SPE Antec Papers
Mold Filling Imbalances in Geometrically Balanced Runner Systems
By: John P. Beaumont, Jack H. Young
Most multi-cavity injection molds are designed with “naturally balanced” (geo-metrically balanced) runner systems in order to minimize variations between cav-ities during production. However, even when naturally balanced runners are used, fill and part variations are sometimes observed. These flow imbalances have his-torically been attributed to variations in mold temperature and/or mold deflection. This paper presents the results of a series of experimental tests and finite element mold filling analyses that demonstrate that these imbalances result from non-symmetrical shear distribution within the melt as it travels through the runner system. These imbalances are independent of mold temperature variations or mold deflections. These variations exist in “naturally balanced H” and modified “H” patterned runner layouts feeding eight or more cavities. Flow rate variations be-tween the inner and outer cavities of the geometrically balanced injection mold can be as high as 94% in extreme cases.
Solving Mold Filling Imbalances in Multi-Cavity Injection Molds
By: John P. Beaumont, Jack H. Young, Matthew J. Jaworski
It has previously been reported that significant flow and thermal imbalances are developed in the naturally, or geometrically, balanced runner systems typically used in injection molding (1). These imbalances can mean that as much as 95% of the melt can flow to inner cavities in an eight cavity naturally balanced runner system. This paper presents a solution to these flow imbalances through a means of flipping and rotating the melt in the runner. The use of the melt flipping technique developed in the study creates a thermal, flow and material property balance to all cavities, thereby improving product quality and productivity. This paper also expands on previously reported findings to include imbalance test results on additional plastic materials. A study has been conducted to determine which material characteristics contribute to the imbalances and variations for runner and mold layouts that are susceptible to the impact of these flow imbalances.
Troubleshooting Cavity to Cavity Variations in Multi-Cavity Injection Molds
By: John P. Beaumont, John Ralston, Adam Shuttleworth, Matthew Carnovale
Significant differences are commonly seen between parts molded in multi-cavity injection molds. The elimination of these variations is complicated by the large number of variables existing within the mold, the injection molding process, and the material. This paper presents a means of isolating and quantifying the primary causes of these variations. By isolating the causes, the molder can more effectively and efficiently address the differences between parts molded in different cavities and thereby maximize productivity.
Controlling Balanced Molding through New Hot Runner Manifold Designs
By: John P. Beaumont, Kevin Boell
Shear induced variations created during flow results in variations between parts produced in many of today’s conventional geometrically balanced hot manifold designs. Understanding of these shear imbalances has led to new design strategies which address these variations and provide both uniform filling and uniform material conditions to each cavity.
Revolutionizing Runner Designs in Hot & Cold Runner Molds
By: John P. Beaumont
A next generation runner design is proving to yield unprecedented consistency in multi-cavity molds as well as providing new process aids which can control distribution of melt conditions in a cavity. This paper explains how variations in melt conditions are created in cold and hot runner molds and how they impact Cpk, productivity and molded product characteristics. These variations are rarely understood or appreciated, yet are possibly the most significant influencing factors in the successful production of injection molded products today. A next generation runner is revealed which provides the performance of a small cavitation mold, improves product consistency, and increases productivity and process control of injection molding to a new level.
Thermoset Filling Imbalances in Geometrically Balanced Runner Systems
By: David A. Hoffman & John P. Beaumont Beaumont Runner Technologies, Inc. Penn State University, Erie
Shear induced variations created within runner systems dramatically affect the filling of the industry standard geometrically balanced runner systems. These variations not only cause imbalances in cavity filling, but may also impact the polymer curing properties and the mechanical properties of the molded product. This paper reveals the severity of the imbalance within thermosetting materials, its potential effect on the molded product, and a new technique used to solve the imbalances.
Artificially Balancing Of Geometrically Balance Runner Systems
By: Brian Young, John Beaumont, Kevin Boell
A commonly used practice of dealing with filling imbalances in injection molding is to artificially balance melt delivery systems. This artificial balance is attempted through tweaking runner and gate sizes or varying hot runner temperatures. These approaches at best only provide an extremely delicate pressure balance rather than address the root cause of the problem. This paper presents the results of a study that examined the robustness of artificial balancing and compares it to new advancements that address the root cause.
Numerical Simulation of a Multiple Valve Flow Control System During Injection Molding Processes
By: Gregory S. Layser, John P. Coulter, Alexander I. Beaumont
Process control is an important factor for improving the performance and consistency of thermoplastic parts manufactured by injection molding processes. A critical process parameter for manufacturing of high quality plastic parts is cavity pressure. This paper presents a continuation of a numerical based study of flow control utilized during multi-cavity injection molding processes. The capabilities of the current system design are limited by multiple valve interactions. Obviously, the valves are coupled with one injection source. Valve interaction may produce undesirable effects on pressure distribution in multiple cavities and should be studied further. With much attention addressed to multi-cavity family molding, the extension to multiple valve systems of 4, 6, and 8 would be beneficial and an interesting study. Understanding the flow modeling details through a single valve system is essential, thereby reducing the computational work involved with a multiple valve system.
Controlling Intra-Cavity Melt Flow and Weld Strengths Throught New Runner Design
By: John P. Beaumont, Christopher Stewart, Mark Ezzo
The development of high sheared laminates are shown to have a significant effect on filling pattern. New methods are shown to manage these hotter high sheared laminates to control filling pattern and position them so as to increase weld line strength. Significant shear and thermal variations are developed in a polymer melt as it flows through a runner. These melt variations have been shown to regularly result in mold filling imbalances in multi-cavity molds of more than 30%. This study shows how these same melt variations are a major factor even in parts formed in single cavity molds. These melt variations regularly create unanticipated filling patterns and affect the physical attributes of the molded part. The study further evaluates a new process technology which manages these melt variations to strategically manipulate filling patterns and product characteristics without changing gating locations or part design. The study also reveals that the same melt management technology can be used to significantly improved weld line integrity.
The Effect of Primary Runner Length on Fill Imbalance in a Geometrically-Balanced Eight Cavity Polymer Injection Mold
By: Kevin R. Takarada, John P. Coulter, Mason Myers, John P. Beaumont,
This study investigates the effect primary runner length has on fill imbalance characteristics for a geometrically balanced multi-cavity runner system, during a polymer injection molding process. The experimentation utilizes three settings of the primary runner length – long, medium, short – and four injection velocity settings, creating a relationship of fill imbalance to both the primary runner system’s length-to-diameter ratio (L/D) and injection velocity. The experiment’s goal is to provide data that would build on prior studies’ findings on the topic of shear induced flow imbalances in geometrically balanced molds.
Controlling Warpage Through Melt Rotation Technology
By: John Beaumont, Christopher Welsh, Joseph Huegel, Mason Myers
During the injectionmolding process, high shear conditions developed in the runner can create significant material and melt temperature variations across its diameter. As the melt continues into the cavity, laminar flow conditions segregate these melt variations and cause them to be distributed into distinctly different regions within the part. The resultant uncontrolled distribution of thesemelt variationsmay be the root cause of warpage in many plastic parts. It must be understood that thesemelt variations cannot be controlled by the molding machine. However newmethods demonstrated in this paper showthat they can be controlledwithin themelt delivery systemof the mold. This paper presents the results of a study which proves that the segregated melt conditions developed in a runner are a significant contributor to warpage. Additionally the paper presents new methods of controlling the resultant warp through the strategic positioning of these melt conditions within the part.
Investigation of Reversed Shear-Induced Melt Imbalances in Injection Molds
By: Alex Ingram Beaumont, Penn State University, The Behrend College
It has been proven that shear induced melt variations cause both cavity to cavity and intra-cavity filling imbalances. Cavity to cavity imbalances have been shown to result from the shear induced melt variations becoming separated in a runner branch. The high sheared outer laminates will follow the inside corner side of a branching runner and the low sheared material will follow along the opposite side of a branching runner. Unsupported theories suggest that these imbalances are a result of the local shear at the corner itself. This paper presents a study which shows that there is an additional phenomenon that occurs at the corner of a runner which is unrelated to either of the above mentioned theories, and that the effects are opposite. These opposite effects can be significant and are shown to cause filling imbalances of over 20%.
The Effect of Melt Rotation Technology on Particle Distribution during Injection Molding
By: Kory Slye, John Coulter, Burak Bekisli, Tyler Skiba, John Beaumont, John P. Beaumont
The melt rotation technology has been proposed to reduce the distribution variations of filler particles due to shear-induced migration in injection molded parts. The technique had been successfully employed to address the filling imbalances due to shear gradients formed during the polymer flow through runners. An experimental analysis has been carried out this time for a filled polymer. Glass-filled polypropylene has been injection molded using a multi-cavity mold system both with and without melt rotation implementations and parts have been analyzed by microscopic imaging. The preliminary results suggest that application of melt rotation results in more balanced filler concentration levels.
Runner Diameter and Length Effects on Molded-in Stresses of Injection Molded Parts
By: Scott Robert Cleveland, Joseph Philip Latchaw
Molded-in stresses are present in all injection molded parts and can be altered by the melt delivery system of a mold. The length and diameter of runners will have a direct effect on the amount of shear the material is exposed to prior to entering the part cavity and its melt conditions as it flows through the cavity. Various runner diameters and flow lengths are evaluated as to their influence on, and relationship to, the development of residual stresses in a molded part.
Isolating and Quantifying the Development of Shear vs. Pressure Generated Heat in the Plastic Melt During Injection Molding
By: Scott Robert Cleveland, Andrew Jackson, David Magenau
Whether pressure or shearing of a material has a larger effect on its temperature rise through a typical injection molding cycle is a debated subject. Both of these factors may have a theoretical effect, but they have not been quantified. This experiment utilizes temperature and pressure sensing equipment with conventional injection molding to respond to this issue. From the data collected, both shear and pressure heating affects on the melt can be quantified and will be contrasted to that predicted by injection molding simulations.
Artificially Balancing Of Geometrically Balance Runner Systems
By: Brian Young, John Beaumont, Kevin Boell
A commonly used practice of dealing with filling imbalances in injection molding is to artificially balance melt delivery systems. This artificial balance is attempted through tweaking runner and gate sizes or varying hot runner temperatures. These approaches at best only provide an extremely delicate pressure balance rather than address the root cause of the problem. This paper presents the results of a study that examined the robustness of artificial balancing and compares it to new advancements that address the root cause.
The Effect Of Runner Shape On Mold Filling And Product Variation
By: Amanda Neely, Mark Hennebicque
In the plastics industry today it is generally accepted that full round runners provide the most efficient flow channel. However, when full round runners are implemented it is common for misalignment of the two halves of the runner to occur. This paper presents the effects that this misalignment has on mold filling and the resultant product. It is also common, in many instances and for many reasons, for other cross-sectional designs to be used. This paper also examines how subtle variations in runner design dramatically affect filling pressure, resulting in variations in molded parts.
THE EFFECT OF SHARP CORNERS AND RUNNER LENGTH ON MELT FLOW IMBALANCES
By: Raymond W. McKee, Joshua A. Hoover
This study revealed that the use of 90 degree sharp corners has virtually no effect on mold filling imbalance. The study also found that mold fill rates can have a significant impact on the shear induced imbalances found in multi-cavity molds. Further, the study found that increasing the length of the secondary runner will initially decrease the shear induced imbalance developed in the primary runner. Continuing to increase the length has a diminishing effect on the degree the imbalance decreases.
Powder Metal Injection Molding- The Effect Of Runner Design On Material Properties And Filling Imbalances
By: Brian Martonik, Andrew Schenck
Imbalances occur in powder injection molding of multi cavity molds, which are opposite to the shear induced imbalances of conventional plastic materials. In a previous study it was found that melt rotation technology, not only reduced imbalances, but also helped reduce differences between the mechanical properties of parts molded in multi cavity molds. This paper presents the results of a study that expands on a previous work to include effects of fill rate, additional variations in runner geometries, and designs of melt rotation technologies for eliminating the variations.
