The research study evaluated the effect of different manufacturability feedback modalities on design engineers’ ability to improve the manufacturability of their designs. A manufacturability feedback tool called the Three Dimensional Integrated Feedback (3DIF) has been developed and evaluated, the purpose of which is to provide manufacturability feedback information to design engineers early at the conceptual design stage. Conceptual design is an important factor which determines most of the overall manufacturing cost, resources and time, but design engineers are not manufacturing specialists. Providing early manufacturability feedback to design engineers assist them to improve the manufacturability of their designs. Studies have shown that mode of data representation affects its interpretability. An evaluation study was conducted with design engineers to evaluate how different feedback modalities affected their design performance, usability and workload. Results show that providing feedback in three-dimensional modality significantly improved the design manufacturability with less mental workload compared to textual and no feedback. Providing textual feedback was no better than providing no feedback. This study will benefit manufacturing industries by demonstrating that easy-to-use, three-dimensional manufacturing feedback can significantly improve the design, increase usability, reduce workload, and potentially lower the cost of the design process.