Line balancing as a technique is most usually applied to assembly lines, where products can move easily from work station to work station in sequence, often one piece at a time. The principle of line balancing is very simple; ensure that you have allocated and arranged sufficient production resources (machines, manpower, time) for each process step to produce the required customer demand, within the time available to meet that demand.
A common way of calculating the required rate of production to meet the Customer demand is known as Takt Time. This is the production rate (or ‘drum beat’) that a production line needs to achieve, within the available production time, to meet customer demand and NOT overproduce. In simple terms, balancing capacity with demand – but doing so for each process step to allow the product to flow.
The following is an example of a Takt Time calculation;
A Customer orders 3,000 widgets per week from a Supplier. The Supplier dedicates a production line working a single 40 hour/5 day per week shift pattern to make these products. Subtracting any planned downtime such as lunch and other rest breaks, planned maintenance, team briefs etc. that are expected to happen over this working week pattern, we are left with the available production time. Let’s say that the planned downtime amounts to 50 minutes per day. So the available production time per week would be (40hrs x 60mins) – (50mins/day x 5 days) = 2,150 mins/week.
Therefore Takt Time would be (2,150 mins/week) / (3,000 widgets per week) = 0.717 mins/widget, or more simply; 43 seconds.
So, if a good quality widget comes off the end of the production line every 43 seconds, then over the working week, Customer demand will be met exactly, and there will be no over production.
Of course, in real life there will be some hiccups – so it is common practice to balance the production line so it cycles slightly faster than Takt (90–95% is common). This allows the line to accommodate small stoppages and still meet customer demand within the available production time.
A critical piece of information to allow companies to efficiently balance their production lines is to properly understand the cycle time for each process within the line. This is where standard work really supports Line Balancing. It is essential that processes are standardised and performed consistently. This involves identifying and standardising the ‘Best Known Way’ to perform each task, and ensuring operators are trained and competent to follow this standard. Once this is achieved, the process can be recorded (video footage is often the easiest way to do this), and the process broken down into individual steps, or ‘elements’, for which individual times can be recorded. These times should be consistent – too much variation would suggest the process has not yet been sufficiently standardised. These element times then become the building blocks that can be used for the Line Balancing activity. Once you have understood the manual work content of the product you are making, and have correctly calculated Takt Time, it is easy to work out what the ‘ideal’ or minimum manning level for the production line is. Distributing the work element times evenly across the number of workers will balance the line, and support the smooth flow of products through the production line.
There are many benefits to this approach – minimising work in progress, reducing production lead time and improving quality to name but a few. A more in depth explanation of the approach can be found in the publication, ‘Implementing Standardised Work – A Guide’ – published by SMMT, and referred to as a Best Practice within Annex B. of the Automotive Quality Standard IATF 16949:2016.
– February 2020 authored by Mike Scull
A Bit More About Mike
Mike Scull has over 30 years of manufacturing experience within the automotive, aerospace, electronics, off highway, white goods and apparel sectors. Joining Industry Forum in January 1998, Mike underwent training and mentoring in the implementation of Lean Manufacturing with Japanese Master Engineers from Toyota, Nissan and Honda. Mike’s current role at Industry Forum is Principal Consultant – Lean Manufacturing.
Mike is a Chartered Engineer (CEng MIMechE), and has a BSc (Hons) in Civil Engineering. He has professional qualifications including APICS Certified Supply Chain Professional (CSCP) and Certified Production and Inventory Management (CPIM), Certified Demand Driven Planner, PRINCE2 Practitioner and is a Certified Six Sigma Black Belt. He is also an Assessor for the National Manufacturing Competitiveness Levels (NMCL) programme.
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