## 1 Introduction  
Additive manufacturing technology is a process that uses a discrete-stacking approach to stack materials layer by layer to eventually form a three-dimensional solid [1, 2]. It can generate parts directly from 3D solid models without process planning, which can greatly reduce the difficulty of machining complex parts. Additive manufacturing technology has many advantages; firstly, it can manufacture extremely complex parts that are difficult to produce by traditional processing methods. Secondly, it saves materials, and some materials of additive manufacturing technology can be recycled multiple times, etc. Because of its advantages, additive manufacturing technology is now being used in the medical, aerospace, automotive, food, and engineering industries. For example, the medical industry has started to experiment with the use of 3D printing technology to develop tissues, organs, and cellular structures [3, 4]. The use of 3D printing in the automotive industry has reduced the time required to process molds and reduced the cost of manufacturing prototypes [5, 6]. The aerospace industry has used 3D printing to reduce fuel consumption and material waste by lightweight traditional structures or replacing them with new geometries that are structurally complex but more practical [7, 8]. Additive manufacturing technologies include photopolymer molding technology, selective laser sintering, 3D printing technology, and fused deposition manufacturing [9]. Among them, FFF is the simplest and most commonly used technique in additive manufacturing technology, which has simple equipment and is easy to use. In this paper, we choose the FFF 3D printing technique, which prints pre-prepared fiber filaments through a nozzle [10]. After passing through a nozzle with a heated section, the filament is driven by the nozzle to lay the filament in a pre-set path, and the layers are stacked to finally obtain the required prototype part. The choice of filament material depends on the application and the desired properties. Today, commonly used materials include polylactic acid (PLA), PETG, HIPS, and ABS. Among them, PLA is widely used for printing in FFF technology due to its good mechanical properties and printing performance. However, the tensile properties and strength of pure PLA are not enough, and in order to improve the strength most of the current methods are to add nanofibers, [11] short fibers [12; 13], or continuous fibers [14] to it. There are many researches on the printing process parameters of FDM matrix printing and short fiber reinforced composite printing. [PERSON] et al. [15] studied the pure matrix FFF printing process parameters, and they believed that layer height, infill percentage, printing speed, shell thickness, printing temperature, retraction, and supports existence have immense contribution towards achieving desired printing results, and the range of setting process parameters is proposed. [PERSON] et al. [16] investigated the effect of process parameters on the surface roughness and tensile strength of PLA samples. The samples were made according to ASTM standards and the Taguchi L16 experimental design. The results showed that the print layer thickness and print head speed were the main factors affecting the surface roughness. [PERSON] et al. [17] analyzed the effect of print parameters on the sample quality using statistical and graphical methods and performed an analysis of variance (ANOVA). It can be seen that the layer height and wall thickness are the factors that affect the surface roughness. The layer height was the most significant. For a wall thickness of 1 mm, a layer height of 0.15 mm resulted in the lowest surface roughness. [PERSON] et al. [18] investigated the main effects of printing parameters on dimensional accuracy, dimensional repeatability, and mechanical properties in the FFF process using Taguchi's DOE.