In textile industry, the demand from customers fluctuates beyond imagination and this often affects the supply chain. The customer orders will most likely fluctuate from day-to-day. One day customers will want 10 pieces of a white silk fabric and 7 pieces of a red chiffon fabric, the next day could be 12 red and 7 white pieces. The obvious problem in this is the variation in demand by the customers. Whatever the numbers, they will vary.
In such a scenario, textile industries struggle to keep up with the varying demand. There are some inventory management methods that have been developed to ensure that the variance is smoothed out. In such a scenario Heijunka, a technique used in lean manufacturing for reducing the waste can be effectively utilised for production smoothening and product mix levelling. The main aim of applying the Heijunka method is to supply goods at a constant rate so that upstream and downstream processes can also function at a constant and predictable rate, thus reducing the inventory.
Take example of a textile firm struggling to keep up production as per demand. If customer demand of a garment is 15 pieces on one day and then the demand fluctuates by three-four pieces per day, the firm can use the Heijunka method to control this variation. The firm can set the level volume at 15 garments per day according to the demand, production would replenish the 15 garments that are ordered. On the second day, if the order is of 19 garments (4 garments higher than levelized production volume) the company would still produce 15 garments and the shipping area would take 4 garments from an inventory known as 'Fluctuation stock'. On the third day, if the order will be 13 garments, which is two less than the Heijunka volume, two garments can be rebuilt and put back into fluctuation stock. This is a very basic idea of how the concept works.
Heijunka method implies that there is even distribution of production volume and mix. Heijunka converts the uneven demand into even and predictable manufacturing process thereby helping to bring stability in a manufacturing process. This method is very different from the traditional approach.
The traditional approach focuses on varying production scheduling in harmony with the changing pace of demand. Nevertheless, this approach can result in higher inventory level, several number of defects, idle time and also overtime. Another shortcoming of the traditional approach is that with higher level of inventory of a particular garment can result in over-production of garments not in immediate demand.
The basis of Heijunka is to use small batches of different styles in the midway stage. So speaking of textile process involving Cut-Sew-Finish, the batches will be used in sewing. In Heijunka, the rate of production of intermediate products is maintained at steady rate, so processes employed for product finalisation like special finishes, washes, etc. require less and predictable time. Consistent product quantities can help to maintain constant process parameters at subsequent processes like washing, surface finishing, which can help achieve more predictable process output. Heijunka achieves this through two tools, namely - Demand smoothening and Production levelling.
In demand smoothening, the long-term demand for the style that is in order is calculated to ensure that the production process runs smoothly. Thus, irrespective of short term fluctuations in demand, demand smoothening tries to schedule production as per calculated long-term demand.
In product leveling, unlike traditional scheduling, where similar styles are grouped to make large batches, smaller lots of different styles are scheduled together. For cost viability, a textile industry needs to minimise change over and set up time, thereby ensuring that smaller batches are not prohibitive and lost production time is not significant. Product levelling will ensure that demand for parts upstream is also levelled. To simplify levelling of products with different demand levels a visual scheduling board known as a Heijunka box is used.
There are several reasons for implementing Heijunka. First reason is that an even mix of products is critical to avoid impact of changes in demand. With application of Heijunka, consumption of raw materials improves, as only that which is required is produced. It is much easier to avert manufacturing too much of one product and also consuming components that are needed for another should be a thing of the past. Another major benefit is a reduction of stress levels in the production area. The production schedule should no longer be a guessing game as staff will know each day how much product is expected and be able to plan accordingly. This can go a long way towards improving morale. The Heijunka technique is popular in countries like U.S.A. and Japan.
Heijunka technique ensures that, irrespective of the business domain, companies focus on speed, efficiency, and customer value, as these factors are significant for global success. The long-term competitiveness and agility of textile sector depends on organisation's commitment to continuous improvement and Heijunka ensures that the problems of varying demands are solved and work process is improved.