This report explores whether speed-modulated ironing (SMI) can be effectively used for enhancing mechanical properties of 3D prints and presents two design applications that illustrate the potential of this technique. SMI is a technique which utilizes the second nozzle of a dual nozzle 3D printer to precisely re-heat printed layers. The G-code for this nozzle is custom made within a Grasshopper script, allowing for precise control over its speed and location. 3-point bending and tensile tests were conducted on 3D printed PLA specimens ironed with various speeds to evaluate the impact of SMI on material bonding both within and between print layers. Increased bonding within the layers was achieved for tensile dog bones printed with transversal infill. An iron-speed of 3mm/s increased the ultimate tensile strength by 12%. Other infill orientations did not mechanically improve through ironing, suggesting limited benefits for inherently strong infill configurations. Increased interlayer bonding was achieved with 3-point bending specimen printed upright. An Iron-speed of 5mm/s increased the ultimate flexural strength with 87.8% and increased material stiffness by 45%. Through differential scanning calorimetry (DSC) it was found that ironed samples contain more crystalline regions compared to un-ironed samples, which explains the observed increase in material strength and stiffness on a material level. Two applications are presented to demonstrate the potential of speed-modulated ironing for strengthening 3D prints. First, a 3D-printed trombone mouthpiece was reinforced, providing a real-world example of the benefits of SMI. Second, a topology-optimized workflow is proposed that selectively irons the most structurally significant regions within a print, allowing designers to balance mechanical performance and print time. Overall, this report proposes a new method to effectively strengthen 3D prints through speed-modulated ironing, that only requires a dual-nozzle 3D printer and Grasshopper.