1 Title of the Invention
Sand core venting for as cast oil passages through metallic spring.
2 Field of the Invention
The present invention illustrates a special process developed for sand core venting to cast, parts with as cast oil passages using metallic springs and wire. Process developed is useful for complicated aeronautical castings for aero-engine and gear box applications where as cast oil
passages are primary requirements in casting design. The present process can be used for castings non-ferrous alloys (Aluminium and
Magnesium alloys). Casting are being cast with aeronautical grade AI-Si and Mg-Zn-Zr-Rare Earth alloys with newly invented/developed process.
3 Background of the Invention
In aeronautical industry castings are widely used for aero-engine and gear
box applications. Manufacturing of these parts on commercial level is not
feasible by other manufacturing processes due to complex design/profile
requirements of these parts. Due to Higher strength to weight ratio
requirement generally non-ferrous alloys such as Aluminium and Magnesium alloys are us4ed. These alloys are highly reactive in nature
hence inhibitors are used (particularly for magnesium alloys) in sand mix.
Reaction of binders and inhibitors with molten alloy generated gases during pouring and solidification of alloys in mould cavity. Gases
generated during casting process need to be vent off to avoid Gas Holes and Blow in the casting. Venting process is common technique in the field
of foundry and widely used as vent hole in mould. However, for core venting special techniques like mini core technology and flexi vents (made
of fibres) are used. These processes have their limitations. Generally spring removal from Aluminium alloy castings is difficult and leads to
frequent rejection, similarly flexi vents react with molten alloy whenever comes in direct contact (particularly in case of smaller diameter cores.
To overcome these limitations, new process was developed.
3.1 Prior Art
Venting téchniques described in text and commonly used are vent by
spikes in moulds, mini core (using only differential diameter springs),
waxed ropes and flexi vents. Vacuum suction is also used to vent of gases
generated during casting. There is no literature other than above could be
traced by the inventors.
4 Brief Summary of the Invention
Alternate sand core venting process using steel spring is developed which
is not vulnerable to metal -vent material reaction and efficient as well.
Suitable diameter steel/copper wire is selected based on sand core
diameter. The same wire is shaped as per profile of sand core and
inserted in steel spring (Internal diameter of the spring is generally 0.5mm
higher than diameter of reinforcement wire). Sand mix is filled in core box
half. Then reinforcement wire/spring assembly is placed over sand‘
.Wire/spring assembly is covered with sand and second half of the core
box is assembled with first one. Excess sand shall be removed. After 60 to
70 percentage curing of the sand, reinforcement wire is pulled out from the
spring leading to creation of vent passage through spring. Sand mix is
allowed to cure fully before removal from core box. Thus, a sand core with
vent passage using spring is fabricated.
Steel spring diameter used for venting shall be at least? mm lesser than
minimum sand core diameter. The invented/developed process is used to
achieve efficient venting for gases generated during pouring and
solidification of molten alloy in mould cavity.
5 Detail Description of the Drawings
Fig.1 Schematically illustrates the Front view of the casting having multiple
as cast oil passages.
Fig.2 Schematically illustrates the sectional view of the part (Oil Passage).
Fig.3 Schematically illustrates the sectional view of sand core with
reinforcement wire and spring (1
- Sand particles; 2- Spring; 3 — Wire).
Fig.4 Schematically illustrates the sectional view of sand core after wire
removal and creation‘of vent passage through spring(2- Spring).
6 Detail Description of the Invention
1) Mould and core venting techniques are widely used in foundry industry.
However, commonly practiced methods such as waxed rope, mini-core
and flexi vents have their limitations. These methods are vulnerable for
gas/blow holes.
2) To overcome gas/blow hole defects in the casting an alternate sand
core venting process using steel spring.
3) Selection of steel spring diameter and reinforcement wire depends on
diameter of the sand core to be vented.
4) In case of variable diameter sand core. minimum diameter shall be
reference for selecting spring diameter for venting.
5) Steel spring diameter used for venting shall be at least 2 mm lesser
than minimum sand core diameter.
6) Steel wire diameter which is used for reinforcement shaping the spring
to desired shape of sand core shall be at least 0.5 mm lesser than ID of
the spring used for venting.
Construction
The'sand core venting process for as cast oil passage through metallic
spring involves
1. Cutting the reinforcement (steel/copper) wire to the required
length.
2. Shaping the reinforcement wire as per the sand core shape (to be
vented).
3. Cutting the steel spring to required length and inserting
reinforcement wire inside spring to provide it required
shape/profile.
4. Applying the core releasing agent on core box and filling the sand
mix in core box half.
5. Placing the shaped spring on filled core box half and filling the
sand mix to cover the spring. Amount of sand mix according to
core diameter. Placing the other half of the core box on excess
sand filled and tap the core box.
6. Open other half and remove the excess sand mix, repeated the
core box closing and tap for compaction of the sand mix.
7. Once no gap is observed between core box halves allow the sand
mix to cure 60 to 70%
8. Remove the reinforcement wire slowly‘from the spring.
9. Allow the sand core to cure fully before release of core from core
box.
10.Tap the core box and release the sand core (vented ‘through
spring) and store on sand bed or profiled slot to avoid warpage.
Function
The invented/developed process is used to achieve efficient venting for gases generated during pouring and solidification of molten alloy in mould cavity
The established 'process has been successfully implemented for types of casting made of Aluminum and Magnesium Alloys having sand cores of diameter ranging from 6 mm to 25mm. Part made using invented/developed process are used in Aero-Engine and Gear Box Applications.
We Claim,
1. Sand core venting technology for as cast oil passages through
metallic spring core manufacturing process for sand castings. This
method can be used for all the castings made of Aluminum and
Magnesium Alloys.
2. This method is developed as an alternate of flexi vents, waxed rope
and mini-core technology of core venting.
This method can be used for venting sand cores which may be‘
subjected to pouring temperature as high .as up to 790°C.
Preheating of the vented core is required between 60 to 120°C,
depending on the alloy to be cast and diameter of the sand core.
. Sand core venting technology for as cast oil passages involves
operation of (1) Wire (suitable diameter, preferably 1 to 2 mm)
bending in desired shape and length. (2) Inserting the wire in spring
of diameter 2 to 3 mm. (3) Placing the wire spring assembly in core
box and sand mix filling. (4) Semi curing of sand mix. (5) Removal
of Mild Steel/Copper wire from spring, creating vent passage (5)
Allowing the sand mix to fully cure before removal of sand cores
. from core boxes.