Total Quality: Out of Reach or Within Reach?

SHARAD PRASAD

Nouatec Plastics and Chemicals, Co., lnc.

In the recent past, Quality has increasingly gained in importance in the manu- facturing sector on a global scale. Quality Standards like ISO-9000 series, QS-9000 series and Malcolm Baldrige National Quality Award have brought on a movement that seems to be gaining momentum by the day. Development of a Total Quality Program for any manufacturing facility must take some key factors into consider- ation for the program to work. The key factors that need to be considered in a PVC Compounding or a Bottle Blow Molding setup are presented in a generic format to show the merit and applicability to other manufacturing industries. Introductions to some major concepts and tools in Quality Control including Variables, At- tributes, Sampling Plans, Cause-Effect Diagrams, Quality Function Deployment, Statistical Process Control and Quality Auditing are presented to measure the efficacy of the Quality Program to achieve Total Quality.

INTRODUCTION

tal Quality in manufacturing can be achieved T only through a well planned, detailed analysis of “Where We Are” and “Where We Should Be” along with an acceptable definition and understanding of the term “Total Quality” with respect to the operation in question.

A 10-step checklist approach is presented as a no- nonsense, easy to apply and use methodology to un- derstand the importance of the various factors in a manufacturing setup. As each of the 10 steps is pre- sented, the Quality Concept(s) and Tool(s) associated, are also presented to aid in understanding and using this methodology. Examples of the application of this methodology to a PVC Compounding and Extrusion Blow Molding industry are included to further eluci- date the importance of the various steps. Understand- ing of this methodology would enable the user to make “Total Quality” an achievable goal in a manufacturing environment.

METHODOLOGY

The 10 steps forming the backbone of this method- ology are a s follows:

1. Define and understand the “Product(s).” 2. Define and understand the “Customer(s).” 3. Define and understand the “Processes and their

Capacities.” 4. Define and understand the “Variables” of the

“Product.” 5. Define and understand the “Attributes” of the

“Product.” 6. Identify and understand the major “Raw Materi-

als.’’

7. Flowchart “Product Life Cycle” from Raw Material to Finished Product through all the processes.

8. Identify and develop locations for “Variables Sam- pling and Testing.”

9. Identify and develop locations for “Attributes Sampling and Testing.”

10. Establish a “Control System” to document, mea- sure and improve the efficiency of the “Total Qual- ity System.”

1. Define and Understand the “Product(s).”

This step involves identifying the features of the “Product” or “Service” being manufactured or pro- vided. At this step, certain important questions must be asked about the product such as

i. Is the “Product” a commodity product or a spe- cialty product?

ii. Are there other products similar to the “Product” in question, available easily in the market?

iii. What are this “Product’s” strengths and weak- nesses in comparison with competitor’s similar products?

iv. I s any historical data available about the “Prod- uct’s’’ performance in the field?

The user must not lose sight of the objective and must bear in mind that the questions may be more or less than the examples cited above. The objective may be achieved much more easily if an inter-departmen- tal team is involved. The concept of “Quality Teams” or “Quality Circles” must be inculcated with active in- volvement from Sales and Marketing, Quality Control and Manufacturing with a strong, documented com- mitment from Top Management.

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Total Quality: Out of Reach or Within Reach?

2. Define and Understand the “Customer(s).”

This step involves understanding who the “Custom- ers” for the product are, their quality needs, other specific requirements, type of industry involved and so on. Some of the important questions that must be typically asked and answered are

i. I s the “Customer” an internal or an external one? ii. What are the Quality requirements of the “Cus-

tomer” and does the “Customer” conform to a rec- ognized Quality Standard?

iii. What are the features of the product or service that keep the “Customer” from going to other similar vendors?

iv. What type of an industry does the “Customer” ser- vice?

One of the most powerful concepts to help under- stand the customers’ needs is called “Quality Func- tion Deployment.” QFD, as it is known, is born out of “Customers’ Needs” and links the external customer needs and specifications in a matrix form with the internal product development and manufacturing planning needs. QFD involves extensive concurrent engineering in the company (Quality Teams and Qual- ity Circles) which enables priorities to be established, steps to be taken, objectives to be identified, which in turn translate into specific features or improvements that would have to be incorporated into the product or service to make the product acceptable to the in- tended customers.

The two steps presented above may be completed separately or grouped for a QFD analysis. The analy- sis must be conducted in a tiered manner, where the number of tiers will increase, as the level of detail that is desired increases, with respect to the customer needs that are being addressed.

3. Define and Understand the “Processes and Their Capacities.”

This step involves defining and understanding the “Process” that is employed to make the product. Cer- tain questions that would have to be addressed in this step would be

i. I s the “Process” employed to make the product well defined?

ii. Is the “Process” a single stage process or a multi- stage process?

iii. What are the “Capacities” of each stage of the pro- cess in terms of units of the product?

iv. Is there any historical data about the process per- formance in meeting the customer requirements of the product?

The objective of this step to bring to light the nature of the process, the dependence of one subprocess on the other, the nuances of a process and finally, the actual throughput of the process. The throughput of the process is of paramount importance a s the level of Quality achieved by the process, will be based on cer- tain samples taken from the processes; these samples

JOURNAL OF VINYL &ADDITIVE TECHNOLOGY, MARCH 1997,

must be in an acceptable proportion to the maximum output of the process in order to ascertain that the samples are a true representation of the output of the process.

4. Define and Understand the “Variables” of the “Product.”

“Variables” is one of the two possible types of prod- uct data in the world of Quality Control, irrespective of what the product is. Any characteristic of the product which can be measured and can assume any value is called a “Variable” of the product. Variable data is also called measurable data or continuous data as the val- ues that the variable can assume are limitless or con- tinuous. Identification of the Variables of the product are very critical to the understanding of the quality specifications and dimensional requirements of the product. Care must be given to identify only the vari- ables that can be measured with available resources and that have a bearing on the quality of the product. Examples of Variable data would be weight - 20 grams, thickness - 1 inch, specific dimensions of the product etc.

5. Define and Understand the “Attributes” of the “Product.”

“Attributes” is the second of the two types of product data referenced above. Any data of the product char- acteristic which can only assume certain limited val- ues and which usually is a judgment call and a visual assessment and not a result of a measurement pro- cess is called Attribute data. Typical examples would be flow Lines or grease stains on the panel of a bottle, foreign contamination or black specks in the product, where the value the data can assume is either “good” or “bad meaning that the bottle panel is either good- grease free or bad-grease stained.

The “Variable” and “Attribute” characteristics of the product together constitute the quality requirements of the product. Understanding these, will aid the user in linking the products and its features to the custom- ers and their requirements.

6. Identify and Understand the Major “Raw Materials.”

This step involves studying the process to identify the input Raw Material features such a s

i. Number of raw materials. ii. Critical Variables and Attributes of the important

iii. Quality Programs of the Vendors. iv. Historical performance records of the vendors of

The emphasis of this step is to understand the im- portance of consistency and quality in the raw mate- rial. This would also enable the user to develop in- coming raw material testing programs based on the relevance of the various variables and attributes of the

raw materials.

critical raw materials.

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different raw materials on the process and the actual variables and attributes of the finished product itself.

7. Flowchart “Product Life Cycle” From Raw Material to Finished Product Through All the Processes.

Flowcharting of the product life cycle will help in understanding the material flow and the practical as- pects about the whole process. A flowchart for a typi- cal PVC Compounding facility is shown in figure 1. This flowchart includes the capacities of the various stages or machines in the process. The flowcharting process must evolve iteratively from a simple raw ma- terials in - machine -finished product out type, to a complex one which includes machine capacities, ma- terial handling, material sampling, inspection sta- tions and so on. One of the advantages of the flowchart is that, communication becomes very efficient since the involvement, responsibility and authority of the various departments gets well defined and delegated.

8. Identify and Develop Locations for “Variables Sampling and Testing.”

This step involves listing the different variables of the raw materials and finished product according to priorities, available resources and actual location point on the flowchart. The location on the flowchart indicates the actual point in the product life cycle when the sample must be taken for generating the variable data. Collection of samples is a critical part of achieving total quality, since 100% testing or inspec- tion is impractical in the real world. Considerable time must be spent to understand and review the theory of “Acceptance Sampling Plans.” A Sampling Plan in its simplest sense is a table which contains guidelines about the number of samples to be taken from a known volume of product and when to accept or reject the lot being sampled, in order to conform to a prees- tablished Quality Index Level. Some commonly used quality indices are AQL - Acceptable Quality Level and AOQL - Average Outgoing Quality Limit. Depending on the type of product or service, customer, industry and other factors, an acceptable quality index is chosen and the guidelines of the sampling plan are followed to test the plan. The sampling level can be increased or decreased based on the results desired. Though there are established sampling plans like MIL-STD-414 for variables, many industries end up developing a cus- tom sampling plan for their operations.

9. Identify and Develop Locations for “Attributes Sampling and Testing.”

This step is similar to the last step but involves only attributes of the raw material and finished product. As the criticality of the attributes data is different from that of variables data, separate, distinct plans like MIL-STD- 105 for attributes are available. The location of inspection stations for attribute may or may not be the same as the variables on the flow chart. Attribute inspection is a lot faster than variable testing and so,

different plans have to be developed. As with the vari- ables sampling plan, industries generally end up cus- tomizing their attribute sampling plans also.

10. Establish a “Control System” to Document, Measure and Improve the Efficiency of the “Total Quality System.”

This step is the most important step of the method- ology and entails developing a system to monitor and assure the success of the total quality effort. Several tools such as Statistical Process Control (SPC), Cause- Effect Analysis, Quality Auditing, Design of Experi- ments (DOE) must be carefully studied and utilized a s needed. SPC is a n important tool for understanding the strong relationship between product variables and attributes to the process parameters. Limitations of the process can be very well analyzed using SPC, which eventually helps in preventing defects rather than correcting defects. Cause-Effect analysis are re- lationship diagrams which involve brainstorming among designated teams, where the main “Effect” (or Defect) is linked back to probable “Causes” (or sub effects) and the diagrams usually serve as a problem solving tool. DOE as a tool helps in building quality into the product by analyzing the relationships be- tween different factors of the process. Quality Audit- ing can be interpreted both as an internal and a s an external function. Internal Quality Auditing will en- able corrective actions to be instituted for continuous quality improvement and to measure the efficacy of the whole system in achieving total quality. External Quality Auditing usually of vendors of raw materials, helps in assuring good raw material quality on a con- sistent basis. Considerable effort must be spent in this step to establish closed loop systems of communica- tion, with good documenting procedures to be able to review the system periodically for adequacy and con- tinuous improvement.

APPLICATIONS

The application of the 10-step methodology in a typical PVC compounding facility is shown pictorially in Fig. 1. Some generic terms are used to make the applicability of this technique (to other industries like Extrusion Blow Molding] more understandable.

The “Product” in this example is a PVC Compound in pellet form with features such as high quality with minimal complaints, consistent performance, easily replaceable with material from other vendors, excel- lent turnaround time (low lead times), flexible order size and competitive price structure.

The “Customer” for this type of a product is an external one who demands top quality all the time, has a n established quality program like IS0 9002, runs hand to mouth with a JIT (Just-in-Time) inven- tory system, with at least two other suppliers for the same type of compound but a t a slightly higher price, serving end users running on a JIT system also.

The “Process” employed to make the product into a pellet form, consists of two stages - stage 1 is Dry

Sharad Prasad

14 JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, MARCH 1997, Vol. 3, No. 1

Total Quality: Out of Reach or Within Reach?

Finished Product I I ~ - -~

Fig. 1 .

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Sharad Prasad

Blending and stage 2 is Extrusion Pelletizing. Stage 1 consists of conveying of all raw materials from differ- ent physical locations to the blender area, weighing all the ingredients by batch size, physically filling the blender, blending the ingredients and discharging the dry blend into a container or bulk storage, where any of the above operations could be manual or automatic. Stage 2 consists of physically conveying the dry pow- der to the extrusion pelletizer, pelletizing the powder, and conveying the pellets and discharging the pellets into a container or a remote bulk storage. The most obvious observation would be that stage 2 is totally dependent on stage 1 and this system can only run at the maximum output of stage 1, unless a buffer of higher capacity is introduced between stages 1 and 2.

The “Product Variables” in our example are the same for both the stages and are viscosity, thermal stability and color measured by a spectrophotometer. The “Product Attributes” are however very different and include basic contamination on the dry blend to black specks, burnt pellets, size and shape of pellets and clarity of pellets on the pellets side.

The basic “Raw Materials” of this product are differ- entiated as Resin, Impact Modifier and Minor Ingredi- ents.

The flow chart starts with the major raw materials listed above. The first location identified, is for sam- pling Raw Materials for both Attributes and Variables evaluation, with percentage moisture, bulk density and viscosity of resin being some important Variables and contamination being a common Attribute.

Upon meeting all conformance requirements, these ingredients are conveyed to a Blender of a typical batch size of 1000 pounds with a total weigh-in, load, blend and discharge time of 1 hour making the capac- ity of the blender 1000 pounds/hour. An approved Formulation is used (for exact proportions of the raw materials) and upon completion of the blend, Samples are taken at location 2, again for both Variables and Attributes evaluation of the dry blend. Sampling Plans similar to MIL-STD-4 14 for Variables and MIL-STD- 105 for Attributes are used or developed based on the Quality Index chosen. The adequacy of the plan is verified by self auditing for compliance to allowed quality level. As the output of the Blenders change, subsequent analysis and modifications must be made to the sampling plan to assure consistency and com- pliance to quality goals set. Evaluations are made on typical dry blend Attributes like contamination; Vis- cosity, color and thermal stability are some Variables that are also evaluated.

Upon meeting all acceptance criteria, the dry blend is then, either stored in a buffer bulk storage or con-

veyed to the Extrusion Pelletizer directly. An approved set of Process Conditions are used to Pelletize the dry blend at a rage of 1200 pounds/hour. Location 3 is situated at this point, and samples of pellets are taken as before for both Variables and Attributes evaluation using sampling plans developed using the same guidelines as before. Some of the Pellet Variables in- clude color, thermal stability, bulk density and viscos- ity while contamination, black specks, burnt pellets, oversize and undersize pellets constitute some pellet Attributes.

Once the Samples meet standards for conformity to specifications, the material is released into finished goods inventory where it could be packaged into bags, gaylords and stored in bulk storage.

The “Control System” consists of a Statistical Pro- cess Control system using Variables data and linking it to the characteristics of the product and the process conditions; Quality Auditing a t every stage including Raw Material Vendors, In-Process Auditing and Post- Production Auditing to assure adequacy of the proce- dures and process to maintain the goal of Total Qual- ity in Manufacturing.

Material either in dry blend form or pellets form not meeting required specifications of conformance are reworked through approved methods and material that cannot be reworked will end up a s scrap.

CONCLUSIONS

This methodology tries to address concerns and questions most frequently voiced with respect to Total Quality in a manufacturing set up.

The methodology has also been shown generically applied to an Extrusion Bottle Blow Molding operation making Bottles (in the left-hand side of Fig. I), to better understand the applicability of this methodol- ogy to various manufacturing environments. These 10 steps once considered, addressed, understood, ana- lyzed, implemented, controlled, monitored and im- proved periodically, will make Total Quality in Manu- facturing an easier goal to achieve.

REFERENCES

1. R. B. Clements, Handbook ofStatistica1 Methods In M a n - ufacturing, Prentice-Hall, Englewood Cliffs, N.J. ( 199 1).

2. R. G. Day, Quality Function Deployment: Linking a Com- pany with Its Customers, ASQC Quality Press, Milwau- kee (1993).

3. J. M. Juran and F. M. Gryna, Quality Planning and Analysis, 3rd. Ed., McGraw-Hill, Inc., New York (1993).

4. E. G. Schilling, Acceptance Sampling in Quality Control, Marcel Dekker, New York (1982).

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