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The Moulds
The first process is is to prepare the moulds into which the iron will be poured. This is a skilled job and requires a lot of practice. This job is usually done by the same person who pours the iron. He will want his mould to be perfect as he will be responsible for the final cast to come out of it. A special black sand is used which is mixed with a small amount of oil as a bonding agent. A metal box called a matchbox is filled with sand and the pattern is pressed into this to form one half of the mould. Its top surface is then dusted with powder to stop it adhering to the other half of the mould. The other side is then prepared and the two halves put together. A hole is made for the iron it be poured into and smaller holes for the gases to escape through. The pattern used for the moulds are original 140 year old patterns used when the company was originally formed back in 1855. |
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The Iron
The casting process starts off with the raw grey iron. It is comprised of about 95% iron and 5% graphite and silicone The silicone helps carbon to be release quickly from the iron when it melts. Carbon is an unwanted component embedded in the raw iron and will be released as it melts. The graphite acts as a lubricant to assist in pouring the iron. It is broken down into a granular form which makes it easier for the furnace to smelt. |
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The Furnace
The grey iron above is added to the furnace to melt. Kirkpatrick use an induction furnace which is electric. Magnetic coils are energised and the energy passes into the iron through an electrical process called induction. The energy is so great it heats the iron to about 1200 °C at which point it melts. |
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Unwanted products form on the top of the liquid iron as it melts. These need to be removed before it can be poured. |
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The unwanted waste is removed from the furnace and disposed of. Most of it is comprised of carbon and sulphur. |
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Collecting the iron
When the iron is ready the casters prepare to fill their pots with iron. The pots they carry have been pre heated in a small oven as pouring iron directly into a cold pot will make it explode with the differing temperature. |
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The furnace is tipped up and the iron flows from it to be caught by the casters in their pots. |
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Each take it in turns to fill their pots. The iron is very heavy and so every care is taken at this stage from accidentally dropping it. |
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As the last of the men fill their pots others are already pouring the iron into the mould they make earlier. |
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Pouring the Iron
The moulds are all laid out on the floor in even rows. Each one has a heavy weight placed on the top of it. This is the plate with the cross in the centre of it in the picture. The weight is very important as the liquid iron could explode as it makes contact with the cool sand. The weights prevent the iron from exploding apart the sand moulds by keeping them intact. |
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Pouring the iron is heavy work and several pots are filled and poured before all the moulds are full. |
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Care is taken with every pour and a slow but constant flow is required to get the iron to fill the inside on the mould evenly. |
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The iron reacts as it comes in contact with the cooler sand and sparks are generated as it is quickly made to cool. |
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Everybody works together as efficiently as possible when the iron is being poured. Time is of the essence as the iron will be rapidly cooling into a solid state. |
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The heavy weights which prevented the iron from exploding earlier are removed from the tops of the moulds. |
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Cooling
The moulds are now left to cool. The iron will be cold enough to remove in only a few minutes, but will be still too hot to touch. |
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Removing the Casting
The moulds are picked up and taken to the sand pit at the end of the row where the sand is knocked off to reveal the casting. |
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Each casting has a waste run of iron connected to it. This is the path the iron took in the mould to flow around it. This needs to be removed by hand from every casting. |
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The scrap runoffs are collected and weighted ready to be re-melted down in the next batch of iron. Nothing is wasted. |
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At this stage the various castings are still cast iron and are in a rough form with shaper edges. These need to be removed. |
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Barrelling
The barrelling machine is used to smooth off the sharp edges. The barreller is filled with hundreds of the castings and a quantity of abrasive rocks. It then revolves like a washing machine. The components inside rub and knock against each other smoothing their surfaces. |
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Annealing
The annealing process is the special part of the sequence. This turns the cast iron onto malleable iron. This is done using and annealing oven. Round pots are filled to the brim with the cast iron products and are subjected to a heat treatment process known as annealing. In this process castings are heated to around 1000 °C for up to 4 days whilst in contact with haematite ore. The ore acts as an oxidising agent which removes carbon from the casting. It is the presence of carbon in cast iron which causes its brittleness and removing some makes the casting stronger or more malleable. |
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The pots from the annealing oven are stored ready to be reused again. |
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The annealing process makes the iron bend and it comes out of the annealing oven miss-shaped. Each piece then has to be individually hammered back into shape to make it straight again. |
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The straightened castings, which are now malleable iron, are stored ready for the next stage. |
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Grinding and Felting
Each casting still has rough edges and unwanted seams from the mould it came from. They are individually painstakingly removed by hand on grinding and fettling machines. |
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Filing
The cleaned up castings are taken to the large workshop where they will be filed and assembled. |
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Again each casting needs to be painstakingly hand filled in the more intricate places to remove unwanted sharp edges and rough surfaces. |
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Riveting
For items such as window catches and latches as well as hinges a rivet needs to be fitted. The rivets are all hammered into place by hand to ensure a perfect seal is made. Riveting can only be done on malleable iron as cast iron will crack. Cheaper copies are made from cast iron and a rivet fitted in this way cannot be done. Instead they will fit a cheap spring washer to hold the parts together. This will nearly always break over time. Kirkpatrick's rivet will never break or come out. |
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Paint Dipping
All the castings are still bare metal at this stage and will rust if not painted. Two special paint processes are used. Dipping and powder coating. Cheaper imports will not be dipped and this is a crucial stage to ensure the casting will not rust. |
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Dipping is a process where by the castings are hung onto a hanger and lowered into a very liquid paint. This ensures every surface of the casting is coated in a layer of paint to stop it from rusting. As some of the castings have been riveted together this is especially important to make sure the paint soaks into every joint. This is not done with cheaper copy's and so rusting at these points is inevitable. |
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The dipped castings are left out to dry ready for powder coating. |
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Powder Coating
Powder coating is a modern process which gives a superb finish to the iron and a long lasting durability. A special dry powder is sprayed onto the castings in an enclosed chamber. The powder coating for a black colour looks brown but this will change in the next stage. |
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The powder coated casting are attached to hooks ready travel along the conveyer to the oven. |
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The castings travel along the conveyer to where they enter the oven, where they are baked for a few minutes. This hardens the powder coating and also makes them change colour to black. The powder coating hardens in the oven and becomes a very tough hard wearing surface. It also makes to castings look beautiful and last a lifetime. |
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Finishing
After they come out of the oven they are given a light spray of light oil to help prevent them from rusting further while they are in storage. |
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The now finished products are boxed, packaged and stored ready for dispatch. |
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The Quality
The whole process above takes about 6 weeks for each individual product. As you can see every stage is done by skilled craftsman by hand and this gives Kirkpatrick products an unsurpassable quality, look and feel. Owning a Kirkpatrick product ensures you are receiving the very best you can possible buy for your home. The original heritage is still maintained and you will be purchasing a distinctive product which will last you a lifetime. |
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