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Plastics and Plastic Processing
Published in Leo Alting, Geoffrey Boothroyd, Manufacturing Engineering Processes, 2020
Leo Alting, Geoffrey Boothroyd
It should be mentioned that the properties of the components depend to a high degree on the proper filling of the mold, gates, and runners and on the cooling conditions. Consequently, mold or die design plays an important role in injection molding. Since the mold system is rather expensive, a large number of components must be manufactured to make the process economical.
Sintered Metal Bearings and Fluids for Their Lubrication
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
James Aiello, Leslie R. Rudnick
The molding operation of these parts is a robust production process with good repeatability; by tracking two major characteristics, you can rely on the process to produce millions of conforming parts. The raw material (metal powder) is usually purchased from one of several suppliers as a preblend and is press ready when it is received. In some cases the metal powders are blended in-house for additional economy or sensitivity to proprietary information. It is worth noting that material selections can be endless because of the ability of powder metallurgy to change chemical compositions readily by mixing metal powders together. “You can make cinnamon-raisin bread or white bread,” as one enlightened customer expressed it. The metal powder is very fine; tiny particles that are pressed together in the die cavity of the tool set are subjected to great pressure. The particles form a mechanical bond; the particles are irregularly shaped and this enhances the strength of the compacted particles; at this point the part is known as a “green” compact. Norb Arnold, a longtime PM expert, likes to use an example of “two Christmas trees being jammed together”—a mechanical bond is formed. The particles are joined together with this mechanical bond until sintering bonds them thermally.
Plastic Packaging for Parenteral Drug Delivery
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
Lloyd Waxman, Frances L. DeGrazio, Vinod D. Vilivalam
Use of the blow molding process has grown rapidly over the past three decades. The two types of blow molding in use are extrusion blow molding and injection blow molding. A uniform tube of heated resin with one end closed is formed during the extrusion blow molding process and is moved into a mold where the two ends are pinched off, and the material is blown outward taking on the shape of the mold. The injection blow molding process is similar in concept except that it is a two-step process. A preform is molded using a first-stage mold and the principles of injection molding. The form is then transferred into a second mold and blown outward using pressurized air to form the container. Containers produced for healthcare applications, such as tablet bottles, are made primarily using the injection blow molding process. With small containers, this process is more cost-effective than extrusion blow molding because it is capable of handling a large row of preforms simultaneously. Extrusion blow molding lends itself to larger containers where it becomes more economical and practical to eliminate the preform step. The blow molding process enhances the physical, chemical, and barrier properties of certain materials, for example, PET, because it creates a high level of biaxial orientation of the polymer. Daikyo Crystal Zenith®, Zeonex, and Topas resins are used with blow molding to produce vials.
A study of the mechanical properties of pre-oxidized fiber felt/epoxy resin composite material
Published in The Journal of The Textile Institute, 2018
Chuanbing Ge, Yuanjun Liu, Xiaoming Qian, Xiaoming Zhao
This study used pre-oxidized fiber felt as reinforcement and epoxy resin as matrix for the first time, producing a pre-oxidized fiber felt with good mechanical properties. The molding process used here has several advantages: simple operation, short processing time, good reproducibility, and low cost. The mechanical properties of the pretreated composite materials produced were better than those that were untreated. The tensile and bending properties of the composite materials were best when the dosage of curing agent was 60% of the mass of resin and the curing pressure was 3 MPa. Pre-oxidized fiber felt/epoxy resin composite materials have specific absorbing properties. The study lays the foundation for the development of a novel multifunctional composite material, and is expected to develop into a new type of composite materials.
Use of additive manufacturing for the fabrication of cellular and lattice materials: a review
Published in Materials and Manufacturing Processes, 2021
Esmeralda Uribe-Lam, Cecilia D. Treviño-Quintanilla, Enrique Cuan-Urquizo, Oscar Olvera-Silva
The best options for thermoset polymer small parts are stereolithography and digital light processing over fused filament fabrication. These processes have several advantages when compared with the traditional methods such as injection molding, reducing the cost of production as they do not require molds or extra parts that delay the production times.
Cryogenic machining of elastomers: a review
Published in Machining Science and Technology, 2021
Preeti Maurya, Vijay G. S., Raghavendra Kamath C., Basavanna Shivamurthy
The elastomer products used for the applications discussed in the earlier section are produced to the required shape and size by several manufacturing processes. Commonly used elastomer manufacturing processes are extrusion, latex dipping, compression molding, transfer molding, injection molding, coating and calendaring. Each process has its pros and cons. Amongst these processes, the prominent one is the injection molding process. In this process, the elastomer is mixed with several numbers of additives, followed by heating at elevated temperature. Haberstroh and Linhart (2004) explained that these components are produced by injecting the molten elastomer into the mold cavity followed by cooling. Their study describes the batch variations and their effects on the elastomer-processing. The artificial neural networks (ANN) and regression analysis model was used to develop the overall process correlation between individual process parameters and properties of the compound and parts. They claim that heating time and mold temperature were the essential parameters which influence the injection molding process. However, the transfer of used model on other working units such as machines, materials, and moldings, was impossible. Hence, much more analysis would be required to analyze different working units to produce elastomer parts for batch production. Further, there are recent on-going research studies on the micro-injection molding process for thermoplastic elastomers to produce microparts suitable for smart applications. Baruffi et al. (2018) studied the effects of micro-injection molding process parameters on the accuracy and precision of thermoplastic elastomer micro-suspension rings for sensor applications. Their study claimed that mold temperature, holding pressure and melt temperature significantly affect the dimensional tolerance of thermoplastic microrings. However, they studied only soft thermoplastic elastomer. Much more work would be required to address the study of micro-injection molding process effect on microrings made of rigid thermoplastic elastomer. Carraher (2003) also discussed the general steps involved in producing complicated elastomer parts (like tire and footwear tread pattern). He highlighted that several processing sets with the increasing number of molds are required to produce the final product. The increase in the number of molds and processing steps leads to an increase in manufacturing cost and lead time respectively. Thus, machining of elastomers offers an attractive substitute for manufacturing complicated shaped components, and it is an effective and cost-saving process for producing limited numbers of intricate geometry elastomer components.