Grading in the apparel manufacturing industry is well known as the art of proportionally increasing or decreasing a given size pattern part from one size to another, retaining everything true to its original form. The grading network for a block pattern is also the basic network for the components which have been developed from the block pattern.
There are many techniques involved in the grading of garment pattern but they all have one common principle- the basic grade. Grading system can be classified in to the following two broad systems:
1. Track Shift System or Two dimensional grading.
2. Draft Grade System or Three dimensional grading.
Two dimensional grading systems only grades a pattern for girth and height and its application is therefore limited to loose or semi drape garments because it retains the stock size suppression throughout the size range. This system is more apt to a very loose fitting garment such as a shirt or blouse with a limited range to say, 10-12-14, may be safely graded using a two dimensional system.
Three dimensional system:
This system not only increases a pattern for size but it also increases or decreases suppression in the following areas:
- Bust to shoulder
- Hip to Waist
- Elbow to wrist
Three dimensional grading is the optimum system and should be used whenever possible, particularly when grading close fitting or skin-tight garments and garments that progress in size from 10 to 22. The most important garment area is the bust to shoulder suppression quantity. A good working knowledge of pattern cutting is required to use a three-dimensional grading system.
Types of Garment: There are two main categories, they are:
- Close or skin-tight fitting garments
- Loose or semi drape garments.
The closer the garment fit, the more important it is to select a sophisticated garment grading system which adjusts the garment with the garment suppression. If the garment fit is loose the value of adjusting the garment suppression decreases and a two dimensional system becomes more advisable.
Number of sizes: This may depend a little on whether a garment is close or loose-fitting, but it mainly refers to a situation where the company or firm only offers a limited number of sizes, the complexity of the grading system, etc.
Types of Fabric: For grading purpose fabrics may be classified in to two broad types:
Stretch fabrics are more for adjustable and will fit readily to the body contours or silhouettes and therefore, it can be employed. A non stretch fabric has the reverse effect and must be kept under the control and in balance through the size range.
- The draft or multi size (Nested) grade.
- The track or single size
The Draft Grade: This term applies when the pattern is returned to its original block form or when the increment is applied to the actual pattern draft. This results in the entire size range being super imposed one on top of another and can also be described by the term 'Nested' or 'Tracked'. The individual pieces of pattern for each size are then picked or traced off onto card. A draft grade can be either two or three dimensional. The three dimensional draft grade is considered to be the ultimate method for applying grade increments.
The Track Grade: This term is used when grade increments are applied to individual pieces of pattern by moving the base pattern pieces along with the predetermined tracks. Making the pattern section by section and thus altering its size. This system is usually two dimensional but can be adapted to a three dimensional system with difficulty.
Following are the steps for manual grading:
1. To prepare for grading
2. Grading the pattern
3. Check the pattern grading measurements
4. Completing the pattern.
The tools required for grading are as under:
1. Parallel rules
3. Carpenters pencil
4. Proportional divider
5. French curve
6. Arm hole curve
7. Tailors square
8. Notch maker
9. Grade ruler
10. Measuring tape
11. Colour sketch pen or pencils
Size intervals: A sizing system is a pre-determined size interval i.e. the major girth difference between each size. The variation in the size is in the order of plus or minus 2cm then the logical size interval would be 4cm. Practically, intervals smaller than 4cm result into more used sizes of the range.
Size charts: There are two types of size charts in normal use.
1. Body measurements: This type of chart provides the human body measurements for each size and these measurements are used as a basis for constructing a pattern with the requisite amounts of ease.
2. Garment measurements:-This chart gives the details of the finished measurements, specification for each size and is used for pattern grading purpose. A size is a combination of measurements and each combination is designated by a symbol which is a common code between the apparel manufacturer and the consumer.
The 'X ' AXIS and 'Y'AXIS: The x -axis for body and y-axis for body and skirt grades would be a line on, or parallel to the center back or center front. This is always true, if straight y-axis is a line on, or parallel to a major girth line such as the bust, waist, or hip.
The different types of grading that are still in usage are: manual grading, machine grading, and computerized grading are still used. The practice of garment grading is mainly concerned with efficiently producing dimensionally accurate patterns. In order to do this, some basic rules must be always observed. There is no hard and fast rule as how to actually produce the sets of graded patterns and the choice of working method is also dependent on an individual's accuracy and convenience.
R.S. Balakumar has M.A (Sociology), MLM. He is a member of the Council of the ISTE member, New Delhi and specializes in Garment Technology.