Why Detailed Production Scheduling Is Difficult

You can probably name more, but here are some key reasons that production scheduling is difficult and often frustrating:

Demand varies, sometimes a lot.  If you are manufacturing high volume, repetitive, promotionally driven goods, then you may have an opportunity to “level” demand and run a mixed model schedule in a very lean fashion (e.g. assembly line).  Even here, however, the manufacturer can’t completely control the marketplace and simultaneously be pull-driven.  On the other hand, if you run a make-to-order job shop, demand is highly variable by definition.

 

Demand is seasonal.  If you have seasonal demand and lots of idle capacity or a ready cadre of contract manufacturers or co-packers, then this may not be as big of an issue, but in many industries, it is simply too expensive to maintain capacity to handle seasonal peaks.

 

 

Procurement/production lead times always exceed customer tolerated wait times.  This is pretty self-explanatory. 

Constrained capacity.  As demand varies day-to-day and seasonally, there will be times when you just don’t have sufficient capacity for every product demanded, and you have to find a way to maximize, or at lease, prioritize throughput.

 

 

Shifting bottlenecksIf you have a single bottleneck and it is constant (doesn’t shift to another machine, work center or resource), then there are techniques that will work reasonably well for this scenario.  However,  in a job shop, for example, the bottleneck may change often, based on the mix of items being produced.

 

Economies of Scale.  Equipment setup time is never zero.  Capacity is never infinite.  Manufacturing time is never zero.  Therefore, lot sizes are never just one unit, with the exception of completely make-to-order, complex, customized machinery where the customer’s willingness to wait is equal to or exceeds the time it takes to manufacture the item.

 

Sequence dependent setups.  With any more than just a couple of products with different changeovers that depend on the sequence in which they are produced, this becomes pretty challenging to do.

 

 

Dedicated equipment.  The more that factories, work cells, equipment or people are focused on just one product or set of products, flexibility is significantly reduced.  While this means there are less options to evaluate, it also means there are fewer options available to help meet the goals of the scheduling process.

 

Manufacturing Defects.  This can be especially challenging where there are sequential operations and a defect in the last operation can cause the whole lot to be scrapped, effectively wasting not only that operation, but all of the previous operations as well.

     

Next week, I’ll look at why scheduling software packages often fall short.

Thanks once again for taking a moment to allow me to share my thoughts with you.  I leave you with these words from Henry Ford, “Before everything else, getting ready is the secret of success.”

Have a wonderful weekend!

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About Arnold Mark Wells
Industry, software, and consulting background. I help companies do the things about which I write. If you think it might make sense to explore one of these topics for your organization, I would be delighted to hear from you. I am employed by Opalytics.

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