Five pitfalls to avoid in detailed scheduling

Nick Verstraete
Oct 10, 2017 5:38:48 PM

Detailed scheduling is the most granular level of planning, right before the real action starts in Production. In the so-called ‘frozen’ period, which traditionally encompasses a time horizon of 3-12 days, customer orders or planned production orders in the Master Plan are converted into firm production orders. Although scheduling may seem pretty straightforward, it is often quite complex. It is often difficult to keep the frozen period really ‘frozen’ if Sales suddenly wants to push through rush orders or if shortages of packaging or other materials arise. Beside this external pressure on scheduling, there are some other hurdles too, making scheduling a challenging undertaking.

 We have summed up the five main pitfalls regarding detailed scheduling.

1. Lack of clarity about capacity

When schedulers create an optimal sequence for all the production orders that need to be executed, we often see that they place too much focus on the sequence without having a clear view of the available capacity. In other words, they may be planning 26 hours’ worth of work on one day. That’s where scheduling tools come in handy, since they visualize the sequencing of production orders, allowing schedulers to take on-the-spot action when available capacity is exceeded.

2. Taking account of too many constraints

Planners often draw up complex schedules in Excel trying to take account of as many constraints as possible, such as available resources, capacity and materials. However, we believe that scheduling should be approached step by step, starting with the most important orders and then gradually adding other less important production orders for instance. You will never be able to create an optimal plan that incorporates all possible constraints in one go. A better tactic is to create a schedule and to then tackle constraints very pragmatically. If a specific job requires five FTEs resources, for example, but you only have four available at that time, you can still schedule that task in the knowledge that you will have to enlist the help of a temporary worker that day.

Scheduling is not about simply pushing a button and receiving a capacity-feasible plan. If it were, why would the expertise of schedulers be required? The available tools provide a schedule that covers 90% of your needs based on the basic rules that are built into the tool. The schedulers use their expertise to devise solutions for the remaining 10%, also drawing on reliable information about supply, inventories, etc., provided by the Master Plan. So keep it simple and don’t try to model every constraint if your schedulers have the expertise to tackle it themselves.

A scheduling tool will nevertheless set some helpful parameters, such as for monitoring the desired balance between costs and production order planning. Let’s take a plastics manufacturer as an example: in theory it’s possible to first produce a product at a very high temperature and to subsequently produce a product at a very low temperature. From a cost viewpoint, however, it is not advisable to make such a big shift without producing other products (e.g. at a moderate temperature) in between. So while it’s theoretically possible to plan those two actions in sequence, an optimization tool will never propose that approach because the costs involved in making the production changeover outweigh the penalty costs incurred for late delivery.

3. Incorrect input data

Scheduling demands lots of data, and the outcome can only be reliable if the right data is used as input. Schedulers need the maturity to interpret various types of source data, for example from the ERP system, and translate them into valuable scheduling input.

4. Lack of integration

Planning is not a stand-alone process. Although many scheduling tools are limited to the scheduling process, in order to maximize the value of the scheduling process it makes sense to work with a scheduling tool that integrates different processes. Arkieva, for example, integrates tank management into the scheduling process because tank capacity or the sequence of filling the tanks can have a considerable impact on the efficiency of the production process. So once the right scheduling processes are in place, integration is key to add value during scheduling.

5. Striving for perfection

We often see that companies with multiple plants strive to have a model for each plant, when in reality the differences between the manufacturing processes aren’t that great. So why not develop scheduling templates that can be used in several plants? Such templates are often very useful, but they require the right mindset. Users must accept that the scheduling outcome will be good, but not perfect. Actually, that holds true for all mainly forecast-based schedules; since the very nature of forecasts means that they are never 100% correct, the result can’t be 100% perfect either.

So our advice to you is: don’t try to build a single, all-inclusive solution and don’t attempt to reproduce your Excel-based planning approach in a scheduling tool. Tackle scheduling one step at a time and don’t overcomplicate it by including too many details. Start with a basic model and do the fine-tuning – with an eye for integration – afterwards.


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