Casting Questions and Answers – Pattern Materials

1. By which of the following methods pattern can’t be constructed?

  1. Wood
  2. Steel
  3. Oil
  4. Wax

Answer.3. Oil

Explanation

Liquid fuels like furnace oil, diesel, and coal tar fuels (CTF) are very commonly used in various furnaces for melting and heating applications. The various melting units (e.g. crucible furnace, skelner furnace, mixer, open-hearth furnaces) and heating furnaces (e.g. forging furnace and re-rolling mill furnaces) are commonly used.

 

2.  Which of the following is not a factor/requirement for selecting pattern materials?

  1. Method of molding
  2. Establishment of the parting line
  3. Chances of repeat orders
  4. The complexity of the casting

Factor affecting selection of pattern material

The following factors must be taken into consideration while selecting pattern materials.

  1. The number of castings to be produced. Metal patterns are preferred when castings are required large in number.
  2. Type of mold material used.
  3. Kind of molding process.
  4. Method of molding (hand or machine). 5. Degree of dimensional accuracy and surface finish required.
  5. The minimum thickness required.
  6. Shape, complexity, and size of the casting.
  7. Cost of pattern and chances of repeat orders of the pattern.

Note:- A pattern establishes the parting line and parting surfaces are part of the function of the pattern.

 

3. Which of the following wood is most widely used for making patterns?

  1. White Pine
  2. Mahogany
  3. Teak
  4. Maple

Answer.1. White Pine

Explanation;-

Wood is a widely used material for patterns. It is used when a small number of castings are to be produced. The wood used for pattern making should be properly dried and seasoned. It should not contain more than 10% moisture to avoid warping and distortion during subsequent drying. It should be straight-grained and free from knots.

The following types of wood are commonly used for the pattern –

(i) White Pine:- It is the most used wood, because of its straight grain and lightweight and because it is soft, easy to work, and unlikely to warp.

(ii) Mahogany:-  It is harder and more durable than can be worked easily if straight-grained. It is less likely to warp than some other woods.

(iii) Maple, Birch and Cherry:- It woods are harder and heavier than white pine. They tend to warp in large sections, so should be used for small patterns only. They should be carefully treated, because, they pick up moisture readily.

The other common wood materials are Teak, Shisham, Kail, and Deodar.

 

4. The type of woods which can be used for making pattern is/are?

  1. Shisham
  2. Kail
  3. Deodar
  4. All of the above

Answer.4. All of the above

Explanation

The common wood materials used for making pattern is/are

  1. White Pine
  2. Mahogany
  3. Maple
  4. Teak
  5. Shisham
  6. Kail
  7. Deodar

Shisham:- It is dark brown in color having golden and dark brown stripes. It is very hard to work and blunts the cutting tool very soon during cutting. It is very strong and durable.

Kail:-  It has too many knots. It is available in the Himalayas and yields a close-grained, moderately hard, and durable wood. It can be very well painted.

Deodar:-  It is white in color when soft but when hard, its color turns toward light yellow. It is strong and durable. It gives fragrance when smelled. It has some quantity of oil and therefore it is not easily attacked by insects. 

 

5. From the following two statements select the correct statement

Statement 1:- Wooden pattern are inexpensive as compared to the metal pattern

Statement 2:- Wooden pattern is more durable and accurate in size than metal patterns.

  1. Statement 1 is true but statement 2 is false
  2. Statement 2 is true but statement 1 is false
  3. Both statements are false
  4. Both statements are true

Answer.1. Statement 1 is true but statement 2 is false

Explanation:- 

Wood is the most popular and commonly used material for pattern making. It is cheap, easily available in abundance, repairable, and easily fabricated in various forms using resin and glues. It is very light and can produce a highly smooth surface. Wood can preserve its surface by application of a shellac coating for longer life of the pattern.

Advantages of wooden patterns

  • Wood can be easily worked.
  • It is light in weight.
  • It is easily available.
  • It is very cheap.
  • It is easy to join.
  • It is easy to obtain good surface finish.
  • Wooden laminated patterns are strong.
  • It can be easily repaired.

Note:-  Metals are more durable and accurate in size than wooden patterns.

 

6. Which of the following is the limitation of wooden patterns?

  1. Not easy to join
  2. Absorb moisture
  3. Poor surface finish
  4. Wooden pattern can’t be repaired

Answer.2. Absorb Moisture

Explanation:-

One of the disadvantages of using wood as pattern is the change in its shape due to the absorption of moisture from the atmosphere or any damp places. Absorption of moisture leads to drying of the wood mass after some period of time, which creates distortion in the wood grains and a change in the shape of the wood. Wood also tends to get scratches from molding sand when packed and to get warped due to improper storing techniques or by extensive use of the same wood pattern again and again.

Wood has poor resistance against the abrasive action of the sand and because of this fails early as compared to the metal pattern.

Limitation of wood Pattern

Limitations :

  • Wooden patterns are weak as compared to metal patterns.
  • They cannot withstand rough handling.
  • They possess poor wear resistance and hence they are abraded easily by sand action.
  • They absorb moisture, hence get warped and change the shape and size.

 

7. When the number of casting required is large the pattern material generally used is

  1. Wood
  2. Wax
  3. Plastic
  4. Metal

Answer.4. Metal

Explanation:-

Metal patterns are extensively used for the large quantity production of casting and for closer dimensional tolerances on castings. required is large enough to justify their use.

These patterns are not much affected by moisture as the wooden patterns. The wear and tear of this pattern are very less and hence possess longer life. Moreover, metal is easier to shape the pattern with good precision, surface finish, and intricacy in shapes. It can withstand against corrosion and handling for a longer period.

It possesses excellent strength to weight ratio. The main disadvantages of metallic patterns are higher cost, higher weight and tendency of rusting. It is preferred for the production of castings in large quantities with the same pattern. The metals commonly used for pattern making are cast iron, brass and bronzes and aluminum alloys.

 

8. The metal commonly used for pattern making are

  1. Gold
  2. Silver
  3. White Metal
  4. Chromium

Answer.3. White Metal

Explanation:-

The common metals used for pattern making are :

(i) Cast Iron:- The cast iron is widely used as pattern material because of its low cost, ease of machining, dimensional stability, good resistance against the abrasive action of the sand, no warping, and ability to withstand rough handling.

(ii) Brass:- May be easily worked and built up by soldering or brazing. It has a smooth, closed pore structure. It is expensive, therefore, generally used for small cast parts.

(iii) Aluminium:- Aluminum alloy patterns are more popular and best among all the metallic patterns because of their high lightness, good surface finish, low melting point, and good strength. They also possess good resistance to corrosion and abrasion by sand and thereby enhancing the longer life of the pattern. These materials do not withstand against rough handling. These have poor repairability and are preferred for making large castings.

(iv) White Metal:- It has low shrinkage, can be cast easily, has a low melting point, is light in weight, and maybe built up by soldering. However, it is subject to wear by the abrasive action of the sand.

 

9. From the following two statements select the correct statement

Statement 1:- Plastic material used for pattern making has lightweight and high strength

Statement 2:- Laminated plastic patterns surface is as smooth as glass

  1. Both statements -1 and statement – 2 are true and statement – 2 is the correct explanation of statement – 1
  2. Both statements -1 and statement – 2 are true but a statement – 2 is not the correct explanation of statement – 1
  3. Statement -1 is true and statement – 2 is false
  4. Statement -1 is false and statement – 2 is true

Answer.1. Both statements -1 and statement – 2 are true and statement – 2 is the correct explanation of statement – 1

Explanation:-

Plastics are getting more popular nowadays because the patterns made of these materials are lighter, stronger, moisture and wear-resistant, non-sticky to molding sand, durable, and are not affected by the moisture of the molding sand. Moreover, they impart a very smooth surface finish on the pattern surface.

Laminated plastic patterns with surfaces as smooth as glass are more durable than wood patterns. They draw more easily, are not prone to wear and scratches in service, and can be repaired quickly when damaged. A laminated fiberglass core box can resist tremendous pressures and rough treatments in foundry practice.

 

10. Which of the following metal patterns can not withstand rough handling?

  1. Aluminum
  2. Cast iron
  3. Brass
  4. Steel

Answer.1. Aluminum

Explanation:-

Aluminum:- Aluminum alloy patterns are more popular and best among all the metallic patterns because of their high lightness, good surface finish, low melting point, and good strength. They also possess good resistance to corrosion and abrasion by sand and thereby enhancing the longer life of the pattern. These materials do not withstand against rough handling because being soft material, the Al alloy-based patterns are prone to get damaged during sand ramming inside the mold by the molding tools. These have poor repairability and are preferred for making large castings.

 

11. Which of the following metal pattern has the lowest melting point?

  1. Cast Iron
  2. Steel
  3. White Metal
  4. Brass

Answer.3. White Metal

Explanation:- 

White Metal:-  It is not used to any great extent for patterns, but is the best material used for lining stripping plates because it can be cast into the narrow cavities between the master pattern and frame of the stripping plate. It is an alloy of lead, copper, and antimony and has a low melting point of about 260° C. The white metal patterns are soft and easily worn away by the molding sand. Since it is commonly used for die casting, therefore, it may be called a die casting alloy.

 

12. Which of the following metal pattern is also called a Die casting alloy?

  1. Aluminium Alloy
  2. White Metal
  3. Cast Iron
  4. Brass alloy

Answer.2. White Metal

Explanation:-

The white metal can also be called die casting alloy due to its use in pattern making for die casting processes. The advantage lies in its ability to get manipulated into any complex intricate shapes. It is not used for other pattern-making purposes.

 

13. Which of the following metal pattern is the heaviest among all?

  1. White
  2. Brass
  3. Cast Iron
  4. Aluminum

Answer.3. Cast Iron

Explanation:-

Brass:- Brass is rigid, strong, resistant to rust, resistant to moisture, exhibits a good surface finish (better than cast iron), and resistant to wear and tear from sand mold particles. Its only limitation is that it is heavy due to which it is only used for manufacturing small patterns where the weight does not matter much.

Note:-  Aluminum and white Metals are lightweight and Cast Iron and Brass are heavy-weight metal. But brass is the most heaviest among all the pattern-making metal.

 

14. Which of the following patterns has high compressive strength?

  1. Plastic pattern
  2. Wax pattern
  3. Polystyrene pattern
  4. Plaster pattern

Answer.1. Plaster Pattern

Explanation:-

Plaster of peris: Plaster of Paris or gypsum can be used as a pattern-making material, due to its high compressibility, ease of shaping using wooden tools or working on them. Gypsum pattern can be prepared by simply pouring the gypsum paste (obtained by adding water into a mixture of talc and cement powder) into the pattern mold or by simply machining it into shape. It possesses high compressive strength up to 300kg/cm2 and controlled expansion. It is used for making small patterns and core boxes of intricate shapes. From liquid to solid transformation it will not shrinkage but expands. used for small and complicated shape and also for follow board in the molding process.

 

15. Which of the following pattern material is called investment casting?

  1. Wax Pattern
  2. Metal Pattern
  3. Wooden Pattern
  4. Plastic Pattern

Answer.1. Wax Pattern

Explanation:-

Investment casting is generally used for making complex-shaped components that require tighter tolerances, thinner walls and better surface finish than can be obtained with sand casting.

Investment casting is also called lost-wax process, lost pattern process, or precision casting process because of its nature of mold construction, dimensional accuracy or surface finish.

Patterns made from wax are excellent for the investment casting process. The materials used are blends of several types of waxes, and other additives which act as polymerizing agents, stabilizers, etc. The commonly used waxes are paraffin wax, shellac wax, beeswax, cerasin wax, and microcrystalline wax. The properties desired in a good wax pattern include low ash content up to 0.05 percent, resistance to the primary coat material used for investment, high tensile strength and hardness, and substantial weld strength.

 

16. Which of the following is an advantage of Wax casting

  1. Used in Machine molding
  2. Good surface finish
  3. Low cost
  4. All of the above

Answer.2. Good Surface finish

Explanation:-

The wax pattern is used where a very small quantity of job is to be cast or where only one or two castings is prepared. This pattern provides a high degree of surface finish and dimensional accuracy. After being molded, the wax pattern is not taken out from mold like other patterns but it is inverted and heated, the molten wax will come out from the mold, thus, there is no chance of mold cavity getting damaged while removing the pattern. Wax patterns are made in water-cooled molds or dies. the most commonly used waxes are Paraffin, Carnauba, shellac, bees, and ceresin wax. Wax patterns are used in investment casting processes. It possesses the following advantages

  • Draft allowance is not required
  • Separate core or core box not required
  • Better surface finish.
  • The complicated pattern is easily prepared and mold is not taken out so the mold walls will not be affected.

A single pattern is required for single casting. It is costly and not used in the machine molding process. Much care is required for handling because of the lightweight.

 

17. Which of the following qualifies as a precision casting process?

  1. Ingot casting
  2. Investment casting
  3. Sand casting
  4. Shell molding

Answer.2. Investment Casting

Explanation:-

Investment Casting (Precision casting process or Lost Wax casting process). This is the process where the mold is prepared around an expendable pattern. 

Investment castings have excellent surfaces and dimensional accuracy and for this reason, they are used for parts made of non-machinable and non-forgeable alloys. All extremely complex sections can be produced by this method since there are no problems with the draft, parting lines, and so on (as in sand casting).

 

18. The main disadvantage of cast iron pattern material is

  1. Expensive
  2. Not easily available
  3. High Degradation
  4. Low stability

Answer.3. High Degredation

Explanation:-

The main disadvantage of the cast iron patterns is their weight. Easy breakability and susceptibility to environmental degradation such as rusting are the other problems commonly found with cast iron patterns.

 

19. The types of plastic used for pattern making is

  1. Thermosetting
  2. Thermoplastic
  3. Both 1 & 2
  4. None of the above

Answer.3. Both 1 & 2

Explanation:-

Thermosetting and thermoplastic materials are used for pattern work. Generally, thermosetting epoxy and polyester resins are used. In the thermoplastic type, polystyrene has become popular.

 

20. What are the important function of the pattern to be considered for the pattern material

  1. Better surface finishing
  2. Minimum defect in the casting
  3. Core Print
  4. All of the above

Answer.4. All of the above

Explanation:-

Functions of a Pattern.

The following are the functions of the pattern:

(i) Required size and shape cavity is prepared so while pouring metal in the cavity the required dimension components are achieved.

(ii) If the hole is required in casting, a core in the mold is used. Adjustment in mold required for placing core. Core print is used for projection in core placing.

(iii) Parting surface and line is established by pattern in mold.

(iv) Special locating points are established by patterns in mold. These points are used for the measurement of casting, machining, and surface location to each other.

(v) Minimum defects in casting depend on the pattern

(vi) Cost is minimized by proper pattern selection

(vii) Better surface finish on casting.

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