ppt 4

Question 1

Functions of Patterns

Answer 1

-molding the gating system
-establishing the parting line
-making core provisions
-establish locating points
-minimize casting defects attributable to the pattern
-economy in molding

Question 2

Types of Patterns

Answer 2

-single/ loose pattern/ solid
-gated pattern
-match plate pattern
- cope and drag pattern
-special patterns and designs

Question 3

are single copies of the casting but incorporating
the allowances and core prints necessary to
producing the casting.

Answer 3

-single/ loose pattern/ solid

Question 4

Gating systems are hand-cut in the sand.

Answer 4

-single/ loose pattern/ solid

Question 5

The gating system is actually a
part of the pattern and eliminates
hand cutting of the gates

Answer 5

-gated patterns

Question 6

an improvement on ungated loose
patterns.

Answer 6

-gated patterns

Question 7

Large quantity production of small castings
requires this type of pattern or more specialized
types of pattern equipment.

Answer 7

-match plate pattern

Question 8

The cope and drag portions of the pattern are
mounted on opposite sides of a wood or metal
plate conforming to the parting line.

Answer 8

-match plate pattern

Question 9

___________ are also integrally cast, in which
case pattern and plate are cast as one piece in
sand or plaster molds

Answer 9

-match plate

Question 10

Consist of the cope and drag parts of the pattern
mounted on separate plates.

Answer 10

-cope and drag pattern

Question 11

The halves of the mold may be made separately by
workers on different molding machines

Answer 11

-cope and drag pattern

Question 12

Separate pattern plates require accurate alignment of
the two mold halves by means of guide and locating
pins and bushings

Answer 12

-cope and drag pattern

Question 13

The shape, finished sizes, and other details
pertaining to a certain casting are usually obtained
from a _______

Answer 13

drawing

Question 14

Methods or procedure are planned in arranging
and constructing the pattern so that ________
may be obtained at a ___________.

Answer 14

good castings; minimum costs

Question 15

Considerations in Making a Pattern

Answer 15

Corners, angles, and section thickness
Shrinkage/ compaction
Flat surfaces
Parting line
Draft
Tolerance
Machining allowance

Question 16

[Considerations in Making a Pattern] Corners, angles, and section thickness

Answer 16

Sharp corners, angles and fillets should be
avoided as they cause cracking and tearing
during solidification.
Fillet should be selected to reduce stress
concentration and to ensure proper liquid
metal flow

Question 17

_______ are concave connecting pieces
used at the intersection of two surfaces
that form an internal angle or corner

Answer 17

fillets

Question 18

Three Stages of Volume Change between pouring the
molten metal and retrieving the casting from the mould:

Answer 18

1. Liquid changes which take place during the fall in
   temperature from pouring to freezing or solidification.
2. Shrinkage during freezing (solidification)
3. Solid shrinkage, or contraction, on the solidified
   casting as it cools to atmospheric temperature.

Question 19

[Considerations in Making a Pattern] Shrinkage/contraction

Answer 19

Allowance for shrinkage during solidification and
cooling to room temperature to achieve desired
casting dimension.

Question 20

[Considerations in Making a Pattern] Flat Surfaces

Answer 20

Large flat areas should be avoided, as they warp
because of temperature gradients during cooling or
develop poor surface finish because of uneven flow
of metal

Question 21

[Considerations in Making a Pattern] Parting Line

Answer 21

▪ It is desirable for the parting line to be along a flat plane.
▪ The location of the parting line influences mold design,
ease of molding, number and shape of cores, method of
support and the gating system

Question 22

[Considerations in Making a Pattern] Draft

Answer 22

▪ A small draft (taper) is provided in the
sand mold pattern for easy withdrawal of
the pattern without damaging the mold.
▪ Draft angle ranges from 0.5 to 2

Question 23

[Considerations in Making a Pattern] Tolerance

Answer 23

▪ The permissible variations in the dimensions of a part
▪ Depend on the particular casting process, size of the
casting and type of pattern used
▪ Should be as wide as possible but within the limits of
good part performance

Question 24

[Considerations in Making a Pattern] Machining Allowance

Answer 24

▪ For castings that require additional
finishing operation such as machining,
allowance should be made.
▪ Allowances usually range from 2 mm to 5
mm for small casting, to more than 25
mm for large casting

Question 25

Full-scale model of interior surfaces of part

Answer 25

Core

Question 26

Cores may require supports to hold it in position in the
mold cavity during pouring, called ______

Answer 26

chaplets

Question 27

used for making cores

Answer 27

core boxes

Question 28

projections on patterns required for supporting the cores

Answer 28

core prints

Question 29

Types of Cores

Answer 29

Horizontal
Vertical
Balanced
Hanging/ cover
Wing

Question 30

Like pattern, __________________
are also provided in core.

Answer 30

shrinkage allowances

Question 31

Cores are usually made of __________, ______

Answer 31

compacted sand; metal

Question 32

In order to avoid the effect of _________, chaplets are used to hold the core in the cavity of the mold.

Answer 32

buoyancy force

Question 33

Formula of buoyance force during pouring

Answer 33

Buoyancy force= weight of molten metal displaced- weight of core