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Why centre-lining is the secret to process perfection

Why centre-lining is the secret to process perfection

To meet or beat the often-changing demands of your customers consistently, you must be flexible, reliable and valuable. This is where centre-lining can help. Applied properly, centre-lining not only reduces variability in quality, it also increases machine efficiency and stabilises production.

Centre-lining is a collaborative process, typically used to identify and optimise KPIs within a production line. It can help you rationalise operating expense as a KPI where process improvement opportunities can be identified to ‘lean out’ machine utilisation. This means accounting for operating the production line assets only when necessary, using standard work operations and functions.

The two objectives of centre-lining are to determine the best settings for a production process and to ensure that the best settings are always used during production. As a result, centre-lining reduces variability in quality, increases machine efficiency and stabilises production.

The centre-lining methodology uses established process settings to ensure a consistent manufacturing process. These process settings often consist of ranges – with upper and lower control limits – to allow for flexibility to deal with outside influences. See graph below:

To prepare for centre-lining a process, take these four steps first:

1. Identify the important process factors or variables

The key variables in your manufacturing process can be determined by operators and agreed upon by the relevant stakeholders. It’s important to select the correct variables if you truly expect to have a positive effect on the process and product quality. That’s why it’s advisable to get a subject matter expert, such as a process, technical or quality specialist, to evaluate your process and identify the variables you’ll centre-line.

2. Determine the best settings and ranges for all of the important variables – by grade or product if multiple products are being produced

Your next step will be to create limits for these key variables. Here, you’re basically determining the acceptable range for each variable. Anything falling outside of the acceptable range will result in unacceptable product quality. The implementation of these settings will be the responsibility of asset care personnel.

3. Determine how these variables affect the process and the product

Once your key variables and variable limits have been established, you’ll need to monitor them to evaluate your newly centre-lined process. This is where access to accurate, clearly presented data is enormously important. (It’s certainly possible to evaluate a centre-lined process using manual methods of data recording, but it takes considerable time to record and recall that data and the possibility of data error is quite high.)

4. Ensure that the centre-lined settings are always used during production

Now that you’ve figured out your optimal process, here’s where you refine your formula. Inform operators and engineers about your new processes and make resources available that allow them to easily understand any changes you’ve implemented. At this stage, you’ll want to make sure you have solid reporting on an hourly, daily or weekly basis to evaluate product quality against centre lines.

The infographic 12 steps to reduce variation with centre-lining unpacks the implementation process in greater detail.

Centre-lining is a never-ending process, and continuous work on all of these steps is needed in order to reap the most benefits. Centre-lining can also help in the detection of process upsets, which allows corrective or preventative actions to be taken.

Centre-lining alone, however, cannot achieve all of the potential benefits. The best results can only be achieved if the equipment is properly maintained and upstream processes are also centre-lined. Additionally, easy access to process data and trends from past runs can enhance centre-lining efforts by making it easy to determine where the process is, where it’s supposed to be, and where it has been historically.

Download How To Guide: Developing a customer-focused quality improvement plan for more tools and techniques to drive process and product improvement.


The TRACC framework helps organisations build standardised and integrated good practice and performance capacity across their Plan, Source, Make and Deliver functions. Simultaneously it accelerates their collaboration and alignment capacity to build world class end-to-end value chains, enabling the organisation itself to become the ultimate source of sustainable competitive advantage.


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