Stack Mould: the mould is primary used for mass production of null and shallow types. In this type of moulding more than one cavity is locked and filled at time. A multi level injection mould in which two sets of cavities are filled simultaneously. The stack mould reduces the clamping force required by multi-cavities mould. Typically multiple cavities are oriented on a single parting line and the requirement clamping force is the sum of the clamp needed by each cavities, die on two or more stacked parting line. The injection force exited on the plate rerating parting lines, so the resulting clamp force is the same as for just one part line.
Stack mould provided more parts fn cycle then would otherwise be possible in a given size moulding process. The stacked injection mould is just what the name implies. A multiple two plate mould is placed one on top of the other.
This construction can be used with three plate moulds and hot runner mould. A stacked two plate mould construction doubles the output from a single process and reduces the clamping pressure required to one half as compared to a mould of the same number of cavities in a two-plate mould. This method is sometimes called “two-level moulding”.
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Stack Molds are a series of molding faces “stacked” together to create multiple faces or levels for molding. Each level or face is a parting line and produces molded product. The benefit of stack molding is to increase the output of a given molding machine and operation.
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The defining characteristic of a stack mold are the two (or more) mold parting surfaces or mold split lines. A stack mold does not require much more clamp force than a single face mold because the projected part surface areas of the cavities on both sides of the center block cancel out each others force. A rule of thumb for a clamp force estimate is to take the projected part surface area times the melt pressure and multiply it by a factor of 1.1.
Gate-to-Gate Melt Transfer
Increasingly more popular is the melt transfer through the first mold parting surface without a sprue bar because it eliminates the sprue bar as an obstacle. The basic principle of a “sprue-bar-less” melt transfer is a nozzle-to-nozzle melt transfer.
As the mold parting surfaces close, two nozzle front ends establish a melt passage. These nozzles separate when the mold opens. A leak free connection or seal at 2000 bar or 30,000 psi is accomplished with the specially designed manifold system for stack molds from Mold Hotrunner Solutions. During mold opening, the transfer nozzles provide a dry surface with absolutely no stringing or drooling of the melt.
A fully automated 24/7 molding operation with stack molds requires a functional melt transfer which operates over millions of cycles.
Sequentially controlled stack mold valve gate manifold with a four nozzle valve gate to valve gate melt transfer through the mold parting line featuring cooling free Black Box™ actuators.
Generally, flat parts are more suitable for stack mold consideration than are deep core parts because of the machine opening stroke and the increased mold height of a stack mold. It is also important to check the shot capacity of the machine barrel ensuring that the injection unit can supply enough melt volume cycle for cycle and for all cavities.
MHS stack molds using Rheo-Pro® hot runner systems have a long track record for application success in thin wall packaging, caps and closures, containers and lids, collapsible crates, trays, panels, grills and large surface parts for appliances.
Tandem Molding: Tandem molding is a type of stack molding process in which the parts are injected in alternating cycles. While the molding machine opens to demold one parting line, the other is held together by a locking system. The technology can be employed in almost any standard injection molding machine and offers all of the benefits of stack molding as well as extended cooling times.
Cycle 1 Cycle 2
Part A Cooling Part A Filling
Part B Filling Part B Cooling
Compact Valve Gate Stack Molds
The Rheo-Pro is an internal actuated valve gate system with no external cyclinder and no elastomeric seals. It requires no cooling. iVG™ represents the latest and most innovative valve gate technology in the industry and is ideal for compact, reliable stack mold solutions.
The Rheo-Pro is an internal actuated valve gate system with no external cyclinder and no elastomeric seals. It requires no cooling. iVG™ represents the latest and most innovative valve gate technology in the industry and is ideal for compact, reliable stack mold solutions.
Black Box™ and iVG™ hot runners represent a new generation of valve gate systems that does not require maintenance during the life of the mold. These systems eliminate all quality issues related to cooling water such as corrosion and contamination. Less plumbing also simplifies the design and assembly of the mold. New cooling-free technology can benefit all valve gate applications, including high temperature plastics such as PEEK, LCP, PSU, PEI, and PPS, known for their special properties. Processing these materials requires high melt temperatures of up to 450°C in the hot runner and mold temperatures of over 200°C. Black Box™ and iVG™ hot runner systems deliver uninterrupted performance under extreme conditions without cooling or wear. The result is a significant increase in reliability and mold uptime.
Internal Valve Gate
Clean, Compact and Durable: Its world's first and only internal valve gate nozzle. It is the only pneumatic valve gate hot runner that operates entirely without elastomeric seals, lubricants, or cylinder cooling. Unlike electric actuators, the valve can operate at extreme temperatures of up to 400°C (750°F). Its patented design completely rewrites the rules of valve gating technology and creates endless new possibilities, from high cavitation to single drop hot runner systems.

The versatile range of iVG™ nozzles opens up new possibilities for cost effective production with all stack mold and tandem mold applications. In addition to back-to-back valve gating, the new technology can also be used inside a stack mold as a simple and reliable way to transfer melt from the stationary mold to the first parting line. The larger iVG30 nozzle can be extended and comes with melt bore diameters up to 20 mm. This is an easy and effective way to double production of large and heavy weight parts.
Stack Molds for All Part Sizes
The versatile range of nozzles opens up new possibilities for cost effective production with all stack mold and tandem mold applications. In addition to back-to-back valve gating, the new technology can also be used inside a stack mold as a simple and reliable way to transfer melt from the stationary mold to the first parting line. The larger iVG30 nozzle can be extended and comes with melt bore diameters up to 20 mm. This is an easy and effective way to double production of large and heavy weight parts.
Advantages
1. Doubled Part Output: Instead of increasing the mold size by adding more cavities, a stack mold maintains mold size and machine size by adding a second layer of cavities parallel to the first layer. The fill, pack and cooling time remain the same for a stack mold and only the mold open and mold close time will add slightly to the cycle time.
2. Reduced Part Price: The part price is determined by the machine hour rate, which is directly related to the machine clamp tonnage. A stack mold requires only about half the clamp tonnage than a single-face mold with the same number of cavities.
3. Efficiency and Improved Automation: Stack molds can produce multi-component assemblies in one shot and in one machine using the same parameters. By comparison, single-face molds would require the production synchronization between multiple machines, complicating post-molding operations.
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