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論文 |
論文
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閻, 喜仁 ; 白瀬, 敬一 ; 河端, 裕 ; 平尾, 政利 ; 安井, 武司
概要:
The productivity of machining centers is influenced strongly by the quality of NC programs. To investigate the productivity, an NC program simulator has been developed to analyze and evaluate an NC program by decoding its NC codes. With
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the simulator, even before the actual machining, the tool paths can be displayed and the operational times occupied in the positioning feed motion and cutting feed motion, etc. can be calculated. The effects of the maximum speed and the acceleration of positioning feed on the productivity have been analyzed. Additionally, the influence of feedrate override function to shorten the operational time has been investigated in the conventional and the high speed cutting, respectively. From the results obtained from analyzing three NC programs, it is found that the effectiveness of the override function depends on the relation among the average moving distance, the commanded feedrate and the acceleration of cutting feed. Especially, in the case of the NC program for machining dies or molds, the productivity will be hardly improved using faster feedrate, because the actual feedrate hardly increases as expected due to the tiny moving distances of NC blocks. High speed & high precision function, which is an advanced optional function, is much more effective not only to improve the productivity but also to keep the machining accuracy of high speed cutting.
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論文 |
論文
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閻, 喜仁 ; 白瀬, 敬一 ; 河端, 裕 ; 平尾, 政利 ; 安井, 武司
概要:
(1) 生産性評価指数として有効送り速度比を導出し, 生産性の良否には, 位置決め制御系の時定数, 工具の1ブロック当たり平均移動距離, 工具移動ベクトルの向きの変化が影響を及ぼすことを示した. (2) 斜面加工で同じ加工精度を目標に, 同
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じ半径方向の切込み条件で加工時間を比較すると, 斜面の勾配が0°または90°に近くない限り, スクウェアエンドミルよりもボールエンドミルを用いた方が生産性が良くなる.また, 工具径が大きいほどボールエンドミルがスクウェアエンドミルより効率的である. (3) 典型的な加工形状に対して, 生産性評価指数eを用いて工具経路パターンの違いによる生産性評価を行い, 等高線パターンによるeが, Zigzagパターンによるeよりも大きいことを示した. (4) 加工時間の比較でも, 一般に等高線パターンはZigzagパターンに比べて加工時間が短い.例外は, 波状スプライン面をZigzagパターンで波状に沿って加工する場合であった. (5) 等動力, 中高送りでの加工では, 一般に小径工具の方が加工時間が短い.例外は, 島があるポケット加工の場合であった. The productivity of machining centers is affected not only by the effective feed rates and average tool travel per block studied in the first report, but also by the generated tool paths, especially the variation of moving vectors of the tool. In this paper, first of all, the factor of productivity evaluation is defined extensively to the case of multi-F code, and furthermore expressed as a function of the time constants, feed, average travel per block and the moving vectors of the tool. The expression of the factor shows that the smaller the time constants and the average variation per block of moving vectors, the higher the productivity is, and the longer the average travel per block, the higher the productivity is. Then with feature-based work models, namely, spline plane, slope, boss, island and pocket, being exemplified, the productivity of those NC programs generated by I-DEAS CAM tool is analyzed by the self-developed NC program simulator in two patterns of tool paths, namely the contour line and zigzag. The results show that in most cases, the productivity of the tool path in contour line pattern is higher, and the productivity of machining with a tool of smaller diameter is higher when the cutting power is kept constant. The theoretic and simulative studies on the tool path will contribute to the development of new CAM tools.
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