Sand Casting Our Metal Garden Furniture

1.     Mold-making - A sand mold is formed by packing sand into each half of the mold. The sand is packed around the pattern, which is a replica of the external shape of the casting. The cavity that will form the casting remains when the pattern is removed. Most metal garden furniture factories will use a cheap mdf pattern, we use a much more expensive resin pattern that achieves a cleaner and sharper surface finish.                                    
2.    Clamping - Once the mold has been made, it must be prepared for the molten metal to be poured. The surface of the mold cavity is first lubricated to facilitate the removal of the casting. Then the mold halves are closed and securely clamped together.

3.    Pouring - The molten metal is maintained at a set temperature in a furnace. After the mold has been clamped, the molten metal can be ladled from its holding container in the furnace and poured into the mold. Many of our competitors use a charcoal furnace, whereas we use an electric furnace. Consequently, the temperature is constant – avoiding bubbling within the cast. Bubbling - think of Aero chocolate, causes metal fatigue, shrinkage, cracks or incomplete sections.

4.    Cooling - The molten metal that is poured into the mold will begin to cool and solidify once it enters the cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of the casting is formed.

5.    Removal - After the predetermined solidification time has passed, the sand mold can simply be broken, and the casting removed. At Outdoor Edge this step, sometimes called shakeout, is performed by a vibrating machine that shakes the sand and casting out of the flask.

6.    Trimming - During cooling, the material from the channels in the mold solidifies and is attached to the cast part. This excess material is trimmed from the casting via a trimming press.

7.    Welding – apart from correct, constant weld temperature the bare metal parts must be thoroughly cleaned before welding. Aluminium is a very reactive metal, within minutes pure aluminium will combine with oxygen to form aluminium oxide, which forms a very thin, whitish bloom. This coating prevents the metal from reacting further with oxygen and protects the metal from further corrosion (rusting). Aluminium oxide melts at 3 times the temperature of pure aluminium, so if the oxide is present the weld will eventually fail.

8.     Painting – we use powder coating which will last approximately 15 years. Many producers just use metal paint which starts to flake and peel off after a couple of years. Again, it is crucial that the aluminium is scrupulously cleaned, otherwise the aluminium oxide will prevail and a white bloom will eventually appear through the powder coating.

Metal outdoor chair