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Stitch Inspection Training

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Stitch Inspection
Training
Presented by
Marcie Dickson
Honeywell Quality Engineer
NASA Safety and Mission Assurance
marcie.l.dickson@nasa.gov
Purpose
• Provide personnel with the knowledge and standards that
will be required to perform work associated with the
control of NASA flight hardware and soft-goods.
• Stitch inspection of flight soft-goods are vital to ensuring
that quality products are fabricated to specifications and to
ensure a safe manned space flight program. Without
inspections on the finished materials we cannot guaranty
that the fabrication was actually done to the required
standards. Knowing the standards and understanding how
to apply these standards make sure that the soft-goods will
be able to handle the desired loads and meet the form, fit
and function requirements.
Knowledge Requirements
•
Personnel fabricating soft-goods shall know:
– How to complete the Form 881
– Be knowledgeable of Sewing Terms and their definitions
– Process for items being logged IN/OUT from controlled storage.
•
Student Quality Assurance (SQA) Stitch Inspector (SI) shall know:
– How to complete the Form 881
– What information is required next to stamp (date)
– Be knowledgeable of Sewing Terms and their definitions and how it applies in writing
up sewing anomalies in the anomaly log
– Be knowledgeable about the “Classification of Defects” and how it applies in writing up
sewing anomalies in the anomaly log
Supporting Documentation
• JSC CSD-A-533 Inspection and Acceptance
Criteria for Stitches, Seams and Stitching
• ASTM D-6193 Standard Practice for Stitches
and Seams
Testing
Personnel working controlled storage will be given a written test.
• SQA will be required to make a minimum of 90 on the test.
• Fabricator of soft-goods (without stamping privileges) will be required
to make a minimum of 70 on the test.
• The written test will be administered only once to any person wanting
to assume the SQA responsibility.
• If the person does not pass, but want to perform this task then
additional training will be provided and retest will be performed if
approved by test administrator.
• The NASA HUNCH office will keep the test results on file.
Stamp Control
Stitch Inspection (SI)
• Stamps will only be issued to students who receive a 90 or better on the
written exam.
• Each school/class will be issued stamps for up to two students and the
teacher(s).
• The Controlled Storage stamp will be identified as HUNCH SI XX, were XX is
the stamp number.
• Stamps will be kept in a lock box in controlled storage.
• Students will not take their stamps home.
• If the student is not in the program the following year the stamp will be
reassigned to another student the following year
• A stamp log will be maintained to identify who stamps are issued to.
• It is the students responsibility to ensure only approved inspected work is
stamped.
General Stitching Information
Thread breaks, skips and run-offs shall be overstitched by not less than ВЅ inch.
All seams shall be uniformly constricted and shall be free from pinholes, tears,
cuts, chafed spots or other imperfections which could impair end item
effectiveness.
End of stitching that are not secured in other seams or stitching shall be secured
by back stitched a minimum of ВЅ inches.
All materials shall be protected from contamination such as dirt, grease, oil or
other foreign matter during the fabrication process.
All stitches, seams and stitching shall be inspected for quality of workmanship,
and shall be examined visually and dimensionally for major and / or minor
defects to determine conformance to the classification and list of defects as
identified.
All straps, handles, labels, Velcro and subcomponents shall be compared the
assembly drawings for item orientation definition.
JSC Form 881
(Subassembly Process Sheet)
• The purpose of the JSC Form 881 is to allow soft-good technicians and
student quality assurance (SQA) the ability to document the fabrication
process.
• There are important pieces of information that needs to be recorded on
the 881. Two of the most important are the part and serial number that
appear at the top of page one. These two numbers identify the part and
unit that is being fabrication.
• The remaining information is also important; it is identified during the
fabrication process.
• As new parts or components are cut it is important that these are the
correct pedigree and cut to the correct length. Therefore it is important to
log the lot number, document the tools used and record the actual cut
length.
• Some items that are used during the fabrication process have expiration
dates. These dates indicate that these products should not be used if the
date is in the past.
JSC Form 881 Fields
•
Calibration Number:
– This is a blank or column where you will log the steel scale calibration number.
•
Calibration Due Date:
– This is a blank or column where you will log the steel scale calibration due date.
•
Part ______ mm:
– This is a blank and it is where you will log the actual measurement of the cut part.
•
Date Column:
– The date that this step was completed.
•
Tech Column:
– The initials of the soft-goods technician that performed the task.
•
LM Column:
– Where the QA stamps and dates the transaction. Every time a person uses their stamp
they shall write in the date next to the stamp.
•
Lot Number blank:
– These Blanks are found in the STEP section of the 881. Write the Lot as it appears in
block 2 of the 911 tag. The 911 tag is a manila tag that is on the material when you
check it out of controlled storage.
•
Expiration Date blank:
– These Blanks are found in the STEP section of the 881. The product is no longer usable
once this date is past. Write the expiration date as it appears on the 911 tag.
Anomaly Log
•
•
•
The purpose of the anomaly log is to document and track anomalies until they are
repaired or corrected.
When the Stitch Inspector (SI) finds an anomaly the finding is logged.
It is the SI responsibility to complete the anomaly log
Part #/Part Name






Serial #
Description of Finding
Disposition of Finding
Date
Part # / Part Name: Part number and name are found at the top of the 881
Serial #: The serial number is found at the top of the 881
Description of Finding: Using sewing terms to explain the finding and location
Disposition of Finding: Using sewing terms to explain the disposition.
Date: The date anomaly resolved
QA Stamp: The SI or QC stamp
QA Stamp
Sewing Terminology
Sewing Term
Definition
Back Stitching
To start or finish a row of stitching by sewing over the original stitching a short distance to retard
raveling.
One which does not show
Fabric being torn and bruised from the teeth of the feed dogs and presser foot.
Blind stitch
Feed dog &
Presser foot
Chews
Hand tack
Incomplete
assembly
Margin
Misassembled
Missed Stitch
Needle damage
Open Seam
Raw edge
Run off
Seam
Stitch produced by hand sewing
Components are missing
Space from outer-row of stitching to edge of fabric or fold of fabric
Material caught in unrelated seams
Aka Skipped Stitch, The distance between adjacent stitches exceeds the stitch length
In sewing fabrics, the partial or complete yarn severance or fiber fusing caused by a needle passing
through a fabric during sewing.
When one or more stitches joining a seam are broken. On double stitched seams, a seam is considered
open when either one side or both sides of the seam are open.
A cut of fabric, raw edges not securely caught in stitching shall be classified as an open seam
When the stitching runs off of one of the items that it is suppose to be sewing
A line where two or more fabrics are joined, usually near the edge. The security of a sewn seam
depends chiefly upon the stitch type, stitches per inch, and its susceptibility to become unraveled. The
stitch must be well set to the material to prevent snagging that can cause rupture of the tread and
unraveling of certain stitch types.
Seam allowance
The distance from the edge of the fabric to the parallel stitch line furthest from that edge.
Seam assembly
The composite structure obtained when fabrics are joined by means of a seam.
Sewing Terminology cont.
Seam Type
An alphanumeric designation relating to the essential characteristics of fabric positioning and rows of stitching
in a specified sewn fabric seam. SSa and SSq are the two seam types.
Sewing Terminology cont.
Sew
To unite or fasten with stitches
Sewing pattern
A design outlined in drawings for joining parts, a box or a cross-box are examples
Sewing thread
A flexible, small-diameter yarn or strand, usually treated with a surface coating, lubricant, or both, intended to be
used to stitch one or more pieces of material or an object to a material.
The configuration of the interlacing of sewing thread in a specific repeated unit. All stitches and seams shall be
machine sewn. Stitch type 301 will be used.
Stitch
Stitch density
The number of stitches per unit length in one row of stitching in the seam, typically stitches per inch (spi)
Stitch type
A numerical designation relating to the essential characteristics of the interlacing of sewing threads in a specified
stitch.
Yarn slippage
The displacement of one or more yarns from the original position, causing differences in alignment, spacing or
both.
Classifications of Defects
Major
Run-off resulting in more than three (3) feed dog and presser
foot chews outside of seam formation.
Back and/or over stitching missing on all completed seams
Minor
Row of stitches missing (4,5)
Incorrect or improperly located seams
Skipped stitches (3)
Tight stitching tension resulting in the breaking of the stitches
when normal pull is applied to the material
Loose tension on thread top or bottom resulting in a loose
seam
Open seams
Broken stitches (3)
Incomplete assembly
Run-offs (3)
Misassembled
Number of stitches plus or minus 1 per inch exceeding the
specified limits.
Over stitching less then ВЅ inch in length (4)
Incorrect cross box or sewing pattern
Number of stitches plus or minus 2 per inch exceeding the
specified limits.
Bobbin and top thread not of specified type, style and size
Cuts, tears or chafed seam material
Bunched stitches (1)
Raw edges of material exposed on outer portion of finished
items unless otherwise specified
Erratic variation of the distance between rows of stitching (6)
Improper orientation of components when compared to the
controlled sample.
Incomplete seams (4,5)
Run-off resulting in three (3) or less needle chews outside of
seam formation
Cross box or sewing pattern missing (4, 5)
Back stitching less then ВЅ inch in length (4)
Footnotes:
•The defect shall be classified as major when it seriously affects the serviceability and/or appearance
of the item, otherwise it is to be classified as a minor defect.
•Puckering is evidence of tight tension, When puckering is evident, the seam shall be tested by
exerting normal pull in the lengthwise direction of the seams.
•When no more than three breaks or three skips or three run-offs or any combination not to exceed a
total three of these defects occur within a distance of 48 inches or less and no more than three (3)
broken stitches, skipped stitches or run-offs exist per each occurrence, these defects may be repaired.
•Any required operation which can be corrected per drawing after the items have been fabricated
shall be re-inspected.
•If mission or required operation cannot be completed after fabrication, the defect shall be classified
as Major.
•Variation in the distance between rows of stitching that does not adversely affect the strength
and/or appearance of the item shall be acceptable.
Questions
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