Presentation on theme: "Group Technology GT Job shop production System Batch production System"— Presentation transcript:
1 Group Technology GT Job shop production System Batch production System Mass production SystemGT
2 Group TechnologyGroup technology (GT) is a manufacturing philosophy that seeks to improve productivity by grouping parts and products with similar characteristics into families and forming production cells with a group of dissimilar machines and processes.The group of similar parts is known as part family and the group of machineries used to process an individual part family is known as machine cell. It is not necessary for each part of a part family to be processed by every machine of corresponding machine cell.
3 Group TechnologyGroup technology begun by grouping parts into families, based on their attributes (Geometry, manufacturing process ).Geometric classification of families is normally based on size and shape, while production process classification is based on the type, sequence, and number of operations. The type of operation is determined by such things as the method of processing, the method of holding the part, the tooling.There are three methods that can be used to form part families:Manual visual inspectionProduction flow analysisClassification and codingManual visual inspection involves arranging a set of parts into groups by visually inspecting the physical characteristics of the parts.
4 Manual visual inspection Part Family 1Part Family 2
5 Production flow analysis: 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)
7 Rank Order Clustering Algorithm: Rank Order Clustering Algorithm is a simple algorithm used to form machine-part groups.Step 1: Assign binary weight and calculate a decimal weight for each row.Step 2: Rank the rows in order of decreasing decimal weight values.Step 3: Repeat steps 1 and 2 for each column.Step 4: Continue preceding steps until there is no change in the position of each element in the row and the column.
8 Example #1 Part ‘Number’ Machine ID 1 2 3 4 5 6 A B C D E Consider a problem of 5 machines and 6 parts. Try to group them by using Rank Order Clustering Algorithm.Part ‘Number’Machine ID123456ABCDE
9 Step 1: Part Numbers Machine ID 1 2 3 4 5 6 B. Wt: 25 24 23 22 21 20 A DecimalequivalentRankMachine ID123456B. Wt:252423222120A23+21 = 10B24+23 = 24C25+22=36D= 26E=37Step 2: Must Reorder!
14 Example #2 Part Number 1 2 3 4 5 6 7 A 41 B C 105 D 82 E 40 Step 1: Assign binary weight and calculate a decimal weight for each rowPart Number1234567Equivalent decimal valueRankMachine IDBinary wt.26252423222120A41BC105D82E40
15 Example #2 Part Number 1 2 3 4 5 6 7 C D A E B Step 3: Reorder the matrix according to rankPart NumberMachine ID1234567CDAEB
16 Example #2 Part Number 1 2 3 4 5 6 7 C 16 D 8 A E B 24 20 11 22 10 Step 4: Assign binary weight and calculate a decimal weight for each ColumnPart NumberMachine IDBinary wt.1234567C16D8AEBEqu. Decimal Value2420112210Rank
17 Example #2 Part Number 1 4 2 7 3 6 5 C D A E B Step 5: Reorder the matrix according to rankPart NumberMachine ID1427365CDAEB
18 Example #2 Part Number 1 4 2 7 3 6 5 C 120 D 70 A 56 E 39 B Repeat Step 1&2: Assign binary weight and calculate a decimal weight for each rowPart Number1427365Equivalent decimal valueRankMachine IDBinary wt.26252423222120C120D70A56E39BOrder stays the same:
19 Order stays the same: STOP! Example #2Repeat Step 4 & 5Part NumberMachine IDBinary wt.1427365C16D8AEBEqu. Decimal Value2422201110RankOrder stays the same: STOP!
20 Example #2 Part Number Machine ID 1 4 2 7 3 6 5 C D A E B Voids Exceptional partsPart NumberMachine ID1427365CDAEBPart family 1: Part Nos. 1, 4, 2 & 7Machine Cell 1: C, D & APart family 2: Part Nos. 3, 5, and 5Machine Cell 2: E & BNo. of exceptional Parts: 3No. of Voids: 5No. of bottleneck machines: 2(Machines D & E)Solutions for overcoming this problem?Duplicate machinesAlternate process plansSubcontract these operations
21 Duplicate machines Part Number Machine ID 1 4 2 7 3 6 5 C D A E B No. of exceptional Parts: 3No. of Voids: 5No. of bottleneck machines: 2(Machines D & E)No. of exceptional Parts: 0No. of Voids: 9No. of bottleneck machines: 0No. of duplicate machine: 2(Machines D & E
22 Alternate process plans Part NumberMachine ID1427365CAEBDPart NumberMachine ID1427365CDAEBNo. of exceptional Parts: 3No. of Voids: 5No. of bottleneck machines: 2(Machines D & E)No. of exceptional Parts: 2No. of Voids: 3No. of bottleneck machines: 2(Machines D & E
34 Grouping of parts using Clustering Methods Similarity coefficients of machine pairsMachinepairsABACADAEBCBDBECDCEDESC.330.67.67ADBCE0.670.33Dendrogram
35 Classification and Coding Coding refers to the process of assigning symbols to the partsThe symbols represent design attributes of parts or manufacturing features of part familiesAlthough well over 100 classification and coding systems have been developed for group technology applications, all of them can be grouped into three basic types:Monocode or hierarchical codePolycode or attributeHybrid or mixed code
36 MONOCODE (HIERARCHICAL CODE) This coding system was originally developed for biological classification in 18th century.In this type of code, the meaning of each character is dependent on the meaning of the previous character; that is, each character amplifies the information of the previous character. Such a coding system can be depicted using a tree structureMonocode of Fig. 1: A-1-1-B-2Fig. 1 Spur gear
38 POLYCODE (ATTRIBUTE CODE): The code symbols are independent of each otherEach digit in specific location of the code describes a unique property of the workpieceit is easy to learn and useful in manufacturing situations where the manufacturing process have to be describedthe length of a polycode may become excessive because of its unlimited combinational features
39 POLYCODE (ATTRIBUTE CODE): Polycode for the spur gear (Fig. 1):
40 MIXED CODE (HYBRID CODE): In reality, most coding systems use a hybrid (mixed) code so that the advantages of each type of system can be utilized. The first digit for example, might be used to denote the type of part, such as gear. The next five position might be reserved for a short attribute code that would describe the attribute of the gear. The next digit (7th digit) might be used to designate another subgroup, such as material, followed by another attribute code that would describe the attributes.