Chapter 14

Question 1

Three categories of casting

Answer 1

Single use molds with multiple use patterns. Single use molds with single use patterns. Multiple use molds.

Question 2

Expendable mold casting processes

Answer 2

Single use molds with either multiple or single use patterns.

Question 3

Most common metals casted

Answer 3

Cast iron and aluminum are the most common because of their low cost and good fluidity.

Question 4

Sand casting

Answer 4

The most common and the most versatile of the casting processes. Used for iron and steel casting.

Question 5

Sprue

Answer 5

An opening is cut from the top of the mold through the sand and fo next to the system of horizontal channels called runners.

Question 6

Gates

Answer 6

Mold metal is poured down the sprue and enters the savory through here.

Question 7

Pattern

Answer 7

First step in making sand casting is the design of the pattern.

Question 8

Material of patterns

Answer 8

Wood is easy to make, but not stable. Metal is expensive, but durable.

Question 9

One piece of solid patterns

Answer 9

Simplest and least expensive. Used when the shape is relatively simple and the number of duplicate castings is rather small.

Question 10

Split patterns

Answer 10

Used when moderate quantities of a casting are desired.

Question 11

Match plate patterns

Answer 11

Can be coupled with modern molding machines to produce large quantities of duplicate molds. Used when moderate quantities of casting are desired

Question 12

Match plate

Answer 12

Cope and drag of a split pattern and permanently fastened to opposite sides of this.

Question 13

Sands are compounded with additives to net requirements:

Answer 13

1) refractoriness ability to withstand high temps without melting. 2 cohesiveness ability to retain a given shape when packed into a mold. 3 permeability the ability of mold cavity mold and gases to escape the sands. 4 collapsibility the ability accommodate metal shrinkage after solidification and provide for easy remove of casting through mold disintegration, shakeout.

Question 14

Green sand mixture

Answer 14

Molding material is often reclaimed and recycled. This ingredients are put through a mullet, a device with kneads on it, to ensure each grain of sand is coated uniformly.

Question 15

Green sand casting

Answer 15

Most widely used process for casting both ferrous and nonferrous metals. Material is imposed if sand, clay, water, additives. Tools cost are low, very inexpensive. Rough surface finish, and a need for machining.

Question 16

Cores

Answer 16

Used for holes, also used to improve casting design and permit optimization.

Question 17

Green sand cores

Answer 17

Have relatively low strength, may be difficult to withdraw pattern without breaking them.

Question 18

Dry sand cores

Answer 18

Produced separate from the remainder of the mold then inserted into core prints that hold them in position.

Question 19

How is dry sand cores made

Answer 19

Packed into a box with the desired core shape, called a dump core box. A plate is placed over the box and it is inverted. Baking and gardening and sanding is done on the product. A coating such as graphite silica or. Mica can be sprayed in the surface for greater heat resistance.

Question 20

Plastic molding

Answer 20

The mold material is plaster of Paris, combines with various additives to improve strength, permeability.

Question 21

How is plastic molding made

Answer 21

The mold material is mixed, then poured over a metal or plastic pattern and allowed to set. Hydration of the mold is done. It is baked to remove excess water.

Question 22

With metal patterns and plaster mold material

Answer 22

Surface finish and dimensional accuracy are excellent. Cooling is slower, and is limited to lower melting temperature nonferrous alloys.

Question 23

Ceramic mold casting

Answer 23

Similar to plaster mold, but made from a ceramic material that can withstand the higher melting temperatures of metals. Greater cost of the mold material, long mold preparation time. Production is limited to small size castings in small to medium quantities.

Question 24

In large molds, the ceramic can be used

Answer 24

To produce a facing around the patterns, which is back up by a less expensive material such as reusable fire clay.

Question 25

Investment casting

Answer 25

A very old process, used in China and Egypt, and performed by dentists and jewelers. Offer unlimited freedom in the complexity of shapes and the types of materials that can be cast.

Question 26

Step 1 of investment casting

Answer 26

Produce a master pattern

Question 27

Step 2 of investment casting

Answer 27

From the master pattern, produce a master die.

Question 28

Step 3 of investment

Answer 28

Produce a wax pattern. Patterns are made by pouring molten wax into the master due or injecting it under pressure and allowing it to harden.

Question 29

Tree

Answer 29

Assemble the wax patterns into a common wax sprue. Using heated tools and melted wax, a number of wax patterns cna be attached to a central sprue and runner system to create a pattern cluster, or tree.

Question 30

Step 5 on investment

Answer 30

Coast the cluster or tree with a thin layer of investment material. This ensures a smooth surface and good detail in the final product.

Question 31

Step 6 of investment

Answer 31

Form additional investment around the coated cluster. The cluster can be refilled, and refractory aggregate is rained over the surface In a processes called stuccoing.

Question 32

Step 7 of investment

Answer 32

Allow the investment to fully harden

Question 33

Step 8

Answer 33

Remove the wax pattern from the mold by melting or dissolving.

Question 34

Lost wax process

Answer 34

When molds are placed in the oven, the wax disappeared.

Question 35

Step 9

Answer 35

Heat the mold in preparation for pouring. Heat to 550-1100 C, this ensures complete removal of the wax, and cured the mold to give extra strength.

Question 36

Step 10

Answer 36

Pour the molten metal.

Question 37

Step 11

Answer 37

Remove the solidified casting from the mold.

Question 38

Pros and cons of investment

Answer 38

Complex and expensive. Complex shapes can be cast as a single piece. No draft required. Excellent dimensional precision.

Question 39

She’ll cracking

Answer 39

A common problem during wax removal, is this, which destroys the shell and results in loss of the time and expense of reaching that stage of manufacture.

Question 40

So how use exoendablemold

Answer 40

Green sand min is the most common, with no bake molding a second. Then gas hardened, investment, vertical parted green sand, shell molding, plaster molding, lost foam.

Question 41

Core production

Answer 41

She’ll and no bake are the two most common methods, followed by green sand, gas hardened, cold box, core oil.