VECTORFORM LIFTER SYSTEMS Dual Rod Design Benefits
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How to Incorporate Dual-Rod Technology As shown in Fig. 1 , an ejector housing cross-section must be designed with the desired plate thickness and necessary ejector stroke. By increasing the lifter core angle, mold designers can achieve faster part ejection and a larger undercut feature.
A guide plate is used to retain the second guide rod, as well as align the lifter core rod. Sufficient space around the lifter core rod is needed when placing and sizing the guide plate. Starting from the retaining feature for the guide rod in the guide plate (in this case, a dowel), a line parallel to the centerline of the lifter core rod should be drawn into place. Ideally, standard components for these lifter systems will be developed ensuring all guide rods feature a round design, as opposed to one with a rectangular cross-section. A sliding assembly, such as a block base, may be used to reciprocate along the plane of the ejector plate assembly as the machine’s ejector rod moves though the extent of the ejector stroke. Both the primary lifter core rod and the second guide rod are aligned and retained by the sliding base within the ejector plate assembly. Since the second guide rod must not move, it is retained further down in the base of the ejector box assembly, as seen in Fig. 1 . To retain the second guide rod, use a pivoting guide bushing, held in with a pin to the sliding plate. Since the loads acting on the pin are minimal, the pin can be small. Next, the lifter core must be physically connected to the sliding plate. A mold designer has several options, each with different benefits. If the anticipated loads acting axially on the lifter core will be excessive (the weight of the lifter core itself may even qualify as excessive), then making a tapered surface cut into the sliding plate will enable sufficient backup and support behind the lifter core rod.
By increasing the lifter core angle, mold designers can achieve faster part ejection and a larger undercut feature. If the expected axial load in the lifter core rod is moderate to low, then a pin or similar device is sufficient to retain the lifter core rod. Mold designers should note, however, that the strength of the assembly will be that of the weakest link; in this case, the joint pins retaining the lifter core rod. Make sure the joint pin and the overall lifter are sized accordingly. In the final stages of lifter system design, the mold designer adds clearances for the slot used to retain the sliding plate, as well as clearances for the guide and lifter core rods. Use of a guide plate, slide plate and base-mounted retainer bushing eliminates the need of machining tightly toleranced, angled holes into the mold plates themselves. By using a pivoting guide bushing with sufficient close-fit tolerance to the guide rod, in combination with a loose-fit installation on the base-mounted retainer bushing, the guide rod and sliding base assembly will effectively self-align. When the assembly technician is satisfied that the ejector plate assembly and lifter core system all move freely, the base-mounted retainer bushing can finally be bolted in place, providing the necessary guide rod retention for normal use. Another benefit to the sliding base design is the rigid backup to the lifter core rod, which allows the use of lifter core cooling
DME HYDRAULIC UNSCREWING DEVICES STANDARDIZED SYSTEMS FOR MOLDING INTERNAL THREADS.
(provided the lifter core rod and overall assembly is large enough to accommodate the diametrical size of the intended waterlines, seals and fittings without affecting the lifter rod rigidity required to move the intended lifter core mass). Refer to Fig. 3 for more detail regarding the addition of cooling to the lifter core assembly. The use of a guide rod to guide the slide base in the moving ejector plate assembly reduces stress on the lifter rod and allows for use of a smaller lifter core assembly. This also means that multiple lifter rods and the attached cores can be ganged together, and are actuated by either more or less slide base and guide rod assemblies, depending on the needs of the application. The level of flexibility and functionality offered by this approach can lead to increased competitive advantage Through incorporating a second guide rod in lifter core assemblies, mold designers can reduce reactionary forces in the mold and enable smaller assemblies. Without the conventional drawback of increased friction and loading due to bending moments, the dual-rod design allows deeper undercuts using steeper lifter core angles – leading to increased cost savings. The ease of design and assembly make it simple to add lifter cores to molding applications, as well as increase the molder’s capabilities when a small mold footprint is critical. for both the moldmaker and end user. Many Advantages to Dual-Rod Design
Hydraulic Unscrewing Device Components...80-83. Calculations/Specifications .....................84-86 Applications..............................................87-88 Table of Contents
Fig. 3 Example of lifter core assemblies with internal cooling features. This example also shows how two slide base assemblies may be “ganged” together to actuate and support a single large lifter core.
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