## 4 Conclusions  
This study comprehensively evaluated the performance of toy parts manufactured using both plastic injection molding and Fused Deposition Modeling (FDM), offering valuable insights into their mechanical properties, dimensional accuracy, surface quality, and cost-effectiveness.  
Our findings reveal significant differences in compressive strength. ABS parts produced via injection molding demonstrated the highest resistance, enduring 3.93 kN. This was followed by PLA parts printed with FDM at 2.97 kN, and then ABS-FDM parts at 0.95 kN. This superior performance of injection-molded parts is attributed to the inherent molding process, which effectively minimizes internal voids and promotes a denser, stronger structure. Microscopic analysis, particularly through SEM images, corroborated this, clearly showing a greater prevalence of voids and microstructural irregularities in 3D-printed parts, especially in ABS-FDM samples, likely due to incomplete layer bonding during extrusion. While ABS-FDM exhibited lower compressive strength, PLA-FDM performed comparatively better than ABS in the FDM process, suggesting its suitability for toy applications that do not demand high load-bearing capacity.  
In terms of dimensional accuracy, injection-molded parts showed the closest adherence to the original CAD model. While 3D-printed parts, particularly those made from PLA, displayed more variation, their average deviation generally remained within acceptable limits for general use, indicating that FDM can produce dimensionally adequate parts for less stringent applications.  
Surface roughness measurements further supported these observations. Molded parts consistently exhibited smoother finishes, whereas FDM parts displayed more visible layers and surface irregularities, with PLA prints showing particularly higher roughness values.  
From a cost perspective, injection molding becomes economically advantageous at high production volumes due to its lower per-unit cost. However, this method necessitates substantial initial investments in expensive molds and specialized equipment. Conversely, for production quantities below approximately 735 pieces, 3D printing emerges as the more practical and cost-effective option, particularly when lower initial cost, faster setup times, and greater design flexibility are priorities.  
Finally, our TOPSIS analysis provided a comprehensive decision-making framework by integrating all evaluated criteria. The results indicate that ABS-Injection molding ranks highest when large-scale, cost-effective production is the primary objective. In contrast, PLA-FDM proves to be the more favorable option in scenarios where low-volume production and limited budget are key concerns.  
This study underscores that the optimal manufacturing method for toy parts is highly dependent on specific requirements related to mechanical performance, dimensional precision, surface quality, and most critically, production volume and cost constraints.  
In summary, while injection molding remains the superior option for mass production demanding stringent mechanical and dimensional requirements, 3D printing--particularly with PLA--offers a viable alternative for small-batch manufacturing, rapid prototyping, or customized toy production.  
Conceptualization, S.D. and A.O.E.; methodology, S.D. and A.O.E.; software, S.D.; validation, S.D. and A.O.E.; formal analysis, S.D. and A.O.E.; investigation, S.D. and A.O.E.; resources, S.D.; data curation, S.D. and A.O.E.; writing--original draft preparation, S.D. and A.O.E.; writing--review and editing, A.O.E.; visualization, S.D.; supervision, A.O.E.; project administration, A.O.E.; funding acquisition, S.D. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Data Availability Statement: The original contributions presented in this study are included in the article.  
The authors declare no conflict of interest.