Flash control molding for molds

A flash control molding is provided for use in association with a pattern for forming a casting cavity in a metal casting mold. The flash control molding includes an elongated strip of pliable material having a predetermined cross sectional configuration to define a thick portion for forming a flash control chamber in the mold, and a thin edge along one side of the thick portion to form a restricted opening between the flash control chamber and the casting cavity so that a casting subsequently produced in the mold is formed with controlled shaped flash which has a built-in fracture line immediately adjacent the casting proper, thereby making the flash easily and cleanly removable from the casting.

BACKGROUND OF THE INVENTION 
This invention relates generally to a method and apparatus for forming 
molds for making metal castings and more particularly to a flash control 
molding for use in making controlled shaped flash about the periphery of 
such castings. 
Obtaining a proper match between the cope and drag about the periphery of a 
casting cavity of a mold is sometimes quite difficult. Those skilled in 
the art will appreciate that if a gap occurs between the respective 
parting surfaces of the cope and drag when the mold is closed, flashing 
will occur along the parting line of the casting when it is poured. 
Typically, such flash must be chipped and/or ground off the casting to 
make the casting ready for subsequent machining or other finishing 
operations. 
Alternately, if there is too much interference between such parting 
surfaces adjacent the cavity, the corners of the mold formed by the cavity 
and the parting line may be crushed, causing portions of the mold material 
to break off and fall into the cavity. This results in what is known as a 
crush defect in the casting. 
In the past, the problem of crush defects has been somewhat alleviated by 
placing a relatively thin, flat strip of metal about the periphery of the 
pattern used to form the casting cavity in the mold. This strip produces a 
predetemined separation or gap between the parting surfaces of the mold 
about the casting cavity, thus alleviating the possibility of the corners 
being crushed when the mold is closed. The strips typically used are from 
approximately 0.03 to 0.10 inches in thickness and from approximately 1/4 
to 3/4 inches in width, thus providing a thin flash cavity in the mold. 
Typically, such strips have to be hand cut and trimmed so as to be fitted 
about the intricate shapes of typical patterns. As will be appreciated, 
this operation is extremely time-consuming and consequenty quite costly. 
It will also be appreciated that the use of such strip will result in the 
production of flash about the casting which must subsequently be removed. 
The normal flash produced by such prior art strips is quite difficult to 
remove because they produce a flash fin which is strongest at its 
connection with the casting. This is due to the slight rounding of the 
corners between the casting and flash cavities together with the 
progressively decreasing filling of the thin flash cavity by the molten 
metal which gives the fins a somewhat tapered or wedge shaped 
configuration. Thus, the flash fins, when struck with a hammer or other 
tool, will tend to break off in little chunks at a point away from the 
casting itself. This leaves a ridge about the casting which typically has 
to be ground away with a grinding wheel. Such grinding and chipping is 
normally quite time consuming and tedious and significantly contributes to 
the overall cost of the casting. 
SUMMARY AND OBJECTS OF THE INVENTION 
Accordingly, it is an object of this invention to provide a method and 
apparatus of making a casting free from crush defects more economically 
than castings made by prior foundry practices. 
Another object of this invention is to provide a flash control molding for 
making a flash chamber in the parting line of a mold about the casting 
cavity of such mold so as to produce controlled shape flash which has a 
built-in fracture line contiguous to the casting so that the flash is 
cleanly and easily removed from the casting.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring more particularly to the drawings, a flash control molding 
embodying the principles of the present invention is generally indicated 
at 10 in FIG. 1 in association with a pattern assembly 12. The pattern 
assembly 12 is of a conventional construction and includes a split-type 
pattern 14 which may be made in any well known manner. 
The pattern 14 is provided with a flat side 15 for mounting against a true 
surface 16 of a match or pattern plate 18. The flat side of the pattern 
and its adjacent sidewall define a peripheral edge 19 disposed along the 
true surface 16 of the pattern plate. 
In general, the flash control molding 10 includes an elongated strip 20 of 
pliable material to allow the strip to be bent and shaped to conform to 
whatever peripheral shape the pattern 14 may have. While many suitable 
pliable materials may be used, a soft metal, such as aluminum, is 
preferred because of its inherent resistance to abrasion. This, as will be 
more fully understood, is important for molding purposes, hereinafter more 
fully described, because of the longer useful life it provides. the strip 
also preferably has a fixed cross sectional configuration to permit the 
economical forming of the strip by extrusion. 
As best shown in FIG., 7, the strip has a predetermined cross sectional 
configuration which includes a thick portion having a substantially flat 
face 22, and an opposite contoured face 23. The flat face 22, it will be 
appreciated, is provided for mating engagement against the true surface 16 
of the pattern plate 18. The contoured face 23 is provided for varying the 
lateral thickness of the strip so as to provide a thin edge 25 along the 
one side of the thick portion in adjoining relationship with the faces 22 
and 23. Such thin edge should be substantially less than the thick portion 
of the strip and preferably less than 1/2 the maximum thickness thereof. 
Also, the point of maximum thickness of the strip is preferably as far as 
possible from the thin edge, such as along the opposite side 26 thereof. 
In the embodiment shown in FIG. 7, the contoured face 23 is simply 
provided by a generally flat surface which is angled relative to the flat 
face 22, thus giving the strip a generally wedge shaped cross sectional 
configuration. 
the thin edge 25, as shown in FIG. 1, is disposed in abutting engagement 
against the periphery of the pattern. The strip is secured in such 
position by any suitable means, such as by a plurality of pins, one of 
which is shown at 27, which are driven into suitable holes drilled through 
the strip and into the pattern plate 18. 
The above described pattern is then used to form a mold 30, such as 
depicted in FIG. 3. The mold 30 illustrated is of the commonly used 
book-type having opposite cope and drag portions 31 and 32, respectively, 
which form opposite mating halves of a mold or casting cavity 34. In this 
regard, it will be understood that the pattern assembly 12 is used to form 
the cope portion of the mold and another suitable pattern, not shown, of a 
conventional design is used to form the drag portion of the mold or vice 
versa. The cope and drag portions are joined together in a conventional 
manner along a parting line 35 formed by the true surfaces of their 
respective pattern plates, as will be understood by those skilled in the 
art. Both the cope and drag portions are made from any suitable mold 
material commonly employed in the metal founding industry, such as sand or 
the like. 
It will be appreciated that with the flash control molding 10 being mounted 
about the peripheral edge 19 of the pattern 14 when the mold 30 is made, 
the mold will have formed therein a flash control chamber 37 which has a 
shape conforming to that of the strip 20. Thus, the chamber will lie along 
the parting line 35 and communicate with the casting cavity, through a 
restricted opening 38 formed by the thin edge 25. 
The pouring of molten metal, such as iron or steel, into the mold 30 in a 
conventional casting operation will produce a casting, such as shown at 40 
in FIG. 5. The casting 40 will have a body portion 41 conforming to the 
shape of the casting cavity 34 of the mold and controlled shaped flash 42 
formed about the periphery of the body portion conforming to the shape of 
the flash chamber 37. 
The controlled shape flash 42 is connected to the body portion of the 
casting by a relatively thin neck 44 provided by the restricted opening 38 
of the flash chamber 37. The flash also has a substantially thicker mass 
spaced outwardly from such neck conforming to the thick portion of the 
strip. As a result, the flash is provided with a built-in fracture line, 
such as indicated along line A--A, immediately adjacent the casting body 
so that by striking the flash with a tool, such as a hammer or chisel, the 
flash will break off cleanly from the body along such fracture line 
without leaving a sizeable ridge or other protruberance which must 
subsequently be removed by a grinding wheel or the like. 
The present invention also contemplates the use of a similar flash control 
molding, as shown at 46 in FIG. 2 on a similar pattern assembly 47 for use 
in combination with the pattern assembly 12 of FIG. 1. 
When the two pattern assemblies 12 and 47 are used together to form a mold 
50, as shown in FIG. 4, a casting cavity 51 is formed having two mating 
flash chambers 52 and 53, each formed in respective ones of the cope and 
drag portions 31, 32 of the mold about the periphery of such casting 
cavity. This ultimately forms a casting 54, as shown in FIG. 6, which has 
a body portion 55 with controlled shaped flash 56 about its periphery 
which is double the size of the flash of FIG. 5. The above described use 
of two molding strips is one way of varying the size of flash. The 
particular flash size desired depends upon many factors, as those skilled 
in the art will appreciate, such as the type of metal being used, its 
pouring temperature, the size of casting being poured, and the desired 
characteristics of the casting to be formed. Other ways of varying the 
flash are by merely changing the size of the strip used or by changing the 
shape of such strip. In general, however, the width of the strip is 
preferably within a range of from 1/4 to 2 inches, with the maximum 
thickness varying from 1/8 to 1/4 inches. 
Two alternate strip shapes are shown in FIGS. 8 and 9, respectively. In the 
embodiment of FIG. 8, a strip 58 is shown which has a flat face 59 similar 
to face 22 of the strip 20, and an opposite contoured face 60, which is 
described by a pair of tangentially disposed radii R.sub.1 and R.sub.2, 
respectively, to provide a concave configuration adjacent one side thereof 
and a semicircular configuration adjacent the opposite side thereof, with 
the concave configuration defining a thin edge 61. 
The embodiment of FIG. 9, in turn, shows a strip 65 having a similar flat 
face 66 and an opposite contoured face 67. The contoured face of this 
embodiment has an angled portion 69 to reduce the thickness along one side 
thereof to provide a thin edge 70 and a straight portion 71 parallel to 
the flat face 66. This configuration allows the width of the strip to be 
varied without its thickness becoming unduly great, thus minimizing the 
mass of the flash produced thereby. 
Thus, as is readily apparent from the foregoing, the particular 
construction of the flash control molding of the present invention is 
capable of forming controlled shaped flash about a casting, which flash 
has a built-in fracture line immediately adjacent the body of the casting 
so as to enable such flash to be cleanly knocked off the body without 
leaving any undesirable ridge or the like which must be subsequently 
removed by grinding or other operation. 
While the present invention has been described and shown with particular 
reference to the preferred embodiments thereof, it will be apparent the 
variations might be possible that would fall within the scope of the 
present invention which is not intended to be limited except as defined in 
the following claims.