Green sand and other types of casting sands are usually housed in what foundry moulders refer to as flasks which are nothing more than fabricated timber or steel boxes without a bottom or lid. The mould box consists of two parts and they are split into two halves which are stacked one on top of the other, the two halves are referred to as the cope which is the top part, and the drag flask which is the bottom part of the box. Suitable mould boxes for a hobby foundry can be constructed by the practical home engineer from timber or steel. Some people may find that constructing mould boxes from steel a little more difficult than timber. It depends whether you feel more comfortable working with either timber or steel, and also the kind of tools you currently have in your workshop. You may choose to build your mould boxes from timber, but if you want to construct from steel then you should do that. The writer of this article built four 10 X 12" steel mould boxes many years ago, and they are as good as the day they were built...timber may not have the long term durability of steel. The mould box project described here, deals with constructing the cope & drag mould boxes from light mild steel. A good size for hobby work is a mould box measuring 9 X 10 " (250 X 30mm). But you can make them larger or smaller to suit your requirements. Mould boxes can be made to suit the size of castings you will be making, the size above will serve the hobby foundry worker throughout the learning period hobby metal casting. Most home workshop owners usually posses some of the basic tools noted in the following list, you wont need to own them all, as many tools can be hired from equipment hire suppliers, but you'll need most listed below to build a set of steel mould boxes for your hobby foundry. Your equipment should include: Bench vice - Ball peen, or engineer's hammer - Hacksaw - Arc or MIG welder. At least two 90 Deg corner angle clamps - One 4"Angle grinder - Bench drill, or hand held power drill - Oxy welding set with small welding tip. (A charcoal forge will suffice to heat 5/16" MS rod)Or a small propane heating torch. None of the above tools are difficult to operate, but of course you will need welding skills to be able to weld the boxes together, but if you can't weld, I'm sure you know someone who can.(But normal safety procdures should be followed of course when using any tool.) The steel boxes can be made in a square shape, or rectangular shape, rectangular seems to work better than square, so we will stay with that format. The first thing to do is to clean up the rough cut edges of the steel lengths that will make the side of the boxes. They are then assembled with the 90Deg clamp and carefully tack welded together. Clamp and set up two pieces at a time, one short -one long, repeat the operation for the other two. Go through the same steps for the second box. Check both sets boxes for squareness before completing the final welding operation. Once that is done. The most difficult part about building mould boxes is locating the register pins accurately. For each box you will need to make two long tapered locating or alignment pins, which are fixed (welded) onto the drag box at each end, and four short flat pieces of flat steel, which act as the pin register holder, and the pin locator. All four of the plates should be ganged together in the drill vice to enable accurate drilling of the hole for the pin locator. To understand this principle fully the step-by-step process is explained using pictures and text in the free ebook "How To Build Mould Boxes" that is included with the hobby foundry ebook package Metal Casting Made Easy. Once the steel lugs are securely welded to the boxes, all you need to do is to bend up some steel lifting handles from small diameter rod, they need to be welded to the cope (top) mould box; make them a comfortable fit for your hands, as you will be the one using them the most. To stop the moulding sand from dropping out of the box after ramming, simply weld some short lengths of 5/16" Dia rods on the inside of each box, about mid distance from the top, that is all you need to stop any sand dropping out of the mould box during sand moulding operations. Another essential item required for efficient moulding is a bottom board, or moulders board, it is made from thick ply and is larger in size than the flask or box that is being rammed up. It also has two 1.5" X 1.5" square timber ribs attached to the underside to provide a solid base, and provides a secure hand grip to pick up the mould boxes to turn them over during the moulding process. The complete hobby foundry ebook package is designed to give you all the information required to set up your own hobby foundry. the info will enable you to start creating those wonderful castings you have been dreaming about. You should not rush the learning; it may take you several weeks or months to make at all come together for you. Once you have your mould boxes (Timber or Steel) you can then start to practice setting patterns & ramming up sand in both boxes, and understanding the methods and techniques of sand moulding, it is a lot of fun and 99% of people get enormous personal satisfaction from hobby metal casting. |
