High Schools United with NASA to Create Hardware

(HUNCH)

Linear Measurement Training

Presented by

Marcie DicksonHoneywell Quality Engineer

NASA Safety and Mission Assurancemarcie.l.dickson@nasa.gov

Purpose• Train personnel with the knowledge and standards that will

be required to perform work associated with linear measurement of cut material for the fabrication of class I soft-goods.

• Accurate linear measurement 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 materials length we cannot guaranty that the fabrication was done to the required standards. Knowing tolerances and understanding how to apply these tolerances ensure that the soft-goods will be able to handle the desired loads and meet the fit, form and function requirements.

Knowledge Requirements

• Personnel fabricating soft-goods shall know how to fill out the blanks of the JSC Form 881.

• Quality Assurance (QA) representative stamping soft-goods shall know how to fill out the blanks of the JSC Form 881.

• QA Stamping JSC Form 881 in the “LM” location shall know what information is required next to the stamp.

• The person fabricating and QA Stamping JSC Form 881 in the “LM” location shall be skilled at reading a metric scale.

TestingPersonnel fabricating and inspecting soft-goods will be given a written test.

• QA person that stamps paper work will be required to make a 90 on the test.

• Person fabricating soft-goods without stamping privileges will be required to make a 80 on the test.

• The written test will be administered once to any person wanting to assume the QA 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• 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 Linear Measurement stamp will be identified as HUNCH LM 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.

• It is the students responsibility to ensure only approved inspected work is stamped.

Linear MeasurementThe photograph below shows the beginning of a metric scale. The scale is marked in 1mm

(millimeter) tick marks down one edge and 0.5mm tick marks down the other edge. The 1mm side is easier to read, due to fewer marks and is the edge that we should use. All of the reading that we will document will be to the nearest mm. The major tick marks are labeled

down the center of the scale, every 10mm. Therefore to read the scale one counts the minor tick marks past the last 10mm major tick mark and add it to the 10mm major tick mark.

Point 1 on the scale would be 4mm. It is 4 minor tick marks from

the 0mm major tick mark.

Point 3 on the scale would be 42mm. It is 2 minor tick

marks from the 40mm major tick mark.

Remember to always read forward on the scale when reading minor tick marks. Or read tick marks from the smaller value of major tick mark toward the larger value.

Point 6 on the scale would be 98mm,

because it is 8 minor tick marks from the 90mm

major tick mark.

Measurement Tolerances• What is a Tolerance?

– A tolerance is how close does the part have to be to the requirements.

• Tolerance Class V (very coarse) from DIN ISO 2768-1 will be used on the ATV CTB project. Fabric will stretch and shrink, therefore a very coarse tolerance is required.

• If the requirement is to cut to part so it is 50mm long, but after you cut it you measure it and it is 47mm long, is the part usable?

• The 881 has upper and lower limits, the chart below is how those lengths were determined. Notice that as the length increases so does the tolerance.

Length 3-6mm 7-30mm 31-120mm 121-400mm 401-1000mm

1001-2000mm

2001-4000mm

Tolerance +/- 0.5mm +/- 1mm +/- 1.5mm +/- 2.5mm +/- 4mm +/- 6mm +/- 8mm

If the part is too long cut it to the length so it is in tolerance.If the part is too short and out of tolerance it needs to be discarded.

JSC Form 881(Subassembly Process Sheet)

• The purpose of the JSC Form 881 is to allow soft-good technicians and quality control personnel the ability to document the fabrication process.

• There are important pieces of quality 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 and document the tools used and 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.

Measurement Tools• The tools used to measure the cut components are steel scales. • These scales have been calibrated.

– A calibrated scale has been compared to standard using a microscope to make sure that the marks are in the correct locations.

• Each tool that has been calibrated is given a calibration number and a calibration due date. The calibration number is a unique number to track that tool. The calibration due date is the date that the calibration will expire.

• Do not use a steel scale that the calibration due date is in the past. • Record the calibration number and the due date on the JSC Form 881• Every time one cuts a part the part will be measured and the actual

length will be written on the 881.

If the part is cut too long, it should be cut shorter.If the part is cut too short it should be trashed and a new part cut.

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.

Questions