Stitch InspectionTraining

Presented by

Marcie DicksonHoneywell Quality Engineer

NASA Safety and Mission Assurancemarcie.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

TestingPersonnel 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 ControlStitch 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 InformationThread breaks, skips and run-offs shall be overstitched by not less than ½ 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 ½ 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: 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

Part #/Part Name Serial # Description of Finding Disposition of Finding Date QA Stamp

Sewing TerminologySewing Term Definition

Back Stitching To start or finish a row of stitching by sewing over the original stitching a short distance to retard raveling.

Blind stitch One which does not showFeed dog & Presser foot Chews

Fabric being torn and bruised from the teeth of the feed dogs and presser foot.

Hand tack Stitch produced by hand sewingIncomplete assembly

Components are missing

Margin Space from outer-row of stitching to edge of fabric or fold of fabricMisassembled Material caught in unrelated seamsMissed Stitch Aka Skipped Stitch, The distance between adjacent stitches exceeds the stitch lengthNeedle damage In sewing fabrics, the partial or complete yarn severance or fiber fusing caused by a needle passing

through a fabric during sewing.Open Seam 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.Raw edge A cut of fabric, raw edges not securely caught in stitching shall be classified as an open seamRun off When the stitching runs off of one of the items that it is suppose to be sewingSeam 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.

Stitch 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 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 DefectsMajor Minor

Run-off resulting in more than three (3) feed dog and presser foot chews outside of seam formation.

Row of stitches missing (4,5)

Back and/or over stitching missing on all completed seams Incomplete seams (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

Broken stitches (3)

Loose tension on thread top or bottom resulting in a loose seam

Run-off resulting in three (3) or less needle chews outside of seam formation

Open seams Cross box or sewing pattern missing (4, 5)

Incomplete assembly Run-offs (3)

Misassembled Number of stitches plus or minus 1 per inch exceeding the specified limits.

Incorrect cross box or sewing pattern Over stitching less then ½ inch in length (4)

Number of stitches plus or minus 2 per inch exceeding the specified limits.

Back stitching less then ½ inch in length (4)

Bobbin and top thread not of specified type, style and size

Cuts, tears or chafed seam materialBunched stitches (1)Raw edges of material exposed on outer portion of finished items unless otherwise specifiedErratic variation of the distance between rows of stitching (6)

Improper orientation of components when compared to the controlled sample.

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