Recent Developments in Scientific Balloon Quality Assurance
Michael W. Zimmerman, Quality ManagerLoren G. Seely, Plant Manager
Raven Industries, Inc.Sulphur Springs, Texas
Abstract
Recent growth of Raven Manufacturing operationshas not only introduced new people and qualityissues to the environment, but new ideas aboutassessing and improving the quality of balloons aswell. This paper will explore some of those newideas. In particular:
The way BSA (Balloon Section Audit) data isreviewed graphically with maps.
• An exercise developed to minimizeblemishes caused by handling duringmanufacturing by allowing assemblers tosee first hand the affects of their handling.
• A non-destructive audit process developed toprovide a more global inspection of theballoon and simultaneously encourageownership of quality by the balloonassemblers.
introduction
Plastic high altitude balloons have been in use for fiftyyears. Some of the larger ones may contain enough0.8 mil plastic to cover twenty acres. This largeamount of plastic is fashioned into a balloon by layingit out on tables and sealing pieces into sections calledgores. There may be as many as one hundred-seventy-two gores in a large balloon. Each gore canbe as much as one hundred inches wide at the widestpoint. The process takes seven assemblers aboutthree weeks to complete one balloon.
This labor intensive process is dependent upon
craftsmanship skills normally developed over severalyears. Due to the acquisition of the Winzen balloonmanufacturing operations by Raven Industries, Inc.in 1995, the number of production employees hasdoubled at the Sulphur Springs plant. This influx ofnew people and the merging of ideas from twocultures has acted as a catalyst for the introduction ofprogressive management approaches including waysof accelerating the learning curve for new balloonassemblers and new ways of using traditional qualityassessment tools.
1. Balloon Section Audits (BSA)
Balloon Section Audits (BSA) are destructive auditsconsisting of the removal of one day's production,normally ten to fifteen gores, from a balloon inprogress. The section is cut into ten foot lengths andinspected using polarized light. Material andmanpower requirements for this type of audit are:
A full assembly crew needs about a half dayto remove the balloon section and preparethe balloon table for resuming production.
A full crew is needed for a full day to re-manufacture the removed gores.
Five people are needed for two days toactually inspect the section.
Approximately five hundred pounds of film,fifteen rolls of loadtape and five rolls of back-up tape.
This makes an estimated cost of $10,000 or moreper BSA sample. This changes depending on whattype of balloon, how many gores were manufactured
and if any accessories were included in the section.
Historical Application of BSA Data
Out of approximately 250 days of productivity, two tofour days are inspected per year with a BSA. Datagenerated by the BSA is given back to the balloonassemblers as totals of various flaw types. Thisfeedback is usually two or three weeks after theproduction date of the sample.
The feedback does not contain information as tolocation of findings, or of the relationship thesefindings have with each other or with repairs in thesection. In short, the historical application of BSAdata is only a semi-annual report on anomalies foundin isolated and unrelated samples.
BSA Maps
One way BSA data is made more useable forprocess improvement, is by mapping the findingsgraphically. When mapped, information that is notclear in a summary of data becomes clearer with aglobal view.
The BSA map in Figure 1 shows a systematicdistribution of unrepaired and repaired anomalies.For instance, the gores between seals 102 and 110represent half the sample, but less than twenty-fivepercent of the total anomalies.
To read BSA maps, the station is the number of feetfrom the apex toward the base. Gores are betweenthe seals. Anomalies are identified as repaired orunrepaired and are located on the seal related to theanomaly at the appropriate station or foot mark.Fullness, accessories or other unique features can beplotted on the map in the same way.
Accessories such as vent ducts and inflation tubesare installed in the balloons as sub-assemblies. Thehandling and labor associated with assembling andinstalling accessory gores is ten times that of othergores. Historically, the gores related to accessorieshave a higher frequency of repaired and unrepairedanomalies.
As seen in the BSA map in Figure 2, seals 83, 84 and85 are duct gore seals. Seals 86 and 87 are inflationgore seals. These accessory seals average fiveanomalies per seal, yet the non-accessory seals hadan average of 0.5 anomalies per seal, a difference ofninety percent.
Base
700 -
o
S300-
0 -
Aug 95 - BSA Map
<•
i
fHh( (T)^t
r " " ',
Ttf-
>
\;'" '''•;
s
It t T 1 1 14-
^
•
80 81 82 83 84 85 86 87 88 89 90 91 92 93* Seal Number
O Unrepaired w Repaired .- ; MM**,!,** •'""" Fullness
Figure 2O
BSA Study Results
Not only have BSA maps helped us understand thatblemishes inherent in the balloon materials or causedduring manufacturing are found in varyingconcentrations throughout the same balloon, but that"hot spots" can be identified. Some of the "hot spots"identified so far include:
The bottom third of the balloon'after rolling airfrom the balloon stack. There is a tendencyfor finger abrasions to occur when aiding theescape of the trapped air.
Individual rolls of film may have a higherproportion of extrusion blemishes and bedistributed over several gores.
2. Material Handling
Experience Levei
In May 1996, an increase in the percentage ofanomalies unrepaired was noticed. The percentageof unrepaired items found in BSAs was also found tobe proportional to the experience of the balloonassembly crew (Figure 3).
% of Findings Unrepaired and% of Labor By New Employees
B| % Hours From New Assemblers-O- % Of Findings Unrepaired
Figure 3
Repairs for the type of blemishes found in BSAs aremade by simply applying a piece of repair tape to theaffected area. Determining if a blemish requires arepair is subjective. It is unknown whether thisincrease in unrepaired anomalies was due to theblemishes being unnoticed or due to the assemblersdeciding the blemishes did not require a repair.
Historically, the balloon assemblers developed theireye for seeing small blemishes in a sea of film and afeel for sensing finger abrasions with years ofexperience. The subjective ability to judge whether ablemish should be repaired or not was also
developed over time. It was decided that since alarge percentage of the labor force did not havethese years of experience, a new approach to shortenthe learning curve was needed.
Material Handling Exercise
A material handling exercise was developed to teachthese learned skills:
How to handle film without making abrasionsor bruises.
How to tell by feel when abrasions weremade when handling film.
Determine when and how to make a repair.
This exercise consists of pulling a weight about sixfeet long and weighing six and a half pounds forapproximately one-hundred inches using a"gathering" motion with 0.8 mil balloon film. The filmis then inspected under polarized light for handlingabrasions. The results of the first use of this exercisecan be seen in Figure 4.
An interesting discovery was made as a result of theexercise. Seventy-three percent of the abrasions leftwere made while assemblers were wearing softcotton gloves. It had long been thought that softgloves would protect the thin film from theassemblers hands. In reality, gloves hinder theassemblers ability to feel the film. Before theexercise, forty percent of the assemblers preferredthe gloves and felt they would cause less damagewearing them. This turned out to be a false sense ofsecurity.
The exercise has been repeated several times, allwith the same results. Most of the senior employeeswere able to pull the weight without causingabrasions. Regardless of experience level, glovedhands almost always generated more abrasions. Itusually takes about a day of this exercise for newassemblers to develop a feel for "gathering" withoutgloves.
In an effort to accelerate the learning curve forhandling material, new employees are now requiredto perform this exercise and modify their techniqueuntil they are able to handle the film consistentlywithout causing abrasions. The exercise provides theassembler with direct feedback on what effect theirhandling technique has on the film. Since using thisapproach, improvement has been detected in BSAsand table top audits.
3. Daily Table Top Audits
When process changes were made like relaxing theglove policy, it became clear that real-time feedbackwas needed to monitor the effects of these changes.BSAs were not well suited for this purpose becausethe frequency is too small (2 to 4 times per year) andbecause the BSA sections do not relate to each otherwell for comparative purposes. A broader samplingof the balloon, preferably each balloon, was needed.There was also a desire to foster a sense ofownership for the product and the audit process bythe balloon assemblers. With these needs in mind,
the table top audit system was developed.
Procedure
After the Raven Quality Assurance auditor selects thegore to audit, the auditor and one of the balloonassemblers inspect the gore behind the sealingmachine as the seal is being run. Working acrossfrom each other, they pull the film until they have anunobstructed view across the completed gore. Theremaining balloon assemblers come behind theauditors and continue the inversion process inpreparation for the next seal.
Audit Focus
The audit covers:
Seal defects caused by the machine,operators or materials that are undetectedby the tailpuller (normal seal inspector).
The quality and documentation of repairs.
The inverted seal for handling blemishescaused by the inversion process or the tableweights used to hold the balloon on thetable.
The gore for unrepaired items that had beenmarked during inspection of materials, whichconsist mainly of extrusion blemishes.
Fullness, which is a difference in widthbetween one or more of the plastic sheetsforming the cap area at the top of theballoon.
Corrective Action
Any anomalies found during the audit aredocumented and submitted to productionmanagement for corrective action. This correctiveaction consists of repairing the anomaly, identifyingpreventive measures, and assessing individual needsfor on-the-job training.
Audit results are also continually reviewed by the
Manufacturing Review Board to identify trends or already been found with the non-destructive table topaudit. The thirteen unrepaired findings were on thetwo gores that did not receive table top audits.
other issues to be addressed.
Base Line
In May 1996, several changes were made to theballoon assembly process in order to facilitate theimplementation of daily table top audits. Thosechanges include:
Developing ways of tracing individualworkmanship.
Developing a corrective action process.
Assigning and training individuals to performthe audits.
The first month of daily audits had the results foundin Figure 5.
Single Gore Audits - GeneralMay 20-June 17
1 2 3 4Anomalies Per Sample
Figure 5
Each table top audit is plotted in the histogramaccording to the number of anomalies found. InFigure 5, one table top audit had six unrepaired itemsfound. There were seven table top audits with nounrepaired items found.
To confirm the audits were accurate, a "mini" threegore destructive BSA was performed. Thirteenunrepaired anomalies were found. The "mini" BSAalso included a gore that had been inspected by thenon-destructive table top method. The table top auditcaused no damage to the balloon and was accurate.Nothing was found in the audit gore that had not
Second Month of Self Audits
During the second month of self auditing activity,management initiated several improvement activitiesincluding:
A team was activated to improve repairrecords.
• A team was formed to address the issue offoreign object damage (FOD) from tapescraps.
Drive wheels were changed on sealingmachines.
Certain weights were found to causeabrasions on film and were removed.
Three new employees received modifiedtraining including the material handlingexercise and the viewing of a new trainingvideo.
Management began strategically locatingkey assemblers.
The results of the second month of self audits can befound in Figure 6.
A "mini" three gore destructive BSA was againperformed to validate the table top audit. This time,only two unrepaired items were found. This second"mini" BSA also included a gore that had beeninspected using the table top method. Like the first"mini" BSA, no damage was caused by the table topaudit and no findings were made that had not alreadybeen repaired as a result of the table-top audit.
Third Month of Self Audits
During the third month of non-destructive table topaudits, the following changes were put in place:
A team was initiated to investigate thesources of unrepaired scratches found in theaudits.
A team was initiated to solve the problem ofanomalies being marked but unrepaired.
Back-up tape brushes were added to thesealing machines to wipe away foreignobjects found in the back-up tape.
Balloon assemblers began participating inthe daily table top audits.
The results of the third month of self audits can befound in Figure 7.
Single Gore Audits - GeneralJuly 19-August 15
Anomalies Per SampleFigure 7
BSA maps confirmed that duct gores were a "hot
spot" and these gores were included in the dailyaudits. Because the duct gores are assembled andinstalled in a different process, the audit data is keptseparate. Duct gore audit data for the third month isfound in Figure 8.
Single Gore Audits - DuctsJuly 19 - August 15
1 2 3 4Anomalies Per Sample
Figure 8
For a third time, a destructive three gore "mini" BSAwas performed to verify accuracy of the table topaudit. Again, the sample included a gore that hadpreviously been audited using the table top method.Two unrepaired items were found in the two goresthat had not been audited, and the audited gore wasnot damaged by the audit.
Fourth Month of Self Audits
During the fourth month, improvement activityfocused on duct gores. The changes include:
All duct gores underwent inspection forblemishes incurred during sub-assembly andtransfer by the balloon assemblers when thegores were unfolded on the balloon table.
A self directed study of the accessoryprocess was sponsored.
It became policy to audit the last seal ofevery duct set after the set is installed.
Results of the daily table top audits for non-accessorygores are found in Figure 9.
Single Gore Audits - GeneralAugust 16 - November 13
2 3 4Anomalies Per Sample
Figure 9
Results of the table top audits of duct gores for thisfourth month are found in Figure 10.
Single Gore Audits - DuctsAugust 16 - October 24
2 3 4 5 6Anomalies Per Sample
Figure 10
Daily Table Top Audit Results
The improvements made during this exercise weredramatic. There were roughly eighty percent fewerunrepaired anomalies per seal for non-accessorygores from the time the exercise started to the end ofthe fourth month. There were roughly seventy-twopercent fewer anomalies unrepaired per seal forduct related seals during the three months duct goreswere audited. The processes were also morepredictable with roughly a fifty percent reduction instandard deviation.
Table top audits have several beneficial aspects.Like BSAs, they provide information that is not foundin repair records by assessing anomalies that escapedetection in the normal production process. UnlikeBSAs, they provide a global view of the balloon and
the production operation. All this is done withoutdestroying the sample, degrading the balloon ordisrupting the production cycle for more than fifteenminutes per audit.
Table top audits can be focused on problemareas.
Table top audits provide real time feedbackto the source.
Table top audits only require two people toperform the inspection.
Table top audits condition the balloonassemblers to inspect and be accountablefor their work.
Four full BSAs have been performed since putting thetable top audit process in place. Two of the BSAswere self imposed and three of the BSAs includedgores that had previously been inspected using thetable top method. As with the three "mini" BSAs, thetable top method proved to be effective.
Two of the BSAs performed were after the fourmonth study and included employees that had beencalled back from a layoff and some new employees.These employees were given two hours of classroomtraining that included "lessons learned" from the four-month exercise. They were also given up to six hoursof material handling training. They performed theexercise until it could be done repeatedly withoutmaking abrasions when not wearing gloves.
The results of these full BSAs are compared to thetwelve gore BSA performed in May 1996, before theabove described process changes, in Figure 11. Theanomalies that were both repaired and unrepairedare plotted. The data is normalized by referencing itper hundred feet of seal. Improvement in anomalyprevention is clearly seen and the chart suggests theimprovement is holding.
Impact On PreventionRepaired & Unrepaired Anomalies
M«y3SFull BSA
Figure 11
4. Conclusion
BSA's using polarized light for inspection havehistorically been the primary method of assessinganomalies that escape detection in the normalproduction process. By reviewing data in new wayslike with BSA maps, it is possible to uncover issuesbefore unseen, like "hot spots" or trends and theirrelationship to other anomalies and location in theballoon. It is also possible to recognize that BSA'shave shortcomings.
• BSAs are destructive.
BSAs are labor intensive.
BSAs do not give real-time feedback to theballoon assemblers. They foster reactiveimprovement efforts.
BSAs are a one day "snapshot" from lessthan 2% of the manufacturing days.
BSAs only represent 10% to 20% of theballoons manufactured.
Table top audits are comparativelyinexpensive.
Table top audits foster proactiveimprovements by allowing the productionemployees to take ownership of the processand providing them with real-time feedback.
Table top audits sample from 100% of themanufacturing days of 100% of the balloonsproduced.
Table top audits will continue to be used to providedata concerning process output. The present trendis to move away from BSAs and take a morepreventive approach to quality issues by making theassemblers process owners, including the auditprocess itself. The concept has even been applied toother processes including small balloon fabrication,accessory assembly, polarized light inspection of filmand data packages.
As the team environment now being implementeddevelops, more uses for self audit data will arise.Teams will analyze this data in new ways, like withmaps, to uncover the sources of issues that are nowtaken as unavoidable. Once the source is identified,process changes including progressive trainingapproaches like the material handling exercise canlead to prevention.
5. Acknowledgment
Raven Industries would like to thank NASA andNSBF for personnel and support of BSA activity.
BSAs are expensive.To date, seven gores inspected by the table topmethod have undergone destructive BSA verification.All showed the table top method to be as accurate asthe destructive polarized light inspection. Even moreimportant, the table top audit activity has manybenefits over BSAs:
![Page 1: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/1.jpg)
![Page 2: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/2.jpg)
![Page 3: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/3.jpg)
![Page 4: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/4.jpg)
![Page 5: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/5.jpg)
![Page 6: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/6.jpg)
![Page 7: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/7.jpg)
![Page 8: [American Institute of Aeronautics and Astronautics International Balloon Technology Conference - San Francisco,CA,U.S.A. (03 June 1997 - 05 June 1997)] International Balloon Technology](https://reader031.documents.pub/reader031/viewer/2022020614/575094c21a28abbf6bbbda9c/html5/thumbnails/8.jpg)
