We mainly outline basic rules for the implementation of Workload Control. The detailed implementation of Lean Work Design is different for every firm - every firm is special.
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Important Questions before Starting the Implementation of Workload Control?
If you are considering implementing Workload Control in your company, the first question you should ask yourself is:
Is this the right solution for my shop?
Workload Control is considered by many to be the leading production planning and control solution for make-to-order companies producing products in response to customer demand. These are typically high-variety shops producing customized products, perhaps for the first time or on a repeat basis. Products take varying routes through the shop, processing times vary and are often uncertain, and set-up times also vary. Few companies are pure make-to-order companies – assembling some products to-order or producing others in advance of customer demand – but the dominant production strategy is likely to be a make-to-order one.
Having established that Workload Control is the right approach, it then becomes important to ask:
How does this approach differ from what we do already?
The greater the degree of change required, the more time and emphasis will be required in preparing the ground for implementation, training personnel, etc. Workload Control emphasizes, for example, the need to delay the release of orders to speed up completion. This can be quite a counter-intuitive idea requiring a change in mind-set.
You may then ask:
What form will Workload Control take in my company?
Some implementations of Workload Control have been achieved by programming a decision support system (e.g. Hendry et al., 2013); others have been achieved using simple spread sheets (e.g. Silva et al., 2015) . In addition, implementation could take the form of COBACABANA a card-based system similar in some ways to Kanban but suitable for high-variety manufacturing . The choice is likely to depend on the size of the company, the current software in use within the company, the programming skills available, etc. A small shop may choose a simple card-based solution or find a spreadsheet to be appropriate. A larger company may have the resources to develop a specialist software system that may also be linked to existing data and systems, such as an Enterprise Resource Planning (ERP) system.
Implementing Workload Control
To implement Workload Control it is important to group machines on the shop floor into work centers. This may be particularly important if there are, for example, more than 10 machines in the shop. As Workload Control involves regulating the workloads of shop floor resources, it is necessary to limit the number of resources or the approach may become unmanageable. By grouping machines, the workload of the work center rather than that of the individual machines can be controlled. But grouping the capacities relies on the machines being reasonably interchangeable. If there are a large number of machines and they cannot be grouped, it may be necessary to restrict the use of Workload Control to a subset of the shop’s resources, e.g. key constraints.
To implement Customer Enquiry Management:
1 - Establish the feedback loops: In other words, start counting the workload. But maintain the previous due date setting procedure. This is necessary as the workload currently in the pool and on the shop floor is not accounted for by the forward finite loading procedure.
2 - Start setting due dates through Workload Control, once all of the workload in the pool and on the shop floor is accounted for.
To implement Customer Enquiry Management - COBACABANA:
1 - Establish the feedback loops: In other words, start counting the workload in the pool.
2 - Determine operation throughput times: Establish a good estimate of the operation throughput times on the shop floor.
To implement Order Release:
1 - Introduce a periodic release procedure: Rather than releasing all jobs when they arrive release them in periodic time intervals. Here you still use an infinite norm, e.g. all jobs are released in periodic time intervals. Introduce the continuous starvation avoidance trigger e.g. by allowing the worker to pull a job from the pool if he/she has no work.
2 - Establish the feedback loops: In other words, start counting the workload. Each job contributes to the workload when it is released. Note that it is only required to know whether the workload contribution is small, medium or large to realize most of the performance benefits of Workload Control. In this case, the small, medium or large workload contribution represents a certain range of load contributions, rounded to the estimated average in that range (Thürer et al., 2014). Before release, the workload of each work center is updated by subtracting the contribution of the operations already done. This calculation only needs to take place periodically. In other words, feedback from the shop floor on which operations are already completed is only required when the periodic release decision is taken (i.e. in periodic time intervals).
3 - Limit the workload by introducing the workload norm: Once release procedure and feedback loops are established start introducing a workload norm. The major variable in the Workload Control (and COBACABANA) system is the workload norm level.
It is necessary to set a workload norm (or limit) for each work center that will be controlled, although all of these norms could be set equal to each other if the capacity is equal. When setting these norms, it is important to think about the shop floor throughput times that you would like to be able to achieve and the need to balance the shop floor throughput with the pool waiting time (and therefore the overall lead time). If the norms are set too high then jobs will be easily released onto the shop floor, but there will be long queues on the shop floor and operators can ‘cherry pick’ from the queue in front of a resource. As a result, shop floor throughput times will escalate. If the norms are too low or too tight then orders will flow quickly through the shop, and operators will be forced to work on the most important orders, but it will be difficult to release jobs – particularly large jobs – from the pool. As a result, the pool waiting time will be very long. It is therefore important to find the ‘sweet spot’ that achieves the best balance between the pool and shop floor times. In practice, this is likely to rely on some trial and error combined with experience of the company’s particular manufacturing system. When first implementing Workload Control, it may also be necessary to gradually tighten the norms, both to find the best level iteratively and to avoid dramatically reducing the workload limits and ‘shocking the system’ in the short term.
Lowering workload levels too fast may have several negative implications:
On the Shop Floor: Lowering norms - and consequently workload levels - too fast, can temporarily deplete the direct load buffer in front of a work center introducing work center idleness and associated performance loss.
At Customer Enquiry Management: Lowering norms - and consequently workload levels - too fast increases the number of jobs in the pool and consequently the variability of the pool load which makes due date estimation more difficult.
Rather workload norms should be lowered step-wise.
This gives sales the time to gather experience with the due date estimation procedure. This is especially important in periods of high load when e.g. capacity adjustment need to be planned. Meanwhile, people on the shop floor have time to solve e.g. quality problems previously hidden by high work-in-process which may now become evident.
Once such problems have been resolved, it may be possible to tighten the workload norms even further.
The above gives an impression of some of the key Workload Control specific considerations. But, of course, some elements of a Workload Control implementation are like the implementation project of any other system. For example, it is important to have commitment to the project, to have top management support, to have the right people involved in an implementation, to commit enough time to training, to communicate (including with key customers) and involve shop floor employees in the process, to ensure project momentum is maintained and that the implementation is sustained, and so on.
Finally, having implemented Workload Control, it is good practice to occasionally revisit and review the parameters set to assess whether they need to be adjusted.