Different manufacturing methods and processes are used to make the the various parts and types of dry wall rasps. The three main manufacturing processes are injection moulding, die-casting and sheet punching.
What is injection moulding?
The plastic parts of dry wall rasps are made using a process called injection moulding. This involves raw plastic beads being fed from a hopper into a heated barrel chamber. This melts the plastic, which is then pushed though the barrel by a screw mechanism and into the cavity within the mould.
The molten plastic solidifies within the mould cavity. When the two halves of the mould are separated, the finished part is revealed. Injection moulding can be used to make a wide range of products such as plastic toys and mobile phone covers as it’s a very quick and cost-effective way of manufacturing high volume products.
A second injection process using a TPE (thermoplastic elastomer), sometimes called TPR (thermoplastic rubber), can be used to give a rubberised surface to the handles for improved comfort and grip.
What is die-casting?
Die-casting is a manufacturing process that uses a mould which can be reused. The mould is normally made of steel, although tungsten moulds may be used to cast metals with a higher melting point such as steel.
The parts used in a die-casting process are:
The pot
The chamber
The plunger
Nozzle
Cavity
Fixed die half
Movable die half
Ejector pins
Molten metal from within the chamber is forced into the mould cavity between the two die halves, under high pressure from the plunger. This pressure is maintained while the metal solidifies.
Once the molten metal has solidified, the movable die half separates from the fixed die half and the ejector pins release the finished part from the mould.
What is punching?
Punching is a manufacturing method used with sheet metal. It is used to make the blades of some dry wall rasps.
This process is carried out in a single step by a punch and die. The punch presses down on the sheet steel from above, while the die underneath the sheet metal has a cut-out shape of the bit that is removed. This creates a shearing action that cuts the holes in the sheet of steel which will become the dry wall rasp blade.
