Moulding machines may be classified as hand moulding or machine moulding according to whether the mould is prepared by hand tools or with the aid of some moulding machine. Hand moulding is generally found to be economical when the castings are required in a small number.
Definition of Moulding Machines:
Moulding machines are machine tools in the sand moulding industry that employ tools (pattern plate, core box) to manufacture the workpieces (mould parts, mould halves and cores) from necessary materials (moulding material and core moulding material) in order to produce the castings.
When a large number of castings must be made, hand moulding requires more time and labour, and the precision and regularity of the castings produced might be inconsistent. Machines are utilised in the process of moulding to solve this issue. There are many components to this green sand casting squeeze moulding machine, such as the table, the shock piston, the solid iron compaction piston, and the compaction cylinder.
Molding machines must be capable of doing the following functions:
- Placement of the mould boxes on the pattern plate after they have been loaded
- Filling the mould box with green sand mixtures (which is a time-consuming process)
- Compaction is a term used to describe the process of compacting the sand mixtures (solidification of the moulding material)
- Demolding is the process of separating the mould from the pattern and removing the cast from the mould.
Moulding Machines are classified as follows:
Molding machines can be divided into many categories based on their characteristics. The following are the most important classification factors:
- The method or procedure by which the mould is separated from the pattern (demolding principle)
- Concept of propulsion (manual, pneumatic, hydraulic operation of the moulding machine)
- The number of workstations that are employed to complete the necessary work procedures and stages for mould manufacture.
- The number of moulding machines that are used in a moulding facility (simplex, duplex machine)
- Method of moulding (boxless or box moulding machine)
- Molding material is compacted using a specific method.
- Number of compaction stages (one- or two-stage)
- The type of connection formed between the moulding machine and the pattern device; the vast majority of machines are equipped with a rigid connection, which means that a single machine is only meant for the manufacture of a single box size.
- Design of the mould parting (machines with horizontal or vertical mould parting planes for boxless molds)
Various molding methods are:
- Bench molding
- Floor Molding
- Pit molding
- Machine molding
Molding is done on a bench of desirable level. On benches, small and light moulds are being prepared. In order to form the mould, the moulder must stand. Bench moulding may be used to create moulds for both green and dry sand. Bench moulds are used to create moulds for both ferrous and non ferrous castings. Both the cope and the drag are squeezed into the back of the bench.
When the mould size is large and the moulding cannot be completed on a bench, the work is performed on the foundry floor. The process of floor moulding is used to create medium and large-sized castings. The mold’s drag section is located in the floor, and the cope piece may be shoved into a flask and inverted on the drag portion of the mould. Floor moulding may be used to create moulds for both green and dry sand.
Pit moulding is used for very large castings that cannot be formed in flasks and must be moulded in pits excavated on the floor instead. Pit moulding is capable of handling and casting very huge tasks with ease. The drag component of the mould in pit moulding is much larger than the drag part in floor moulding. When pit moulding, the moulder has the option of entering the drag and preparing it. A pit is a rectangle or square-shaped depression in the ground.
Both the sides and the bottom of the drag are lined with brick, and the drag is finished with moulding sand. The cope, which is a separate flask, is shoved over the pit while the pattern is in place. The cope is used to construct gates, a runner, a pouring basin, a sprue, and other features. After the mould has dried, it is put together. Lifting and situating the cope above drag may be accomplished with the use of a crane. The cope may be secured in place using a clamp. The mould has been prepared for pouring.
Machine moulding differs from bench, floor, and pit moulding in that the various moulding operations are carried out by the molder’s hands, whereas in machine moulding, various moulding operations such as sand ramming, rolling the mould over, withdrawing the pattern, and so on are carried out by machines. These activities are carried out considerably more quickly, more efficiently, and in a much better manner by the machines.
Molding machines are capable of producing castings that are similar and consistent. Molding machines make castings that are higher in quality and less expensive than by hand. Molding machines are chosen for large-scale production of castings, while manual moulding (bench, pit, and floor) is utilised for small-scale production or prototypes. Machine moulding is not a totally automated process; although many activities may be handled by machines, certain others must be completed by hand in order for the process to be considered complete.
Types of Moulding machine:
1. Hand Operated molding machine
- Pattern draw type
- Pattern draw and Squeeze type
- Pin Lift type machine
- Roll Over type machine
2. Power operated Molding Machine
- Squeeze machine
- Jolt machine
- Jolt squeeze machine
- Jolt squeeze roll over pattern draw machine
- Sand Slinger
A squeeze machine is very useful for shallow patterns. A squeezer (squeeze head) plate or presser board slides inside the flask to compress the sand above and around the pattern.
For squeezing action the squeeze piston may by forced upward, pushing the flask up against the squeezer or presser board the presser board being forced into the flask.
The sand is rammed harder at the back of the mould and softer on the pattern face. In other words sand has greatest density at the surface where pressure is applied to sand and sand density decreases progressively towards the pattern.
Moulding force (Mf) = P (π. d2/4)-W
Where, P – Pressure in squeeze cylinder
d – Piston diameter
W – Weight of flask pattern and sand
This machine is fitted with adjustable flask lifting pins, which allows it to accommodate flasks of varying sizes within the machine’s capacity. This machine table is put on top of the flask, which is raised a brief distance by the machine table during operation, and then allowed to fall freely under the influence of gravity once it is raised.
The sand is compacted uniformly around the pattern as a result of this quick motion. It is most dense around the pattern and around the separating line, where the sand is most compact. As you go farther away from the pattern, the density continues to decrease. In addition, since the moulding sand is tightly packed around the pattern, the mould is very sturdy and there is very little chance of swells, scabs, or run-outs occurring.
The sand ramming function is just one of the many duties that every moulding machine is required to carry out. Following the ramming of one portion of the full mould, the first section is rolled over so that the second half may be created as well, and the pattern from the first part is scraped away. An air or electrically controlled vibrator connected to the pattern plate is often used to rap the design into the sand, while it is possible to remove the pattern by hand.
Jolt Squeeze Moulding Machine
In addition to being a full buffer, high frequency, low amplitude pneumatic micro-vibration compaction moulding machine, the Jolt Squeeze moulding machine also has the following features: The effect of shock on the foundation may be reduced by using a spring buffer in conjunction with a pneumatic micro-seismic mechanism.
When producing a large number of castings, hand moulding requires more time and work. The precision and consistency of the castings produced by hand moulding also varies. In order to solve this challenge, jolt squeeze moulding machines are used in the moulding process. Using a Jolt Squeeze moulding machine for clay sand casting manufacturing is a cost-effective alternative for both manual and simple automation production. The jolt squeeze moulding machine does not need a large amount of floor space. Additionally, it is adaptable to expand the number of moulding machines as casting output increases.
It is a combination of the operational principles of both jolt and squeeze moulding machines, resulting in the consistent ramming of sand in all areas of the moulds.
Sand is compressed in this machine by the use of compressed air or other appropriate force, which is delivered via a piston-table arrangement, which squeezes the sand against a platen, in order to increase its density.
It combines in single machine the operating principles of the jolt and squeeze machines. Combination of jolting and squeezing produces beneficial compaction effects on sand density and thus a more uniform hardness throughout the mould is attained. A jolt-squeeze machine makes use of match plate moulding.
Sand Slinger Machine:
The moulding sand is propelled into the flask by an impeller mechanism in this machine, which forces the sand to pack into the flask due to the force of gravity. This approach produces the most homogeneous sand density across all of the layers, making it the most suitable method for any sort of mould.
It is possible to alter the density by varying the impeller’s rotational speed, which typically ranges between 1200 and 1800 revolutions per minute (RPM). It is, on the other hand, best suited to jobs ranging in size from medium to extremely big. In general, the machine is offered in a variety of sizes, with the sand flowing at a speed of around 3000 m/min. The moulding sand should be blended with appropriate binders and other additives so that it can flow easily into position and harden once it has been placed.
The sand slinger consists of a base, a sand bin, a bucket elevator, a swinging or movable arm, a belt conveyor and the sand impeller. Prepared sand lying in the sand bin is picked up by the elevator buckets and is dropped on to the belt conveyor which takes the same to the impeller head.
Inside the impeller head, rapidly rotating cup shaped blade picks up the sand and throws it downward into the moulding box as a continuous stream of sand with machine gun rapidity and great force.
The sand is discharged into the moulding box at a rate of 300 to 2000 kg/minute. This force is great enough to ram the mould satisfactorily.
In moulding boxes, sand is filled and rammed at the same time. The density of sand which is the result of sand’s inertia is uniform throughout the mould
Step by Step Process of creating Sand Casting Machine Moulding
Numerous other types of moulding machines are described in detail, with the schematic drawings of each machine being self-explanatory.
- In a ramming machine, the ramming is better at the sand platen interface, where pressure is exerted, rather than near the pattern, but in a Jolt machine, the ramming is best close to the pattern. So the greatest results are obtained when the operations of jolting and squeezing are combined. Both operations may be performed in a single machine, which is termed the “Jolt and squeeze moulding machine.” If the depth of the mould is not too deep, it is possible to create both portions of the mould at the same time by pure squeezing. Its use is often restricted to rather superficial tasks. It makes use of a match plate pattern, which is located between the cope and the drag box.
- The whole assembly is put on a table with the drag box in the middle of the table.
- The table is controlled by two pistons in air cylinders, one of which is contained inside the other. While one piston, referred to as the ‘Jolt piston,’ continually rises and lowers the table for a specified number of times, another piston, referred to as the ‘squeeze piston,’ pushes the table higher in order to press the sand in the flask against the squeeze plate. When the machine is in operation, sand is loaded into the drag box and the drag box is shocked repeatedly by running the jolt piston.
- After being jolted, the whole mould assembly is turned over by hand to the other side.
- The cope is filled with sand, and the mould assembly is lifted against the squeeze plate by running the squeeze piston. This action results in the sand in the mould box being evenly packed at the conclusion of the process.
- The match plate has been vibrated and is currently being removed. The mould has been completed and is ready to be filled with material.
- The sand flask serves as a support for the mould. Two-piece moulds are made up of a cope on top and a drag on the bottom; the seam that separates them serves as the parting line for the mould. If a sand mould has more than two components, the extra pieces are referred to as cheeks.
- In a pouring basin or a pouring cup, molten metal is poured; in a sprue, molten metal is forced downward through a hole.
the route that transports the molten metal between sprue and mould cavity is known as a “runner.”
- The inlets into the mould cavity are referred to as gates.
- Riser: This component is responsible for supplying more molten metal to the casting when it shrinks during the solidification process.
- In order to make hollow sections or otherwise define the inner surface of a casting, cores and vents are put in the mould to remove the gases produced when the molten metal comes into contact with the sand in the mould and core, respectively.
Advantages of Moulding Machines:
- When the number of castings is substantial, the additional cost of metallic patterns and other equipment is compensated by the high rate of production, and the overall cost per piece works out lower than in the case of hand moulding.
- It affords great saving in time, especially when a large number of similar castings in small sizes are required.
- A semi-skilled worker can do the machine job whereas hand moulding requires skilled craftsmanship.
- The castings obtained are more uniform in size and shape and more accurate than those obtained by hand moulding due to steadier lift of the pattern.
- Easy to operate and requires low maintenance
- More consistent mould will be produced
- Ability to increase the squeeze force generated upto 50 % more than conventional type moulding machine
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