Nowadays, as consumer electronics, information, and aero-space industry grow, the demand for aspheric lens for camcoder, CD player, and optical instrument increases higher. The aspheric lenses have various shapes according to their application and often require several tens nanometer in the form accuracy. Therefore, CAM systems for ultra-precision machining of aspheric surface are needed.
In ultra-precision machining, the relative motion of tool and workpiece is precisely copied onto the workpiece. Accordingly, interpolation of aspherical surface must meet the allowable tolerance exactly. In fitting aspheric curve, linear interpolation generates huge amount of NC codes for satisfying the very small tolerance, and makes the cutting time longer because of the acceleration and deceleration of tool in every linear motion. On the other hand, arc interpolation generates a shorter NC code than linear interpolation. Thus arc interpolation can save the cutting time. Besides, it can make the 1st differential value to be continuous at the connection points of each arc. However, the existing arc interpolation needs a large amount of calculations to meet tolerance exactly. For the fast calculation of error between the arc and the aspheric curve, we developed Tri-arc and New Bi-arc interpolation method that the location of maximum error is fixed.
In ultra-precision machining, to avoid bad surface roughness due to machining affected layer, a operator must carry out several contour cuttings. So, the cutting condition input module is necessary for user to give the several contour cutting condition conveniently.
In this CAM software, tool path verification module can perform dynamic simulation and analytical verification. Dynamic simulation make it possible to verify NC code visually. Analytical verification can check invisible overcut through comparison of tool geometry with aspheric curve.
Consequently, this software can generate NC code for various aspheric surfaces fast and precisely by Tri-arc and New Bi-arc curve interpolation method. The cutting condition input module and the NC code verification module are adequate to ultra-precision machining, so that a operator can obtain ultra-precision aspheric products fast and easily.