Industry Technologies
By Dr.Trevor Little, Professor Emeritus NC State University
Introduction This is Part 2 in a series of articles on Sewing with Threads. Part 1 appeared in The NEEDLE’S EYE April 2023 issue and covered the basics of thread construction and what is involved in selecting a thread. Also, it explored the consumption of thread from a practical perspective which depends on the type of stitch used.
This example in Part 2 will assume that you read the Union Special Machine Company’s book, Thread Consumption (the standard on seams and stitches was published in 1963 and revised in 1974). Another reference is American & Efird’s Estimating Thread Consumption by product.
Remember, you can estimate the amount of thread by unraveling a length of a seam (usually about 3 inches).
So, with these basic tools, we can begin.
Ladies BlousesLet’s assume that we are making ladies' blouses with a total thread consumption of 122 yards of thread per blouse.
We now need to know a few additional things. We need an operations bulletin with the stitch types for every seam, and we also need to know the seam type as a Superimposed Seam will consume less thread than a Lapped Seam (there are 6 basic seam types: SS, LS, BS, FS, EF, OS). These stand for Superimposed Seams, Lapped Seams, Bound Seams, Edge Finished Seams, and Ornamental Stitching.
Let’s look for an operations bulletin. The operations bulletin (see Operations Bulletin by Pegasus below) is really a guide to assembly according to specifications.
In the chart below the eleven (11) triangles at the top of the 'Process Chart of Ladies' Blouse A (Long sleeve type)' signify the start of a sub-assembly or the start of a raw material. Three (3) additional triangles can be found later in the process that also signify the start of a needed component or label. Building a product in this way helps manufacturers lay out assembly lines and locate inspectors during assembly.
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Dr. Trevor Little
To calculate the consumption of thread, get a copy of the Union Special Thread Consumption tables (shown here) and find the stitch type in ISO 4915 standard. Thread manufacturers also prepare charts to assist thread purchasing areas. You may download a copy at: https://www.dropbox.com/s/ctr7zgr9fmn2zop/Thread%20Consumption%20Book.pdf?dl=0.
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More important for Thread Consumption is the type of stitches used to assemble the blouse. The summary chart at the bottom right-hand side shows 16 single needle lockstitch machines (301 stitch), 3 single needles with adjustable feeds for 215 seconds, 1 single needle with top and bottom feed for 140 seconds, 3 buttonholes for 56 seconds (304 zig zag stitch), 2 chainstitches (401 stitch) for 64 seconds, 4 serging machines for 123 seconds (502 or 503 stitch).
Although the machines are different, the stitch type will use similar amounts of thread, so the number of single needle machines becomes 16 + 3 + 1 = 20 single needle machines.
Let's assume that each spool of industrial thread has 6,000 yards (5,486.4 meters) of thread for a color. I think that you are beginning to see the issue. Let’s make a table to clarify.
Now let us look at thread consumption for blouses with one color thread.
If the order size is 100 per color, the required thread is 100 X 119.422 of Tex 27 = 11,942.2 yards or 1.9903 or two packages of 6,000 yds each. Manufacturers will buy enough thread packages to keep all the machines running, in this case, 40 packages of Tex 27 while only 2 packages are needed. As order sizes decrease per color, there will be an excess of thread purchased.
100 per color for button hole thread means 4.12 yards (3.7698 meters) of thread per blouse for 7 button holes (https://textiletutorials.com/sewing-thread-consumption-for-different-stitches/ – line 26.)The Operations Bulletin calls for 6 packages of thread which are 6 X 6,000 yards or 36,000 yards or enough thread for 8,000+ garments. Fortunately, the thread for buttonholes is either white or black.
It is easy to see the conflict in Thread Consumption. While only 2 packages are required, the Operations Bulletin calls for 40 +4 + 8 = 52 of Tex 27. Most manufacturers can supply thread to the machine.
The quantity of thread (Tex 27) purchased would be sufficient to make 2,600+ blouses, i.e. 52 X 6,000/119 = 2,621 blouses.
So there is always a conflict between the Operations Bulletin requirements, order size, and amount of thread. One solution would be to make smaller thread packages so that manufacturers can adjust better to the quantity ordered. Another solution is to rewind the thread at the sewing factory. Another solution is to use digital dyeing (like Twine).
For now, the Operations Bulletin must determine the number of packages needed. There will be an excess thread for smaller orders. That creates storage costs that may not be in the product cost. Thread costs per garment are usually expressed in cents per item while fabric costs are expressed in dollars. In the US, labor will be the next biggest cost. Thread holds the garment together and with thread costs low, it is considered a less important component of cost.
The recommendation is to add 10% to 15% for thread waste as stated in the Thread Consumption and the Operations Bulletin. The Operations Bulletin tells us the number of machines that require thread. The manufacturer follows the Operations Bulletin more than the ideal Thread Consumption.
Nowadays, orders are won and lost on a penny per garment so the thread cost becomes an important component of the total cost of a garment. There is an opportunity to get better cost estimates of thread for a garment. Just look at the number of stores and the SKUs per store. Suppose Walmart has 5,000 stores and wants 5 colors, 5 sizes, and 2 copies of a sewn item per store. That is 5,000 X 5 X 5 X 2 = 250,000 per order. If thread cost is off by 1 cent, that is $25,000, and will make a negative decision for the Buyer.
ConclusionsThread is inexpensive but storage costs of excess thread can be high. Have you ever wondered why buttonholes are made with one color of thread? The answer is simple, use white for all light colors and black for all darker colors.
There is a difference between the theoretical and practical requirements for the thread. It is most important that the sewing machines have a supply of thread and therefore the Operations Bulletin becomes the Thread Consumption guide. I have never heard anyone question the amount of thread needed because of cost nor have I ever heard of anyone trying to optimize orders based on thread consumption. One thing is for sure, the order size per color is decreasing for fashion in the USA.
A simple attachment could convert the industrial thread package into a smaller package like home sewing. This would be an exciting conversation for thread manufacturers, sewing machine manufacturers, and garment manufacturers. It is a needed correction factor to optimize thread usage.