GROUP TECHNOLOGY

GROUP TECHNOLOGY GROUP TECHNOLOGY IS A MANUFACTURING TECHNIQUE AND PHILOSOPHY TO INCREASE PRODUCTION EFFICIENCY BY EXPLOITING THE “UNDERLYING SAMENESS” OF COMPONENT SHAPE, DIMENSIONS, PROCESS ROUTE, ETC.

History of GT

History of GT

First book formalize the concept: Group Technology is the realization that many problems are similar, and that by grouping similar problems, a single solution can be found to a set of problems thus saving time and effort. (Solaja 73) First book formalize the concept: Mitrofanov,S.P. 1958, "The Scientific Principles of Group Technology"

WHY GROUP TECHNOLOGY? AVERAGE LOT SIZE DECREASING PART VARIETY INCREASING INCREASED VARIETY OF MATERIALS WITH DIVERSE PROPERTIES REQUIREMENTS FOR CLOSER TOLERANCES

OTHER BENEFITS OF GROUP TECHNOLOGY EASIER TO JUSTIFY AUTOMATION STANDARDIZATION IN DESIGN DATA RETRIEVAL EASIER, MORE STANDARDIZED PROCESS PLANS INCREASES IN QUALITY

Role of GT in CAD/CAM integration A rapid proliferation of numbers and variety of products, resulting in smaller lot sizes Growing demand for closer tolerances, resulting in a need for economical means Need for increased varieties of materials, heightening the need for more economical means of manufacturing Increase in proportion of cost of materials to total product cost due to increasing labour efficiency, lowering acceptance scrap rates. Increasing communications across the manufacturing functions with a goal of minimizing production costs and maximising production rates.

GT an important element of CAD / CAM integration GT applications provides a common database for effective implementation of CAD/CAM, leading to succesful implementation of CIM. Integration of design, manufacturing and quality Provides a structure and save information about design and manufacturing attributes, process and manufacturing capabilities Common database plays a vital role in the development and implementation of CAD/CAM.

Design attributes

Mnaufacturing attributes

Visual inspection method

GT an important element of CAD / CAM integration GT codes retreive the data for process planning Process planners may modify a process plan for existing process plan of a similar part. The above criteria makes automation possible Manufacturing plans are automating their operations by arranging in theor machines into cells. This concept of cellular manufacturing system is based on GT concept

GT GT AFFECTS MOST EVERY OPERATING AND STAFF FUNCTION. IT IS MORE THAN MERELY A TECHNIQUE, BUT A TOTAL MANUFACTURING PHILOSOPHY. DESIGN ENGINEERING DATA PROCESSING SALES MAINTENANCE INVENTORY TOOL ENGINEERING PLANNING ESTIMATING PURCHASING INDUSTRIAL RELATIONS ASSEMBLY QUALITY CONTROL MANAGEMENT MFG. ENGINEERING R & D COST ACCOUNTING GT SHIPPING & RECEIVING

FUNCTIONAL LAYOUTS ARE INEFFICIENT Lathe Milling Drilling L L M M D D D D L L M M Grinding L L M M G G Assembly L L G G A A Receiving and Shipping G G A A PROCESS-TYPE LAYOUT

GROUP TECHNOLOGY LAYOUT M D G A A Receiving L M G L M D Shipping

CELLULAR LAYOUT Department #2 Department #1 D D M I D I L

2. PRODUCTION FLOW ANALYSIS THREE TECHNIQUES TO FORM PART FAMILIES 1. TACIT JUDGMENT OR VISUAL INSPECTION MAY USE PHOTOS OR PART PRINTS UTILIZES SUBJECTIVE JUDGMENT 2. PRODUCTION FLOW ANALYSIS USES INFORMATION CONTAINED ON THE ROUTE SHEET (THEREFORE ONLY MFG. INFO) PARTS GROUPED BY REQUIRED PROCESSING Cont’d

3. CLASSIFICATION AND CODING CODES GEOMETRY/DESIGN AND MFG. INFO ABOUT A COMPONENT CODES ARE ALPHANUMERIC STRINGS EASIER TO USE FOR OTHER ANALYSES

TYPES OF CLASSIFICATION AND CODING SYSTEMS GT CODING CAN BENEFIT MANY FACETS OF THE FIRM AND FALL INTO ONE OF 3 CATEGORIES: 1. SYSTEMS BASED ON PART DESIGN ATTRIBUTES 2. SYSTEMS BASED ON PART MFG. 3. SYSTEMS BASED ON DESIGN AND MFG.

LENGTH/DIAMETER RATIO TOLERANCES-----MACHINE TOOL EXAMPLES: PART DESIGN ATTRIBUTES BASIC EXTERNAL SHAPE BASIC INTERNAL SHAPE MATERIAL PART MFG. ATTRIBUTES MAJOR PROCESSES MINOR OPERATIONS FIXTURES NEEDED LENGTH/DIAMETER RATIO SURFACE FINISH TOLERANCES-----MACHINE TOOL OPERATION SEQUENCE MAJOR DIMENSION TOOLING BATCH SIZE

THIRTEEN PARTS WITH SIMILAR MANUFACTURING EXAMPLE: THIRTEEN PARTS WITH SIMILAR MANUFACTURING PROCESS REQUIREMENTS BUT DIFFERENT DESIGN ATTRIBUTES

DESIGN AND PART MANUFACTRUING ATTRIBUTES

GT CODE--A SEQUENCE OF NUMERICAL DIGITS THREE MAJOR STRUCTURES: 1. MONOCODE (OR HIERARCHICAL STRUCTURE) A CODE IN WHICH EACH DIGIT AMPLIFIES THE INFORMATION GIVEN IN THE PREVIOUS DIGIT DIFFICULT TO CONSTRUCT PROVIDES A DEEP ANALYSIS USUALLY FOR PERMANENT INFORMATION cont’d

MONOCODE OR HIERACHIAL CODE

HIERARCHICAL STRUCTURE 32XX Hydraulic Electrical 3231 3233 321X 323X Mechanical Power Receiving Transmission 322X 3232 No thread UNC thread UNF thread 3221 3223 3222

HIERARCHIALCODE FOR SPUR GEAR

POLYCODE OR ATTRIBUTE CODE EACH DIGIT IS INDEPENDENT OF ALL OTHERS, PRESENTS INFORMATION NOT DEPENDENT ON PREVIOUS ONES CODES ARE COMPACT EASY TO USE AND DEVELOP SUITABLE FOR COMPUTER ANALYSIS LACKS IN DETAILS OF MONOCODE POLYCODES ARE LARGER THAN MONOCODES

POLYCODE OR ATTRIBUTE CODE

MIXED CODE OR HYBRID CODE HAS SOME DIGITS FORMING MONOCODES, BUT STRINGS THEM TOGETHER IN THE GENERAL ARRANGEMENT OF A POLYCODE BEST FEATURES OF MONOCODE AND POLYCODE SUBGROUPS ARE FORMED AS IN MONOCODE STRUCTURE HYBRID CODE IS COMPACT THAN ATTRIBUTE CODE

Monocode Polycode HYBRID STRUCTURE

MIXED CODE OR HYBRID CODE

TECHNIQUE: 1. DETERMINE PART AND MACHINE REQUIREMENTS 2. NUMERICALLY CODE EACH PART GEOMETRY (& SIZE) MATERIAL OTHER SPECIFICATIONS (TOLERANCE, SURFACE FINISH) 3. FORM A FAMILY OF SIMILAR PARTS WHICH USE (LARGELY) THE SAME SET OF MACHINE TOOLS 4. LAY OUT OF EACH CELL (A GROUP OF MACHINE TOOLS) TO MAKE A FAMILY OF PARTS 5. DESIGN GROUP TOOLING

REDUCTION OF MFG. COSTS BY VARIOUS STEPS OF GROUP TECHNOLOGY APPLICATIONS (ADAPTED FROM HAM442) NOT ALL COST SAVINGS ARE IMMEDIATE... Improvements in Engineering Design Materials Management & Purchasing Benefits Production Control Benefits Manufacturing Engineering Benefits Tooling & Setup Benefits Management Benefits Overall Cost Reduction & Increased Productivity 0 6 12 18 24 36 Time (months)

MAPPING FROM POPULATION SPACE TO CODE SPACE POPULATION SPACE H P CODE SPACE C

CODING SYSTEMS More than 100 coding systems - Opitz classification system - MICLASS system - DCLASS - KK – 3 - CODE system - CUTPLAN system - Part Analog system - COFORM Brisch system RNC system

OPITZ CLASSIFICATION SYSTEM Developed by H. Opitz, University of Aachen, Germany Alpha-numeric symbols used to represent various attributes Digit sequence: 12345 6789 ABCD 12345 – Form code – design attributes 6789 - Supplementary code – Manufacturing related attributes ABCD - Secondary code – particular needs

OPITZ CLASSIFICATION SYSTEM

OPITZ CLASSIFICATION SYSTEM

MICLASS system MICLASS - Metal Institute Classification System Also referred as Multiclass system Digits – 12 to 30 digits. First 12 codes are universal codes Next 18 codes are supplementary codes

MICLASS system

MICLASS CODING First 4 digits deal with form, main shape, shape elements and position Next 4 dimensional information: Main dimension, ratio of various dimensions, auxillary dimensions Digits 9 and 10 – Tolerance information Next 18 digits – supplementary digits: information on lot size, piece time, cost data and operation sequence

MICLASS CODING Parts can be coded using computer interactively – user responds to a series of questions asked by computer – on the basis of questions – computer assigns the code It is difficult to make modifications, when the code does not provide necessary information

DCLASS Coding system DCLASS – Design and Classification Information system Comprises of 8 digits First segment – 3 digits – denotes basic shape Second segment – 4th digit –denotes the complexity of the part (holes, slots, heat treatment and special surface finishes) Third segment – 5th digit – specify the overall size of the coded part Fourth segment – 6th digit – Represents precision Final segment – 7&8 digit – material type - Easily computerised and hence it is a commercial coding system

DCLASS Coding system

Production flow analysis Approach to part family and machine cell formation – pioneered by J. Burbridge Parts that go through common operations are grouped into part families. The machines used to perform these common operations may be grouped as a cell, consequently this technique can be used in facility layout (factory layout)

Production Flow Analysis (PFA) Method for identifying part families and associated machine groupings Part families are the workparts with identical or similar routings Families used to form the machine cells PFA uses manufacturing data rather than design data to identifying part families, which overcomes two part anomalies.

3- Production Flow Analysis (PFA) The procedure of Production flow analysis (PFA) consists of the following steps: Data Collection. The minimum data needed in the analysis are the part number and operation sequence, which is obtained from process plans. Sortation of process plans. A sortation procedure is used to group parts with identical process plans. PFA Chart. The processes used for each group are then displayed in a PFA chart as shown below.

3- Production Flow Analysis (PFA) 4. Clustering Analysis. From the pattern of data in the PFA chart, related groupings are identified and rearranged into a new pattern that brings together groups with similar machine sequences.

Advantages of PFA Design data and PFA uses manufacturing data to identify part families Overcomes two anomalies occur in part classification and coding 1st Anomaly : Basic geometries are quite different, but have same process routings 2nd Anomaly : Part geometries are similar, but require different process routings

Disadvantages of PFA Does not provide any mechanism for rationalizing the manufacturing routings No consideration being given to routing sheet, whether routing sheet are optimal or consistent or logical Final part and machine grouping may be sub optimal, since process sequences from route sheets are prepared by different process planners. Routings may contain processing steps that are non-optimal, illogical and unnecessary

Facility Design in Group technology It is the determination of how to arrange the machines in the shop Facility layout or plant layout physical arrangement of production facilities Configuration of departments, work centres and equipments in the conversion process Layout objective is to economically meet required output quantity and quality

What Is Layout Planning? Layout planning is deciding the best physical arrangement of all resources within a facility Facility resource arrangement can significantly affect productivity Two broad categories of operations: Intermittent processing systems – low volume of many different products Continuous processing systems – high volume of a few standardized products 53

Types of Layouts Four basic layout types consisting of: Functional or Process layouts - Group similar resources together Product or Line layouts - Designed to produce a specific product efficiently Group or Hybrid layouts - Combine aspects of both process and product layouts Fixed-Position layouts - Product is two large to move; e.g. a building 54

Product Layouts Product layout unique characteristics are: Resources are specialized Facilities are capital intensive Processing rates are faster Material handling costs are lower Space requirements for inventory storage are lower Flexibility is low relative to the market © Wiley 2010 55

Product or Line Layout

Product layout

Group Technology GT Job shop production System Batch production System Mass production System Job shop production System Batch production System Mass production System GT

Process Layouts Process layout unique characteristics include: Resources used are general purpose Facilities are less capital intensive Facilities are more labor intensive Resources have greater flexibility Processing rates are slower Material handling costs are higher 59

Process Layouts – con’t Scheduling resources & work flow is more complex Space requirements are higher 60

Product layout Suitable for continuous mass production

Process layout

Designing Process Layouts Step 1: Gather information: Space needed, space available, identify closeness measures Step 2: Develop alternative block plans: Using trial-and-error or decision support tools Step 3: Develop a detailed layout: Consider exact sizes/shapes of departments and work centers including aisles and stairways Tools like drawings, 3-D models, and CAD software are available to facilitate this process © Wiley 2010 63

Special Cases of Process Layouts A number of unique process layouts require special attention. We will look at two of these: Warehouse layouts Office Layouts © Wiley 2010 64

Warehouse Layouts Warehouse Layout Considerations: Primary decision is where to locate each department relative to the dock Departments can be organized to minimize “ld” totals Departments of unequal size require modification of the typical ld calculations to include a calculation of the “ratio of trips to area needed” The usage of “Crossdocking” modifies the traditional warehouse layouts; more docks, less storage space, and less order picking © Wiley 2010 65

Office Layouts Office Layout Considerations: Almost half of US workforce works in an office environment Human interaction and communication are the primary factors in designing office layouts Layouts need to account for physical environment and psychological needs of the organization One key layout trade-off is between proximity and privacy Open concept offices promote understanding & trust Flexible layouts incorporating “office landscaping” help to solve the privacy issue in open office environments © Wiley 2010 66

Designing Product Layouts Designing product layouts requires consideration of: Sequence of tasks to be performed by each workstation Logical order Speed considerations – line balancing © Wiley 2010 67

Designing Product Layouts – con’t Step 1: Identify tasks & immediate predecessors Step 2: Determine output rate Step 3: Determine cycle time Step 4: Compute the Theoretical Minimum number of Stations Step 5: Assign tasks to workstations (balance the line) Step 6: Compute efficiency, idle time & balance delay © Wiley 2010 68

Process vs. Product Layouts Here are the characteristic differences between a process and product layout. 69

PROLIFERATION OF PARTS NOTE: SOME OF THE ABOVE ARE ALMOST THE SAME SELECTION OF OPTICAL INSTRUMENT PARTS IN ONE COMPANY, ILLUSTRATING THE SIMILARITY BETWEEN CERTAIN COMPONENTS NOTE: SOME OF THE ABOVE ARE ALMOST THE SAME

GT FOR DESIGN APPLICATION Design concept can be coded. Code is a rough model of the conceptual design. Conceptual design Coding (rough model) Retrieval existing designs Existing designs Design modification New Design Design archive Retrieve designs of similar shape or function and use them as the examples.

Original shape of raw materials FORM CODE 1st Digit part class 5th Digit additional holes teeth & forming Supplim- entary code Digit 6 7 8 9 Original shape of raw materials Dimensions Material Accuracy 2nd Digit main shape 3rd Digit rotational machining 4th Digit plane surface matching Positions with a digit External shape element Main shape Internal shape element Rotational machining Main bore & rotational Machining of plane surfaces Other holes and teeth teeth and forming 1 2 Rotational 3 4 5 Special 6 7 Non-rotational 8 Opitz coding and classification system. (Reprinted with permission from H. Opitz, A Classification System to Describe Workpieces, Pergamon Press.) 9 Special

TYPICAL PROCESS PLANNING SYSTEM Engineering drawing TYPICAL PROCESS PLANNING SYSTEM Process planner Code or other form of input XXX Process planning system Process Industrial engineer Time standard Operation instruction Layout Production planner Scheduling MPP Part programmer APT Program APT Processor & post-processor

Process planning bridges design and “PROCESS PLANNING” IS THAT FUNCTION WITHIN A MANUFACTURING FACILITY THAT ESTABLISHES WHICH MACHINING PROCESSES AND PARAMETERS ARE TO BE USED (AS WELL AS THOSE MACHINES CAPABLE OF PERFORMING THESE PROCESSES) TO CONVERT (MACHINE) A PIECE PART FROM ITS INITIAL FORM TO A FINAL FORM PREDETERMINED (USUALLY BY A DESIGN ENGINEER) FROM AN ENGINEERING DRAWING. (I.E. THE PREPARATION OF THE DETAILED WORK INSTRUCTIONS TO PRODUCE A PART) Process planning bridges design and manufacturing Bridge Design Manufacturing

VARIANT PROCESS PLANNING USES THE SIMILARITY AMONG COMPONENTS TO RETRIEVE EXISTING PROCESS PLANS (WHICH CAN BE MODIFIED) OVERVIEW: TWO STAGES FOR VP SYSTEMS 1. PREPARATORY STAGE EXISTING PARTS CODED & CLASSIFIED (I.E. GT IS A PREREQUISITE) PART FAMILIES ORGANIZED STANDARD PLANS DEVELOPED DATABASES CREATED (NOTE: THIS STAGE IS LABOR INTENSIVE) Cont’d

1. PREPARATORY STAGE OF VARIANT PROCESS PLANNING Part Drawing Coding Family One Standard Plan File Family Formation (Indexed by Family Matrix) Process Plan

2. PRODUCTON STAGE OF VARIANT PROCESS PLANNING Coding Family Search Standard Plan File Process Plan Editing Standard Plan Retrieval