A CAPACITY PLANNING TOOL Figure 7: Here, we see an MC Assembly worker proudly displaying a freshly completed PCB board off mass solder operation.