sand casting n

Sand casting

Outline

Requirements to sand

Types of sand

Advantages of sand casting

Disadvantages of sand casting

Steps for Sand Casting

Sand casting is a good option, if you already have a part. And you

can draw a parting line on the part so that the both halves can be

pulled from the sand without distorting the sand.

Requirements to sand

• Ability to retain mold shape during packing and pouring.

• High temperature stability.

• Permeability for the gases liberated from the mold and solidifying metal.

• Collapsibility - ability of the sand to be shake out.

Types of sand

• Green sand.

• petro – bound sand

• Sodium silicate bonded sand.

Advantages of sand casting

• Low cost of mold materials and equipment.

• Large casting dimensions may be obtained.

• Wide variety of metals and alloys (ferrous and non-ferrous) may be cast (including high melting point metals).

Disadvantages of sand casting

• Rough surface.

• Poor dimensional accuracy.

• High machining tolerances.

• Coarse Grain structure.

• Limited wall thickness: not higher than 0.1”-0.2” (2.5-5 mm).

Steps for Sand Casting :-

Place your part/s on the molding board. Sprinkle

them with parting dust. Simple Backing Soda works

well as parting dust and it's cheap.

1

Place a frame, called the "drag" around the

part/s, then start adding your sand, being

sure to tamp it in well around the parts,

especially when there are fine details.

2

Once the "drag" is full, level the sand with

the top of the frame using the other board

or "bottom board" that will also be

used to cover the drag. Then hold onto

both boards and turn the flask over so the

"bottom board" really is on the bottom.

3

4

Remove the molding board.

5

Use a knife or blade to excavate the sand

around the part/s just until you can safely

lift the part from the sand without disturbing

the remaining sand.

6

Add a "sprue" or the hole through which

your molten metal will be poured. I am

using a pipe to mold the sprue. First

pushing one end into the sand to remove a

core and form a hole that is a little deeper

that the bottom of the part/s. Then add

parting dust.

7

Place the pipe back in place to from the

sprue. Paper towel rollers work well if you

don't have a piece of pipe. Then set on the

top frame or the "cope". Latch the frame in

place if you have latches.

8

Add more sand and again gently tamp it in around

the part as well as the pipe to from the sprue.

There are special tools for this, almost anything

including your fingers works well. A blunt 5 pound

bock of steel make a good ram for packing frames.

Larger frame will need to be more tightly packed.

9

Flatten off the sand level the the top edge of the

frame or "cope" and also form a funnel cup around

the pipe that is forming the sprue. This will give

you a bit larger target when you pour the molten

metal. Be sure to leave some sand between the

funnel opening and the wood frame.

10

Gently remove the pipe that was forming

the sprue. Then place the "molding board"

on top.

11

Unlatch the frames and carefully lift off the

top frame or "cope" and set it on its

side. You should be able to rest it on its

top, but less movement is better.

12

Using a couple of knife blades, delicately

lift the part/s from the bottom frame or

"drag". Be careful to lift the part/s straight

up so as not the disturb the sand.

13

Using a knife or blade carve out the "gating" system

that will allow the metal to flow into the part and the

air to flow out. The "gates" connect the sprue to the

part a little above the bottom of the sprue. The

vents are very small channels that run from the

smallest section of the part to the edge for cope.

14

Time to melt some aluminum.

15

Pour the flask with molten aluminum. Don't

pour too slowly or the aluminum will harden

too quickly in the gate, coking the part off.

16

After 5 minutes the flask can be opened for

inspection.

17

Final Parts next to original after the being

brushed off.

Any questions ??