###### Abstract  
Fused filament fabrication (FFF) 3D printing technology for continuous fiber-reinforced composite (CFRC) printing has become a trend. This article is based on 'independent extrusion' FFF CFRC printing. The continuous fiber-reinforced filament (CFRF) printing solution is the contour offset method for obtaining executable g-code. When the CFRCF prints at the corner, it is found that the actual CFRC printing trajectory is inconsistent with the ideal laying trajectory. The causes of the error are analyzed, and an angle optimization algorithm is proposed. The corner optimization algorithm is verified by theoretical analysis and experimental analysis. From the experimental results, the corner optimization algorithm improves the 30\({}^{\circ}\) angle fit of CFRF printing by 90% and reliability has also been improved. When the printing length is 127,200 mm, there are 960 printing corners, and the failure rate is 0.  
continuous fiber; composite; continuous fiber-reinforced filament; contour offset; corner optimization algorithm +
Footnote †: journal: Applied  
the composite material pre-impregnated with continuous reinforcing fibers and a thermoplastic resin matrix and then use different print heads to print the resin matrix material and prepreg. The \"independent extrusion\" printing principle is shown in Figure 1b. [PERSON] et al. studied the effect of process parameters on the mechanical properties of the printed parts by pre-preparing CGFRF/PLA and using the printing method of \"independent extrusion\". The tensile and flexural strengths of the specimens were increased by 400% and 204% when the fiber volume fractions were about 5.21% and 6.24%, respectively [13]. [PERSON] et al. studied the influences of process parameters, such as fiber laying direction and fiber volume fraction, on the mechanical properties of CFRC samples and compared the effects of carbon fiber, glass fiber, and Kevlar on enhancing PA [14]. [PERSON] et al. studied the mechanical properties of carbon fiber and glass fiber-reinforced composites and discussed in detail the fracture behavior of each test sample [15]. [PERSON] et al. studied the failure mode of CFRC and found that continuous fibers absorbed a large amount of load and that the matrix would bear impact load when the continuous fibers failed [16]. However, they only studied the effect of process parameters on the performance index of CFRC. Slice processing is a key technology in 3D printing that transforms 3D models into executable code, which determines the quality and efficiency of printed products. Therefore, the slicing process needs to integrate various factors, such as filling path [17], directional characteristics, material characteristics, slicing efficiency, printing time, and so on. Compared with traditional FFF, due to the unique continuity and directionality of CFRF, the regulation of the filling path is particularly important in CFRF printing. It is necessary to design an appropriate printing path to ensure molding quality and printing efficiency, as well as facilitate program implementation. Finally, the g-code for printing is generated by slicing software. At present, there are a few mature commercial slicing software systems on the market, mainly the 'Eiger' system of the Markforged company [18] and the 'Aura' system of the Anisoprint company [19]. However, they are still not flexible, and the process parameters that can be regulated are relatively limited. Three-dimensional printing path planning algorithms mainly include contour offset scanning, reciprocating parallel scanning, layer-to-layer change-of-direction scanning, and composite path scanning algorithms [17]. Among them, contour offset scanning is prone to the problem of contour loop intersection when forming complex parts [20; 21]. The scanning distance of the reciprocating parallel scanning algorithm usually uses a fixed value, which is prone to large errors [22; 23]. To solve the problem of CFRC printing path jump, [PERSON] et al.