WO2018215735A1

WO2018215735A1 - Casting system

Info

Publication number: WO2018215735A1
Application number: PCT/GB2018/051243
Authority: WO
Inventors: Mustafa Evren Arikan; Bedrettin Cemal ANDIC; Eren KOC; Volkan EVNI
Original assignee: Foseco International Limited
Priority date: 2017-05-26
Filing date: 2018-05-09
Publication date: 2018-11-29
Also published as: GB201708450D0; DE202018102896U1; CN108927495A; CN208825479U

Abstract

A vertically parted casting system comprises a first mould half and a second mould half, the first and second mould halves meeting at a vertical parting line and together defining a casting cavity and a feeder cavity. An exothermic feeder unit is located in the feeder cavity, the feeder unit comprising an inlet, a chamber and an outlet which is in fluid communication with the casting cavity, wherein the outlet is separate from the inlet. The system defines a flow path for molten metal from the inlet of the feeder unit to the casting cavity, via the chamber and the outlet of the feeder unit.

Description

Casting system

The present invention relates to a system for the casting of metals in moulds. In particular, the invention relates to vertically parted casting system comprising an exothermic feeder unit.

To satisfy productivity requirements, automated greensand moulding lines have become increasingly popular for the high volume and long run manufacture of small iron castings. Vertically parted moulding machines (such as Disamatic flaskless moulding machines, manufactured by DISA Industries A/S) are capable of producing up to 450-500 moulds per hour and are commonly used for grey iron castings. In the Disamatic machine, one pattern half is fitted onto the end of a hydraulically operated squeeze piston with the other half fitted to a swing plate (so called because of its ability to move and swing away from the mould). Such machines are capable of producing hard, rigid, flaskless greensand moulds. In a typical casting process (horizontally or vertically parted mould), molten metal is poured into a pre~formed mould cavity which defines the shape of the casting. However, as the metal solidifies it shrinks, resulting in shrinkage cavities which in turn result in unacceptable imperfections in the final casting. This is overcome by providing an additional (usually enclosed) volume or cavity which is in communication with the casting cavity, so that molten metal also enters into and fills the additional cavity through an opening leading from the casting cavity to create a reservoir of metal. During solidification, molten metal within this reservoir drains out and flows back through the opening and into the casting cavity to compensate for the shrinkage of the casting. This is known as feeding the casting and the reservoir is commonly known as a 'feeder, 'feeder head' or 'riser. It is important that metal in the feeder sleeve cavity remains molten longer than the metal in the mould cavity, and is placed close to the appropriate section of the casting.

Feeders that are moulded in the same material which forms the mould for the casting, typically sand, are called 'natural feeders'. The feeder cavities are typically cylindrical or truncated cone shaped with an opening in their base, and are usually fully enclosed within the mould. These are commonly known as "closed^" or 'blind' feeders or risers. The feeder may be positioned vertically at the mould parting line when it has been created from two separate mould halves joined together. Alternatively, it may be fully located in one half of the mould and in a horizontal position. The type of feeder will be determined by the dimensions and configuration of the casting(s) and runner systems, in certain casting systems, the feeder may be 'open' whereby the top of the feeder is located at the top of the mould such that, in use, the metal at the top of the feeder will be open to atmosphere. Such a feeder is shown in the casting apparatus described in GB 1357410, whereby metal enters the mould cavity under pressure via an ingate, fills the casting cavity, and then flows upward through an opening into the feeder cavity. When the casting cools and begins to shrink, metal in the feeder flows back down into the casting through the same opening, such that the feeder opening now acts as an outlet, whereas previously it acted as an inlet.

Aided feeders, commonly called feeding systems, are designed to reduce heat loss from the feeder so that it cools down slower and remains liquid longer, thus allowing it to provide a higher volume of feed metal to the casting. This means that the size of a feeder can be reduced (compared to a natural feeder) giving potential benefits of increased casting yields, enabling more castings to be produced on a single pattern plate and thus a single mould, lower fettling (cleaning) costs, etc. These feeding systems or feeder sleeves are typically chemically bonded refractory shapes and are made to be highly insulating and/or exothermic. Exothermic sleeves ignite on contact with the molten metal and generate heat to delay solidification of the metal within the feeder cavity.

Initially, the general approach to feeding castings produced in vertically parted moulds was to use natural sand risers. With the increasing number and complexity of castings being produced in vertically parted moulds, and subsequent demands to increase yields and the number of castings per mould, feeder sleeves started to be used, typically by inserting the sleeves on the joint line of the mould using an automatic core setter during the mouiding cycle. However, applying these sleeves on the moulding joint (or parting) line can be problematic, with sleeves moving out of position before or during mould closure. This problem may be partially alleviated by modifying the sleeve with an external flange as described in GB 2372004A.

The restriction of placing feeders on the moulding joint line also makes it difficult to feed heavier, thicker sections of the casting. This may be overcome by the use of metal padding or chilis to create a feed path to isolated (usually thick) sections of the casting. However, this approach is limited in effectiveness and has several disadvantages, resulting in increased cleaning costs and reduced casting yield. Natural sand risers may also be used in conjunction with padding or chills, however, this approach is limited in effectiveness as it notably reduces casting yield and there is often limited space available on the pattern plate, particularly where there are several castings configured per mould.

The present invention has been devised with these issues in mind, to provide a method to manufacture consistently sound castings efficiently, particularly where multiple castings are produced in a single mould. According to a first aspect of the invention, there is provided a vertically parted casting system comprising:

a first mould half and a second mould half, the first and second mould halves meeting at a vertical parting line and together defining a casting cavity and a feeder cavity; and

an exothermic feeder unit located in the feeder cavity, the feeder unit comprising an inlet, a separate outlet in fluid communication with the casting cavity, and a chamber between the inlet and the outlet,

wherein the system defines a flow path for molten metal from the inlet, through the chamber and the outlet, to the casting cavity. It will be appreciated that the feeder unit is a stand-alone item which is separable from the feeder cavity. The feeder unit is inserted into the feeder cavity, thereby forming the casting system. By "exothermic feeder unit" it will be understood that the feeder unit is formed (partially or entirely) from exothermic material. In use during the casting process, metal enters the mould and travels into the feeder unit via an inlet and out through a separate outlet to the casting cavity. Once the mould is filled, the chamber of the feeder unit located between the inlet and outlet holds a reservoir of molten metal. Since the feeder unit is exothermic the metal enclosed within the chamber remains molten for a longer period of time relative to the metal within the casting cavity, such that the feeder unit feeds the casting through the feeder unit outlet with molten metal as the metal within the casting cavity solidifies and shrinks. The system thus provides improved spot feeding of the casting. It will therefore be understood that "inlet", as used herein, is an opening in the feeder unit through which metal enters the chamber, in use. The inlet may be separated or spaced from a surface of the mould. For example, the metal may flow through the inlet from a pouring cup or runner.

It will also be understood that "outlet", as used herein, is an opening in the feeder unit through which metal exits the chamber, in use. The metal may flow from the chamber, through the outlet, into a casting cavity, a runner, or an ancillary chamber.

In some embodiments, the outlet is not in the same plane as the inlet. In some embodiments, the outlet is orthogonal relative to the inlet. For example, the inlet may be located in a first wall of the feeder unit, and the outlet may be located in a second wall of the feeder unit. In embodiments wherein there are multiple inlets and/or outlets, each inlet/outlet may be located in a different wall of the feeder unit.

In use, the feeder unit defines a flow path for molten metal from the inlet to the outlet via the chamber.

In some embodiments the first and second mould halves further define a pouring cup, which is upstream of and in fluid communication with the inlet of the feeder unit. As will be known to those skilled in the art, a pouring cup is essentially a funnel though which molten metal enters the casting system. The pouring cup has an inlet and an outlet. The inlet is usually much wider than the outlet, so as to provide a large area into which metal can be poured. The outlet of the pouring cup feeds into the inlet of the feeder unit, either directly or via an intermediate ingate connected to the inlet of the feeder unit. The pouring cup may be located between the inlet of the feeder unit and a surface of the mould. It will therefore be appreciated that the pouring cup is a separate feature to the feeder cavity and the feeder unit.

In some embodiments, the system comprises a plurality of casting cavities and, optionally, a plurality of feeder cavities. It will be appreciated that the system according to these embodiments may be arranged in one of any of a number of different ways. For example, the number of casting cavities may be equal to the number of feeder cavities and feeder units. Alternatively, there may be more casting cavities than feeder cavities and feeder units, such that one or more of the feeder cavities and feeder units are arranged to feed more than one casting cavity. It will be understood, however, that in all arrangements a feeder cavity may contain only a single feeder unit.

In some embodiments the first and second mould halves define two or more casting cavities and two or more feeder cavities, wherein a feeder unit is located in each feeder cavity, each feeder unit comprising an outlet which is in fluid communication with only one of the casting cavities.

In some embodiments the first and second mould halves define two or more casting cavities and one feeder cavity, wherein a feeder unit comprising two or more outlets is located in the feeder cavity, each casting cavity being in fluid communication with a different outlet.

In embodiments wherein the system comprises two or more feeder cavities, the feeder cavities may be arranged in series and each feeder cavity may be connected with the next one in the series by a runner. The runner may extend between an outlet of a feeder unit located in one of the feeder cavities and the inlet of a feeder unit located in the next feeder cavity. It will be appreciated that in these embodiments, the feeder unit located in all but the last feeder cavity of the series will comprise one or more outlets than the number of casting cavities fed by that feeder unit. For example, if the feeder unit is in fluid communication with two casting cavities, it must comprise three outlets; two for feeding the casting cavities and one outlet in fluid communication with the runner. The inlet of a feeder unit later in the series may have a smaller aperture than the inlet of a feeder unit at the beginning of the series, in order to prevent the trapping of air within the system. In some embodiments, the first and second mould halves define 2n casting cavities and n feeder cavities, wherein n is an integer between 1 and 5. In some embodiments, n is 1 , 2 or 3. In embodiments wherein n>1 , the feeder cavities may be arranged in series and connected by a runner.. In some embodiments, the first and second mould halves define four casting cavities, and first and second feeder cavities which are arranged in series and connected by a runner, wherein a first feeder unit is located in the first feeder cavity and a second feeder unit is located in the second feeder cavity. The first feeder unit comprises an inlet and three outlets, two of which outlets are each in fluid communication with a casting cavity, and the third being in fluid communication with an inlet of the second feeder unit, via the runner. The second feeder unit comprises two outlets, each of which is in communication with a casting cavity. Thus, each of the four casting cavities is in fluid communication with a different one of the outlets. In some embodiments wherein the system comprises two or more feeder cavities arranged in series, the feeder cavities are vertically aligned.

In some embodiments, the or each casting cavity comprises a core. According to a second aspect of the invention there is provided a feeder unit for use in the casting system of the first aspect of the invention, the feeder unit comprising an inlet, a separate outlet, and a chamber between the inlet and the outlet.

In use the feeder unit defines a flow path for molten metal from the inlet to the outlet, via the chamber.

In some embodiments the feeder unit has at least two outlets. The feeder unit may have three, four or even five outlets. In some embodiments the inlet and at least one of the outlets are not in the same plane. In some embodiment at least one outlet is orthogonal to the inlet.

In some embodiments the feeder unit further comprises an external protrusion for securing the feeder unit in the feeder cavity. The protrusion may take the form of a peg (e.g. a square or rectangular peg) which extends from an outer surface of the feeder unit. When the feeder unit is located within the feeder cavity, the protrusion may be received in a recess formed in one of the first mould half and the second mould half. The shape of the recess may be complementary to that of the protrusion so as to provide a friction fit between the feeder unit and the mould half. In some embodiments the feeder unit further comprises a filter located in the flow path between the inlet and the outlet. The filter may be located adjacent the inlet, so that molten metal flows through the filter before entering the chamber. The filter provides the dual benefits of cleaning the metal by removing inclusions, and reducing turbulence in the metal flow. The location of the filter within the feeder unit itself, rather than placing the filter in an upstream runner system, provides a shortened flow path between the filter and the casting cavity, thereby increasing the purity of the molten metal entering the casting and thus the quality of the casting.

It will be appreciated that it may not be necessary to include a filter within every feeder unit in the casting system. Thus, in some embodiments, only some of the feeder units in the casting system comprise a filter. In some embodiments wherein two or more feeder cavities, and the feeder units located therein, are arranged in series, only the first (upstream) feeder unit in the series may comprise a filter.

The feeder unit may be approximately cuboid in shape, having a first end, a second end and four sidewalls therebetween. The inlet may be constituted by an opening in the first end. The outlets may be provided by openings in one or more of the sidewalls, and/or the second end. Thus, the feeder unit may be considered to be substantially closed or 'blind'.

To accommodate a filter, the feeder unit may comprise one or more interior ledges or walls for locating the filter in the desired position. In some embodiments a plurality of ledges are spaced apart around the internal surfaces of sidewalls of the feeder unit. However, it is preferable that the feeder unit comprises a single ledge or wall extending completely around the interior surfaces of the sidewalls. This not only locates the filter in the desired position, but also supports all of the edges of the filter for when molten metal entering the feeder unit impinges on the face of the filter, and also prevents metal from bypassing the filter during casting.

In some embodiments the feeder unit further comprises an interior wall having an opening therein, the interior wall arranged parallel to the first and second ends and being located closer to the first end than the second. This creates an internal cavity between the first end and the interior wall, in which a filter may be located.

In some embodiments, the feeder unit is formed of two halves that are joined together along a parting line. The two halves may be glued together or joined together by way of a push-fit. One half of the feeder unit is provided with the external protrusion. Cut-outs are provided in one or both halves of the feeder unit. When the two halves are joined together, the cut-outs define openings which form the inlets and outlets of the feeder unit.

The feeder unit may be formed from any suitable refractory or exothermic material. Feeders are typically made from a mixture of low and high density refractory fillers (e.g. silica sand, olivine, alumino-silicate hollow microspheres and fibres, chamotte, alumina, pumice, perlite, vermiculite) and binders. Exothermic feeders additionally comprise a fuel (usually aluminium or aluminium alloy), an oxidant (typically iron oxide, manganese dioxide, or potassium nitrate) and usually initiators/sensitisers (typically cryolite).

According to a third aspect of the present invention, there is provided a method of forming a vertically parted casting system comprising:

forming a first mould half having a first vertical surface which defines a first part of a casting cavity and a first part of a feeder cavity;

- forming a second mould half having a second vertical surface which defines a second part of the casting cavity and a second part of the feeder cavity;

providing an exothermic feeder unit comprising an inlet, a separate outlet, and a chamber between the inlet and the outlet;

inserting the feeder unit into the first or second part of the feeder cavity, such that the outlet is in fluid communication with the first part of the casting cavity; and

bringing the first and second vertical surfaces of the first and second mould halves together to form the vertically parted casting system comprising the casting cavity and the feeder cavity, wherein the feeder unit is located within the feeder cavity. In some embodiments, the method is at least partly automated.

In some embodiments, the first and second mould halves are formed by a vertically parted moulding machine, such as those manufactured by DISA Industries A/S (sold under the trade name DISAMATIC).

The DISAMATIC typically consists of a moulding machine and mould conveyor, and produces an endless string of mould parts, wherein one side of the mould part forms the first mould half of one casting system, and the other side of the same mould part forms the second mould half of the next casting system. One moulding pattern half is fitted onto the end of a hydraulically operated squeeze piston and the other pattern half fitted to a swing plate, so called because of its ability to move and swing upwards away from the completed mould. Greensand moulding mixture is blown into a rectangular steel chamber using compressed air and then squeezed against the two patterns, which are on the two ends of the chamber. After squeezing, the swing plate swings back and upward to open the chamber and the opposite plate pushes the finished mold onto a conveyor. Finally, any cores are automatically set into the mould cavity using an automatic coresetter whilst the next mould is being prepared. The cycle repeats until a chain of finished moulds butt up against each other on the conveyor, ready for casting. The molds are then filled with molten metal and placed on a cooling conveyor, which moves at the same pace as the mould conveyor. Solidified castings are separated from the moulds and the sand is reconditioned and reused in subsequent cycles of the DISAMATIC moulding process.

The step of inserting the feeder unit into the first or second part of the feeder cavity may be automated. In some embodiments, the feeder unit is inserted using a coresetter.

In some embodiments, the method further comprises inserting a core into the first or second part of the casting cavity. A core may be inserted using a coresetter.

In some embodiments, the step of forming the first or second mould half comprises forming a recess in the first or second part of the feeder cavity for receiving a protrusion extending from an outer surface of the feeder unit, and the step of inserting the feeder unit comprises inserting the protrusion into the recess. The recess may be formed by preparing a mould pattern having a protrusion thereon which corresponds in size and shape to that of the feeder unit, which is complementary to the resulting recess.

It will be understood that embodiments described herein in relation to the first, second or third aspects of the invention may equally apply to the other aspects of the invention, unless otherwise stated. Embodiments of the invention will now be described with reference to the accompanying Figures in which:

Figure 1 a shows a plan view of a casting system in accordance with the first aspect of the present invention;

Figure 1 b shows a side view of part of a DISAMATIC moulding machine used to produce the casting system shown in Figure 1 a;

Figure 1 c shows a side view of the casting system shown in Figure 1a;

Figure 2 shows a perspective view of a feeder unit in accordance with an embodiment of the second aspect of the invention; Figure 3 shows a perspective view of a feeder unit in accordance with another embodiment of the second aspect of the invention;

Figure 4a shows a perspective view of part of the feeder unit illustrated in Figure 3;

Figure 4b shows a cross-section through the feeder unit illustrated in Figure 3, further comprising a filter.; and

Figure 5 shows a plan view of a prior art casting system for producing the same casting component as shown in Figure 1 a.

Figures 1 a and 1c show a casting system 100 in accordance with the first aspect of the invention, comprising a first mould half A and a second mould half B which meet at a vertical parting line X (shown in Figure 1 c). In Figure 1 a, the parting line (not shown) lies in the plane of the page. The first mould half A and the second mould half B may be formed of any suitable moulding material, such as clay-bonded greensand. The first mould half A and the second mould half B together define casting cavities 2 and feeder cavities 4, with the feeder cavities 4 connected by a runner 6. Each feeder cavity 4 contains an exothermic feeder unit 8a, 8b. The feeder units 8a, 8b each comprise an inlet 10a, 10b for receiving molten metal and an outlet 12 in fluid communication with each of the casting cavities 2 located on either side of the feeder cavity 4, via ancillary cavities 13. The top feeder unit 8a comprises a further bottom outlet 14 in fluid communication with the runner 6. The inlet 10a of the top feeder unit 8a is in fluid communication with a pouring cup 16, while the inlet 10b of the bottom feeder unit 8b is in fluid communication with the runner 6 and thereby connected to the bottom outlet 14 of the top feeder unit 8a. In use, molten metal flows from the pouring cup 16, through the feeder units 8a, 8b and into the casting cavities 2. Accordingly, in the system shown in Figures 1 a and 1c, the feeder unit 8a is located downstream relative to the pouring cup 16. The casting cavities 2 comprise a core 18, which the molten metal flows around and thereby forms a hollow region in the final casting. The feeder units 8a, 8b function as reservoirs for molten metal, which feed the casting cavities 2 when the molten metal therein cools and shrinks.

Figure 1 b shows part of the moulding machine used to prepare the mould for casting. After compression of the moulding sand by the two pattern halves 3a and 3b, the swing plate 5 pivots 90 degrees upwards in direction P and the squeeze plate 7 moves horizontally in direction Q, pushing the mould 9 along the conveyor 11 .

Figure 1c shows two moulds 9' and 9" produced using the moulding machine and patterns illustrated in Figure 1 b after being moved away from the moulding machine along the conveyor. After release from the patterns, a coresetter (not shown) inserts the cores 18 and feeder units 8a and 8b into mould half B' prior to mould 9" being conveyed along such that mould half A" abuts mould half B' to form the casting system 100. Figure 2 shows a perspective view of a feeder unit 8b in accordance with the second aspect of the invention. The feeder unit 8b is generally cuboid in shape, having a first end 20b, a second end 22b and four sidewalls 24, 26 therebetween. The walls and ends of the feeder unit 8b define a chamber therein. The sidewalls 24, 26 are slightly greater in length than the width of the first and second ends 20b, 22b. The first end 20b comprises a short neck 27b, which has a reduced width relative to the rest of the feeder unit 8b.

The feeder unit 8b further comprises an external projection 28 in the form of a rectangular peg, which extends from an outer surface of one of the sidewalls 24. The projection 28 is located on the sidewall 24 approximately half way between the first end 20b and the second end 22b, and arranged so that the long sides of the rectangular peg are orientated parallel to the first and second ends 20b, 22b.

The inlet 10b of the feeder unit 8b is constituted by a slot in the first end 20b, the slot being located centrally in the first end 20b. The outlets 12 of the feeder unit 8b are provided by generally oblong-shaped openings in the sidewalls 26 on either side of the sidewall 24 from which the projection 28 extends. The outlets 12 are located centrally in the sidewalls 26 and orientated so that the oblong openings extend between the first and second ends 20b, 22b. The openings constituting the outlets 12 are larger than the opening constituting the inlet 10b. The second end 22b does not have an opening.

The feeder unit 8b is formed of two halves 30b, 32b, joined together along parting line Y. The first half 30b comprises the external projection 28, while the second half 32b comprises cut-outs which define the inlet 10b and outlets 12 when the first and second halves 30b, 32b are joined together along the parting line Y. The first half 30b comprises tapered channels 31 in the edges which define the side of the outlets 12. The first and second halves 30b, 32b flare out slightly towards the parting line Y, so that the feeder unit 8b appears to bulge slightly at the seam between the two halves. Figure 3 shows a perspective view of a feeder unit 8a in accordance with another embodiment of the second aspect. The feeder unit 8a is largely similar to the feeder unit 8b illustrated in Figure 2, formed of two halves 30a and 32a joined together along parting line Y. The feeder unit 8a is generally cuboid in shape and has a first end 20a, a second end 22a and four sidewalls 24, 26 therebetween, also comprising an external projection 28 extending from one of the sidewalls 24. The feeder unit 8a further comprises an opening in the second end 22a, which constitutes the bottom outlet 14. The first half 30a comprises the external projection 28, while the second half 32a comprises the cut-outs which define the inlet 10a and outlets 12, 14. The openings constituting the inlet 10a and the bottom outlet 14 are generally trapezoid-shaped, with the inlet 10a being slightly larger and more equilateral than the bottom outlet 14. The neck 27a at the first end 20a of the feeder unit 8a is longer than the neck 27b of the feeder unit 27b illustrated in Figure 2.

Figure 4a shows a perspective view of the feeder half 32a of the feeder unit 8a illustrated in Figure 3.The feeder unit 8a has an interior wall 34 comprising an opening. The interior wall 34 is arranged parallel to the first and second ends 20a, 22a of the feeder unit 8a, but located closer to the first end 20a than the second end 22a. An internal cavity 36 is defined between the first end 20a and the internal wall 34.

Figure 4b shows a cross-section through parting line Y of the feeder unit 8a illustrated in Figure 3, showing a filter 40 located in the cavity 36 between the first end 20a and the interior wall 34, within the neck 27a.

Figure 5 shows a plan view of a prior art casting system 200 which is configured to produce the same casting component 2 as shown in Figure 1 a. In the system shown in Figure 5 there are six natural sand risers (feeders) 208a, 208b, 208c, 208d, 208e, 208f, each of which is connected to an ingate 210a, 210b, 210c, 210d, 210e, 21 Of for supplying molten metal. Each of the two upper natural sand feeders 208a and 208b has an outlet in fluid communication with a single casting cavity 212a, 212b via an ancillary cavity 213. Each feeder 208a, 208b also has a bottom outlet in fluid communication with a runner 206a, which feeds a lower natural sand feeder 208c, 208d via an ingate 210c, 21 Od. The lower natural sand feeders 208c, 208d are each in fluid communication via an ancillary cavity 213 with a lower single casting cavity 212c, 212d located adjacent to the natural sand feeder. The other two central natural sand feeders 208e, 208f are in fluid communication via ancillary cavities 213 with two casting cavities located either side of the natural sand feeder 208e, 208f. The upper natural sand feeder 208e has a further bottom outlet in fluid communication with a runner 206b which feeds the lower natural sand feeder 208f via an ingate 21 Of.

In use, metal flows from a pouring cup 216 into a horizontal cavity or runner 205 and into the upper natural sand feeders 208a, 208b, 208e via ingates 210a, 210b, 21 Oe and into the upper casting cavities 212a, 212b. Metal flows into the lower natural sand feeders 208c, 208d, 208f via the runners 206a, 206b and the ingates 210c, 21 Od, 21 Of and into the lower casting cavities 212c, 212d. The metal in the natural sand risers 208a, 208b, 208c, 208d, 208e, 208f feeds the casting cavities 212a, 212b, 212c, 212d when the molten metal therein cools and shrinks.

Examples

Testing was conducted in a European iron foundry making various grey iron and ductile iron automotive castings.

Comparative Example - Existing Casting Method

Ductile iron brake caliper housing castings were produced on a DISAMATIC automatic moulding line using the casting system 200 shown in Figure 5. Four castings were produced per mould, and were fed by a total of six natural sand feeders. The total poured weight (of the castings, runner system and feeders) was 33 kg and the weight of each casting was 3.65 kg, meaning that the casting yield was 44.2%.

Example 1

Using MAGMASOFT simulation software to predict the flow and solidification of metal, the casting system of the Comparative Example (Figure 5) was modified by replacing the six natural sand feeders with two exothermic feeder units of the invention. MAGMASOFT is a leading simulation tool supplied by MAGMA GieBereitechnologie GmbH that models the mould filling and solidification of castings. It is typically used by foundries to predict the mechanical properties of castings to enable optimisation of the casting method (design of the running system and feeders) so as to avoid expensive and time-consuming foundry trials. Using the full version of MAGMASOFT, the inventors conducted simulations of different methoding configurations and feeder dimensions and sizes to predict the flow (direction and velocity) and solidification (temperature profiles vs time) of metal in the running systems, feeder units and castings. After over 25 different design simulations, the casting system shown in Figure 1 a was designed, utilizing one each of the two feeder units 8a and 8b shown in Figures 2, 3, 4a and 4b.

The pattern plate used by the foundry to produce the castings according to the Comparative Example was modified to enable the foundry to produce castings using exothermic feeder units on their DISAMATIC production line. The feeder units were placed into the feeder cavities in the sand mould during the DISAMATIC moulding cycle, at the same time as the sand cores, such that there were no delays i.e. no increases in cycle time and thus no reduction in productivity.

Castings were produced using the same metal composition and temperature as for the Comparative Example. The pour time was the same (9 seconds). It was found that the total poured weight was only 20.5 kg, equating to a casting yield of 71.2%, which is significantly higher than the Comparative Example. This is due to the reduction in both the number and size of feeders. In addition to the improvements in yield, a 10% reduction in scrap levels due to shrinkage was also observed. Even taking into consideration the cost of the additional exothermic feeder units, the use of the new casting system resulted in a notable cost saving per mould (casting) and an overall reduction in emissions due to the lower amount of metal used.

Claims

1. A vertically parted casting system comprising:

an exothermic feeder unit located in the feeder cavity, the feeder unit comprising an inlet, a chamber and an outlet which is in fluid communication with the casting cavity, wherein the outlet is separate from the inlet,

the system defining a flow path for molten metal from the inlet of the feeder unit to the casting cavity, via the chamber and the outlet of the feeder unit.

2. The casting system of claim 1 , wherein the feeder unit further comprises a filter located in the flow path between the inlet and the outlet.

3. The casting system of claim 1 or claim 2, wherein the first and second mould halves further define a pouring cup which is upstream of and in fluid communication with the inlet of the feeder unit.

4. The casting system of any one of claims 1 to 3, wherein the first and second mould halves define two or more casting cavities.

5. The casting system of claim 4, wherein the feeder unit comprises two or more outlets, each casting cavity being in fluid communication with a single outlet.

6. The casting system claim 4 or claim 5, wherein the first and second mould halves define two or more feeder cavities which are arranged in series and connected by a runner,

the system further comprising two or more feeder units located in their respective feeder cavities, each feeder unit comprising an outlet which is in fluid communication with only one of the casting cavities.

7. The casting system of claim 6, wherein the first and second mould halves define 2n casting cavities, and n feeder cavities, wherein n is an integer between 1 and 5.

8. The casting system of claim 6 or claim 7, wherein the feeder cavities are vertically aligned.

9. The casting system of any one of the preceding claims, wherein the feeder unit comprises an external protrusion which extends into a recess formed in one of the first mould half and the second mould half, for securing the feeder unit in the feeder cavity.

10. The casting system of any one of the preceding claims, wherein the casting cavity further comprises a core.

1 1 . The casting system of any one of the preceding claims, wherein the feeder unit is formed of two halves divided along a parting line, wherein one or both halves comprise cut-outs which define the inlet and outlet(s) of the feeder unit when the two halves are joined together.

12. An exothermic feeder unit for use in the casting system of any one of the preceding claims, the feeder unit comprising an inlet, one or more outlets, a chamber between the inlet and the outlet(s), the feeder unit defining a flow path from the inlet to the outlet(s), via the chamber.

13. The exothermic feeder unit of claim 12, comprising two or more outlets.

14. The exothermic feeder unit of claim 12 or claim 13, wherein at least one outlet is orthogonal to the inlet.

15. The exothermic feeder unit of any one of claims 12 to 14, further comprising an external protrusion for securing the feeder unit in a feeder cavity.

16. The exothermic feeder unit of claim 15, wherein the protrusion is in the form of a peg which extends from an outer surface of the feeder unit.

17. The exothermic feeder unit of any one of claims 12 to 16, wherein the feeder unit is approximately cuboid in shape and comprises a first end, a second end and four sidewalls therebetween, wherein the inlet is constituted by an opening in the first end.

18. The exothermic feeder unit of claim 17, further comprising a filter located in the flow path between the inlet and the outlet.

19. The exothermic feeder unit of claim 18, further comprising one or more interior ledges or walls for locating the filter.

20. The exothermic feeder unit of claim 18 or 19, comprising an interior wall having an opening therein, the interior wall being arranged parallel to the first and second ends so as to define an internal cavity between the first end and the interior wall in which the filter is located.

21 . A method of forming the casting system of any one of claims 1 to 1 1 comprising:

forming a second mould half having a second vertical surface which defines a second part of the casting cavity and a second part of the feeder cavity;

bringing the first and second vertical surfaces of the first and second mould halves together to form the vertically parted casting system comprising the casting cavity and the feeder cavity, wherein the feeder unit is located within the feeder cavity.