What is switch over point in injection molding?
Solution: The V/P switch-over indicates the point – usually a percentage of the total volume – where the injection molding machine (IMM) will change the filling process from a velocity driven (fill) to a pressure driven control (pack).
What is hold on pressure?
Holding pressure can be defined as pressure against the cooling plastic in the cavity image while that plastic solidifies.It is used for the final 5% filling of the cavity image. This will helps to ensure a dense part, molded with uniform pressure and controlled shrinkage.
What is back pressure in injection molding?
Back Pressure in an injection molding process is often defined as “the resistance of the screw to recover as the metering section pumps molten plastic through the non-return valve to the front of the screw.” To remedy this, the screw is decompressed or sucked back just far enough to relieve this pressure.
How do you set holding pressure in injection molding?
During injection molding, the hold pressure, or pack pressure, is used to finish the filling of the mold and pack the part. The rule of thumb is that the hold pressure is 50%–70% of injection pressure.
What is VP switch?
Dec 11, 2018. After approximately 95-98% of part filling the switch between filling and packing phase is made. This point is called VP-Switch (red arrow). It is the change from the flowrate controlled filling to the pressure controlled packing phase.
What are the stages of injection Moulding?
There are four stages in the cycle. These stages are the clamping, injection, cooling and ejection stages.
What is pack and hold in injection molding?
Hold time comes during the second stage of a Decoupled-II process, which occurs after the first stage fills the cavity 95-98% full. During the second stage, the hold pressure is used to completely fill the cavity and pack out any important complex detail or texture.
What is clamp pressure?
Clamping Pressure. A clamp is a device that secures objects to prevent their movement or separation by the application of inward force. Clamping Pressure can be defined as this force divided by the surface area being constrained by the clamp.
What is packing in injection molding?
In the injection molding process, the melted polycarbonate is injected into a mold cavity of the desired shape and then cooled down under a high packing pressure. This process forces the polycarbonate to undergo a complex deformation and thermal history that affects the final properties of the product.
What is shot capacity in injection molding?
Shot Capacity is the maximum volume/weight of material that the screw can inject into one operation cycle. The shot capacity is also known as “Injection Capacity”. The shot weight of a product is the amount of material required to be injected into the mold to manufacture the product, including the feed system.
What is a high injection pressure?
A high pressure injection injury is an injury caused by high-pressure injection of oil, grease, diesel fuel, gasoline, solvents, water, or even air, into the body. But even with pure water or air, these injuries cause compartment syndrome which leads to cell death if surgical intervention is delayed.
What is VP pressure?
velocity pressure (VP) Pressure that is created when air moves in one direction. Velocity pressure is measured in inches of water (Pa). One inch water gauge corresponds to 4005 fpm (standard air) velocity.