*2.5. Raster Width*

Raster width represents the width of the printed beads or roads for rasters. It depends on the nozzle tip size. Some researchers distinguish contour width from raster width [80,81], as shown in Figure 1. However, in most studies, contour width and raster width are regarded as the same parameter, represented by road width [11,65,82].

Gebisa and Lemu [80] focused on processing parameters, such as contour width, raster angle, contour number, raster width, and air gap, on the effect on the flexural properties of PEI-manufactured parts, which could be arranged as importance: raster width and raster angle > contour width and contour number > air gap. They also found that the effect of a minus air gap could differ between two different materials, which was not recommended for PEI. Ang et al. [83] specified process parameters, namely air gap, raster width, build orientation, number of layers, and infill pattern, on the compressive properties and porosity of ABS scaffold structures. The experiment determined raster width and air gap as the most significant parameters. Moreover, porosity decreased when the air gap decreased or raster width increased. In contrast, compressive strength and modulus increased as raster width increased while the air gap decreased. Rayegani and Onwubolu [84] used the group method of data handling (GMDH) and differential evolution (DE) to quantify the effects of air gap, raster angle, build orientation, and raster width on tensile strength. The investigation showed that negative air gap, as well as smaller raster width, significantly improved tensile strength. Particularly, build orientation played a major role, as could be observed from the results. Onwubolu et al. [85] applied the design of experiment (DOE) to study the main and interaction effects of process variables such as build orientation, raster width, layer thickness, air gap, and raster angle on tensile and strength of ABS components. The maximum tensile strength was obtained with zero build orientation, maximum raster width, raster angle, and negative air gap. In Liu et al. [86], five input process parameters such as build orientation, layer thickness, raster orientation, air gap, and raster width were considered to examine their influence on impact, flexural and tensile strengths. The optimum combination was obtained based on analysis of variance and gray relation analysis. Gkartzou et al. [87] examined the influence of raster width on tensile properties of PLA/Lignin composites. The results showed that specimens with different raster widths had similar tensile strength and Young's modulus.

In summary, larger raster width creates a high temperature near the boding surfaces and a larger bonding area, which may improve the diffusion and lead to stronger bond formation [64]. However, a larger raster can also result in stress accumulation along the width of the part, as well as deterioration in thermal conductivity [88]. On the other hand, smaller raster width will require less production time and material. On the whole, at the intermediate value of the raster width, the higher thermal mass that cools slowly can be achieved, which enhances the bonding between the filaments and thus improves the strength [89].
