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Full text of "UTILIZATION OF EXTRUSION AS AN ADVANCED MANUFACTURING TECHNIQUE IN THE MANUFACTURE OF ELECTRIC CONTACTS Copyright IJAET"

International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 



Utilization of Extrusion as an Advanced 
Manufacturing Technique in the Manufacture of 

Electric Contacts 

Virajit A. Gundale ,Vidyadhar M. Dandge 
'Prof. & Academic-Incharge, Sharad Institute of Technology, College of Engineering, 

Yadrav, Kolhapur India. 
2 Asstt. Prof., Dr. J. J. Magdum College of Engineering Jaysingpur, Kolhapur, India 



Abstract 

It is common that each engineering assembly product has A,B and C class components which together 
comprises assembly. A class component has high contribution in product function, cost and profitability of the 
engineering enterprise. A special technical research is must for this class of components. Product assembly is 
another crucial function where all failures are coming on the surface. Where all components are to be available 
simultaneously to complete assembly. This is important stage because if component supply is interrupted 
assembly function stops. Many times the components cannot be supplied due to selection and use of traditional 
manufacturing techniques used at the time of sample lot submission. These short cuts taken during development 
phase are becoming hurdles at the time of commercial or bulk production of assembly. Selection of most 
suitable and advance techniques for manufacturing of all components gives quality and quantity of all 
components and streamlines assembly functions. Keen approach towards manufacturing techniques eliminates 
quality and productivity problems which occur at the supply stage of the product. This also derives long term 
benefits such as customer satisfaction gain, product life cycle growth. 

KEYWORDS: Manufacturing techniques, productivity, product life cycle 

I. Introduction 

This paper presents and discuses the results of the research work of application of advance 
manufacturing techniques used for long term elimination of quality and productivity problems of 
electrical contacts required for electro-mechanical power entry products. Due to highly competitive 
global market the time available for design, development and sample submission of product assembly 
is very short. Every manufacturing industry has to take each customer enquiry as an opportunity for 
business growth. After submission and approval of sample lot of new developing products the next 
immediate demand of the customer is bulk supplies of products. At this juncture the problem faced by 
manufacturing organization and they are unable to expedite the supplies as per customers schedules. 
This problem was taken for investigation after performing why-why analysis with related design and 
development team for this problem. We understood that the root cause for occurrence of this critical 
situation lies in the fact that is supplier has used traditional manufacturing techniques for 
supplying sample lots of brass electrical contacts. This product is socket assembly. The assembly 
has three varieties of components viz-Two types of plastic covers, three Brass contact of same 
specifications, and pair of mild steel fasteners. The BOM of the product indicates that Brass contact 
is a A class component and the supplies of these components are not made from Jamnagar based 
vendor is unable to supply contacts in time results in continuous stoppage of assembly results in 
business loss. This product is socket assembly of export market and brass electrical contact play key 



501 Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 

role in the product assembly function. The samples are approved and at latter stage customer demands 
commercial supplies of the product but the product supplies cannot be rushed with required rates e 
due to low productivity and quality of contacts at vendor end. Frequent occurrence of this situation 
ultimately resulted in the loss of customer satisfaction. This subject is very sensitive for the 
organization starving for business growth. This is so alarming that this product has further no future 
if this situation continues to remain the same. This has become major obstacle in export business 
growth of the organization. Plastic covers and fastener pair have no problems for quality and 
productivity. Hence to overcome this tricky business situation we focused on brass electrical contact 
manufacturing technology used by vendor and used hot extrusion technique followed drawing as 
advance metal forming techniques to give near and neat shape to T section of contact. 

II. Contact Specifications 




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_ ens »r F£ 

■ -■ f SUCdTLV mWJEP 



.1 ±1.1-1 

J 



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4-^4- 



Figure. 1 Contact 
This figure above shows sectional, front & isometric view of said contact. The basic material is 70-30 
Brass. 

2.1 Research Methodology The three phase research methodology is used to achieve desired results. 

Phases are as below. 

Phase 1-Analyze existing Brass contact manufacturing technique and to find causes for low 

productivity and high rejections at various stages. 

Phase 2 -To evaluate and compare probable alternative manufacturing technologies and select the 

most suitable one. 

Phase 3-To select and establish most suitable advance manufacturing technique to come out with 

productivity and quality solutions for bottleneck contacts due to which the assembly work of the 

product is badly affected. This should solve organizational problem and rewarded new life to the 

product. 

Existing technique is manufacturing raw casted contacts using green sand molding technology and 

machining all over. Technical evaluation of existing manufacturing technology this is done in two 

steps. 

Step 1 -Evaluation of green sand molding and casting technology. Step2-Evaluation machining 

processes of the contacts to the finish dimensions. 

The critical points observed as apart of casting process limitations are a) We must provide machining 

allowance of 2.50 mm all over the contact surfaces since we cannot get finish contacts by casting 

technique. Due to low sectional thickness (refer drawing) faster cooling of castings takes place 

results in hard scale formation b) For lower cross sections streamlining metal flow a big question 

mark. As a combined effect of these two heavy casting rejection occurs. This is as tabulated in table 

No 1 



502 



Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 

Table 1. Type of defect and rejection percentage 



No 


Type of defect 


% 


1 


Pin holes and unfilled 


12 


2 


Chilled surfaces 


13 


3 


Scaling and blow holes 


22 



The total rejection is 47%. Existing sequence of operations of manufacturing of raw casted contacts is 
in total 14 operations required to get finish contact. 

Table 2 indicates process and estimation of the cost incurred. 



No 


Operation 


Time 


Estimate Base. 


Per contact. (INR) 


1 


Melting 


On Wt. basis 


Rs 30 /Kg. contact Wt. 
lOgm. 


[NR 0.30 


2 


Material cost. 


Wt. basis 


RateINR315/Kg 


INR 3.15 (Raw Contact Wt. 
10 gm.) 


3 


Design ,Dev. of pattern. 


72Hrs @250 

!NR/Hr=Rs 

18000 


One time cost. 


INR 0.18 (Pattern life 100000 
castings) 


4 


Mounting. 


24 Hrs @INR 
250. 


6000 One time. 


To amortize on 1000 molds 
ie25000castings =INR 0.24 


5 


Mold ing 


100 /shift 


1NR 500/Shift 


25 castings per mold. 
1NR.0.13. 


6 


Pouring. 


10 Min. 


2 persons INR 500/shift 


2=00 Divide by 25 No of 
patterns works INR 0.10 


7 


Knock out.. 


2Min. 


1 person 


1=00/25 works to INR 0.04 


8 


Fettling and cleaning 




On Kg basis 


1=50 works to INR 0.15 


9 


Hardness testing. 




On per piece basis 


0=20 works to INR 0.02 


10 


Facing. 


0.5 Min 


INR 80/Hr. 


INR 0.66 


11 


Straddle milling. 


0.25 Min 


INR 80/Hr 


[NR 0.33 


12 


Slot milling. 


0.5 Min 


1NR80/Hr 


[NR 0.66 


13 


Drilling. 


0.2Min 


1NR25/Hr 


[NR0.10 


14 


Tapping. 


0.30Min 


INR 25/Hr 


[NR 0.15 



The production cost per piece of the contact is Rs.6.07.Add hidden cost5% & the net cost 

=Rs.6.37/Pc. 

It is well understood that the process is non productive and gives poor quality. Cannot be used further 

to satisfy customer's higher quantity demands. Hence search of better manufacturing technique is 

must. 

Research content Phase -2: This mainly covered study of probable alternative techniques through 

industrial surveys and literature review this is as per Table 3. 

Table 3 Industrial Survey findings 



No 


Name 


Advantages 


Limitations 


1 


Die forge. 


Better Material Utilization 


Further finishing by machining 
required. 


2 


Powder Metallurgy 


Finish parts. No machining 


Higher set up and tool cost. 


3 


Press Tool . 


Productive for low thickness 
parts. 


Poor tool life. Higher tool maintenance 
cost. 


4 


Extrusion 


Higher productivity. More 
Yield.. 


Higher set up cost. Usable only for 
long sections. 



The above table concludes that for the said contacts it is preferable to select forward hot extrusion as 
metal forming technique to extrude T-sectional long strips with additional allowance of 0.25 mm per 



503 



Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 

face and further to use drawing technique to remove this allowance to get finish section dimensions. 

Drawing being cold working operation gives better surface finish and closer tolerances as per drawing 

in figure 1 . 

Research content Phase3: Practical implication of Hydraulic forward extrusion and drawing 

operations. These are very high productive techniques hence decided not to make any investment in 

these set ups but to outsource from reliable sources with available spare capacity. The principle of 

outsourcing is no investment needed in set up. We buy only technology and overhead cost saved. 

2.2 Extrusion Die Development 

One important step of extrusion die design & development activity is explained in following Bill of 

Material Table 4. 

Table 4 Extrusion die design & development activity 



No 


Part 


R/M 


Heat treatment done if any 


1 


Sub bolster 


H13 


Std part of press 


2 


Bolster 


Hll 


Std part. 


3 


Backer 


Hll 


Not required. 


4 


Die 


H13 


Quench and temper. 


5 


Die ring. 


Hll 


Not required. 


6 


Die slide 


Hll 


Not required. 


7 


Dummy block 


Hll 


Not required. 



The manufacturing of various die components is done by using Machines such as ram turret milling, 
spark erosion and wire cutting ,as per need lapping is also done manually. The half sectional view of 
two cavity Extrusion die is as shown in the Figure 2. 




DteRIng 



"v Briryston 



Belsstiw 



. Sectional, view of two cavity extrusion Die 

Figure 2 Sectional view of two cavity extrusion Die 
2.3 Extrusion Press Capacity estimation 

Other key area is finding extrusion press capacity. This works out to 250 MT from standard practice 
based on brass max shear stress and extrusion Ration. This is cross verified by comparing capacity 
required for extrusion of similar section components. For initial production runs single cavity die 
design is used so that further two cavity die can be used after freezing die dimensions. The shrinkage 
allowance provided is 2% on all linear cross sectional dimensions for brass. The weight of input and 
output of brass remains constant in the process. Input weight = Output weight .On these basis output 
extrusion sectional length is calculated. Extrusion ram speed is output speed of the cross section 
extruded. This is 1200 mm / Min. & slitting saw width is decided 1 mm. By slitting we cut extruded 
sections to suitable lengths. In this case this is 1000 mm. After extrusion these long sections are 
further drawn so as to get cross sectional finish dimensions. After slitting we have to do three 
machining operations viz.l Side slot milling by using SPM & HSS side and face cutter as cutting 
tool.2 Drilling by using SPM .3Tapping by tapping machine. For design and development of These 



504 



Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 

SPMS we have made a two engineers team dedicated to work with SPM developing vendor. The 
prime objective of developing special purpose machines is to reduce manual handling of work piece 
to reduce labor fatigue and fool proofing of machining operations. The production sequence and cost 
estimation by using this technique as shown in the table Table 5. 

Table 5 Production sequence and cost estimation 



No 


Name of the operation 


Machine or set up used 


Estimate Base . 


Per contact Cost. 


1 


Raw material cost 


Market Rate 


INR315/Kg 


INR.3.15 


2 


Billet casting 
Pouring. 


Melting +Pouring into 
molds 


INR 20/kg 


12 Kg Billet wt=INR 
240/Billet =INR 0.25 


3 


Heating of the billet 


Oil/gas fired furnace 


INR 10/kg 


INR 120/billet= INR 0.12 


4 


Die Design, 
development 


Tool room machines 


48 Tool room Hrs. 
INR 250/Hr 


INR 12,000/- is effective 
of INR 0.12 


5 


Loading the die on 
extrusion press 




Manual( 30 Two 
persons) 


INR. 31.25 /Loading 
INR=0.05 


6 


Extrusion and 
drawing 


Hydraulic extrusion 
press. 


INR/Hr 

280 


Ram Speed 1200 mm. 
/Min=INR 0.05 


7 


Slitting the extrusion 
to suitable length 


Slitting saw 


INR 8/Hr 
Time 0.5 min 


INR 0=06 


8 


Inspection 


Manual 


INR 30/Hr 


INR0.02/Pc 


9 


Milling 


SPM 


INR80/Hr 


INR0.22/Pc 


10 


Drilling 


SPM 


INR12/Hr. 


INR0.05/Pc 


11 


Tapping 


SPM 


INR12/Hr 


INR0.04/Pc 


; tota 


number of operatior 


is is 11 Nos. 







2.4. Commercial impact of the Research Cost per piece of the contacts as per advance 
manufacturing technology is INR 4.13 /Pc add 5% in this for hidden cost.=INR 4.33 /Pc. Cost saved 
per contact INR 2.04.Cost saved /Month=INR 612000 Qty. Basis 300000 is average 
Annual savings= INR 6120000 assuming ten month assuming ten months business per year. 



7 






dating 




5 - 










Extrusion 




AC 








2 
1 























Figure 3 Cost per contact comparison 
2.5 Quality improvement 

Initial cumulative rejection stages =47%. Rejection after using advance manufacturing technique 
average -7 %. Refer graph plotted from for three months field rejection data for both casting and 
extrusion process .Figure 4 as below^ The Graph shows reduction in percentage rejection from 47 to 
average 7 percentage for 3 months. 
Figure 4 indicates process rejection. 



505 



Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 




extrusion 
process 



Castingand 

Machining 
process 



Figure 4 Reduction in percentage rejection 
2.6 Lead Time Reduction 

Lead time reduced from 15 days to 7 days a batch of 100 000 Nos. 



20 
15 
10 

5 




Lead Time in days 





Casting Process Extrusion Process 



Figure 5 Lead Time Reduction 
Figure 5 clearly indicates reduction in lead time. 

2.7 Overall advantages 

The overall advantages are lead time reduction and productivity and quality enhancement. Assembly 
function runs in time .Customer expectations satisfied in time. 

2.8 Results and Discussions 

The estimated cost as per casting and machining process used initially was INR 6.21 per piece of 
electrical contact and after implementation of extrusion technique, the cost reduced to INR 4.10 i.e. 
there is net cost reduction of INR 2.11 per piece or say around 33%. Any saving done due to use of 
advanced manufacturing technique directly contributes to the net profit of the product. Due to high 
cost competition in the market, this cost reduction benefit is passed on to the customer to make 
product more competent in the global market. If we look at cycle time required for completing a batch 
of contacts we see that previously lead time required was 15 days. This is now reduced to 7 days. In 
the long run manufacturer can think of reducing wip inventory. This is again long term benefit to the 
organization. This research has extended product life cycle of the said product which was landed into 
trouble at mass production stage itself. 

III. Conclusions 

Engineering manufacturing houses engaged in the design and development of products and selling 
their products in high competitive market must go for study and practicing use of advance 



506 



Vol. 2, Issue 1, pp. 501-507 



International Journal of Advances in Engineering & Technology, Jan 2012. 

©IJAET ISSN: 2231-1963 

manufacturing techniques suitable to all class of components with priority for A class components 
not at latter stage but at the design, development and prototyping stage of the components. This 
derives long term benefits to the organization which mainly includes higher productivity, consistent 
quality and more competitive prices for sales of the product. By this organization is in position to sell 
the product at lower prices and capture more and more market at global levels. The cost reduction is 
also achieved because of material waste reduction due to utilization of advanced manufacturing 
techniques. Due to higher productivity the return on investment also starts at initial phase of mass 
production. This is long term economic advantage to manufacturing organizations and they should 
consistently starve for establishing a system of appropriate manufacturing technique selection through 
team working with special focus on continuous assessment and updated knowledge of advanced 
manufacturing techniques. 

Acknowledgements 

We are heartily thankful to Vikrant Industries, Jamnagar, Gujarat, INDIA for allowing us to do field 
work for solving their bottle neck in Electric Contact manufacturing and providing necessary 
resources and setup for performing necessary research and trials. 

References 

[1] Rao V. Dukkipatty, Pradip K. Ray. Process design for economy and reliability Publication. Publication - 

New Age International -First Edition I.S.B.N.-978-81-224-2661. 
[2] ASM Handbook Volume- 14,Forming and forging ASM International -The materials information society- 

ISBN-87170-007-7(Vl) SAN-204-7586 Page. No-255- 259 
[3] Richard W. Heine, Carl Loper, Philip C. Rosenthol Principles Of Metal Casting , Publication— Tata Mc. 

GrawhillJSBN- 1 3,978-0-07-099348-. 
[4] Philiphs Ostwald, Jairo Munz, Manufacturing Processes and Systems by Pub. - Wiley, India Pvt. Ltd. 

ISBN-978-81-265-1894- 
[5]Fundamentals of Tool Design - American Society of Tool and Manufacturing Engineers, A Publication of 

ASTME Manufacturing Engineering Series, Pub. Prentice Hall Inc. New lersy.) 
[6] Process and design for manufacturing Sheriff Dlwakil, Narinder Kumar Lijhara for overseas press India (P) 

Ltd.ISBN 81-88689-70 
[7] Fundamentals of metal forming processes By B.L. Juneja -New edge international Publishers ISBN :978- 

8 l-224-3089-9.Pg no 274-303. 

Authors 

Virajit A. Gundale is presently working as the Professor & Academic In-charge at Sharad 
Institute of Technology College of Engineering, Yadrav Dist. Kolhapur, India. He obtained 
his B.E. in Mechanical Engineering from Shivaji University and M.S. in Manufacturing 
Management from BITS, Pilani. He obtained his Ph.D. in Manufacturing Technology from 
UNEM, Costa Rica in 2010. His total experience including Teaching and Industry spans more 
than 11 years. He is also a fellow of the International Institute of Mechanical Engineers, South 
Africa. 

Vidyadhar M. Dandge is presently working as the Assistant Professor at Dr.IJ.Magdum 
College Of Engineering laysingpur, Dist-Kolhapur, India. He obtained his B.E. in Mechanical 
Engineering from Karnataka University and M.E (Production) from Shivaji University. His 
total experience including Teaching and Industry spans more than 25 years. 




t 



507 Vol. 2, Issue 1, pp. 501-507