Purpose: This paper reviews the factors affecting shrinkage of molded parts in injection molding. Methods: A selective screening of the papers published in the last 10 years was adopted. The review was organized according to molding scale (macro or micro) and by considering four branches of influence: material behaviors, processing parameters, mold, and specimen design. Results: Within the interval of confidence, at the macroscale, critical processing parameters were the temperatures, the packing parameters, cooling time, and injection speed; temperatures and packing parameters resulted critical factors at the microscale as well. Concerning the design aspects, the runner size and the ribs affect shrinkage at the macro and microscale, respectively. The analysis of the literature review has shown an absence of statistical approach for determining the material influences, a lack of information on shrinkage occur in powder-molded parts and the absence of data in specimen with dimensions below 10 m. Conclusions: The review collected the factors that affect shrinkage in injection molding, and identified three possible areas for further works.

The aim of this paper is to provide a method for measuring shrinkage in micro injection moulded (μ-IM) partsno standardised approach being reported as yet in the literature. This study investigates the feasibility of implementing the international standards used to investigate shrinkage in conventional (macro) moulding at the micro-scale. Following a similar experimental procedure to the relevant standards, micro-moulded polyoxymethylene (POM) specimens were produced, and the influence of processing parameters on their shrinkage was analysed using the design of experiment (DoE) approach. The analysis results showed that the methodology was capable of detecting factors that had a statistically significant effect on shrinkage at the micro-scale, in both parallel to, and normal to, the flow directions for moulding, post-moulding and total shrinkage.

Attention of this paper is devoted to testing and evaluation of carbon-fibre-reinforced polymer specimens with lock-in thermography. Several specimens were prepared by a vacuum infusion technique using a low-viscosity epoxy system; delaminated areas were simulated by the insertion of thin Kapton® diskettes at a given depth through the thickness. Artificial defects had different shapes (circular or elliptical) and dimensions. Inserts were located at different depths and, in some cases, by overlapping more than one Kapton®-shaped layer (i.e. two or more concentric discs, each of different diameter). A preliminary test campaign was performed by differential scanning calorimetry and rheometry to find optimal processing parameters to achieve fully cured state of matrix and to avoid the formation of defects in accordance with aerospace standards for composites manufacturing. Specimens were non-destructively inspected with optical lock-in thermography; results were presented in terms of phase images. All inserts were discovered and also well outlined under difficult conditions such as in the case of thin overlapped foils.

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The aim of this paper is to optimise process conditions in micro injection moulding (IM) to minimise shrinkage whilst maximising part mass. Method: A Design of Experiment (DoE) approach was implemented for studying the effect of five processing parameters on shrinkage and part mass. A multiple quality criteria based analysis was used to optimise the process. Results: Significant factors were found for shrinkage and part mass. Conclusions: The multi quality criteria could be optimized, and this optimization validated experimentally.

This paper presents a novel in-situ technique to produce articulated components with highprecision, micro-scale movable interfaces by micro-powder injection moulding (μPIM). The presented process route is based on the use of micro-scale sacrificial layer between the movable subcomponents which is eliminated during the debinding step, creating a dimensionally-controlled, micro-scale mobile interface. The fabrication technique combines the advantages of micro-powder overmoulding, catalytic debinding and sintering. The demonstrated example was a finger bone prosthesis joint consisting of two sub-components with an interface between components of 200 μm in size. The geometries of the subcomponents were designed such that they are inseparable throughout the process whilst allowing them to move relative to each other after the debinding stage. The components produced showed the feasibility of the process route to produce readily-assembled meso-, and potentially micro-, scale articulated systems.

The aim of the study presented herein was to investigate the possibility of employing composites in the production of medical diagnostic equipments, and their advantages in terms of costs and performances. In particular, the patient-positioning system of a magnetic resonance apparatus, comprising two elements, the bed tables, and the footrest, was examined with the main goal of enabling a wider range of population to be tested, thanks to a full re-designing of their item. An extensive variety of composites were investigated, in order to select a combination of matrix and reinforcement able to satisfy the specific requirements in terms of magnetic transparency, structural behavior, manufacturing features, and costs. Glass fiber composites were selected and characterized by experimental tests. The patient-positioning system was completely re-designed and analyzed by finite elements method; design optimization led to a simplified structure, offering a series of advantages such as light weight, manoeuvrability, thickness reduction, and cost-saving processes. Final full-scale prototypes were realized and tested according to the Medical Security procedures, achieving as main results not only a reduction of the total production cost, but also an increase in the percentage of people that can be scanned by this magnetic resonance apparatus.

The purpose of this paper was to evaluate the shrinkage behavior of a 316L molding feedstock. The methodology adopted a statistical approach (design of experiment) and a standard microshrinkage measurement approach. The statistical approach identified the mold temperatureparallel to the flow directionand the combined effect of the holding and injection pressurenormal to the flow directionas critical factors. In comparison with the polymer on which the feedstock was based, lower shrinkage values and fewer critical factors were observed. In conclusion, the lower shrinkage values were a consequence of the powder loading. The critical factors identified in the present work have found confirmation in the literature, except the absence of melt temperature between feedstock critical factors.