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How diecast models are made

Lots of us collect them, even more of us enjoyed them as kids, but exactly how do they make a diecast vehicle? Well quite simply as the name suggests they are cast in a die, hence the name. This means that molten metal has been poured into a pre-designed mold, and then allowed to cool before the finishing process takes place.  The majority of diecast vehicles and for that matter most diecast toys are made from a metal called Zamac, which is an alloy made from a mix of aluminium and zinc.  In the toy industries early days of using this technology the manufacturers mainly produced simple shell type castings that had no interior details, after World War II, higher grade alloys were used and this enabled some of the producers to create an interior as well, this was particularly the case in the toy car business.  Of course this became even more prevalent with the introduction of plastic as well.

The process of die casting consists of injecting the molten metal, under very high pressure into reusable steel molds, it is these molds that are known as dies.  Each die consists of two parts, a fixed half and an ejector part, the ejector part being to allow the finished product to be easily removed from the mold.  The diecast machine closes the two parts of the die together using hydraulic pressure, once the two halves are securely and firmly locked together, then injection of the molten metal can begin using one of the two available methods of injecting.How is a diecast car made

The two methods of injecting are known as either hot or cold chamber shot systems, the hot chamber method is what is used for metals that have a low melting point, such as Zinc or Magnesium.  In this method the injector mechanism is immersed in the molten metal and via the use of a plunger forces it into the cavity of the die through a gooseneck.  Once the metal within the mold has cooled the plunger is removed, the die is opened and the casting is then ejected.  The other method is the cold chamber method, this is used for metals with a much higher melting point, such as aluminium or aluminium alloys.  In this method the molten metal is poured into a cold chamber which is a cylindrical sleeve, that sleeve is then sealed by a hydraulically operated plunger, it is this plunger that forces the metal into the die.  Whichever method is used, they are both very fast.  The entire process for a small toy weighing less than about 28 grams, something like a Matchbox or Hot Wheels car can take just a few seconds, or less time than it took to read this article up to now. Of course for some of the larger products that weigh a couple of kilos or more that time frame maybe a few minutes, either way it is not that lengthy.

There are some advantages of using this method, high pressure casting using forces greater than 31000kpa (4500 psi) helps to produce high quality products with smooth surface finishes that are extremely accurate when compared to the original shape of the mold, also there are no separate parts, no welding or other form of joining and they are as strong and hard wearing as the original alloy.

Now that the actual casting has been produced it is then time to begin the finishing process, this is where the casting is then cleaned, primed and finished off before getting to you the consumer.  Firstly you remove the casting from the mold, if there are multiple castings per mold then that is more commonly referred to as a shot.  So you take the shot or casting and then have to clean up some of the excess that maybe attached to it, this would include things like the sprues, runners and flash.  These excess parts can be removed or cleaned up in several ways, it is often done using a hydraulic press and a special trim die, but can also be done using sawing or grinding, but by far the least labour intense method is to tumble the castings in much the same way as you would tumble dry clothes, any excess metal can then be remelted and re-used to make the next casting.

Now that the casting is complete it can then go on to the next process, and that is to paint, polish or plate the casting depending on what is required, this is a very simple process that just passes each casting through a painting machine to ensure that all sides are painted in the chosen manner, some manufacturers do this by running the castings through on a conveyor belt and others use the method of placing each casting on a rotating pole to ensure an even coverage all over the casting.
Once painted, the casting then moves on to the next stage, this will of course depend on the quality of the casting as to where it goes next, if you are looking at the detail of something like the vehicles produced by AutoArt, Revolution Model Cars or Minichamps then the next step would be more detailed painting or tampo printing, the more detailed painting can be done by hand or in most cases it is printed on using the tampo or pad printing method.  This method involves the vehicle being placed into a jig or a device to hold it in an exact position while the pad printing machine stamps the design onto the side of the vehicle in question, this process may have to be repeated several times to get different colours and designs to sit just right on the vehicle.

Once all painting and printing has taken place the vehicle can then be moved to the assembly stage of the process and have its other components fitted, again this process will slightly differ from manufacturer to manufacturer but basically if you consider the basic components of a Matchbox car, then it is during this stage that the car will be fitted with its windows, interior, wheels and base plate.  Once the fully assembled vehicle is ready, it is off to the packaging section of the factory to be boxed and shipped out to the customer.

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