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Foundations of Engineering and Environmental Assessment
Designing and engineering rubber molded parts requires a high degree of specialist knowledge in both materials and mechanics. In demanding industrial situations, these parts are the first line of defense of the machinery and failures on these components can lead to system breakdowns. Designing an effective part is only possible with an in-depth knowledge of the environment in which the part operates because temperature changes and physical stress will dictate the design of the part. Precision is most important during development of the concept, so that the engineer is able to design rubber molded parts that are able to withstand the industrial environment without taking a toll on the physical properties of the part.
Selecting materials and ensuring chemical compatibility
Selecting materials is the most important part of designing rubber molded parts regardless of the application. For industrial applications, materials selection is based on the chemical compatibility and other physical properties, such as use of Shore A hardness and tensile strength. A prime example is that NBR is commonly used in hydraulic applications because of its high oil resistance. EPDM is the better choice for outdoor applications because of its high weathering and heat resistance. During the design stage, the technical data are available that detail the compression set and elongation at break, and applying these data during design to the described function of the product. This is to ensure that the molded parts can withstand some requirements so that the end user will not experience downtime. It is wasteful to select rubber that will disintegrate when exposed to reagents or external pressures.
Geometric Optimization and Manufacturability
Optimizing the geometry of components made of rubber during the molding processes is equally significant to the part’s functionality and it’s ease of manufacture. Examples of this phenomena are seen when designers focus on "functional geometry" to determine draft angles, approximated to be between 1 and 3 degrees, to ease the removal of the part from the mold and the wall thickness of the geometry to avoid the formation of voids when the rubber is cured. Mold flow analysis has been useful to predict rubber behavior upon tooling closure. This allows designers to determine where to place vents and parting lines. Addressing these design issues early on allows for the reduction of waste and guarantees compliance to the appropriate tolerances needed for assembly of components in heavy machinery.
Tooling Precision and Molding Techniques
The technique of molding, either by injection molding or compression molding, is a key concern when it comes to the final quality of a rubber part. Compression molding is more useful for the manufacture of larger, thick wall, lower production volume components whereby elastomeric feedstock is introduced in preform state to a heated mold. On the other hand, injection molding provides the fastest cycle times and volume sales of components that demand complex geometries. The tooling steel used is essential for rubber molding as it is the primary determinant of the quality of the surface finish and uniformity of the density of the rubber. The interplay between design of the components and the quality of the tooling is what defines the success of rubber components in power generation and chemical processing.
Quality Assurance and Standardized Testing
The climax of the design cycle for rubber molded parts is the implementation of quality control and performance testing to worldwide standards such as ASTM or ISO. Each batch undergoes dimensional testing and tests of physical properties, including oil immersion and accelerated aging to prototype real industrial use. Documenting proof of these tests, such as meeting tolerance of +/- 0.05 mm, is the trust-building block for B2B partnerships. Testing as part of the design integration process will guarantee that rubber molded parts manufactured meet the specific requirements of the customers. This serves the industry with a reliable product that utilizes rubber molded parts to the fullest.
