Lean manufacturing is a philosophy that outlines multi-dimensional approaches to reduce waste. This can be applied in day-to-day operations, strategy, customer satisfaction, manpower training and many other places. Over the years, Lean has been misunderstood, misinterpreted and has misled management in many ways. As a result of this, certain myths have emerged about Lean.
Going by the wikipedia definition, “Lean” is a production practice that targets elimination of waste that does not create value for the end-customer. Lean is the set of “tools” like Value Stream Mapping, 5S, Kanban (pull systems), and Poka-Yoke that assist in the identification and steady elimination of waste (muda). The second approach to Lean Manufacturing (which although lacks popularity), is promoted by Toyota, in which the focus is upon improving the “flow” or smoothness of work, thereby steadily eliminating mura (“unevenness”) through the system and not upon ‘waste reduction’ per se. Typical practice in garment industry is to follow one or more of the above tools to implement Lean. Techniques to smoothen flow include production levelling, “pull” production (by means of kanban) and the Heijunka box. There are loads of books and websites defining each tool and technique in detail, in this article I will try to demystify the perceptions about applications.
Value stream mapping, Five S, Seven W are popular Lean approach(s)
Consultants always resort to those practices that are easier to implement, requires negligible cost, and most importantly where existing standard is comparatively low so that showing improvement is easier and quicker. Garment manufacturing factories are generally very disorganized and people tend to cover their backside by keeping buffer. Therefore, it is relatively easy for consultants to plan, organize (by following 5S process) and/or eliminate/reduce buffer (both material and time) by following seven W approach. Value stream mapping maps the VA, NVA, NNVA activities and due to a very low percentage of VA (generally less than 3%) prevailing in the industry, it makes the favourite choice of Lean implementation.
Kanban and Poka-Yoke are less popular Lean approach(s)
Kanban is one of the most promising yet less popular (underutilized) approach to Lean due to poor understanding of logic amongst both manufacturers and consultants. Although some manufacturers unknowingly use kanban (or some improvised version) system in managing accessories inventory without realizing that they already are practicing Lean. Kanban can be potentially helpful in maintaining inventory between cutting & sewing, between different operators in sewing line, and sewing and finishing department; however, rarely anyone attempts the same. Wherever there is a problem of transparency and non-accountability of pieces, one should try to implement kanban approach to limit the stock. Poka-Yoke requires innovative ‘out of box’ thinking and therefore lacking effort from both manufacturers and consultants.
Inventory reduction in one echelon implies Lean implementation in supply chain
Reduction of inventory in supply chain is like an enigma. The supply chain encompasses all departments in an organization and also that of the suppliers and customers of the organization. Lean supply chain means reduction of total inventory in the chain, and not merely shifting inventory from one organization to another. As the common Lean implementation approach is reducing inventory department wise or organization wise, there lays risk of pushing inventory from one department to another or from one organization to another, instead of actually reducing inventory. For example while attempting to reduce inventory (WIP) in sewing line, very often the cut parts inventory in cutting room increases. Similarly while a retailer attempts to reduce inventory, invariably the finished goods inventory increases at manufacturers’ or wholesalers’ end. One should be cautious as the apparel supply chain is downstream dominated; (i.e., a downstream player like retailer is always the dominating partner in relation to manufacturer) very often the inventory is pushed upstream.
Lean implementation compliments quick response retailing
One needs to understand that scale and scope generally does not go together. Quick response works on reduced time to react. Inventory is replacement to information, if we have the correct information what will sell, then we need not maintain inventory. At any given level of information clarity, quick response will require more inventory to be maintained as there is lesser time to react. Technically any company dealing in commodity merchandise can attempt to make the supply chain Lean. In contrary, any company following quick response business model ideally should not wish to be Lean at least in inventory stocking, as the business model requires the company to maintain inventory. That does not mean a quick response company can’t become Lean; the company can implement and practice tools of Lean other than inventory reduction.
Lean implementation compliments fast fashion
Fast fashion is changing of style faster in the store. To change old style faster with new style (and that too with uncertainty), one needs to maintain considerable amount of stock in the supply chain, whereas a commodity product is replenished at slower pace (and with better certainty), meaning information is available, thereby the supply network upstream can be planned in advance. As the certainty of information is better, inventory requirement is lower. Lower inventory means Lean organization.
Kanban implementation in sewing line means Lean approach
There are several ways that Lean can be implemented in the sewing line. An organization which is working in PBU system in sewing line may decide to follow pull system by implementing kanban, where upper limit of WIP that can be created between any two sewing operations be set and adhered to. In this system the last operator controls the flow of material, thus called ‘pull’ system. If any succeeding operator slows down then WIP consumed at slower pace, will reach kanban limit and will slow down the preceding operator eventually. Any organization implementing kanban from PBU system can be attributed to Lean implementation.
Lean implementation in sewing mandates single piece flow
Single piece flow in sewing means Lean implementation, but the reverse is not true, as Lean implementation does not necessarily require single piece flow. There are other ways of implementing Lean in sewing line. Single piece flow means there is zero work in process (WIP) between any two operators in sewing line. This is an extreme form of teamwork, popularly known as Toyota Sewing System (TSS) when pieces moves from hand to hand in a stand up work format and are never kept in bin/trolley. In PBU system, WIP is maximum to ensure continuity, but in TSS number of operators are less than number of sewing machines and multi-skill operators work as self-balanced team in hands-off or bump-back system where succeeding members take the WIP from preceding operators. The objective of Lean is reduction of WIP, therefore Lean implementation may lead to ‘single piece flow’ but not necessarily mandatory.
Reducing inventory across the production line guarantees reduction of manufacturing lead time
Lean considers inventory as one of the seven wastes that needs to be reduced. However, reduction of inventory below a standard value across critical points on the production line, could increase the lead time.
Inventory is rather a buffer against variability. The more the variability, the more the inventory that is required to address it. For example, apparel manufacturing starts with cutting and ends with finishing. Cutting follows a batch production system and sewing is usually a single-piece flow. Inventory (WIP-cut panels-worth one day stock) is kept between cutting and sewing as safety stock for breakdowns and feeding issues experienced in cutting and supply chain respectively. Lack of WIP could starve sewing of panels just in case cutting experiences manufacturing variability.
Management decides to keep standard WIP in critical areas across the production lines to address internal variation. While one could say that reduction in inventory reduces manufacturing lead time, it does not guarantee lead time reduction, because it could lead to starving in system, in turn, leading to capacity losses.
5S (Workplace organization) will always improve production
Workplace organization definitely assures ‘place for everything and everything in its place’. However, the hypothesis that 5S can always improve production numbers is debatable.
Improving production number requires consistency in the application of :
• Workplace Organization
• Waste Elimination
• Process Standardization
• Continuous Improvement
Production numbers improve if we can identify the capacity constraint (bottleneck) and improve the flow through the bottleneck. While 5S may reduce the searching time, it does not always improve production numbers unless we remove the bottleneck across the production lines.
Lean makes you work harder
This is the most common perception about Lean. One fundamental and strong pillar of Lean is ‘Just in Time’. An inextricable element of JIT is Takt Time planning.
Takt Time matches the pace of production to the pace of sales. Logically speaking, Takt Time establishes the production rhythm. Imagine that you are an operator on the production floor, desperately trying to recover production numbers towards the end of the shift. Mistakes are bound to happen with a faster than possible rate of production. Moreover, overburden caused to the operator results in defects and excess inventory creation.
Lean establishes a pacing mechanism throughout the factory. Adopting a standard pace across the factory makes people work smarter and not harder.
Single-piece flow can only improve quality and reduce manufacturing lead time always
To achieve a continuous flow, the ultimate goal recommended by Lean is a single-piece flow. However, single-piece flow may or may not always improve quality and lead time.
Take the example of a shirt production line. We observe that batch production is usually followed in parts production. The reason being that single-piece flow could actually increase one’s non-value add time. Cycle time on workstation consists of:
• Value add time (stitch time – change in the fit, form and function of the product)
• Non-value add time (something that process does not need at all)
• Essential non-value add time (steps that do not add value, but are required currently).
Most experts point out that single-piece flow in parts assembly increases the ENVA (for example, the time it takes to pick the part from the UPS conveyor to stick and place it back on the conveyor, may take more time than the stitch time). Therefore, in such a case, batch production is faster than the single-piece flow.
Quality can be improved using both batch production and single-piece flow, usually when labour-intensive work is involved. The output largely depends on the operator’s skills, and as long as skills are upgraded and consistent, the quality also remains reliable as well.
Lean is a destination
Lean is more of a transformational journey in itself, rather than being a destination. Most companies deploy Lean tools and techniques for a period of 18-24 months. Sometimes, quality and production improves only by applying these techniques, but one observes that unless a strong culture is established, the improved results soon wither away.
Lean can only be sustained by reinforcing the following elements on a daily basis:
• Visual Factory (Detecting abnormalities visually)
• Daily Accountability (Culture of having meeting at the right time and right place with the right people)
• Standard work executed at all organizational levels
• Institutionalization of a Continuous Improvement (Kaizen) Culture.
Lean production not only successfully challenged the accepted mass production practices in the automotive industry, significantly shifting the trade-off between productivity and quality, but it also led to a rethinking of a wide range of manufacturing and service operations beyond the high-volume repetitive manufacturing environment. Most importantly we need to understand why we need Lean… To reduce inventory? To better organize things? To checkmate mistakes? What is our priority? Instead of starting to think about Lean, we should start thinking about the objective first which will help us identify the correct Lean tool. As waste is eliminated gradually, quality improves while production time and cost are reduced.