Technology for Back Pocket Attachment on Jeans

Back Pocket Attaching Machine – Basic Level

The basic level of technology involves creasing and sewing operations being performed manually and is controlled by the skill of the operator. The equipment used in this level of technology includes iron for pressing and lock stitch machines. The operator first places the pre-hemmed patch pocket on a template and folds the three edges. To mark the creases, it is ironed. Then, the pocket is placed correctly on the back panel as per the marking and attached using a single needle lock stitch machine, followed by the second stitch (Figure 2). The total SAM of these operations is 1.95. Sewing line manufacturing denim using the basic level of technology produces approximately 1600 pairs of jeans in a day (8 hr shift). 

• A helper to perform the creasing using iron
• Operator 1 to attach the back pocket using lockstitch machine
• Operator 2 to perform the 2nd stitch using lockstitch machine

Back pocket attaching in jeans is done generally by double line of stitching, but not parallel stitching lines. Therefore even though pocket attaching and topstitch operations could be done in combination by a double-needle lock stitch machine, it cannot be used to get a similar look. When stitched using single needle sewing machine, the quality depends on operator skill and any inconsistency in spacing between sewing lines will be visually unappealing. Secondly to achieve perfection operator will be slower at the basic level. The efficiency of the operator is around 65-70%. Thus, to combat the issues of quality and productivity, jeans manufacturers are opting for higher levels of technology as discussed further. Table 1 shows specifications of two models of SNLS machines that can be used for sewing denim jeans, and specifications of a typical ironing unit is mentioned in Table 2.

Table 1: SNLS Machines in Basic Level of Technology

Table 2: Specifications of a Vacuum Ironing Unit

Jeans Back Pocket Attaching Machine – Intermediate Level

With the up-gradation in technology, semi-automatic machines ease the work of the operator; ensure more accurate work, as well as speed-up the process. Automatic pocket creasing machines and semi-automatic pocket attaching machines have been considered as the intermediate level of technology. An operator creases the back pocket using the pocket creasing machine; the creased pocket is then taken to the pocket attaching machine, which is handled by another operator.

The specifications of pocket creasing machine and pocket attaching machines (for pre-creased pockets) are shown in Table 3 and Table 4 respectively.

Table 3: Automatic Pressing-Creasing Unit Specifications

Semi-Automatic pocket setters have been specifically designed for being capable of placing the next sewing pocket while engaging in placing the current pocket (preliminary folded) on the garment body and sewing it. They are available in single sewing head as well as double sewing head (for multi-colour thread). The machine is equipped with direct-drive lockstitch programmable electronic pattern sewing head, by adopting a simple template clamp which is easily exchangeable. These pocket setters ensure high quality and high production efficiency can be reached without the need of any skilled operator. The productivity the machine offers is 1200 pairs/8-hour shift, which is nearly five times the number produced in basic level by the same number of operators manually. Semi-Automatic pocket setter units are shown in Figure 3.

Figure 4: Semi-Automatic Pocket Setter Unit (for Pre-Creased Pockets)

Jeans Back Pocket Attaching Machine – Advanced Level

Automated solutions ensure good and consistent quality with high output performance. Although the first thought of an automat seems to be a matter of investment and concern, manufacturers need to focus on an enlarged analysis, understanding the technicalities in detail and thinking of medium and long term goals. The fully-automatic workstation that makes all the pocket setting processes such as creasing of a pocket, placement of the pocket on the panel, sewing, bar-tack, and stacking automatic come under the advanced level of technology. 

In both the lower levels of technology, the folding devices were not suitable for stretch denim fabric, but fully automatic machines are equipped with a cold folding device which is the unique solution for such fabric. The versions of these machines have single and two sewing heads. Two sewing heads can produce extra 25% as compared to single head pocket setter unit. Also, two sewing heads give the opportunity to stitch a pocket with two different colour threads. Specifications of fully automatic pocket attaching machine (single and double head) are shown in Table 5.

Table 5: Specifications of Fully Automatic Pocket Attaching Machine

As discussed earlier, for operating this automat, the operator skill required is low. However, it is unethical to lower the salary of the already existing operator if a new machine is brought in the manufacturing unit. Thus, to have a better return on investment, instead of 1:1 man to machine ratio, 1:2 ratio can be configured. For 1:1 ratio (single head machine), the SAM value for a single operation is 0.430, and that for 1:2 ratio drops down to 0.248. (Mondal, 2019). A helper transports the completed pieces from the stacker to the next operation of jeans sewing. Models of fully automatic back pocket setters are shown in Figure 5.

Figure 5: Fully Automatic Back Pocket Setter

ROI Calculation for different technology level

To evaluate the efficiency of investing in higher technology, Return on Investment (ROI) and Payback Period are suitable performance measures. However, these two factors are not solely responsible for decision making to make an investment. There could be several other reasons for technology up-gradation, one being their goal to be state-of-the-art manufacturers.

The formulas used for ROI and payback period calculation are:

• Production per annum= (Shift hrs X 60 X Working Days X Months X Operator Efficiency) / SAM
• CM Price per Pocket= (Sewing Cost/ Total SAM of Garment) X Pocket Setting SAM
• Cost Output per annum= Production per annum X CM Price per Pocket
• No. of Machines Required= Production Target/ Production per operator per day
• CM Price per Machine= Cost Output per Annum X No. of Machines
• Cash Inflow= CM Price from Machines – Total Machine Running Expense per Annum
• ROI for 1st Year= Cash Inflow/ Depreciated Value of Machine after 1 Year
• Payback Period= Total Machine Cost (Investment)/ Cash Inflow

Key Performance Indicators

Key Performance Indicators are crucial to direct the team in a project by creating an analytical basis for decision making. With a matrix depicting the KPIs that automation improves (Table 6), it can aid one in making correct decisions for the betterment of the organization.

Table 6: Key Performance Indicators

• Jana, D. P., 2017. Automation has now become relevant and ‘affordable’. Industry 4.0, December, pp. 17-19.
• Jana, P., 2018. Automation in Sewing Technology. In: R. P. Rajkishore Nayak, ed. Automation in Garment Manufacturing. s.l.: Woodhead Publishing, pp. 199-236.
• Mondal, P., 2019. Sewing Automat Solution for Jeans Manufacturing. Annual Journal of TANTU Textile Alumni Association, September, Volume 7, pp. 30-33.

[1] https://www.zionmarketresearch.com/report/denim-jeans-market
[2] https://sourcingjournal.com/denim/denim-innovations/levis-laser-automation-denim-124738/
[3] https://www.thelaststitch.com/how-to-sew-jeans-back-pockets/