Research on NC Technologies of Loxodromic Normal-Arc Bevel Gear

Normal circular-arc spiral bevel gear is a new type gear based on Bertrand conjugation principle. Normal circular-arc bevel gear selects directrix on the basis of paying attention to machining planning process. When the directrix serves as loxodrome, the formed tooth profile surface not only has fine transmissibility like general arc bevel gear, but also is convenient to machining. Starting with differential geometry, the geometry nature and inner relationship of Bertrand conjugation surface are studied. Then the normal circular-arc surface id put forward which is a typical Bertrand surface; the conjugation theory of loxodrome normal circular-arc bevel gears is studied. The characters of loxodrome line are analyzed. The tooth profile of loxodrome normal circular-arc bevel gears, the primary condition the directrix line must be satisfied, the relative curvature of the conjugating surfaces, the relations between non-interventional condition and curvature axle of the directrix line is provided; the NC machining theory of normal circular-arc bevel gears is studied, including the designing and manufacture of the tool, the movement of the machine, the adjustment of the tool under the condition of tangency and non-interventional condition and so on.

Tool Posture Optimization Subjected to the Rigidity of Multi-Axis Machine Tool

In order to achieve higher product quality for sculptured surface productions, an advanced strategy are proposed for machining planning, namely a tool-posture-control strategy. In the tool-posture-control strategy, machining chatter is reduced by controlling the machine rigidity along cutting feed direction. This proposed strategy, which improved product quality of sculptured surface when subjected to both the part geometry and the machine rigidity constrains, is described in this paper. A new machining-planning aid called local stiffness index is developed to help tool posture planning. This proposed strategy subjected to multi-constrains help a part programmer to choice the optimum tool posture. In order to illustrate the application of stiffness index map and the proposed strategy, the applications of the proposed strategy to real three-dimensional complex surface (e.g. a turbine blade) are presented in this paper.

Greedy Tool Heuristic for Rough Milling of Complex Pockets

The milling of complex pockets bounded by NURBS surfaces is usually broken into rough and finish milling, with the former taking up the bulk of the machining time. This time can be reduced if the proper combination of end-mills of different sizes are used to machine in different regions. The greedy tool heuristic presented in this paper is a new approach for determination of the machining volume that should be allocated to different tools selected from among a large set of available tools. Subsequent machining planning can then be performed by repeated application of standard 2D milling algorithms. This new approach in multiple-tool rough milling of complex shapes promises to reduce machining time of parts with complex shapes, such as modern moulds and casting patterns.

Cutting Path and Feedrate Optimization for Complex Surface Machining Using Ball End Milling Process

A new machining strategy, called cutting-path/adaptive-feedrate strategy, is proposed to improve the productivity of sculptured-surface productions subjected to force and dimensional constraints. In this proposed strategy, a new machining-planning aid, called maximum feedrate map, is developed. In this map, the maximum allowable feedrates at each control point along all machining directions subjected to the specified constraints are determined using a surface generation model. These local maximum-feedrate boundaries indicate the acceptable range of feedrates that a part programmer can use in the NC programming. In addition, the maximum feedrate map also provides the part programmer an important aid in selecting the cutting directions. The proposed strategy was applied to the machining planning for turbine blade die productions. Both computer simulation and experimental study were performed.