## 1 Introduction  
Additive manufacturing or 3D printing makes it possible to produce exceptional architecture with different complexity grades [1; 2]. Additionally, additive manufacturing has several advantages, such as formability, variability, practicability, mass delivery, and surface property designs [3]. Various technologies of additive manufacturing for polymers have been developed, e.g., fused deposition modeling (FDM), bioprinting, selective laser sintering, selective heat sintering, digital light projection, and laminated object manufacturing [4; 5]. The polymeric materials employed in these technologies are pellets, polymerizable resins, powders, gels, dispersed solutions, and filaments. Furthermore, the FDM limitations are the high-temperature manufacturing of polymeric filaments prior to 3D printing, exclusivity for thermoplastic polymers, and the lack of polymeric filaments available at the industrial level with mechanical properties suitable for 3D printing [1; 6]. The filament extrusion conditions have a few reports in this field [7; 8; 9]. For example, [PERSON] et al. [8] produced uniform filaments extruded with a nozzle diameter of 2.85 mm and a temperature range from 175 to 180 \({}^{\circ}\)C for semi-crystalline PLA. Similarly, [PERSON] et al. [9] obtained PLA-wood filaments at a higher temperature (230 \({}^{\circ}\)C) with a nozzle of 0.4 mm. Finally, the additive manufacturing applications cover diverse areas, specifically biomedical fields such as scaffolds [10; 11; 12; 13], drug delivery systems [14], surgical tools, and implantable devices [15; 16], among others.  
Moreover, PLA has been reported for additive manufacturing [16; 17; 18; 19; 20; 21]. For instance, [PERSON] et al. [16] replicated an amputee's finger through FDM using PLA/copper nanoparticlecomposites. [PERSON] et al. [19] printed semi-crystalline PLA under the following conditions: Temperature = 210 \({}^{\circ}\)C, feed rate = 20 mm/s, and a filament diameter of 1.75 mm. For polymethyl methacrylate (PMMA), [PERSON] et al. [22] reported printing parameters as follows: Temperature = 275 \({}^{\circ}\)C, print speed = 10 mm/s, and a nozzle diameter of 0.4 mm.  
Notwithstanding, PLA can be mixed with other (co)polymers, natural or synthetic, as poly(S-_co_-MMA), producing polymer blends with specific characteristics or properties for a given application [23]. In addition, semi-crystalline PLA, PMMA, and polystyrene (PS) have been studied, with potential applications in orthopedics, scaffolds, and tissue engineering. The semi-crystalline PLA focus has been on cell proliferation, vascularization, shape-memory, and mechanical properties [15; 24; 25; 26; 27; 28; 29; 30]. PLA can be biodegraded under natural body conditions [31]. However, new scaffold architectures can be designed by delaying or anticipating the amorphous PLA biodegradation when PLA is blended with non-biodegradable polymers. In contrast, traditionally commercially available prepolymers of PMMA, PMMA-_co_-PS, or their mixtures, constitute the main component of acrylic bone cement [32]. Therefore, PLA,/poly(S-_co_-MMA), blends can open new opportunities for device production through additive manufacturing [15; 17]. Additionally, the polymer blends containing PS, PMMA, or both have had several reports concerning miscibility and compatibility between materials [33; 34]. Contrarily, few authors support PS/PMMA blend immiscibility [35; 36].  
In the present study, we reported the processing conditions for filament extrusion and additive manufacturing for PLA,/poly(S-_co_-MMA), depends, as well as their mechanical, thermal, and rheological properties. The key question of this research was whether a polymer blend could be made between amorphous PLA and poly(S-_co_-MMA) to improve on the processability of PLA during polymeric filament extrusion and 3D printing, but preserving physicochemical properties of PLA.