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INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011 1 Optimisation: Need of today’s competitive age A case study on simulation using AutoCAST A. Harshwardhan Pandit, B. Uday Dabade A. P.G. student, Department of Mechanical Engineering, Walchand College of Engineering, Sangli. B. Asst. Professor, Department of Mechanical Engineering, Walchand College of Engineering, Sangli. Abstract-- In today’s competitive age foundries are required to be more active, efficient. They need to respond fast. More and more competition calls for the fast response to buyer. In this quest maintaining quality is also a key issue. In particular, one is interested in quantifying the performance of a system under study for various values of its input parameters. Such quantified measures of performance can be very useful in the managerial decision process. The cost concerns of the metal casting company focus on the extra time and energy spent in changing the setup configurations in the manufacturing system. The methods layout of a casting is an important activity in tooling development. It involves critical decisions regarding part orientation in mold, parting line, cores, cavity layout, feeders, feedaids and gating system. An improper layout leads to either poor quality or low yield, affecting manufacturing costs and productivity. The objective is to design the methoding system and optimize it. Optimisation can be achieved with various techniques. In this paper optimisation of methoding parameters with the help of simulation is discussed and it is tried to minimize efforts and avoid conventional trial and error practice. The simulation model is built to assess the methoding parameters. Index words—Casting, simulation, optmisation, I. INTRODUCTION n a business and manufacturing environment, most of the organisations optimize their production schedules and flow lines in order to meet the customer demands. The main objective is to satisfy customer demands with minimum production cost. In the competitive business environment today, many industries focus attention especially on rapidity for responding to their customers’ needs. For this reason, continuous improvements are needed to increase response times to customer changes. Methods design is usually carried out manually on the part to be cast. The tooling is then fabricated; trial castings are produced in the foundry in small batches, and inspected. If these castings contain defects, then the methoding is modified and the process is repeated. Each such iteration can take up several days which delays delivery schedule, lead time and hence the customer is dissatisfied. After a few iterations, the foundry may find the best alternative for the methoding which may help to solve the problems stated earlier. It may also help to increase yield, reduce the rejection rates. This is especially true in the case of large castings, where the cost of a trial or repair can be too excessive. Casting simulation can take care of the above problems as the virtual trials do not involve wastage of material, energy and labor, and do not hold up regular production. In this process of simulation we first create the solid model of casting and then a suitable methoding is generated by iterations using software. However, most of the simulation programs available today are not easy to use. They may take longer times depending upon the user expertise available and their accuracy is affected by material properties and boundary conditions specified by users. The problem is the preparation of 3D model of the casting along with mold, cores, feeders, gating, etc., which requires CAD skills and takes considerable time for even simple parts. Methoding is an important task in casting production, directly affecting casting quality and yield. It involves several decisions, such as the size of mold box and number of cavities, orientation of casting in the mold, location of the parting line, design of core prints, and the location, shape and size of feeders and gating elements. The methoding is validated and improved through several iterations of design, pattern modification, trial production and inspection. The goal is to consistently produce castings with zero internal defects (such as shrinkage porosity, inclusions, blowholes, cold shuts and inadequate mechanical properties), while ensuring the maximum possible yield. I

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INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011

1

Optimisation: Need of today’s competitive age

A case study on simulation using AutoCAST

A. Harshwardhan Pandit, B. Uday Dabade

A. P.G. student, Department of Mechanical Engineering, Walchand College of Engineering, Sangli.

B. Asst. Professor, Department of Mechanical Engineering, Walchand College of Engineering, Sangli.

Abstract-- In today’s competitive age foundries are required

to be more active, efficient. They need to respond fast. More

and more competition calls for the fast response to buyer. In

this quest maintaining quality is also a key issue. In

particular, one is interested in quantifying the performance

of a system under study for various values of its input

parameters. Such quantified measures of performance can be

very useful in the managerial decision process. The cost

concerns of the metal casting company focus on the extra

time and energy spent in changing the setup configurations in

the manufacturing system. The methods layout of a casting is

an important activity in tooling development. It involves

critical decisions regarding part orientation in mold, parting

line, cores, cavity layout, feeders, feedaids and gating system.

An improper layout leads to either poor quality or low yield,

affecting manufacturing costs and productivity. The objective

is to design the methoding system and optimize it.

Optimisation can be achieved with various techniques. In this

paper optimisation of methoding parameters with the help of

simulation is discussed and it is tried to minimize efforts and

avoid conventional trial and error practice. The simulation

model is built to assess the methoding parameters.

Index words—Casting, simulation, optmisation,

I. INTRODUCTION

n a business and manufacturing environment, most of

the organisations optimize their production schedules

and flow lines in order to meet the customer demands. The

main objective is to satisfy customer demands with

minimum production cost. In the competitive business

environment today, many industries focus attention

especially on rapidity for responding to their customers’

needs. For this reason, continuous improvements are

needed to increase response times to customer changes.

Methods design is usually carried out manually on the part

to be cast. The tooling is then fabricated; trial castings are

produced in the foundry in small batches, and inspected. If

these castings contain defects, then the methoding is

modified and the process is repeated. Each such iteration

can take up several days which delays delivery schedule,

lead time and hence the customer is dissatisfied. After a

few iterations, the foundry may find the best alternative for

the methoding which may help to solve the problems

stated earlier. It may also help to increase yield, reduce the

rejection rates. This is especially true in the case of large

castings, where the cost of a trial or repair can be too

excessive. Casting simulation can take care of the above

problems as the virtual trials do not involve wastage of

material, energy and labor, and do not hold up regular

production.

In this process of simulation we first create the solid model

of casting and then a suitable methoding is generated by

iterations using software. However, most of the simulation

programs available today are not easy to use. They may

take longer times depending upon the user expertise

available and their accuracy is affected by material

properties and boundary conditions specified by users. The

problem is the preparation of 3D model of the casting

along with mold, cores, feeders, gating, etc., which

requires CAD skills and takes considerable time for even

simple parts. Methoding is an important task in casting

production, directly affecting casting quality and yield. It

involves several decisions, such as the size of mold box

and number of cavities, orientation of casting in the mold,

location of the parting line, design of core prints, and the

location, shape and size of feeders and gating elements.

The methoding is validated and improved through several

iterations of design, pattern modification, trial production

and inspection. The goal is to consistently produce castings

with zero internal defects (such as shrinkage porosity,

inclusions, blowholes, cold shuts and inadequate

mechanical properties), while ensuring the maximum

possible yield.

I

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, ‘NUiCONE – 2011’

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Fig.1. Optmisation in foundry at various stages [1]

For achieving an end, some means is required. If casting is

an end, gating can be considered as a means. An efficient

and effective means is a prerequisite to achieve a

satisfactory and desired level of end in good manner.

Gating:

Various parts of gating system like sprue, runner etc., have

some specific purpose. Sprue is required for facilitating the

pouring operation. Metal has to be transferred from ladle

to casting at sufficient pressure without causing it to

freeze. Sprue serves as a means to create the pressure in

the system. Without sprue head, travel to casting shall not

be at required pressure. Runner helps in transferring the

pressure from sprue through the mould up to the casting

like a conductor in electrical system. Finally, ingates are

required to pass on the metal to the casting which act as a

connectors. Choke in gating system acts like a current

limiter. Gating should ensure that metal reaches the

remotest portion of the casting. For this, it shall be

necessary to have large enough sizes of runner bars

carrying the metal to the inaccessible portion of the

casting. At times, some special method shall be required to

reach the casting. It is very much required that all the

portions of the casting be filled nearly simultaneously.

Here, proportioning of gating system plays a role. A long

casting may require several ingates along the length.

Streamlining of the gating components helps in ensuring

smooth flow.

Risering:

Riser acts like a reservoir or UPS. When power fails UPS

starts its function. Similarly, after pouring stops, risers

keep on feeding the liquid metal to the casting. It is very

important to have proper connections between riser and

casting. Otherwise, feeding shall not be effective.

II. NEED FOR OPTIMISATION

Optimisation is the process of finding the best way of

using your resources, at the same time not violating any of

the constraints that are imposed. By "best" we usually

mean highest profit, or lowest cost. Even after spending

significant resources i.e. man-hours, materials, machine

overheads and energy etc for casting development, one of

the following situations may arise during regular

production [2]:

(a) Under design: resulting in high percentage of defective

castings. This usually happens when the number or size of

feeders and gating elements are inadequate, or their

placement is incorrect. Sometimes the cause is an

undersized neck or a thin intermediate casting section,

which prevents feed metal flow from the feeder to the hot

spot inside the casting.

(b) Over design: leading to acceptable quality level, but

poor yield and thereby higher cost. In this case, the number

and/or size of feeders and gating elements are much higher

than their respective optimal values. This situation usually

arises because of lack of time or resources to fine-tune the

methoding solution or to try other alternative solutions.

(c) Borderline design: irregular defect levels during

regular production, although sample castings are defect-

free. This happens when the methoding solution is just

optimal (perhaps by accident), which will produce good

castings only under controlled conditions. This is difficult

to expect in practice, especially with manual molding and

pouring.

Foundries try to reduce rejections by experimenting with

process parameters (like alloy composition, mold coating,

and pouring temperature). When these measures are

ineffective, then methods design (gating and feeding) is

modified. When even this is not effective, then tooling

design (part orientation, parting line, cores and cavity

layout) is modified. The effect of any change in tooling,

methods or process parameters is ascertained by pouring

and inspecting test castings. Studies show that replacing

shop-floor trials by computer simulation saves time,

provides a better insight, and helps in reducing the

rejections [3].

III. CASE STUDY [4, 5]

1) Selected Product:

The selected product for the methoding design is Gear

Case Cover

• Material: FG 260

• Unit weight of casting: 7.20 kg

• Number of components poured in a box: 2

• Size of box:

– Cope: 4.5 inch

– Drag: 4.5 inch

• Shape of box: Rectangular

• Type of gating system used: Pressurized Gating system

For the component first of all the manual

calculations were done with the help of standard

formulae.

2) Geometric Model:

The input for the AutoCAST is the geometric model

created in the CATIA software. This model is imported in

the AutoCAST as the .stl format.

INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011

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3) Procedure:

The following steps were performed on AutoCAST

software so as to get the Methoding for the casting i.e.

Gear case cover.

1. Import the solid model of the gear case cover in the

AutoCAST software. The 3-D model from CATIA is

converted in to the STL Format.

2. The model is assigned the material- FG 260.

3. The process selected as- Sand Casting.

4. The properties were calculated, which shows the surface

area, number of holes, volume, weight etc.

5. The parting line and parting plane is suitably adjusted

taking into consideration the ease of removing the pattern

from the cope and drag part.

6. The cored characters were generated.

7. For the whole assembly the mould box is selected as per

the company’s regular practice.

8. Next feeding function is carried out so as to know about

the possible areas which are prone to shrinkage. Probably

the area with the highest massive thickness is the area for

generation of shrinkage.

9. The analysis through it showed the two dominant areas

which were prone to the shrinkage and micro porosities.

10. For these areas to be taken care of the feeders were

provided as visible in the figures.

11. The number of ingates was finalized and the locations

also were finalized by us considering the cooling analysis

of the gear case cover.

12. The runner bar was designed so as to feed the molten

metal to the farthest point from point of metal pouring.

13. The sprue is designed.

14. The total model is created and the pouring is simulated.

Since the pouring time calculations showed that for gear

case cover the pouring time of around 8-12 seconds is

sufficient, the system was again designed for that much

second and simulation is carried out. This given the idea of

the sizes of ingates, runner, sprue etc.

15. The quality health checks were calculated.

Fig.2. Casting in case study The solid modeling is carried out in CATIA. The model is

imported in .stl format in AutoCAST (refer fig.3). The

areas for maximum and minimum section thickness were

checked (refer fig.4).The casting properties are then

checked. It showed the massive area where the hot spot

occurrence possibility is more (refer fig.5). A feeder is

arranged near this area so as to take care of shrinkage

arising out of hot spot (refer fig.6). The property analysis

showed that hot spots are still in casting. So there is need

to increase riser size (refer fig.7). Thus riser size is

increased (refer fig.8). Then it is observed that hot spots

are absorbed inside riser. So these dimensions are finalized

(refer fig.9). The tail end portion of casting showed small

hot spot so a chill is placed (refer fig.10, 11). The cross

section showed hot spots are minimized due to riser and

chill (refer fig.12). To take care of productivity concern

two castings in a single mold box are molded (refer

fig.13). The arrangement is adjusted so that a central

gating system common to both can be made (refer fig.14).

The pouring simulation showed the mould filling

phenomenon (refer fig.15). It is then observed that in this

methoding the hotspots are avoided and also the cross

section ensured the same fact (refer fig.16, 17). The final

methoding is then suggested (refer fig.18). Fig. 19 shows a

methoding system adapted as per given suggestions.

Fig.3. Casting solid model is imported in AutoCAST

Fig.4. Areas for maximum section thickness are checked

Fig.5. Massive section shows chances of hotspots

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, ‘NUiCONE – 2011’

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Fig.6. A riser is provided near hot spot.

Fig.7. Hot spots absorbed partially in side riser

Fig.8. The size of riser increased

Fig.9. For increased riser dimensions hotspots are absorbed in riser

Fig.10. Chill is added to take care of hotspot at end as in fig.8

Fig.11. Hot spots absorbed in riser

Fig.12. Cross section of casting showing no hotspots

Fig.13. For productivity two casting in single box are added

INSTITUTE OF TECHNOLOGY, NIRMA UNIVERSITY, AHMEDABAD – 382 481, 08-10 DECEMBER, 2011

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Fig.14. The casting connected by runners

Fig.15. Simulation of mould filling

Fig.16. Hot spots in riser and methoding system

Fig.17. Cross section of assembly showing hot spot in riser

Fig.18. Suggested final methoding system

Fig.19. Final methoding system and casting

In the above cases number of iterations was carried out in

order to reach to the optimum dimensions of the feeders,

sprue, runners etc. The dimensions were optimized in such

a way that the yield can be maintained to its maximum

level. The process is carried out under the limiting

conditions of mold box sizes. To take care of productivity

two components were molded in single mold box.

Optimisation of dimensions leads to material saving.

The following are the advantages gained by using

simulation software for the design of methoding for

casting:

1. The time required is very less as compared to the

conventional method of design of methoding.

2. Number of options were made available to suitably

select the same.

3. The cost was much lower as compared to the

conventional trial and error method.

4. Visualisation of mold filling phenomenon makes the

process easy to understand to the user.

5. Hot spots were easily located where probable chance of

occurrence of defect was more.

6. The key parameters of the process were identified

easily.

7. The rejection due to the defects arising out of methoding

design was reduced to some extent.

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN TECHNOLOGY, ‘NUiCONE – 2011’

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Thus the optimisation by using aid of simulation leads to

following noticeable outcomes.

In regards of costing we can say that,

1. Faster Design + Fewer Trials + Information Retrieval

=HIGHER OUTPUT.

2. Design for casting + Economic Tooling + Improved

Partnership = LOWER COST.

3. Higher yield + Reduced Scrap + Value Addition

= HIGHER PROFIT.

IV. CONCLUSION

Optimisation plays vital role in business. It is an effort

towards making the things run smoothly with efficient

utilisation of available resources. Optimisation is the

philosophy of life. When applied to the engineering sector,

that too to foundry it saves unnecessary wastage of

resources. This leads to the noticeable savings in terms of

cost.

V. REFERENCES

1. B. Ravi, “A Holistic Approach to Zero Defect Castings,” Technical

Paper for 59th Indian Foundry Congress, Chandigarh, February

2011.

2. B. Ravi, “Digital Methoding: Child’s Play? Yes and No.”,

Technical paper for presentation at Steel and Alloy Steel Castings

(SAS-2001), April 14-15, 2001, Mumbai.

3. B. Ravi and Durgesh Joshi, “10-Year Survey of Computer

Applications in Indian Foundry Industry,” Indian Foundry Journal,

56(1), 2010.

4. Harshwardhan Pandit, Sarvesh Naik,Nitin Patil, and Laxmi Nikam,

“Design for Methoding of Casting and Rejection Analysis”,

Production Engineering Graduation Dissertation Work at K.I.T’s

College of Engineering, Kolhapur, 2008-09.

5. Harshwardhan Pandit, “Casting Simulation Case Study- Gear Case

Cover (CI, GSC),”Indian Foundry Journal, 57(4), 2011.