WO2005014207A1

WO2005014207A1 - Combined sand removal and heat treatment

Info

Publication number: WO2005014207A1
Application number: PCT/AU2004/001066
Authority: WO
Inventors: Robert J. Bend
Original assignee: Equipment Merchants International Inc.
Priority date: 2003-08-11
Filing date: 2004-08-11
Publication date: 2005-02-17
Also published as: AU2003904220A0

Abstract

The invention relates to a combined sand removal and heat treatment method for castings. Post casting, the external mould components are removed. These external mould components are adapted to be removed by robotic manipulators, in a sequence that corresponds with the order in which the external mould components are designed to be disassembled. Once the external mould components have been removed, the casting is placed into a solution furnace for simultaneous heat treatment and internal sand removal.

Description

Combined sand removal and heat treatment.

TECHNICAL FIELD

The present invention relates to a combined sand removal and heat treatment method for removing sand from castings.

For the purposes of explanation, reference will be made to the use of the present invention with respect to the casting of aluminium cylinder blocks. It should be understood by those of ordinary skill in the art however, that the invention is not limited to use in casting cylinder blocks, and can be used in the casting of other products. Cylinder blocks have traditionally been manufactured as a casting in cast iron, and more recently in aluminium.

BACKGROUND ART

The mould and core assembly for a cylinder block is comprised of a multiplicity of sand-type foundry components, or cores, formed from particulate foundry sand, and a binding agent. In relation to cylinder blocks, the core is intended to define the inner walls of a cavity, which will ultimately become the crankcase of the cylinder block. A series of external mould components define the outer walls of the cylinder block.

Subsequent to the pouring and solidification of a casting, it is necessary to remove the completed cast component from the sand mould, and any sand cores from the inside of the component. This is commonly achieved by placing the mould in a solution furnace, where the resins that bind the sand grains together are thermally broken down. In order to effect the thermal breakdown of the resins binding the sand grains together, the cores need to be heated to a temperature in excess of 400°C and have a plentiful supply of oxygen.

It is also common practice to heat-treat the cast component in a solution furnace. Solution treatment consists of heating the metal to a high temperature and holding it there long enough for soluble alloying elements to diffuse evenly throughout the metal in solid solution. Precise temperature control and timing are important for effective solution heat treatment. There are now 3 in 1 systems which combine heat treatment, sand removal and sand reclamation in the one operation. In these systems the complete mould and casting are placed in a convection oven to remove and reclaim external, and internal sand whilst simultaneously heat treating the casting. While such systems are an elegant solution to many of the problems associated with handling freshly cast moulds, their ability to efficiently process the heat treatment of the casting while removing and reclaiming the sand has been questioned.

Typically, the solution heat treatment temperature for 319 aluminium alloy, as used for cylinder block production is 495°C (923°F). To obtain the optimum mechanical properties the casting needs to remain at the solution temperature for a prolonged period, for a cylinder block casting this could be between 4 and 8 hours. The costs associated with maintaining a furnace at this temperature, for these durations is considerable.

It is an object of the present invention to provide a method for removing sand from a casting and heat treating the casting that is more efficient than the processes of the prior art.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

DISCLOSURE OF THE INVENTION

In one form of this invention although this may not necessarily be the only or indeed the broadest form of this, there is proposed a combined sand removal and heat treatment method for castings, including the steps of removing all external mould components, and placing the casting into a solution furnace for simultaneous heat treatment and internal sand removal.

Preferably, there are included the further steps of:

filling the mould with molten metal;

allowing the casting to solidify; removing at least one external mould component using manipulation means, to expose a portion of the casting;

positioning the mould and casting on a fixture via the exposed portion of the casting, using manipulation means;

securely retaining the casting via clamping means;

removing the remainder of the external mould components using manipulation means;

releasing the clamping means;

placing the casting ready for entry into the solution furnace using manipulation means.

Preferably, the manipulation means are robotic devices.

Preferably, the casting is clamped via the exposed bulkheads.

Preferably, the clamping means are pneumatic or hydraulic cylinders.

Preferably, the mould is placed on a pallet prior to placement in the furnace.

Preferably, the process is controlled by a PLC.

It has been found, that the time taken for cylinder block castings to reach solution temperature when placed in a solution furnace, is heavily dependent upon the condition of the casting when it enters the furnace. Possible alternative states for the casting prior to being placed in the furnace include: > Cylinder block at ambient temperature with no retained sand, and risers removed.

> Cylinder block at ambient temperature with risers and retained internal sand.

> Cylinder block is in external sand mould at solidus temperature. > Cylinder block at solidus temperature with external sand removed, in accordance with the method of the present invention.

Chart 1 illustrates the dependence of casting time at solution temperature upon the condition of the mould at the time it enters the furnace:

MOLD IN FURNACE AT SOLIDUS EXTERNAL SAND REMOVED AT SOLIDUS AT AMBIENT WITH SAND & RISERS AT AMBIENT WITHOUT SAND AND RISERS

Time (hrs )

As such, it can be seen that it is a significant advantage of the method according to the present invention that it is the most efficient method of sand removal and heat treatment. Using this method gets the casting up to the required temperature one hour sooner than the next quickest alternate method, and two hours quicker than the remaining two alternate methods.

When the external sand is removed prior to heat treatment in this fashion, the forced convection air of the furnace is in direct contact with the casting raising it to the solution temperature very quickly. If the external sand is left in place, the casting exterior is encased in sand, which insulates the casting and prevents oxygen from reaching the internal cores, which can result in the incomplete combustion of the core resins and retained sand. With the external sand removed however, the casting does not undergo the significant drop in temperature, and consequently recovers to solution temperature in 1 hour. Any manipulation of the mould and casting so close to solidus is problematic however, not to mention dangerous, due to the amount of residual heat retained in them from the casting process.

It is a further object of the invention therefore to provide an external casting mould assembly that overcomes or at least substantially ameliorates this problem.

In a further form of the invention, it can be said to lie in an external mould assembly for use in a combined sand removal and heat treatment process, wherein the external components of the mould are adapted to facilitate removal thereof from the cast object via manipulation means, the external mould components including:

interlocking assembly means; and

external attachment points.

Preferably, the manipulation means are robotic devices.

Preferably, the interlocking assembly means includes a labyrinth shut-off.

Preferably, the external attachment points are adapted to securely couple with corresponding attachment means on the manipulation means.

Preferably, the interlocking assembly means are adapted to be removed in a sequence that corresponds with the order in which the manipulation means are designed to remove them.

Preferably, the runners and risers between mould components have tapers, in order to facilitate their removal from the casting in a sequence that corresponds with the order in which the manipulation means are designed to remove them.

Labyrinth seals are a well known technique for sealing potential run out areas from molten metal in casting operations, due to the fact that the molten metal is forced to change direction through 90°, in some cases a number of times, before it can reach the outside of the mould. A labyrinth seal increases the surface area of the shut-off, and negotiating the labyrinth reduces the velocity of the molten metal, increasing the effectiveness of the seal. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of this invention it will now be described with respect to the preferred embodiment which shall be described herein with the assistance of drawings wherein;

Figure 1 is a plan view of a cylinder block placed on a bulkhead fixture, still enclosed in its external mould, with the robotic manipulation means poised to remove the external mould components according to the preferred embodiment of the present invention; and

Figures 2 and 3 are plan views of a cylinder block placed on a bulkhead fixture as in Figure 1 , illustrating the clamping means in operation, and the robotic manipulation means in the process of removing external mould components.

BEST MODE FOR CARRYING OUT THE INVENTION

Now referring to the illustrations, there is a cylinder block 1 , enclosed in its external mould, the external mould comprising a cope 6, a base core 2, side cores 3 and 4, and end cores (not shown in order to permit visibility).

These external mould components have been assembled in a strict sequence that allows the interlocking features on each core segment to locate it to its adjoining core segment. These interlocking features are known as core prints. The interlocking features also act as shut off to seal potential run out areas for the molten metal.

Once the casting has been allowed to solidify for 15-20 minutes, the cope 6, is removed by a robot, and the bulkhead 9 of the cylinder block 1 is exposed.

The cylinder block 1 is then placed in position on a bulkhead fixture 8, and clamped in place by clamping cylinder 30.

Suspended above the production line is a pair of robotic armsl 0 and 15, both having manipulation means, in this case grippers 20 and 25 respectively, at their ends.

It can be seen that there is an interlocking feature known as a labyrinth shut-off 40, at the interface of the base core 2, and the side cores 3, and 4. The labyrinth shut-off has inter-engaging male and female portions, 45, and 50, in the base core, and side cores respectively. These labyrinth interfaces are designed to act as a shut off to seal potential run out areas for the molten metal from the mould. They are also designed to facilitate the removal of the base core 2, before either of the side cores 3 and 4 is removed. That is, the labyrinth shut-offs have been designed so as to allow the cores to be removed in the correct sequence with no interference.

The core pack is designed to come apart; the external faces of the cores 2, 3 and 4, have robotic gripper positions 55, 60 and 65 formed into them, to facilitate manipulation by the grippers 20, and 25, of the robotic arms 10 and 15.

The robotic arms 10, and 15, then set about removing first the base core 2, and then the side cores 3 and 4, of the mould until only the casting, with a residue of external sand remains. The clamping cylinder 30 is then released, and the mould placed in the solution furnace for combination heat treatment and internal sand removal process. The removal of the external mould components only takes about 30 seconds.

It is considered therefore that the method according to the present invention will be of particular benefit to those seeking to reduce the time and cost associated with using a solution furnace for casting heat treatment and sand removal.

Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiment, it is recognised that departures can be made within the scope of the invention, which is not to be limited to the details described herein but is to be accorded the full scope of the appended claims so as to embrace any and all equivalent devices and apparatus.

Claims

1. A combined sand removal and heat treatment method for castings, including the steps of removing all external mould components, and placing the casting into a solution furnace for simultaneous heat treatment and internal sand removal.

2. The combined sand removal and heat treatment method for castings as in the immediately preceding claim, further characterised in that there are included the further steps of:

filling the mould with molten metal;

allowing the casting to solidify;

removing at least one external mould component using manipulation means, to expose a portion of the casting;

securely retaining the casting via clamping means;

releasing the clamping means;

3. The combined sand removal and heat treatment method for castings as in claim 2, wherein the manipulation means are robotic devices.

4. The combined sand removal and heat treatment method for castings as in either of claims 2 or 3, wherein the casting is a cylinder block, and the exposed portion is a bulkhead.

5. The combined sand removal and heat treatment method for castings as in any one of the claims 2 to 4, wherein the clamping means are pneumatic or hydraulic cylinders.

6. The combined sand removal and heat treatment method for castings as in any one of the preceding claims, wherein the casting is placed on a pallet prior to placement in the furnace.

8. The combined sand removal and heat treatment method as in any one of the preceding claims, wherein the process is controlled by a PLC.

9. An external mould assembly for use in a combined sand removal and heat treatment process, wherein the external components of the mould are adapted to facilitate removal thereof from the cast object via manipulation means, the external mould components including:

interlocking assembly means; and

external attachment points.

10. The external mould assembly of claim 9, wherein the manipulation means are robotic devices.

11. The external mould assembly as in any one of claims 9 or 10, wherein the interlocking assembly means includes a labyrinth shut-off.

12. The external mould assembly as in any one of claims 9 to 11 , wherein the external attachment points are adapted to securely couple with corresponding attachment means on the manipulation means.

13. The external mould assembly as in any one of claims 9 to 12, wherein the interlocking assembly means are adapted to be removed in a sequence that corresponds with the order in which the manipulation means are designed to remove them.

14. The external mould assembly as in any one of claims 9 to 13, wherein the runners and risers between mould components have tapers, in order to facilitate their removal from the casting in a sequence that corresponds with the order in which the manipulation means are designed to remove them.

15. A combined sand removal and heat treatment method for castings substantially as described in the specification with reference to and as illustrated by the accompanying illustrations.

16. An external mould assembly substantially as described in the specification with reference to and as illustrated by the accompanying illustrations.