PATTERN
It is the replica of the object to be made with some modifications
These modifications are in the form of allowances and core prints.
PATTERN MATERIALS
- Wood
- Metal and Alloys - Cast iron, Aluminium, Brass, etc.
- plastics - polystyrene, polyethylene, PVC
- Wax or Mercury
TYPES OF PATTERNS
- Solid or Single piece pattern
- Split piece pattern
- Loose piece pattern
- Gated pattern
- Match plate pattern
- Sweep pattern
- Segmental pattern
- Follow board Pattern
1. SOLID OR SINGLE PIECE PATTERN
If an object to be produced is very simple in shape and size without any complex structures then we can use a solid or single piece pattern.
Keep the pattern inside the drag box such that one of its surfaces matches with the parting line.
2. SPLIT PIECE PATTERN
To avoid the mismatch between the object split dowel pins are used.
If the object to be produced is more complex for easy removal of the pattern, it will split into a number of pieces along with the symmetrical axis.
The individual split pieces can be removed from the cope and drag boxes separately.
3. LOOSE PIECE PATTERN
Vertical split can't be possible because along with tapered section mold sand also come out.
If the pattern is having internal projections, it is difficult to remove the pattern as a single piece or split piece pattern. In this case, the internal projection can be made as loose pieces and they will be separated by removing the main part of the pattern.
During Ramming the loose piece are separated as they are less tightly attached and the remaining loose piece is removed through the cavity produced during the removal of earlier parts.
If the width of the loose piece is more than the cavity then it can be removed by using wax made loose piece.
4. GATED PATTERN
To produce a cavity the gating elements must be removed.
Gating pattern becomes an integrated part of the Casting.
Solid and single piece pattern is used to produce a number of small size casting but in mass production, we use gated pattern.
No. of patterns along with gating element will make as a single pattern, once the pattern is removed cavities will be formed along with gating elements.
5. MATCH PLATE PATTERN
A match plate is a reference plane or surface for a split pattern.
Difference between Match plate and Split pattern. The gating element is an integral part of the Match plate pattern but not in a split pattern.
Difference between Match plate and Gated pattern. A simple pattern with gate elements is used in a gated pattern but a complex pattern with gate elements is used in a match plate pattern
The thickness of the Match plate does not affect the resulting pattern.
The object to be produced in complex design, it is difficult to remove as a gated pattern. In this case, the pattern will split into two parts and they will be added on both sides of a match plate along with gating elements.
6. SWEEP PATTERN
Hollow bell is produced by using core. Large-sized bells in the temple are made up of loam sand or low molding sand.
The core is supported by chaplets and core prints.
Chaplets are made up of the same material as the casting material.
To produce 3D solid surfaces with curved surfaces by using two-dimensional plate patterns, we can use a sweep pattern. In this technique, loam sand will be used to prepare the mold. The 2D structure is continuously rotated in rammed sand to obtain a 3D structure.
7. SEGMENTAL PATTERN
In this horizontal rotation takes place but in sweep pattern vertical rotation takes place.
The pattern will be divided into a number of equal segments and one segment will be considered and it will be rotated inside the mold along with a spoke to get the entire 3D mold cavity.
8. FOLLOW BOARD PATTERN
Structurally weak pattern.
Possibility of Distortion of casting.
Follow board is made up of wood.
If the objects are structurally weak then due to ramming force there is a possibility of distortion of the pattern.
To overcome this patterns will be supported by follow board.
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