No abstract

Flow length determination is one of the most important tasks in injection mold design. In order to achieve the perfect filling of the mold, proper designs for the channel depth and other injection parameters (such as melt temperature, injection pressure and etc.) should be conducted. In this research, melt temperature and injection pressure were considered as input parameters to investigate the flow length, in the most commonly used plastics including acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyamide 6.6 (PA 6.6), polyoxymethylene (POM). This study was carried out, based on various channel depths, according to ASTM D 3123. A new method based on a fuzzy logic method was developed to predict the amount of flow length in relation to the input parameters such as pressure, channel depth, and temperature. When the present method is used, the problem of finding the optimum mold design can be solved faster compared to the traditional modeling programs. The largest estimated amounts of flow lengths by the fuzzy logic model were 1215, 596, 963 and 1040 mm for POM, PC, PA 6.6 and ABS, respectively. The maximum measured values were 1235, 579, 948 and 1050 mm for the same material. Experimental tests have been conducted to justify the accuracy of the developed method. It was confirmed by regression analysis that the amount of R 2 for the measured and estimated values was 0.920529. The results of this research show that the fuzzy logic system is a reliable method to predict the short shots in an injection process.

Of the five steps in powder injection molding, namely feedstock formulation, mixing, injection, debinding and sintering, the one which markedly demands more time is debinding. Studying the effect of specimen thickness on debinding time in the current study, 316L stainless steel feedstock was exploited as the material for fabrication cylindrical specimens with varying thicknesses ranging from 2 to 10 mm. The thicker the specimen, the more time-consuming the debinding is. In addition, a novel method has been presented to produce thick components with large sections by powder injection molding, using preformed inserts in the injection stage. By using a wrought insert on which the feedstock is injected, the thickness of the injected section in need of debinding decreased while the whole thickness of the component was still large. Finally, defect-free specimens with diameter of 20 mm have been fabricated using inserts with different sizes, which resulted in dramatic reduction of debinding time from several days to only some hours. Moreover, it revealed that the interface of the insert and injected section was bonded properly, reaching more than 400 MPa of shear strength, depending on insert/part diameter ratio.

In this study, the optimized sintering parameters for a feedstock obtained by mixing the powder of Ti-6Al-7Nb and 31wt% binder system (comprised of high-density polyethylene, Polypropylene, PEG 20000, paraffin wax and stearic acid), were determined. In order to produce a component, Taguchi method was applied to obtain the optimum conditions. As a result of ANOVA, sintering temperature was proven to be the most effective one. It was also proven that for feedstock comprised of 69wt% Ti-6Al-7Nb powder, the suitable set of sintering parameters were as follows: sintering temperature of 1250 °C, dwell time of 60 min, heating rate of 1 °C/min, gas flow rate of 5 L/min.

In this study the mutual investigation of the results obtained from the mechanical stability properties and the IR spectra of polypropylene‐based but differently doped low‐density polyethylene (LDPE) and o‐o‐di‐n‐cresylditio phosphorous (CTPh) acid polymer composites is given. As opposed to the studies of the writers in recent years here, dynamical‐mechanical properties are explained not only by the variations in the oxidation peaks but also by the optical density in the peaks of the variations in the groups in amorphous and crystalline regions. The properties are also explained by the spectra variations in the IR region, which, according to Mamedov (2), is important, and by the extreme variations of the polymer properties. IR spectra analyses show that for both composites, (1) the optical density of the peaks in the crystalline regions for LDPE decreases while for PP those of the peaks in the amorphous regions increase; (2) the optical density of the peaks belonging to the CC groups get higher, whereas those of the peaks 1717, 1748 cm−1 diminish; and (3) the dynamical‐mechanical properties change accordingly, and these changed composites have the maximal characteristics, since the added amount is 0.2–0.3% CTPh by mass and 20–30%LDPE by mass. On the basis of the paper by Abdullayev et al. (3), the mechanism of these processes is given.