Mechanical Sewing Machine & Computerized Sewing Machine :

Mechanical sewing machine is migrating into computerized sewing machine rapidly. A short description is given here about mechanical vs digital sewing machine. Singer use mechanical engineering for mechanical mahine and janome use computerized technology for manufacturing there product and vice versa.  Garments owner purchase sewing machines to progress the efficiency of several sewing tasks. There aere two types of machines are available, mechanical and computerized, which operate differently and contain varying features. Both types can do the basic function of making uniform stitches in fabric using two sources of thread. The decision to purchase one of these machines is heavily based on the customers required functions, skill level, frequency of use.

Mechanical Sewing Machine:

Mechanical sewing machine e.g. singer sewing machine operate on electricity but contain mechanical gears and parts. All of the levers, switches, knobs, and dials require manual control from the user. For adding accessories and parts must be purchased and installed manually. The quality of  sewing machine stitches are different also.

Computerized Sewing Machine:

Computerized  sewing machine contain microprocessors which is digital technology to control the different program. The Stitches are stored on memory. The computer receive the user’s settings for simple setup and operation. The processes are automatically controlled by the machine after the user inputs the desired instruction. The user can download program from internet and can installed for better work. The latest sewing machine are called portable sewing machine. The latest sewing machine is treated as best sewing machine on the market.

Standard Operating Procedures of Sewing:

Sewing: It is the process of joining the cut parts by formation of Seams to produce a wearable garment having an acceptable level of Quality Standard described by the Buyer.

Importance of Sewing: Sewing is the Backbone of the apparel manufacturing industry, involving utilization of machines and physical manpower. If the sewing department is functioning properly and production methods are followed correctly, it provides an edge in the industry to survive.

Sewing Department: The following sections constitute the Sewing department:

• CPU (Small parts are joined together which are sent to assembly)
• Input Section (Front and Back Parts are prepared)
• Output Section (Assembly operations comprise the output section)

Each sewing line consists of 1 Input Supervisor, 1 Output Supervisor (Line Manager), 2 Roving Q/C’s and one End Line Q/C to maintain production as well as quality of the output.

Case Study About mechanical sewing machine and Computerized Sewing Machine

Manufacturing System

The manufacturing systems can be divided into 2 types, basically

Push system – Anticipates future demands or needs and what we do today is determined by what we think will be needed at some time in the future. In push system, a schedule is prepared in advance for a series of workstations, each workstation pushes its completed work to next station. The orders are evaluated at supplying location. In this, the stock available at the supplier and the distribution to various retailers is taken into account. It is helpful for accomplishing scheduled production in a non-stop flow. It has redesigned, fixed assembly line, single purpose portable sewing machine with high output capacities. The inventory between stages is high.

Pull system – Replacing stock after consumption has occurred what we do today is to replace what was used yesterday.

Pull system is not a preferred system in the company as the labor is cheap and the country does not has a solid retail market, so most manufacturing is done for export purpose.

Disadvantages of Pull system in the sub-continent

• In the sub-continent countries especially Bangladesh, where the retail market is more-or-less absent, the pull system carries the following disadvantages.
• Limited ability to adapt to changes in product or product mix (ex. portable sewing machine are of limited capacity and the tooling necessary for products is not always feasible in a given FMS), and the style variation is very frequent so it loses grounds on that account.
• Substantial pre-planning is required which is a lacking in the country.
• The installation and implementation is expensive, and costs millions of dollars
• Technological problems of exact component positioning and precise timing necessary to process a component
• Sophisticated manufacturing systems

Advantages of Push systems

• The push system helps to cope up with the frequent style changes, which is one of the feature of export based garment manufacturing.
• The work can be done for small lot sizes, and in garments industry, there are many cases in which we get to see small orders for a style or small color wise order of the same style.
• The push system also helps us to meet the short delivery deadlines, which is a major concern with export-based garments and it helps to fulfill this requirement in most of the cases.

Manufacturing System in Auto Group Ltd.

In Auto Group Ltd, there are 15 lines (5lines per floor), these are all assembly lines having around 40 workstations per line and all these operations are assembly related and these lines are assembly lines.

Apart from the assembly lines, there are preparatory-section which work on a modular basis, especially for cuff and collar preparation. The preparatory section consists of the first 4-6 workstations of every line and also, there is another section in the corner of every floor for the same purpose.

In all, we can say that the manufacturing system followed is a blend of two manufacturing systems, namely

• Progressive Bundling Unit (PBU)
• Assembly line

Progressive Bundling Unit (PBU)

In PBS production, sewing operations are broken down by management into a number of distinct Progressive bundling and separate operations depending on the complexity of the garment.

Management assigns an expected sewing time or “standard” (in minutes) for each operation such that the amount of effort required to sew a standard minute is equivalent across tasks.

Workers are paid based on individual piece rates according to the standard set for the operation they undertake. In addition to the piece rate standard, workers also receive an hourly wage, or variance pay, when work is interrupted.

The advantages of the PBU system can be listed as under:

1. Helps to cope up with frequent style changes
2. Helpful for small lot sizes also
3. Allows the garment manufacturer to meet short delivery deadlines

The disadvantages faced on following the PBU system are:

1. Greater amount of WIP
2. Single operator single skill
3. Individual piece rates and incentives
4. Shop floor supervision
5. Productivity effected by rate of absenteeism
6. Worker performs repetitive motions

Assembly Line

An assembly line is a manufacturing process in which interchangeable parts are added to a product in a sequential manner to create a product. It can also be called a process where discrete parts are put together to make a finished product. The assembly line operations are a high volume operation that produces products that are very similar in features and performance. Items are produced in a continuous manner, with usually only one possible routing.

It is a very productive production system, and at the same time, the layout is product oriented. Typically, it is a line of dissimilar portable sewing machine is grouped in the line (sometimes more than one to balance flow). Line balancing is a key in the assembly line system as the amount of output varies by varying the sequence of operations and the material flow. Though the assembly line carries a disadvantage of being very inflexible, as the Computerized Sewing Machine layout cannot be altered very often, yet it is most commonly used in the garments industry.

As a part of internship work, I was supposed to cover 2different styles of shirts in the sewing floor from entering the floor to the dispatch to the finishing section. The study in the style included the time study, the method study (process charts and LH/RH charts for each operations). Based on the time study data, the calculations were done to find out the line efficiency, throughput time and the inventory level.

The sewing department covered the most part of the study and it required many calculations to come up with the right data and figures to support and suggest the appropriate changes to the company. The method study also helped to make suggestions on reducing the idle time and the delays from processes.

For the purpose of study, I covered the 2different styles of shirts

1. Men’s Long Sleeve Hidden B/D Collar Shirt (HAGGAR-PROMINENT APPAREL LTD.)
2. Men’s Long Sleeve Point Collar Shirt (CAPITAL MERCURY, CARHARTT)

Men’s L/S Hidden B/D Collar Shirt

The style was introduced in many stages as it had a very big order size but the color variation was also frequent. Since the fabric is check/stripe, therefore, the problem of shade variation is not very common. Considering this fact, the order was introduced in the line with a very big bundle size of 279 pieces per bundle. This size was actually determined by the number of lays spread in the spreading/cutting department.

In all, one line engages nearly 85 people and only about 32 of them are operators, the rest all are engaged in either the quality inspection, thread trimming or simply as a helper.

Line Efficiency

Line efficiency= Actual pieces/day  x100

Ideal pieces/day

Actual pieces/hour= minimum number of pieces in the line

Ideal pieces per day= No. of operators X Available minutes in a day

SMV of the garment

Now, for this particular style, the minimum number of pieces in the line is 78 pieces

Therefore, actual number of pieces in a day (9hours)= 78X9= 702 pieces

Operators required= 46

Therefore, the operator time taken in a day = 46X5400min= 24840min

Hence, the ideal pieces/day= 24840   = 1489 pieces

16.68

Line efficiency= 702 X100 = 47.15%

1489

From this calculation, it is very clear that the line efficiency is very less and has to be immediately taken into account.

SOP for Sewing: First of all PP Meeting is conducted. This meeting conducted in presence of GM, PM, QM, TM, Line Manager, Maintenance Manager, IE and respective Merchandiser.

• After PP Meeting, Red Tag Sample and Trim Chart is provided by the merchandiser along with the Tech Pack and the Technical sheet. The I.E. Department provides the Style bulletin containing the details of Machinery and Manpower allocation.
• Cut Parts are received from Cutting.
• Pilot run / 1^st Bulk is done. It is checked for Quality / Measurement and Shrinkage Issues, Washing issues and also the product safety issues are also discussed .In case of any issue, immediate meeting is conducted and attended by GM, PM, QM and TM to sort out the issue.
• Once, all the quality / measurement issues are resolved, approval for bulk cutting is provided and accordingly Bulk Sewing commences.
• The Roving Q/C checks randomly 7 pcs from random work stations. In case of any Quality issues, it is immediately highlighted to the Line manager as well as the Technical manager. These issues are sorted immediately.
• The End Line Q/C checks 100 % garments for Quality and 2Pcs every Hour for Measurement. Any issues are immediately highlighted to the PM, QM and TM for sorting out the issue.
• All the Q/C Pass pcs are sent for wash. Washing is done Style/ Color/ Lot/ Recipe wise. 100 % pcs are checked for Hand feel, Washing Standard and Measurement. If any issues are encountered, rewash is done to achieve the acceptable quality standard.
• After washing, garments are issued to finishing (Size/ Lot wise).

Reports in Sewing Section: Ten reports are being made in the Sewing Section:

1. Random Number Table.
2. Random Inspection Record
3. List of Un cleared operations
4. Bundle Control Sheet
5. Sewing Quality Inspection report
6. Measurement Chart Fit Audit Report
7. Style/ Line OQL Summary
8. Sewing Cross Audit Report
9. Weekly Root Cause Analysis Chart
10. Sewing Q/C and Operator Counseling Report

 

Md. Ahsanul Hossain, Textile Engineer, Pabna Gov. Textile College. Email:  hamontopabna@yahoo.com,  Cell# 01766463921