Lean has become a key transformational buzzword in the apparel manufacturing industry. However, a lot of confusion exists in understanding the principles and applying them practically on the shopfloor. Understanding the connection between strategy and principles is key to implementing LEAN on the shopfloor. In this series of articles, Anand Deshpande, Founder and CEO – Admaa Consulting connects the principles with measurables and strategy to achieve those measurables on the apparel shopfloor. In short, it provides a structured approach to design a lean process and suggest major factors and strategies to consider in doing so. The second part of the series discusses how to develop a plant-wide strategy for designing a lean process with a total of 19 strategies with brief examples.
Ensure materials flow in the direction of assembly area To avoid the back and forth movement of materials, generally speaking, the materials must flow from the parts section in a linear manner into the assembly area. This strategy will also reduce the throughput time, inventory and operating expense.
Incorporate feeding areas next to the point of use Having feed areas next to the point of use eliminates the need for a remote storage or double handling.
Reduce material transfer distance between processes Reducing the material transfer distance between departments has many advantages:
• Reduction in lead time
• Decrease in amount of inventory required between departments
• Reduction of space requirements
• Reduction in transportation requirements
• Support to single-piece flow
• Quick communication between departments
Allow waste after processing to flow away from assembly lines Strategy: 5
Get rid of multiple storage locations for same parts By deploying single storage for threads as shown, we can save space and reduce communication.
Create a SuperMarket between cutting and sewing processes Application of Kanban System between cutting and sewing departments in an apparel factory.
Strategy: 7 Develop a single-piece flow wherever possible (reduce lot sizes continually) Single-piece flow refers where one item is produced at a time. Each piece is moved to the next process step without any stagnation in between. The single-piece flow reduces process and lot delays. Process delay occurs when an entire lot is waiting to be processed while the previous lot is processed, inspected and moved. Lot delay occurs when one piece is processed, the other pieces in the lot have to wait. In garment industry, all the processes after cutting are usually run in a single-piece flow. This type of production reduces lead time and quality defects.
Production capacity and output must be higher in upstream process The illustration is an example of a typical apparel manufacturing unit. Generally speaking, the cycle times in assembly lines are faster, therefore they pull the line quicker than feeding rates from parts assembly. The strategy should be to have higher capacities output in the upstream process.
Create Visual Constraints on the floor to reduce inventory Markings on the shopfloor to mark the machine location, inventory storage areas, physical barriers, etc. help in ensuring production compliance.
Strategy: 10 Integrate parts production into assembly lines (create value stream) We observe that in most production plants, the parts assembly is run separately as a unit whereas the final assembly is run like a value stream. The biggest disadvantage of this approach is that operators doing parts assembly do not know the immediate priority of final assembly. For example, in trouser making, pocketing, small parts, waistband and zippers are produced in a separate section. This leads to chaos as far as production priorities are concerned. In order to avoid this, create an end-to-end value stream, wherein cutting, parts assembly, final assembly and finishing are all part of one value stream and arranged in a sequence wherever possible. Also, bring related parts closer to each other. If you have the waistband, zippers attachments, operations, etc. integrated into the main assembly line, communication gap will reduce and production priorities will be adjusted accordingly.
Strategy: 11 Level production volume An apparel manufacturing unit receives an order of 1,000 pieces on a weekly basis. (Refer Table 1) Assuming that the plant operates on a five-day schedule, the average daily volume scheduled at pacesetter would be 200 pieces. We must plan the production on the basis of a constant volume of 200 pieces per day. Basic levelling helps in takt time planning and therefore process standardization. If we fail to plan on a constant volume basis per day, the resultant outcome would be an overburden on the system. Takt Time = Available time per day/demand per day If available time is 480 minutes and demand is 200 pieces, then takt time is 144 seconds. This means that each operator in a sequential process must complete his/her work within 144 seconds per piece. In order to do that we must devise a standard method that delivers an output in each cycle under 144 seconds.
|Table 1: Daily customer demand is as follows:|
|Customer Demand (Pieces)||150||250||150||250||150|
|Daily production (Pieces)||200||200||200||200||200|
Strategy: 12 Follow-up on colour clearance on daily basis The most common reason for late shipments is colour clearance. We invariably observe that container is delayed because a few pieces are left out (somewhere in the production floor in a semi-processed state) to complete the shipment.
To improve this aspect, focus on the following:
• Reduce unnecessary buffer stock.
• Reduce WIP.
• Insist on clearing an alteration piece within a time window (e.g. 4 hours after being discovered).
• Improve FTT% in the finishing and packing section.
• Use 8D for causal analysis and permanent corrective action.
• Monitor the top five defects daily and aim to reduce them.
Strategy: 13 Remove visual barriers from the line Excessive stock storage (thread, button storage, etc.), cupboards, unnecessary boards in the wrong location result in the creation of visual barriers along the line. Control on production line stems out from the fact of observing an abnormality or defect as soon as it occurs. By reducing barriers to see through the line, we in fact improve the response-speed to correct an abnormality.
The strategy would be to:
• Eliminate excess stocking of threads, etc. in cupboards.
• Avoid satellite storage of same items.
• Remove boards from the middle of the lines that obstruct the view.
• Create a common communication centre to hold meetings.
Mandate material conveyance routes and avoid traffic jam In order to have accurate material deliveries on time, the conveyance route must be mandated as much as it is possible. This strategy can also reduce the material transfer distance between departments…
Strategy: 15 Control inventory by stipulating SWIP SWIP is Standard Work in Progress and WIP is Work in Progress. We can stipulate the SWIP in each section and also in the stock buffer zones. This has to be followed up by reviewing the WIP to SWIP report for each section and the buffer zone.
The purpose of tracking WIP to SWIP report is to:
• Determine the inventory balance in the production line.
• Measure the effectiveness of the pull system.
• Support workplace organization.
Figure 1 helps us to understand the WIP to SWIP Ratio. Let us assume that this a lining section of the jacket assembly line. The SWIP is stipulated at 20 pieces as against the actual WIP of 24 pieces. The WIP to SWIP is (24/20) = 1.2 If the ratio is greater than 1, there is more inventory and therefore overproduction. If the ratio is less than one, then there could be starving in the system and therefore underproduction. It is also possible that the Cycle Time is more than the takt time.
Eliminate unused, non-value add space This strategy aligns best with increasing the density of machines on the production floor. More availability of space will attract defects, overproduction and excess machines.
Bring related processes close to each other To promote single-piece flow and reduce the material transfer distance, related processes must be brought close to each other. Consolidate existing operations into available area. Strategy: 18 Introduce visual and communication centres on shopfloor Meetings on new product introduction or style changeover happen typically somewhere in the middle of the assembly line. The facility should have dedicated space to hold hourly meetings and communicate with operators on technical specifications of a new product.
Reduce style changeover time continually Production lines are expected to be flexible as orders now come in smaller quantities. Typically the style changeover time varies from 2 hours to 1 day in jacket production. This can be brought down to at least under 30 minutes. Application of ‘Single Minute Exchange of Dies (SMED)’ is a very practical technique to achieve these ends.
Through SMED, the changeover time is reduced in four phases as follows:
Phase 1: List all activities required to do a changeover from one product to another.
Phase 2: Separate the activities into External Work and Internal Work. External Work is the activity that is conducted without stopping the machine like bringing threads for a changeover, while Internal Work is the activity that can only be done by stopping the machine, like changing guides on the machine.
Phase 3: Convert as many activities into external work as possible.
Phase 4: Reduce the time taken for Internal Work. The 19 plant-wide strategies discussed above are practical implementation action points to translate a flow-centric production management vision into a reality. The success of plant-wide strategies depends on organization’s action. Strategies are not one-time exercises. They require evaluation and review on a regular basis. The strategies mentioned above can for sure manifest the vision of creating a lean organization by designing it around these strategies.