Molds with hot runner or valve gate systems will simplify end-of-arm-tooling (EOAT) design and reduce cost by eliminating runner grippers or vacuum cups and allow for faster part removal. If a mold must have a cold runner,
try to sub-gate the parts from the runner and have round pads for vacuum removal, this will eliminate the need for a post mold degating device and save cycle time for other operations. Vacuum runner removal is faster, lighter and less expensive when compared to pneumatic grippers.
When the mold cannot have sub-gated parts a degating station will be needed. A degating station can be as simple as a pneumatic nipper mounted on the robot traverse beam to a sophisticated floor-mounted station with guillotine style shears to cut long fan gates. A simple degating station with two to four nippers can cost as little as $5,000 to $7,000.
Try to keep the gates accessible when designing for scissor-like cutters. Do not have curls in the runner or have runner branches close to the part obstructing the nipper blades.
Often referred to as runnerless molding or hot-manifold systems, hot runner molds describe a set of temperature control heating-devices installed in the mold. 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.
Hot runner molding systems consist of two plates heated by a manifold system inside one-half of the mold that sends the melted material to nozzles, which feed the part cavities. The system consists of two parts: the hot manifold and the drops. The manifold moves the rubber on a single plane and parallel to the parting line to a location above the cavity. Positioned perpendicular to the manifold, the drops move the rubber from the manifold to the component.
Cold runner injection molding systems consist of two or three plates contained within the mold. The system injects the plastic into the mold through the sprue and feeds the runners, which lead to the parts in the mold cavity. The simplest type of cold runner system consists of two plate molds, which has a parting line that separates the two plates. This system has the runner and part attached. You can only gate the part of its perimeter. An ejection system separates both the runner and part from the mold.
Three-plate cold runner systems consist of three plates. There are two parting planes that allow the mold to separate into three sections upon ejection of the part. The runner connects to a separate plate and only the part requires ejection. Three plate molds allow for greater design flexibility and allow flexibility for gate installation based on the requirements of the application. Both types of plates require the runner to be recycled and reground (or disposed of) to reduce waste, which adds to the cycle time.
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this is a good article
the cost of hot runner and cold runner is also different
how to choose, it depends on your mold cost
thank you for sharing an article like this, it is very helpful for many primary mold engineers
actually they are really quite different
after reading this blog, I got it, thanks! however, hot runner system has been very popular
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now hot runner and cold runner system are often used in our mold industry, your introduction is very good!
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