What is shrinkage casting?
Shrinkage occurs because metals are less dense as a liquid than a solid. A shrinkage cavity is a depression in a casting which occurs during the solidification process. Shrinkage porosity appears with angular edges, compared to the round surfaces of gas porosity.
How do you identify drag and cope?
The Parting Line will separate the top and bottom of the Pattern. The top half is known as the Cope and it’s compliment on the bottom is known as the Drag. The line separating the two halves is known as the Parting Line.
What is meant by cope and drag?
In foundry work, the terms cope and drag refer respectively to the top and bottom parts of a two-part casting flask, used in sand casting. In the simplest sand casting procedure, the drag is placed upside down on a board, around a pattern of the part to be cast. The pattern is a model of the desired casting.
What is the difference between casting and pattern?
Casting is the process of pouring liquid metal into a mold, where it cools and solidifies. A pattern makes an impression on the mold, liquid metal is poured into the mold, and the metal solidifies in the shape of the original pattern.
What is Cope in foundry?
Cope – The top half of a two-part casting flask used in sand casting. Drag – The bottom half of a two-part casting flask used in sand casting. Filter – Filters are used to prevent inclusions in a casting.
What is cheek in casting?
Cheek- intermediate sections of a mold used to create multiple parting lines and mold difficult shapes. Chill- verb- to cool rapidly. noun- an object placed integral with the surface of the mold cavity to cool rapidly specific sections of the casting.
What is gating casting?
A gating system refers to the channels through which the molten metal flows to the die cavity. Its key objective is to ensure its smooth and complete flow from the ladle to the mold cavity. To achieve perfect castings, it is important to have a gating system that is well designed.
Why riser is used in casting?
A riser, also known as a feeder, is a reservoir built into a metal casting mold to prevent cavities due to shrinkage. Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify.
Why riser is not used in die casting?
Using risers would of course slow the cooling time, and therefore they are economically undesirable. Further, the metals that are used in die casting will therefore be ones that develop internal shrinkage porosity, but do not separate from the mold wall, so that risers are not as necessary.
Why the sprue hole is tapered?
Sprue – a hole where the metal enters the mold. It is ideally tapered to prevent air from entering the casting. Because the riser is larger, it will cool slower and feed liquid metal to the shrinking casting, thus preventing a number of defects.
What are sprue marks?
All fire marks have a “casting mark,” which is the rough area where the molten iron was either poured directly into the mold cavity or flowed, through channels in the sand, into the mold cavity. In casting, the “sprue” refers to the hole and passage through which the molten iron, or “meld,” is poured into the mold.
Which one defines the gating ratio?
With the Unpressurized Gating System, the gating ratio is usually 1: 2: 2 or 1: 3: 3 or 1: 1: 3. This system is called a “Choke control system” because the choke controls the flow of the metal….Gating ratio.
| Materials | Gating ratio |
|---|---|
| Ductile iron | 1.15:1.1:1 1.25:1.13:1 1.33:2.67:1 |