What is insulated runner mold?
Insulated runners are oversized passages formed in the mold plate. As shown in the following diagram, the oversized passages allow an open, molten flow path to be maintained because of the insulating effect of the plastic that freezes on the runner wall, combined with the heat applied to the system with each shot.
What are the key factors while selecting hot runner system for Mould?
When selecting a hot runner supplier a mouldmaker must consider three qualities: (1) analysis capabilities, (2) design input and (3) product range. During the infant stages of a new mould build it is critical that your hot runner designer can provide input and feedback on the part design and layout of the mould.
Why Mould cooling is required?
Injection Mould Cooling serves to dissipate the heat of the molding quickly and uniformly, fast cooling is necessary to obtain economical production and uniform cooling is required for product quality. Adequate mold temperature control is essential for consistent molding.
What is the benefit of a hot runner distribution system in plastic injection molding?
The purpose of a hot runner injection system is to maintain a molten flow of plastics or rubber from the injection molding machine nozzle to the gate in a plastic injection mold — keeping the runner above the melting point of the plastic.
What is the purpose of a hot runner system?
A hot runner system delivers liquid plastic to a number of mold cavities in order to create a plastic product. It is an injection molding assembly that uses a heated manifold to keep plastic in a molten state.
What is the ideal profile of a sprue?
Although the above equation indicates that the ideal sprue should have a parabolic taper, straight sided taper has been found to suffice in practice as shown in Figure (1-57). In addition to its shape, the height of the sprue also effects its filling.
What is the purpose of a runner on a mold?
A runner is a channel cut into the mold that allows plastic material to flow from the nozzle to the cavity. A change in pressure is expected whenever the viscosity changes or the flow channel thickness (or diameter) changes. Pressure will increase when you have a reduced thickness.
What is sprue runner and gate for?
It is small and designed to freeze before the part, runner, or sprue freeze. This keeps the cavity packed to avoid sink marks (recessed surfaces) during cooling. Excessive pressure on gate freezing causes sticking in the mold.
What is a sprue mark?
A sprue is the place where the metal is poured into a casting. The resulting column of metal ‘feeds’ the casting as the body begins to cool and shrink. The gate is the area where the metal enters the item that is being cast. What is called a sprue mark is round – the sprue was directly above the item being cast.
Why sprue design is made tapered instead of straight?
Explanation: Pressure balance is maintained, to avoid the negative pressure (to ensure positive pressure anywhere in the liquid column), the sprue should be tapered. The ideal shape of the sprue is parabola but to reduce the manufacturing difficulty shape of the sprue is considered as tapered cylinder.
Which pattern is used to produce a number of casting?
Explanation: Match plate pattern are usually used for manufacturing small castings on a big scale. Hence, piston rings of the engine are made using this pattern.
What is the general shape of an open riser?
cylindrical
What is the shape of the sprue Mcq?
9. What is the shape of the sprue? Explanation: The sprue is essentially tapered, giving it a trapezoidal look.
Why is sprue made in taper shape?
Sprue – a hole where the metal enters the mold. It is ideally tapered to prevent air from entering the casting. Because the riser is larger, it will cool slower and feed liquid metal to the shrinking casting, thus preventing a number of defects. Gate – the place or places where the metal enters the casting.
Which method is used for non symmetrical castings?
Centrifuging
What are all the disadvantages of shell mold casting?
The followings are the disadvantages of this process.
- High production costs and casting prices. The phenolic resin sand is more expensive than green sand and furan resin sand, and it could not be recyclable.
- High pattern costs.
- Size and weight limitation.
Which of the following will have better plasticity?
Which of the following will have better plasticity? Explanation: Plasticity is the ability of sand particles to undergo unrecoverable deformation at constant volume without cracking and crumbling. Fine grained sand particles will have better plasticity.
Which one of the following is a negative allowance?
4. Which one of the following is a negative allowance? Explanation: All metals shrink when cooling except perhaps bismuth. This is because of the inter-atomic vibrations which are amplified by an increase in temeprature.
What is negative allowance?
There are no standard values for this allowance, as it is heavily dependent on the personnel. This allowance is a negative allowance, and a common way of going around this allowance is to increase the draft allowance. Shaking of the pattern causes an enlargement of the mould cavity and results in a bigger casting.
Which of the following is pattern allowance?
The following allowances are commonly provided on a pattern: 1. Draft Allowances 2. Shrinkage Allowance 3. Machining Allowance 4.
Which of the following is not a pattern allowance?
Which of the following is ‘not’ an allowance given to the pattern for casting? Explanation: A hole is made during the machining or finishing of the casting and is not a type of allowance given to the pattern.
Which of the following pattern is cheapest?
Right Answer is: D Skeleton pattern uses the least amount of material for the operations on pattern and therefore, it does not need a lot of investment on its materials, making it inexpensive.