Speed Sintering Research Articles

Effect of Print Density on the Properties of High Speed Sintered Elastomers

High Speed Sintering is an additive manufacturing process that creates parts by combining inkjet printing and infra-red lamps rather than laser systems employed in Laser Sintering. This research investigated the effects of altering the dosage of ink (via grayscale/dithering) on the properties of parts produced from elastomers. The results indicate that print density may be optimized to maximize mechanical properties and have achieved an elongation at break as high as 365 pct. The findings also open up the possibility of creating parts with added functionality. Using differing amounts of ink per layer it may be possible to create parts with varying properties throughout.

Speed and Accuracy of High Speed Sintering

High Speed Sintering is a novel powder based additive manufacturing process that retains the major benefits of Laser Sintering but eliminates some major drawbacks. The process uses inkjet print head and infrared lamps to fabricate parts layer by layer using polymer powder. The purpose of this research was to evaluate the speed and accuracy of High Speed Sintering by closely following a method published in the research paper of Rapid Prototyping Journal, entitled 'Speed and Accuracy Evaluation of Additive Manufacturing Machines'. This methodology involves the manufacturing of test parts defined in the paper analysis using the method provided, speed and accuracy of High Speed Sintering is assessed and then benchmarked against four other Additive Manufacturing processes. Based on a theoretical speed evaluation, results show that High Speed Sintering is able to achieved superior average manufacturing speed than the other specified Additive Manufacturing technologies.

Effect of Sintering Parameters and Flow Agent on the Mechanical Properties of High Speed Sintered Elastomer

High speed sintering (HSS) is an additive manufacturing (AM) process that creates parts by sintering powder particles using inkjet and infrared (IR) lamp technology rather than laser systems employed in laser sintering (LS). This research investigated the effects of machine parameters (lamp speed, bed temperature) and the addition of fumed silica flow agent on the tensile properties of thermoplastic elastomer (TPE) parts processed using HSS. The results showed improved elongation at break (EaB) values by a factor of more than 2× compared to reported values for LS of the same TPE. At constant parameters, improved tensile strength and tensile modulus were observed with the addition of flow agent into the sintering mixture.

High Speed Sintering: Assessing the influence of print density on microstructure and mechanical properties of nylon parts

High Speed Sintering is a novel Additive Manufacturing technology that functions by inkjet deposition of a radiation absorbing material directly on to the powder surface followed by the infrared irradiation of the entire build surface. The area deposited with radiation absorbing material absorbs significantly more energy than areas without, sufficient to cause the powder to sinter. Mechanical properties are known to be related to crystallinity, however, no work to date has yet been performed to investigate the relationship between print densities, how this influences crystallinity and the resulting mechanical performance. Dithered patterns were used to vary print density, part crystallinity analysed by Differential Scanning Calorimetry and mechanical properties evaluated by tensile testing. Results showed crystallinity decreased as print density increased. This was reflected by mechanical properties which showed stiffness and tensile strength increased with crystallinity at the expense of ductility. Moreover, High Speed Sintered parts show comparable crystallinity to Laser Sintering indicating the radiation absorbing material has little effect on part microstructure.

Materials for high speed sintering

Abstract

High Speed Sintering: The influence of print density on feature resolution and accuracy

High Speed Sintering is a novel additive manufacturing technology which uses an InkJet printhead and infra-red radiation. The printhead deposits a radiation absorbing material directly onto a powder bed, the entire bed is then irradiated by an infra-red lamp. Areas printed with radiation absorbing material will absorb sufficient energy to sinter, whereas areas without will not. Another layer of powder is deposited and the process repeats until the part is complete. To date, a large proportion of research has used the maximum print density possible, very little research has focused on how altering print density influences the minimum feature size and dimensional accuracy. As such this research was designed to investigate how print density influences feature resolution, accuracy and powder removability. Results showed improved powder removal and feature resolution can be achieved using a print that is not fully dense. However, beyond a certain point the print density becomes too low and the parts fail. Thus it is imperative that the correct balance is struck if parts are to be manufactured successfully and possess improved accuracy and feature resolution.

Evaluation of Parts Produced by a Novel Additive Manufacturing Process

Rapid prototyping refers to building three dimensional parts in a tool-less, layer by layer manner using the CAD geometry of the part. Additive Manufacturing (AM) is the name given to the application of rapid prototyping technologies to produce functional, end use items. Since AM is relatively new area of manufacturing processes, various processes are being developed and analyzed for their performance (mainly speed and accuracy). This paper deals with the design of a new benchmark part to analyze the flatness of parts produced on High Speed Sintering (HSS) which is a novel Additive Manufacturing process and is currently being developed at Loughborough University. The designed benchmark part comprised of various features such as cubes, holes, cylinders, spheres and cones on a flat base and the build material used for these parts was nylon 12 powder. Flatness and curvature of the base of these parts were measured using a coordinate measuring machine (CMM) and the results are discussed in relation to the operating parameters of the process.The result show changes in the flatness of part with the depth of part in the bed which is attributed to the thermal gradient within the build envelope during build.

Analysis of Vanadium-Bearing Titanomagnetite Sintering Process by Dissection of Sintering Bed

Many problems appear in the sintering process of vanadium-bearing titanomagnetite, such as high energy consumption and low productivity; sinter quality is also very poor for its low tumble strength and high reduction degradation. Sinter productivity and quality are dominated by bed permeability and mineralogy structure, which are highly influenced by the thermal state of sintering bed, so the sintering process of titanomagnetite is researched by bed dissection in this work. Temperature evolution curves of sinter materials were measured, and the results show that melting duration, peak temperature duration and sintering temperature of different layers differ greatly from each other; flame front speed and vertical sintering speed of bed lower region are much smaller than those of bed upper region. Simultaneously, sinter samples were collected from different layers, and their mineralogy characteristics are analyzed; sinters from bed lower region have poor mineralogy structure, and the amounts of perovskite and dicalcium silicate increase intensively, which are bad for sinter strength and reduction degradation property. Measures are proposed to improve the quality and productivity of titanomagnetite sinter.

Effect of infra‐red power level on the sintering behaviour in the high speed sintering process

PurposeTo investigate the effects of the infra‐red power level on sintering behaviour in the high speed sintering (HSS) process.Design/methodology/approachSingle‐layer parts were produced using the HSS process, in order to determine the effect of the infra‐red power level on the maximum achievable layer thickness, and the degree of sintering. The parts were examined using both optical microscopy and contact methods.FindingsIt was initially expected that an increase in the infra‐red lamp powder might allow an increase in the depth of sintering that could be achieved, as a result of increased thermal transfer through the powder. However, results in fact indicated that there is a maximum layer thickness that can be achieved, as a result of part shrinkage in the z direction. Optical microscopy images have shown that a greater degree of sintering occurs at higher power levels, which would be expected to correspond to an improvement in the mechanical properties of the parts produced. These images also indicate that the radiation absorbing material forms in small “islands” on the powder bed surface. As sintering progresses, these islands begin to merge; this occurs to a greater extent at higher infra‐red lamp powers.Research limitations/implicationsThese results are based only on single layer parts. Further work will examine the sintering characteristics of multiple layer parts.Practical implicationsResults have shown that, whilst it is not possible to increase the achievable layer thickness of the parts produced by modifying the infra‐red lamp power, the degree of sintering can be improved greatly by increasing the power.Originality/valueHSS is an entirely new process which is currently still under development; the results presented here will directly impact the direction of further development and research into this process.

高速度工具鋼と低合金鋼の焼結接合材の組織と強度

High speed steel and low alloy steel were bonded by powder sintering processes in order to investigate the effects of carbon content of high speed steel and sintering temperature on the bonding behavior. Two type bonding methods were studied, i.e. the process A in which high speed steel and low alloy steel green compacts were bonded by sintering without a bonding pressure, and the process B in which two-layer powders of the steels compacted and then sintered. The density, microstructure and four-point bending strength of the bonded specimens were examined. It was found in the process A that the two steels were not bonded at lower sintering temperature than the temperature (Ts) at which the relative density of sintered high speed steel reached 98%, and that bonded specimens showed the highest bending strength at higher sintering temperature than the Ts by 20K. In the process B, there was no significant influence of carbon content and sintering temperature on the bending strength, and the maximum bending strength was lower than that of the bonded specimens by the process A. This was considered to be due to both the micro-pores produced at the interface and the residual tensile stress of the bonded specimens.

K-1013 粉末を利用した高速度工具鋼と低合金鋼の焼結接合(S12-2 粉末成形とその評価(2))(S12 粉末成形とその評価)

High speed steel and low-alloyed steel were bonded by powder sintering processes in order to investigate the effects of carbon content of high speed steel and sintering temperature on the bonding behavior. Two type bonding methods were studied: (1) high speed steel and low-alloyed steel compacts were bonded by sintering without bonding pressure, (2) two-layer powder of the steels compacted and then sintered. The density, microstructure and four-point bending rupture strength of the bonded specimens were examined. It was found that the sintered temperature at which the bonded specimens of two compacts showed the highest rupture strength was 20 K higher than the temperature at which sintered high speed steel specimens showed the highest rupture strength, and that there was no significant influence of carbon content and sintering temperature on the rupture strength for the specimens bonded by two-layer powder compacting.