Supply Chain Dynamics in Indian Apparel Export Manufacturing: Critical Chain Approach

Swati Gupta, Chandrashekhar Joshi, Prabir Jana & Dr. Alistair Knox

The article is based on annual research carried out at GMT Department, NIFT during 2001-02 sponsored by Creative Garments, India and with technical assistance from Creatnet Technologies, India. This is part of doctoral research by Prabir Jana at Nottingham Trent University, UK.

Garment pre-production (also known as merchandising) activities are characterised by people oriented functions. Interdependent activities are synchronized between succeeding and preceding activities to make the process network. The longest chain of activities considering task dependencies is called critical path. Critical path based time action calendar concepts have been used for scheduling pre-production activities with a goal to deliver order within the original delivery date. Lead-time reduction in the existing network is only possible by any of the following principles.

•Elimination (Remove a process)
•Compression (Remove time within a process)
•Integration (Re-engineering interfaces between successive processes)
•Concurrence (Operate processes in parallel)

It is important to note that the pre-production process networks are unique for every single enterprise, every single buyer, even sometimes for every single order. In the absence of a standardised pre-production process network, elimination, concurrence and/or integration approach will be too case specific to be applicable across industry. In an effort to explore a generalised or standardised solutions/techniques that can be applied across the industry a time compression technique called Critical Chain was selected for exploration.

What is Critical Chain?

In 1997, Dr. Eliyahu Goldratt introduced the first significant new approach to project management in over thirty years with the publication of his best selling business novel, Critical Chain. The genius of Goldratt’s approach addresses both the human side and the algorithmic methodology side of project management in a unified discipline.

Why Critical Chain Approach?

Like project management environment pre-production activities in garment manufacturing are also primarily human driven. Further more some of the Critical Chain characteristics have commonalties with garment pre-production activities like reverse scheduling, multitasking and resource dependencies.

Task Estimating

While estimating task duration, people worry about the effect of unplanned work interruptions and generally add hidden safety. A 10-day task duration may have 5 days of safety. The safety is called hidden because the task is entered in the project as a 10-day task. It’s perfectly reasonable to have safety factor (especially with third party activities), but being hidden, often the purpose is lost.

Student Syndrome

General humane nature is to put off starting of any task until the last minute, thus eating away the safety buffer in the beginning. Unfortunately, if the task then faces unplanned work interruptions then the task will overrun estimate no matter how hard one works, as there was simply not enough safety left to recover.

Parkinson’s Law

Most of us have heard about Parkinson’s Law and seen it in action on projects. Work expands to fit the allotted time. If a task is estimated at 10 days, it usually doesn’t take less, people will simply adjust the level of effort to keep busy for the entire task schedule.

Multi-tasking

Most of us work in a multi-project environment. We all have experiences of having to stop working on one task so that progress can be accomplished on another task in another project. Often, we wonder if all this jumping around makes sense because it comes with the penalties of reduced focus and loss of efficiency. Resources tend to migrate between projects in response to the latest, loudest customer demand in an attempt to keep as many customers satisfied as possible. This focus on showing progress on as many active projects as possible is the major cause of multi-tasking.

No Early Finishes!

It is important to notice that tasks seem to either finish on time, or late, but rarely early? As conventional wisdom rarely reward early finishes. In fact, early finishers often being accused of sandbagging their estimates instead of being rewarded for completing ahead of schedule. In this environment, people worry about their future estimates being cut based upon history so they quietly enjoy the lull, and officially finish on schedule.

Traditional work environments stress not being late, but they do not even promote being early. Which encourages hidden safety, the student syndrome, and Parkinson’s Law effects.

Tasks are scheduled as-soon-as-possible (ASAP) from the project start date. Every task has a published start and finish date. While this task scheduled start and finish dates seems logical, it does not promote speed-to-market driven performance. In fact, it ensures that early finishes are lost, and only late finishes accumulate in the schedule.

Let’s elaborate upon the salient characteristics of critical chain concept.

Task Estimating

Task is estimated at per actual working days (without buffer). The buffer days are then cumulated and added at the end of network or at important milestones. As pooled buffers are known to everyone (unlike hidden) time management is transparent.

As-Late-As-Possible Scheduling

Tasks are scheduled as-late-as-possible (ALAP) based upon the target end date. There are many benefits to delaying project work as-late-as-possible:

• Using a production analogy, work-in-progress (WIP) are minimized and not incurring costs earlier than necessary.

• From the project manager’s viewpoint, there is better focus at the critical start of the project because there simply aren’t as many tasks scheduled to start.

And one drawback:

•As all tasks are critical once you are in tracking mode. An increase in duration of any task will push out the project end date by the increased amount.

Relay Race Approach

This means that when one task is getting close to completion, next task’s resource should be on the track and ready to go as-soon-as-possible after the preceding task completes. This relay race approach means de-emphasizing the task scheduled start and finish dates and concentrate, instead, on triggering their preparation and start on the preceding task’s progress. Importantly, once a task is started, the resources work as fast as possible towards completion without clocking themselves to the scheduled finish date.

Resource Constraint & Allocation

Critical Chain is defined as the longest chain of tasks that consider both task dependencies and resource dependencies. Critical Path is defined as the longest chain of tasks based upon only task dependencies; this is a subtle, but important difference.

Critical Chain recognizes that a delay in resource availability can delay a schedule just as a delay in dependent tasks. The above example illustrates the problem better. Let’s imagine there are 4 tasks A, B, C and D with task dependency shown in picture one. Time estimates for each tasks are A = 2, B = 3, C = 1 and D = 2 man-days. One common imagination in Critical Path Concepts is resources are freely (infinitely!) available, that means if 4 different persons are available then the project would take 7 man-days to complete, A-B-D being the critical path. In practical circumstances resources are not aplenty, let’s imagine task B & C have to be done by same person. So with resource dependencies (i.e. only 3 different persons available) the same project would take 8 man-days to complete. This phenomenon is very common in actual work environment (especially in garment pre-production environment) while critical path does not address this.

Pilot experimentation of Critical Chain concept in Delta Fashion

Set Up Mode

1. Select orders and team of people: Three orders were selected for experimentation. Post order merchandise activities were monitored for all three orders.

2. Briefing: The critical chain concept was briefed to all team members

3. Reverse Scheduling: Developed a plan of all activities (task dependencies network or PERT diagram) backwards from the target delivery date for all three orders.

4. Duration Estimates: Each activity time is estimated following critical chain concept. Time estimation were collected from two sources, first the merchandisers who are in charge of the activity, and second, the related authority who actually performs the work in the unit.

5. ALAP Scheduling: Schedule each tasks as per critical path (ASAP) concept as well as Critical chain (ALAP) concepts. This is done to compare actual with both.

6. Pooled Buffers: Buffers were inserted at end of project and/or distribute at different milestone levels.

All the interdependent activities are plotted in PERT network (picture I). The activities (tasks) are classified based on internal dependent, transportation or external dependent. Then the duration of each activity are estimated and put into PERT network. Picture II shows each activity durations, above every arrow, project buffer and the total order completion date.

Picture 1: Supply network for Delta Fashions (click image to enlarge)

Picture 2: Critical chain network with buffer (click image to enlarge)

Source: Critical Chain, Changing the Apparel Industry

Follow Up Mode

No due dates for individual tasks, but finish as early as possible and handover to next person for next tasks. As the order activities moved forward respective executives were pre-informed and prepared for tasks to arrive, thus ensuring priotisation and speedy execution of tasks. Actual performance i.e no. of working days to complete the order was compared with scheduled no. of days as per critical path and as per critical chain. It was observed that order was completed as per critical chain schedule and well before time as per critical path. It is important to note that critical chain completion date is always followed by project buffer, and even the order overshoots the critical chain timing the order was very much completed within buffer dates.

Garment pre production activities are basically fire-fighting operations in absence of any pre planning. People attend to problem wherever needed and migrate to another leaving the earlier half finished is a common phenomena.

Three activities namely CAD (CAD operator), sampling (sampling tailor) and patternmaking (Pattern master) were selected where multitasking is frequent, and the loudest and nosiest customer is catered first. The day-to-day activities of all the three departments was collected including the lunch breaks, the standard time for similar activities was noted. Data was collected for 1 months involving 2-pattern master, one CAD operator and 3 sampling tailors.

The summarised findings are:

1. Multitasking induces start up loss (due to lack of focus) measured at average 43%.

2. The increase in lead-time of a particular task can be as much as three days instead of two hours.

3. For pattern master the time lost on multitasking was 32.85%.

4. The time lost on multitasking by CAD department was 38.80%.

Pattern making activity in multitasking environment


Legend

Above chart shows that Style ABC and TSR was abandoned half way and another two new styles (XYZ and Jumper) were worked on before coming back and complete the half finished styles. A different scenario below shows if proper priority were given to patternmaster and multitasking were not followed, three styles (ABC, XYZ and Jumper) could have been completed earlier without affecting the completion time of other styles.

Pattern making activity in without any multitasking

Conclusion

While traditional “time-action-plan” concept application in pre-production activities tries to control lateness while still breeding “me-first” mentalities, critical chain approach actually induces team-working spirit and have potential to compress the time further.

The first ever pilot experimentation in garment industry promises huge benefit by planning schedule and prioritise tasks is a common-resource but multi-style environment, thus minimising or eliminating multitasking can result considerable gain in internal activities

Any organization interested in experimentation of Critical Chain concept may please write to prabirjana@rediffmail.com with a brief company profile.

References:

Towill, D.R, Time Compression and Supply Chain management- a guided tour, Logistics Information management, Vol 9 No 6 1996 pp41-53

Goldratt, Eliyahu M. Critical Chain, The North River Press, 1997

Gupta Swati and Joshi Chandrashekhar, Critical Chain, Chaining the Apparel Industry, 2002, GMT Diploma Project Report, NIFT

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