STEP-NC compliant data model for freeform surface manufacturing based on T-spline

STEP-NC is a new interface standard between CAD/CAM and CNC. Most of the studies focus on the 2.5D features machining using STEP-NC. However, freeform surface is widely used in the field of aerospace, automotive and dies/moulds. Beyond that, due to the drawbacks of NURBS that is the only representation for freeform surface in STEP, the research of STEP-NC for freeform surface is rare. In the paper, STEP-NC compliant data model is proposed for freeform surface manufacturing based on T-spline. We contribute three advantages: (1) a modified STEP data model is constructed that can represent and exchange arbitrary T-spline surface for STEP-NC-based manufacturing, (2) a general framework is proposed for evaluation of arbitrary T-spline surface that can be used for STEP-NC-based freeform surface evaluation, (3) a concept of Manufacturing-Suitable Region is proposed, which can divide T-spline surface into a set of regions for STEP-NC-based manufacturing. Some testing models show that the modified STEP data model is more efficient than the NURBS-based STEP data model for storage, and the feasibility to process arbitrary T-spline surface is verified using the general framework. In addition to this, a case study is researched to demonstrate the advantage of Manufacturing-Suitable Region for STEP-NC-based freeform surface manufacturing.