Sewing seam Tension- Quality Management Guideline

USAT - sBU USA

Sewing seam Tension- Quality Management Guideline

Contents: -                                                                                                                 Mr. Rajkumar Mariam 

• Introduction                                                                                                                 
• Seam Type
• Machine Type
• Stich Formation Methodology
• Industrial Wash Shrinkage VS Before wash stich Tension predetermination
• Effective Sewing   R&D to define before wash stich tension, SPI guideline
• Proactive and Preventive Maintenance
• Pre-production to Bulk Integration

QA & QC plan                                                                                                                             

Introduction: -

 

*The apparel quality determines by material, fit, finish, comfort, safety and also on sewing seam quality.

Sewing seam quality performance largely correlate with sewing condition against fabric characteristics, wash shrinkages, sewing-thread properties, seam type.

Sewing condition such as sewing-thread tension, stitches per inch, size of needle and thread size and operation of sewing machines total preventive maintenance.

In a good quality garment first impression of the outlook and functional requirements of the seam are major key elements to affect customer

attraction to purchase.

The seam stitch line performance deteriorates the quality of garment by reducing seam strength and seam-slippage, seam puckering, tension unbalance and irregularity,      

Types of seams universally in apparel manufacturing: -

Class-01: Superimposed seam,

Class-02: Lapped seam,

Class-03: Bound seam,

Class-04: Flat seam,

Class-05: Ornamental seam,

Class-06: Edge neatening seam,

Class-07: Applied seam

Class-08: Others seam

In Addition to SNL/OL other common MCs in Jeans sewing operations.          

                        

       

Stitch line formation method: 

Largely in apparels 2 type of straight stitch line formation using in sewing operations.

 1.    SN or DN Locked stitch Needle and Bobbin combinedly form the stitch line.

2. Needle and looper hook combinedly from the stich line

Industrial wash shrinkage vs before wash seam tension predetermination guideline:

Apparels commonly design with warp and weft weaving mechanism fabric or knit construction in loop form structures. It’s washing shrinkages determine through fabric characteristics in fabric data sheet (FDS) and industrial wash complexity.

It is mandatory to perform appropriate Sewing R&D during Product development, preproduction to identify the industrial wash shrinkages in width x length x diagonal directions along seams by style, finishes. 

Maintenance team should work on fabrication to categorize as,

Rigid, Medium stretch and Super stretch, Two-way stretch,

Sewing seam direction also key factor to focus on before- wash stitch tension and BW SPI.

Seam thickness (Number of layers) also need to notify during R&D, preproduction to define multi needles sewing constructions. Seam thickness direct impact on tension setting and different shrinkage degrees, recovery and elongations during industrial washes

Note: -

Core Spun Polyester threads are very minimal shrinkages during industrial wash.

Whereas elastane, polyester mixed fabrics gets high shrinkages.

 Fabric Risk Assessment Template: –

General guideline to recognize thread specifications involving on seams: -

(Note: Date sheet must collect from relevant suppliers)

USAT sBU USA - Proactive Maintenance: -

 

Proactive Maintenance principles, policies and preventive maintenance schedules review by factory management periodically to identify area of improvements, technology enhancements to strengthen the process accuracy, consistently. Organization continuously invests to ensure error free methodology in its manufacturing processes.

 

Proactive Maintenance spread over in 4 segments in seam stitch total quality management.

1.        Feasibility and Risk Assessments - Product Development. 

2.        Preproduction – Pilot run – Innovation.                                

3.        Bulk setting – Calibration & Controlling.                               

                   4.      Training – Mechanical staff, technical staff, Operation staff and Operators. 

Thread stand configuration   

Thread stand is not vertically & horizontally aligned. Thread stand configuration should be like the picture.

Thread through guide

Thread not properly guided through thread guide & Needle thread guide

Tension Disk & Check Spring should be clean & Check Spring setting should be proper adjusted properly

Check Spring & Tension Disk Condition 

• Rusty and malfunctioning check spring & tension disc
• Tension Disk & Check Spring should be clean & Check Spring setting should be proper adjusted properly

Tension Post & Check Spring

Throat Plate Hole & Presser foot Condition 

Throat Plate & needle size combination 

In some machine there was big difference between needle & throat plate size combination for example for needle size 18, throat plate 26 was used. This could lead several quality related issues in sensitive & light Wight garments. 

Bobbin Winding

Improper bobbin winding found

 

• 6Curved Bobbin winding leads to improper tension adjustment. It also increases risk of Skip Stitches
• Rusty bobbin winder causes more friction, leading to loose thread lubrication or abrasion resistance 

Dirty & Rusty Machine Parts

Damaged needles/Poor quality seams

Needle heat - Fusion

FUSION CAUSES

Poor quality thread Inconsistent / poor lubrication. Dense or harshly finished material. Damaged or poor condition of the needle. Thread breakage can sometimes occur after the machine stops; this is because needle temp increases when thread stops running through the needle.

Unbalanced stitches

Needle Mark/Fabric damage

Thread Package Alignment

•        All thread packages should be positioned exactly central & aligned upright on package creel.

•        Thread package distance to creel guide should be approximately 2.5 times the length of thread package.

Operator Wound Bobbins

Operator should extra careful while wounding the bobbin thread Too much thread wound onto the bobbin, thread wastage. Bobbin wounds unevenly so that the thread jams and breaks.  Uneven off winding tension causes skip stitches. More bobbin changes required. Lower productivity.

Rewinding of thread

Rewinding is a Quality issue& should be eliminated.

Many Quality issues can be a result of rewinding.

•  Tension                                                                               
• Removal of lubrication                                                          
•                                                           Damage to the bond resulting in ply separation                                                
•          Adds extra twist creating a lively thread                                       
• Filament damage                                                                     
•        Loss of original strength                                                                

Uses of extra silicone oil

Adding silicone or oil to the thread to try and improve sewing performance of a poor-quality thread can adversely affect the quality of the garments and can result in many problems, for instance; The thread color by changing the shade. Large variations in friction resulting in inconsistent tension issues Permanent staining of the material around the stitch line Excessive oil   can atomize and create a health risk for operators 

Machine Parts

General Stitch Ratio Guideline

Note:                                                                        1)   This ratio is indicating average number only.

2) This is a general guideline considering denim fabric & style. It will vary based on fabric type/thickness, garments style & quality requirement.

Manual Stitch Ratio Detection

Method:                                                           

  Cut 1/3/5 inch of stitch area after m/c tension setting. Measure Needle/looper/2nd looper/spreader, all different thread separately. Divide those with inch to find out the actual length of thread in different parts like needle/looper etc.

USAT sBU USA - Proactive Maintenance Cont. 

THREAD TENSION CHECK PROCEDURE

THREAD TENSION METRE

LOCK STITCH SINGLE NEEDLE / DOUBLE NEEDLE / BARTACK MACHIN NEEDLE THREAD TENSION CHECK

LOCK STITCH BOBBIN TENSION CHECK

KANSAI MACHINE NEEDLE TENSION CHECK

KANSAI MACHINE LOOPER TENSION CHECK

FOA MACHINE NEEDLE TENSION CHECK

FOA MACHINE LOOPER TENSION CHECK

Sewing operations before - wash Bulk integration example template.

Operation Wise Before Wash Stitch Guide Line
Buyer :	AEO		Styel #		7329		Fabrication:		70% COTTON 20% RECYCLED POLYESTER 8% VISCOSE 2% ELASTANE			Wash Shrinkage			L= (-0% to-2%) W= (-10% to-16%)
Sewing Operation	MC Type	Brand / Modle #	# Of layers	BW Thickness	AW Thickness	Needle Tex	Thread Quality	Needle Size/ Type/ Brand	Bobbin / Chain Tex	Thread Quality	BW SPI	AW SPI	BW Needle Tension	BW Bobbin/ Chain Tension	BW Stitch Ratio	AW Stitch Ratio
Coin pocket rolling	DNL-301	Juki	3	1.42mm	1.46mm	105	Epic	14	80	Epic	9	11	380	400	60:40	55:45
Coin pocket attach	DNL-301	Juki	3	1.40mm	1.70mm	105	Epic	16	80	Epic	10	11	430	400	54:46	52:48
Scoop pocket mouth top stitch	DNL-301	Juki	2	1.12mm	1.25mm	105	Epic	16	80	Epic	10	11	410	400	62:38	66:34
Fly J stitch	DNL-301	Juki	2	1.0mm	1.15mm	105	Epic	16	80	Epic	10	11	450	400	50:50	53:47
High top stitch	DNL-301	Juki	3	1.43mm	1.70mm	105	Epic	16	80	Epic	10	11	430	390	55:45	52:48
Back pocket rolling	SNL-401	Juki	3	1.52mm	1.78mm	105	Epic	16	80	Epic	9	11	420	400	33:67	35:65
Back pocket attach	DNL-301	Brother	3	1.50mm	1.62mm	105	Epic	16	80	Epic	10	11	430	400	50:50	52:48
Back yoke top stitch	DNC-401	Juki	3	1.67mm	1.78mm	105	Epic	18	80	Epic	9	11	450	400	30:70	35:35
Back rise top stitch	FOA-401	Brother	3	1.50mm	1.66mm	105	Epic	20	80	Epic	10	11	450	400	30:70	35:35
Inseam top stitch	FOA-401	Brother	3	1.30mm	1.50mm	105	Epic	20	80	Epic	10	11	460	66	35:65	40:60
Side seam join	SNL-401	Juki	2	1.1mm	1.9mm	105	Epic	16	80	Epic	9	10	450	380	43:57	44:56
Side cord stitch	SNL-301	Brother	3	1.50mm	1.61mm	105	Epic	18	80	Epic	10	11	420	400	47:53	48:52
W.Band attach	KNS-401	Kansai	4	2.34mm	2.50mm	105	Epic	20	80	Epic	9	11	450	90	45:55	48:52
W.Band mouth close both side	SNL-301	Brother	4	2.34mm	2.50mm	105	Epic	18	80	Epic	9	11	430	400	55:45	52:48
Baby hem operation	SNL-301	Brother	2	.70mm	.75mm	60	Epic	14	60	Epic	11	12	360	390	50:50	52:48

USAT sBU – USA Sewing Seam - Quality Assurance and Quality Control Philosophy

Attribute	Quality Assurance	Quality Controls
Concept	Defects elimination	Finding out defects
System	Preventive base	Corrective base
Approach	Proactive & Verification stage activity	Reactive & Validation stage activity
Focus	Planning, Setting, Training, Calibration	Inspections, Monitoring
Emphasis	Process Quality	Product Quality
Statistical Techniques	(SPC) Statistical Process Control data	(SQC) Statistical Quality Control data
Level Activity	High Level Activity – Expertise	Mid-Level Activity – Experience

    

USAT sBU USA - Sewing Seam Quality Assurance: -

•   Style hand over – Approved operation bulleting.                                                          
•    PPR Pilot run review and verification.                                                                              
• Line feeding certification with approved mockup, report.                               
•  Individual CTQ process clear detail mockups.                                                                            
•   Daily machine calibration check list.                                                                                  
•   Daily process wise SPI mockup verification.                                                                                                     
•   Operator threading, needle insert training records.                                                             
•  On CTQ MC’s threading visual guideline sticker                                                                                                 
•   Process wise needle calendar format.                                                                                                               
•   Daily needle changing process report verification.                                                                                         

•   Thread cone changeover, Bobbin changeover process verification.                                                                                                                                                                          USAT sBU – USA Sewing Seam Quality Control: -  

ü  Operator check 5pcs to 1pcs.

ü  7- 0 System validation.          

         ü  Sewing In line In Station 100% inspections. 

ü  End Line 100% inspections.    

ü  End line 20% lot audit.            

ü  Finishing 100% alter validation.

          ü  100% Trolly audit 20% sample size zero defects.

ü  Prefinals validation.                     

ü  Finals validation.