For Apparel Merchandising, in today’s competitive marketplace, there is a need for tight cost control. A realistic estimation of potential thread requirements for particular garment styles or contracts will not only end up saving money, and warehouse maintenance. As, if you buy sewing threads more than you require that will be a matter of extra warehouse maintenance. To understand sewing thread consumption we also need to understand the Seam and Stitch analysis. I will try to write or present it if possible. Several factors determine the extent of thread consumption in any sewn product, such as stitch type, seam type, material thickness, number of layers, construction and SPI (stitches per inch). However, these factors are not constant with the different style preferences. Hence, thread consumption is never standard for sewn product categories such as shirts, trousers and footwear. There are some ways people may generally use to calculate the amount of thread in a seam and hence the thread consumption in the sewn product: ·
Mathematical Formula:
There is a standard formula for determining thread consumption. In that formula you will get multiplying factors according to machine type and stitching classes. To define thread consumption you just have to multiply seam length with that factors. Thus, one can estimate total requirement of thread for making a garments. But actual thread consumption for a unit length of seam depends on many factors. Likes-
- Stitch Classes,
- Stitches per inches (SPI)
- Fabric thickness
- Thread tension Thread count (thickness of sewing thread)
So I will advise you to calculate garment thread consumption by your own. You can develop multiplying factor according to your product categories and requirement using following simple steps.
Step 1: To calculate thread ratio, you need sewing machine, fabric and sewing thread that will be used for bulk production. For fabric and thread you can take similar thickness and same thread count in case actual is not available.
Step 2: Sew a seam of 12 cms long and take 10 cms seam out of it by trimming 1 cm from both edges.
Step 3: Unravel both needle thread and bobbin thread from the seam. Remove crimp from the unraveled thread and measure its length in cm. Generally it will be higher than the seam length. Now find the multiplying factor by dividing thread length with seam length. Assume unravelled needle thread length is 12.5 cm then needle thread multiplying factor is 12.5/10 or 1.25. Using this method you can find out any types of machines’ thread consumption factors.
Step 4: Once you have consumption factors then it is easy to calculate total thread consumption. Measure seam length of all operations of the garment and get thread requirement by multiplying thread consumption factor. Add thread wastage 5% for the thread that trim out from each ends of the seam. ·
Measuring Actual Thread Consumed
A specified length of a given seam is measured and then the thread is pulled out of this length. We can use the amount pulled out of this specified length to calculate the ratio of thread consumed in the entire seam. By dividing the amount of thread by the seam length, we get the ratio of thread consumed. If we multiply this factor times the total length of seam, we can determine the total thread consumed for that seam.
Example:
Length of seam = 100 cm (1 metre)
Stitch class 401 = 2-Thread Chain stitch
Length of seam for which thread is removed = 15 cm
Needle thread removed = 19.5 cm
Definition of Needle Thread:
Needle thread factor = 19.5/15 = 1.3
Looper thread removed = 62.0 cm
The Definition of Looper Thread:
Looper thread factor = 62.0/15 = 4.1
The definition of thread factor:
Total Needle thread = 100 cm x 1.3 = 130 cm
Total Looper thread = 100 cm x 4.1 = 410 cm
Total thread consumed = 130 + 410 = 540 cm
Add 15% wastage* = 540 cm x 1.15 = 621 cm
Another Example:
Length of seam is 42 inches or 1.17 yards.
Stitch and seam construction: 401 SSa-1.
Specified length of thread removed from a seam equals 3 inches.
Needle thread removed = 9 inches
Looper thread removed = 8 inches
Calculation:
Needle thread factor = 9 ?3 = 3 inches of needle thread per inch of seam.
Looper thread factor = 8 ?3 = 2.67 inches of looper thread per inch of seam.
Total needle thread consumed = factor 3 X 1.17yds = 3.51 yds
Total looper thread consumed = factor 2.67 X 1.17yds = 3.12 yds
Total Thread = 3.51 + 3.12 = 6.63 yards per seam.
Generally a 15 to 20% waste factor is added due to chaining-off, thread breaks, repairs, etc. If a waste factor of 15% is selected then: 6.63 yards/seam X 1.15 = 7.62 yards/seam including 15% waste factor.
*Generally, 10% to 15% wastage of thread is added to the consumption derived. This wastage occurs due to shop-floor conditions like machine running, thread breakage, repairs, etc. The above example shows the total thread consumed for one type of stitch class in a garment. By following a similar procedure, anyone can calculate the thread consumed for different stitching operations in a garment. ·
Thread Consumption Ratios:
Union Special Machine Company published a "Thread Consumption Booklet" that consists of a number of thread consumption formulas for various stitch types based on the stitch length and thickness of the seam. These mathematically derived consumption factors can be multiplied times the length of the seam to estimate the combined amount of top and bottom thread. On some overedge and coverstitch types it is necessary to also know the seam width or needle spacing to properly calculate the amount of thread consumed.
The easier method is to use the generally applicable Thread Consumption Ratios for the various stitch types that are listed in the table below. By relating these ratios to the length of seams using each stitch type, total thread consumption can be calculated.
As you can also get information from the Union Special chart, the more stitches per inch and the thickness of the seam impacts the amount of thread consumed. However, most heavy fabrics are sewn with fewer stitches per inch and most light fabrics are sewn with more stitches per inch. Therefore we have come up with the following estimates based on typical seam thickness and stitch length.
table 1
Note: The above ratios are arrived at with a stitch density of 7 stitches per cm (18 stitches per inch). These ratios are the prescribed minimum in regular conditions and marginally vary with the factors affecting thread consumption. A certain percentage of wastage is to be added to the above ratios as per shop floor conditions. It may vary from 10% to 15%.
Example:
Length of seam = 100 cm (1 metre)
Stitch class 401 = 2-Thread Chainstitch From the table, total thread usage per cm of seam = 5.5 cm Total thread consumption = 100 cm x 5.5 = 550 cm
Estimated Needle thread = 550 x 0.25 = 138 cm
Estimated Looper thread = 550 x 0.75 = 412 cm
Add 15% wastage = 550 cm x 1.15 = 633 cm of thread per seam
By applying thread, consumption ratios in a manner similar to the calculation in the above example, a sample consumption working for an average sized knitted t-shirt is shown in the table below.
Example:
Thread consumption for an average-sized knitted t-shirt table 2 Another
Example:
Union Special 401 Chain stitch Chart:
Seam Thickness 8 SPI .055 .060 .065 .070 .075 4.88 4.96 5.04 5.12 5.20 Example: Stitch and seam: 401 SSa-1 Stitches per inch: 8 Thickness of the seam: .075 inches (measured with a micrometer) Length of the seam: 42 inches or 1.17 yds. Calculation (Consumption based on the mathematical equation): C = 4 + 2ts C = 4 + 2(.075 X 8) = 5.20 t = thickness of the seam s = stitches per inch 1.17 yds X 5.20 = 6.08 yds / seam. 6.08 yds/seam X 1.15 = 7.00 yds per seam including a 15% waste factor. Example: Stitch & seam: 401 SSa-1 Length of seam: 42 inches or 1.17 yards Fabric weight:
Light weight Estimated Thread Consumption: 1.17 yds. X 5.0 (Ratio) = 5.85 yds. / seam 5.85 yds/seam X 1.15 = 6.73 yds/seam, including a 15% waste factor
Estimated needle thread: 6.73 X 40% = 2.69 yds
Estimated looper thread: 6.73 X 60% = 4.04 yds
Note: Stitch density, stitch / seam chioce, variations in style, fabric thickness and number of plies are factors that can affect thread consumption. It is also necessary to make provision for possible thread wastage (usually 15%) while calculating thread consumption.
Using Online Resource or Software:
Coats Seamworks™
Apart from these regular methods that are used, there is a quick, simple and efficient option available to our customers called Coats Seamworks. Using this software, it is possible to calculate thread consumption metering and costing without having to pick up the thread from the seam. Seamworks is a sewing management software solution that can calculate thread consumption for any sewn product. Not only does it calculate the consumption for a single product, it also enables you to choose the right thread ordering pattern, which is necessary for optimal usage of the ordered thread in the shop floor.
Salient features:
- Easy-to-use
- familiar Explorer-type interface
- Support for metric and imperial measurement systems
- Increased data integrity
- Enhanced calculation engine
- Multi-lingual support
In the next Post I shall show you how to use this Seamwork.In this post I could not share all the things I could know, but I will make this post more resourceful in next, be with me....
