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The purpose of this paper is to describe work carried out as part of a £350,000 project aimed at improving understanding of polymer sintering processes. This particular package of research was performed in order to identify the effects of different section thicknesses (and therefore different thermal conditions) in parts produced by laser sintering (LS), on the resultant mechanical properties of these parts.

Laser sintered nylon‐12 parts were produced in a range of thicknesses between 2 and 6 mm, and in three different orientations, to identify the effects of each on the tensile properties of these parts.

Results indicated that, at any of the orientations tested, the section thickness had no significant effect on any of the main tensile properties, or on the repeatability of these properties. Crucially, this is in direct contradiction with the trends identified previously in this project, whereby changes in section thickness have been shown to correlate with changes in fracture toughness.

Further work could investigate a wider range of section thicknesses or geometries, in order to continue building a more complete picture of the effects of geometry on laser sintered part properties.

These results are directly applicable to designers using, or wishing to use, LS to manufacture their products.

Whilst there is a large range of published literature on the effects of processing parameters on mechanical properties of laser sintered parts, and on the resolution and accuracy achievable with these, there is minimal information available on the effects of geometry on mechanical properties. This paper therefore represents a novel addition to the global LS knowledge base.

In stereolithography (SL), the total exposure absorbed by photopolymer is variable and is a function of height. This phenomenon causes heterogeneous properties and develops residual stresses during process. Consequently, a pronounced deformation occurs especially when small and more intricate objects are fabricated. The purpose of this paper is to predict this deformation when miniature and complicated parts are fabricated.

In this paper classical lamination theory is employed to model mechanical properties of layers, layers shrinkage and residual stress growth during SL process. Distortion is predicted based on the developed model.

Results show that final distortion is proportional to part thickness and it increases exponentially as parts thickness or layers thickness decrease.

To verify the results, several test pieces were built with SLA 5000 machine and SOMOS 11120 resins. Their distortions were measured with video measuring machine (VMM‐3020D machine). The estimation agrees very well with the experimental results (less than 10 per cent error).

The paper considers the heterogeneous properties of SL parts during fabrication process; an item which was ignored in previous researches. This theoretical and experimental study provides useful information about estimation of deformation of SL parts after building. This information helps the SL machine user to select the best parameters when fabricating miniature and intricate features, especially for biomechanics parts.

In binder jetting, the interaction between the liquid binder droplets and the powder particles defines the shape of the printed primitives. The purpose of this study is to explore the interaction of the relative size of powder particles and binder droplets and the subsequent effects on macro-scale part properties.

The effects of different particle size distribution (5–25 µm and 15–45 µm) of stainless steel 316 L powders and droplet sizes (10 and 30 pL) on part density, shrinkage, mechanical strength, pore morphology and distribution are investigated. Experimental samples were fabricated in two different layer thicknesses (50 and 100 µm).

While 15–45 µm samples demonstrated higher green density (53.10 ± 0.25%) than 5–25 µm samples (50.31 ± 1.06%), higher sintered densities were achieved in 5–25 µm samples (70.60 ± 6.18%) compared to 15–45 µm samples (65.23 ± 3.24%). Samples of 5–25 µm also demonstrated superior ultimate tensile strength (94.66 ± 25.92 MPa) compared to 15–45 µm samples (39.34 ± 7.33 MPa). Droplet size effects were found to be negligible on both green and sintered densities; however, specimens printed with 10-pL droplets had higher ultimate tensile strength (79.70 ± 42.31 MPa) compared to those made from 30-pL droplets (54.29 ± 23.35 MPa).

To the best of the authors’ knowledge, this paper details the first report of the combined effects of different particle size distribution with different binder droplet sizes on the part macro-scale properties. The results can inform appropriate process parameters to achieve desired final part properties.

The evaluation of novel materials such as the acrylonitrile styrene acrylate (ASA) for tribological and mechanical conditions can provide a structural protection against the environmental and wear effects that results in the long-term integrity of the 3 D printed parts. Results of the experimental stage are intended to identify the influence of the printing conditions on the functional characteristics of ASA parts that results in variations of the friction coefficient, wear rate and tensile response. In addition, this study aims to highlight the relevance of printing parameters to avoid the use of chemical post-processing stages, increasing the performance and sustainability of the process.

In this research, an evaluation of the influence of printing parameters of layer thickness and temperature on the mechanical and tribological response have been carried out for ASA specimens manufactured by fused filament fabrication technology. For this purpose, a range of three different values of thickness of fused layer and three different printing temperatures were combined in the manufacturing process of tests samples. Mechanical behavior of the printed parts was evaluated by standard tensile tests, and friction forces were measured by pin-on-disk tribological tests against steel spheres.

Higher layer thickness of the printed parts shows lower resistance to tribological wear effects; in terms of friction coefficient and wear rate, this type of parts also presents lower tensile strength. It has been detected that mechanical and tribological behavior is highly related to the micro-geometrical characteristics of the printed surfaces, which can be controlled by the manufacturing parameters. Under this consideration, a reduction in the coefficient of friction near to 65% in the average value was obtained through the variation of the layer thickness of printed surfaces.

This research aims to fill a gap in the scientific literature about the use of specific additive manufacturing materials under dynamic contact. This paper is mainly focused on the influence of the manufacturing parameters on the tribological and mechanical behavior of a weather resistant polymer (ASA).

The purpose of this paper is to investigate effects of layer thickness on densification, surface morphology, microstructure and mechanical and corrosion properties of 420 stainless steel fabricated by laser-powder bed fusion (L-PBF).

Standard specimens were printed at layer thickness of 10, 20 and 30 µm to characterize Archimedes density, surface roughness, tensile strength, elongation, hardness, microstructural phases and corrosion performance in the as-printed and heat-treated condition.

Archimedes density slightly increased from 7.67 ± 0.02 to 7.70 ± 0.02g/cm³ and notably decreased to 7.35 ± 0.05 g/cm³ as the layer thickness was changed from 20 µm to 10 and 30 µm, respectively. The sensitivity to layer thickness variation was also evident in properties, the ultimate tensile strength of as-printed parts increased from 1050 ± 25 MPa to 1130 ± 35 MPa and decreased to 760 ± 35 MPa, elongation increased from 2.5 ± 0.2% to 2.8 ± 0.3% and decreased to 1.5 ± 0.2, and hardness increased from 55 ± 1 HRC to 57 ± 1 HRC and decreased to 51 ± 1 HRC, respectively. Following heat treatment, the ultimate tensile strength and elongation improved but the general trends of effects of layer thickness remained the same.

Properties obtained by L-PBF are superior to reported properties of 420 stainless steel fabricated by metal injection molding and comparable to wrought properties.

This study successfully the sensitivity of mechanical and corrosion properties of the as-printed and heat-treated parts to not only physical density but also microstructure (martensite content and tempering), as a result of changing the layer thickness. This manuscript also demonstrates porosity evolution as a combination of reduced energy flux and lower packing density for parts processed at an increasing layer thickness.

This paper provides a quantitative and qualitative assessment of the effects of electroplating on polymer parts made by stereolithography (SL) and laser sintering. A series of test samples were coated with copper and nickel with varying thickness. Thicker coatings (120 μm) were reproduced with a repeatability that should not adversely affect the tolerances with which such parts may be produced given the tolerances of the initial rapid prototyping processes themselves. Thinner coatings (20 μm) resulted in a smother surface finish than thicker coatings for SL parts, however the converse was true for laser‐sintered parts. Composite theory was used to predict that thicker coating would lead to higher Young's modulus in parts and this was shown to be true in physical tests although the practical values were lower than the predicted values especially for thicker coatings. Physical tests also confirmed that thicker coatings increased UTS and impact energy but had a minimal effect on the ductility of parts.

This paper aims to investigate the influences of process parameters on part quality, electrical energy consumption. Moreover, the relationship between part quality and energy consumption of UTR9000 photosensitive resin fabricated by stereolithography apparatus (SLA) was also assessed.

Main effect plots and contour maps were used to analyze the interactions and effects of various parameters on energy consumption and part quality, respectively. Then, a growth rate was used defined as the percentage of the value of energy consumption (or the part quality) of the sample compared to the minimum value of the energy consumption (or the same part quality), to jointly analyze relationships between part quality and energy consumption on a specific process parameter.

The part qualities can be improved with increased energy consumption via adjusting layer thickness, without further increasing energy consumption through adjusting laser power, over-cure and scanning distance. Energy consumption can be highly saved while slightly decreasing the tensile strength by increasing layer thickness from 0.09 mm to 0.12 mm. Energy consumption and surface roughness can be decreased when setting laser power near 290 mW. Setting an appropriate over-cure of about 0.23 mm will improve tensile strength and dimensional accuracy with a little bit more energy consumption. The tensile strength increases nearby 5% at a scanning distance of 0.07 mm compared to that at a scanning distance of 0.1 mm while the energy consumption only increases by 1%.

In this research, energy consumption and multiple part quality for SLA are jointly analyzed first to accelerate the development of sustainable additive manufacturing. This can be used to assist designers to achieve energy-effective fabrication in the process design stage.

Accuracy and building time are two important concerns in rapid prototyping (RP). Usually there exists a trade‐off between these two aspects pertaining to model building in RP. The use of variable thickness slicing can satisfy these two requirements to some extent. Introduces an adaptive variable thickness slicer implemented on a solid CAD modeller. The slicer employs a genetic algorithm to find the minimum layer thickness allowed at referenced height with a given cusp height tolerance. By introducing the variable thickness slicing technique, the optimal orientation for part building in RP systems is considered. Seeks to obtain the optimal orientation with adaptive slicing for part building in stereolithography (SLA) systems. Takes into consideration building time, accuracy and stability of the part when determining the optimal orientation. Results show that the proposed approach gives an effective and practical solution for building parts with curved surfaces.

The purpose of this paper is to investigate the effects of layer thickness, aspect ratio, part thickness and build orientation on distortion to have a better understanding of its behavior in material jetting technology.

Specimens with two layer thicknesses (14 and 28 µm) were printed in two aspect ratios (2:1) and (10:1), four thickness values (1, 2, 3 and 4 mm) and three build orientations (45d, XY and YX) and scanned with a wide-area 3D surface scanner to quantify distortion. The material used to build the test specimens was a commercially available resin, VeroWhitePlus RGD835.

The results of this study showed that all printed specimens by material jetting 3D printers had some level of distortion. The 1-mm thickness specimens, for both layer thicknesses of 14 µm and 28 µm, showed a wide range of anomalies including reverse coil set (RCS), reverse cross bow (RCB), cross bow (CB), wavy edge (WE) and some moderate twisting (T). Similar occurrences were observed for the 2-mm thickness specimens as there were RCS, WE, RCB and T anomalies that show the difference between the thinner specimens (1- and 2-mm) with the thicker ones (3- and 4-mm). In both 3- and 4-mm thickness specimens, there was more consistency in terms of distortion with mainly RCS and RCB anomalies. In total, six different types of flatness anomalies were found to occur with the following incidences: reverse coil set (91 specimens, 63.19%), reverse cross bow (50 specimens, 34.72%), wavy edge (23 specimens, 15.97%), twist (19 specimens, 12.50%), coil set (11 specimens, 7.64%) and cross bow (7 specimens, 4.86%).

This study expands the research on how the preprocess parameters such as layer thickness and build orientation and the geometrical parameters such as part thickness and aspect ratio cause dimensional distortion. Distortion is a pervasive consequence of the curing process in photopolymerization and explores one of the most common defects that come across in polymeric-based additive manufacturing. In addition to the characterization of the type and magnitude of distortion, the contributions of this work also include establishing the foundation for design guidelines aiming at minimizing distortion in material jetting.

Material variation is inevitable in volume production, especially the sheet metal thickness variation, which influences part stiffness characteristic. The purpose of this paper is to present a new variation model of compliant sheet metal assembly with consideration of material variation influence.

The theory of computational solid mechanics is used to obtain the relationship between part stiffness matrix and material characteristic. The method of influence coefficients is adopted to deduce the assembly variation model.

Material variation‐induced influence coefficients to assembly variation are obtained, and a variation model of compliant sheet metal assembly with sources of material variations, part geometric variations and fixture variations is presented. Analysis shows that material variation has an important influence to assembly variations.

A quantitative relationship between assembly variations and material thickness variations is firstly given and a new variation model of compliant sheet metal assembly is presented to help designers to more exactly predict the assembly variation and diagnose variation sources.