Sand

Sand Casting - INTRODUCTION Philip White & jenny dunseath

pwhite — Fri, 11 Nov 2011 13:07:21 +0000

Introduction for Sand Casting Process with Philip White and Jenny Dunseath in the foundry at Camberwell college of Art London. Video by Chris Follows part of the Process Arts Project.

LINKS TO OTHER VIDEOS FEATURED WITH THIS POST:
Sand Casting at Camberwell with Philip White and Jenny Dunseath :

PART ONE SAND CASTING

PART TWO SAND CASTING

PART THREE SAND CASTING

Text Information supplied by Jenny Dunseath:

Pattern Making:

The Pattern is a full size model of the part that makes an impression in the sand mold, with dimensional allocation for shrinkage and finishing.
If the casting is hollow, additional patterns called cores are used to create these cavities in the finished product.
Patterns are usually made of wood, plastic, metal, or plaster; however, other materials or combinations of materials are used if there are additional specific properties required of the pattern.
Every Pattern must have a draft angle of approximately 2° - 3° to all walls parallel to the parting direction to facilitate removing the part from the mold.
Paint the surface of the Pattern with Varnish or Shellac to make it water tight and to ensure that the sand does not stick.
For a Flat back pattern- put screw holes in the back to aid its removal from the sand.

Molding:

Molding is the multi-step process in which molds are created.
In horizontal casting, the mold is contained in a two piece frame, called a Flask. The upper portion of the flask is called a Cope and the lower portion is a Drag.
First, molding sand is packed into a Flask around the pattern. After the pattern is removed, Gating and Runner arrangements are positioned in the drag half of the mold cavity and the Sprue is placed in the cope portion.
Gating systems are necessary for the molten metal to flow into the mold cavity.
Cores are also placed in the drag portion of the mold if they are needed. To finish the mold, the Cope (top) section is placed on the Drag (bottom) section, and the mold is closed and clamped together.

Sand:
Two main routes are used for bonding the sand moulds:
The "green sand" consists of mixtures of sand, clay (Bentonite) and moisture. If the sand can be squeezed together and hold its shape, it is suitable for use.
The "dry sand" consists of sand and synthetic binders cured thermally or chemically.
The sand cores used for forming the inside shape of hollow parts of the casting are made using dry sand components.
Between uses, the sand is rejuvenated by adding water and mulling (mixing and smashing). If you do not let the sand dry out all the way, you do not have to mull, just add water. Sand grit is determined just like sandpaper. 150 is very fine and 50 grit is coarse. Fine sand will give good detail, coarse sand will give a pebbly or rough texture.

MaterialsMelting temperature
Aluminum alloys1220 °F (660 °C)
Brass alloys1980 °F (1082 °C)
Cast iron1990-2300 °F (1088-1260 °C)
Cast steel2500 °F (1371 °C)

Websites:
www.metal-technologies.com/SandCasting.a spx
www.airnyc.org/list/78478/1/sand-casting -step-by-step.html
www.foundry101.com
www.custompartnet.com/wu/SandCasting

Books:
The Complete Handbook of Sand Casting - by CW Ammen
Metal Casting: A Sand Casting Manual for the ... - by Steve Chastain

NOTE: Because the sand is used in a damp condition there is minimal sand dust,and this occurs at the mould face immediately arround the hot metal casting ,clearly visible when the casting is knocked out. At this stage a small watering can or spray will help to stableize this dry material.A standard dust mask could be worn.It is always worth taking sensible precautions with all processes.With sand casting on the scale immagined here keep a water spray handy and use it when cleanig away any dry material.

Core sand casting experiment - Part 2

pwhite — Mon, 09 May 2011 13:51:15 +0000

Part 2 of 3 Core sand casting experiment tutorials

Following the HUGE success of the Sand casting introduction tutorials

The team at Camberwell spent the day experimenting with core making.

"Whilst the foundry was historically a sculpture resource,for the past four years it has opperated independently from the subject and is considered to be a part of the colleges 3D resource and so under the current structure neither Bill nor myself are subject based. Before I introduced sand casting the interest in foundry processes and mould making had fallen away,particularly where the sculpture course was concerned. Now we are very active and have a far wider appeal accross subjects and level .i.e FE, UG, MA." Philip White

Core sand casting experiment Part 1

Core sand casting experiment Part 2

Core sand casting experiment - Part 3

....Some details of the ingredients of the cores that we made but they're still in the experimental stage for us.The core mould was a metal tube about an inch in diameter cut in half lengthways,care been taken to get it exactly in half otherwise the core would stick as you saw.

For the oil cores I used a mixture of silica sand and fine sharp sand, about 50% of each.To this mixture was added 3% of boiled linseed oil and then well mixed plus a small amount of water, just to slightly dampen it and make it more usable. This mix was quite soft and difficult to get out of the mould without breaking, so I added about 50% green sand which seemed to work OK. The resulting cores should then be baked to harden or in this case put on a metal plate on top of the furnace after a pour had taken place.

As the cores were cylindrical, after about half an hour I moved the cores along the metal plate to distribute the heat more evenly, as the furnace was cooling down. They were then left on the cooling furnace until the next day.

As for the cores that were hardened by CO2, again a mixture of silica sand 60% and fine sharp sand 40%, to this was added about 3% of sodium silicate, which was quite difficult to mix in, plus a small amount of water to make it usable. (In later experiment I added water to the sodium silicate to add to the sand but this produced a core that was quite hard and difficult to get out of the metal casting. Possibly due to a higher amount of sodium silicate and water? More experimentation needed here.) The core mix was then compacted in the core mould with a vent made by a wire through the middle to aid in the dispersion of the CO2 and gases during the metal pour. CO2 was then introduced into the core mix while it was still in the mould and left for a few minutes to harden before removal from the mould.

This is just a quick run-down of events, I hope it is of some use.

Regards
Bill

Core sand casting experiments

Featured — Wed, 23 Mar 2011 23:42:43 +0000

Following the HUGE success of the Sand casting introduction tutorials The sculpture team at Camberwell spent the day experimenting with core making, more information to follow.

Core sand casting experiment - Part 1

Core sand casting experiment - Part 2

Core sand casting experiment - Part 3

Sand

Sand Casting - INTRODUCTION Philip White & jenny dunseath

LINKS TO OTHER VIDEOS FEATURED WITH THIS POST: Sand Casting at Camberwell with Philip White and Jenny Dunseath :

Core sand casting experiment - Part 2

Core sand casting experiments

LINKS TO OTHER VIDEOS FEATURED WITH THIS POST:
Sand Casting at Camberwell with Philip White and Jenny Dunseath :