Prabir Jana, Associate Professor, NIFT is a renowned technologist, having vast experience in garment manufacturing. Way back in 1995, he was India’s first GSD practitioner.
In the area of industrial engineering application in garment production and work measurement, no phrase has been more talked about recently than GSD (General Sewing Data), which has been growing in popularity for the last couple of years. The consulting firms are preaching it and the tech-savvy companies are eating it up. What is it? Is it a software? A technique? A database? I will try to demystify GSD in this feature.
GSD is a technique (precisely predetermined motion time system) for method analysis and setting up of time standards for needle trade environment such as cutting, sewing, pressing, examination and packing. GSD consists of 25 codes at the general level, supplemented by Get/Put data and selected MTM codes for complete coverage. The basic motion sequences used are Get/Put data from MTM core data. There is also a sewing formula to calculate time spent in sewing.
Shortly after the development of MTM-I, industrial engineers applying the system recognised its constraints and put in efforts to find an easier solution. The concept was to recognise and segregate motion patterns specific to needle trade and to make bigger building blocks (macros) using the MTM-I values for easier and quicker application. GSD was devised by Peter Evans of Methods Workshop Limited using MTM core data. The principal movers in researching and developing GSD in the mid ’70s were Jim Mercer, Alan Sheffield and Bob Hetherington. GSD initially was a manual system and hit the market in numbers in 1978-79.
“How you do what you do is going to decide how long you will take to do it”. Time is a by-product of method being followed. Once you define the method, GSD can tell you the time required for that method. Remember GSD can’t decide the right method for an operation.
I will explain this with an example of an operation – collar run stitch.
Step 1: First you have to decide on what method you are going to follow, which includes processes (like placement and height of pick-up rack, disposal bin, pick up by one hand or both hand simultaneously etc.) and machine parameters (like thread insertion should be at collar point or not, vertical edge trimmer machine should be used or not, jig template should be used or not, UBT machines should be used or not etc.)
Step 2: Once the method is decided, operation needs to be broken into elements. The elements are further visualised into motion sequence based on workplace design.
Step 3: Once motion sequences are decided, it is about simply arriving on GSD codes based on different motion sequences and ultimately time value in TMU.
Step 4: All TMUs are added to get the basic operation time.
By now if you must have realised the catch, yes there you are! Visualising the motions. This is the most important portion of GSD. A GSD practitioner should be able to visualise the motion correctly from the operation description, method and workplace. The whole expertise of a GSD practitioner depends on how accurately he/she able to visualise the motions and subsequently the codes! One week (roughly 32 hours) of extensive training followed by practical and written test qualifies a GSD practitioner. It is very important that only practitioner certificate is not enough and regular on-the-job practice hones a GSD practitioner’s skills further.
GSD data codes are classified under different categories of motions which are necessary for any sewing operation – obtain (pick up) and match parts, alignments of parts, forming or creasing of parts, trimming threads and other tool use, disposing of parts etc. For example, GSD code for ‘align and reposition assembly under presser foot’ is ARPN. This is a very common element for pivoting at corner while sewing pocket. The motion sequence for ARPN is –raise presser foot – hand reaches to gain control of the parts – turn or pivot – get new hold of part – place to presser foot – lower the foot. The total element time is 75 TMU (2.7 seconds). Similarly by combining different motion sequences, different macros are created and each one is given one code name and corresponding value.
The more curious readers must have some questions already up their arms. How runstitch collar for 100 per cent poplin, yarn dyed check and or linen can take same time? Can GSD differentiate? Here again emphasis is on visualising the motions. While visualizing the motions, one has to keep in mind the fabric to be handled. A linen fabric might need additional nail-creasing to fold while a yarn dyed check might need frequent stops to match plaid while sewing. Visualising all those realistic motion sequences is very important for a GSD practitioner. Some of these skills come with experience. Based on different fabric types ,motion will be different and so will be the GSD codes and ultimately the timings.
Unlike other systems, GSD uses rated machine speed. GSD takes care of every perceivable scientific and rational parameters which contributes to sewing time. A topstitch (visible in final garment) and a joining stitch (invisible in final garment) require different concentration (which means different time) by sewing operators. Stopping at collar point to pivot (precision stop) and stopping in between long seam to realign (casual stop) require different concentration while calculating sewing time. All such types of parameters are taken care in GSD.
The heart of GSD is the skill of GSD practitioner. Software is only a database of GSD code timings – as you keep deciding on codes for an operation, the timings are automatically retrieved from database and added. The software also stores common macros for repetitive and commonly used operations for quicker calculations. The software acts as library of operation timings, and over the years, it has become a handy reference database for similar operations. Till 1993, GSD was a MS DOS based software and only of late, 1995 Windows version has become popular and widely accepted.
GSD implementation is generally done in two stages:
- Standardising and improving upon the existing operations: To implement GSD, a practitioner should first videotape the selected operations, analyse the motions correctly, show the video to particular operator explaining the unnecessary motions, modify certain motions and strive to achieve the coded timings.
- Arriving at method and standard time directly from analysing sample: An experienced GSD practitioner may decide on correct method, motion sequence and time standard for operations for a style without even going to shopfloor. Then operators are asked to match the timings as given by GSD practitioner.
Advantages of GSD
- Accurate, consistent and transferable between locations
- Easy to understand and communicate
- Like any synthetic data, GSD is a global benchmark time and free from ‘country factor’
- Actual performance can be readily compared with global performance
- No more cumbersome time study and subjective rating procedure
The common myth demystified
- GSD is not a software
- GSD is not a library of database of different operation timings
You should keep in mind
- GSD times do not include any allowances (such as for fatigue recovery, personal needs, incidental work activities like bobbin changes). As allowances vary depending on environmental conditions, products and company policy, it should be done by means of a percentage addition to basic GSD time.
- No rating allowance to be added (for calculating SAM) to basic GSD time as GSD values are timings for a physically normal operator at an effort level that could be easily maintained year after year without requiring him to draw upon his reserves of energy. That is you are getting a synthetic time for a 100 per cent operator.
