Article thumbnail
Location of Repository

[[alternative]]Generating Milling Tool Paths of Arbitrarily Shaped Pockets

By [[author]]沈柏廷, B. T. [[author]]Shen, 沈柏廷 and B. T. Shen

Abstract

[[abstract]]袋形工件之刀具路徑求自於工件輪廓的偏置,本研究以AutoLISP語言自動 識別螢幕上的工件輪廓圖形,並經由輪廓偏移以獲得刀具路徑。偏移過程 中往往有少切或過切的現象發生,故本研究提出〝定位法〞以避免少切現 象,同時也研發〝鄰邊過切檢驗法〞及〝滾球法則〞以去除局部過切現象 ;當這些法則用來求偏置路徑時,則可得本研究所定義之〝準偏置路徑〞 ,此準偏置路徑沒有少切及局部過切現象,惟有卡槽式的過切殘留著,待 將此種過切去除後,就可得本研究所定義之〝偏置路徑〞。當偏移路徑發 生自交時,即表示有過切的現象產生,本研究拋棄了Hansen之偵測過切時 所使用的干涉指數(interference index)法,因為當偏移路徑的自交點密 集在某一偏移(曲)線段圖元時,該(曲)線段的分裂與干涉指數的標示就會 變得複雜;同時,本研究也避免了Tiller及Suh等人之從整個的偏移路徑 中去尋找不過切迴圈的方法,因為當整個偏移路徑求出後再去求不過切迴 圈,將會因自交的檢驗圖元增多而耗費太多的自交計算,而且在尋找不過 切迴圈過程中,若是遇到複雜的偏移路徑自交,往往也難以判斷哪幾個偏 移圖元可組成不過切迴圈。 在本研究實際測試三種目前市場佔有率較 高的PC級CAD/CAM軟體的過程中,都發現有或多或少的少切或過切現象發 生,不過,若應用本研究所研發出的這些法則來求偏置路徑,則可以去除 這些PC級CAD/CAM軟體所無法避免的少切及過切現象,且可達到干涉指數 所無法達到的效果。 關鍵詞:袋形工件,偏置,電腦輔助設計,電腦輔 助製造,刀具路徑,少切,過切。 The milling tool paths of pockets are derived from their profiles. In this research, the profile data are obtained from the screen of the computer monitor automatically by using AutoLISP language. Milling tool paths are calculated out from these profile data. In the process of offsetting , overcutting or uncutting can be seen frequently. Hence , in this research , "location methods" are proposed to avoid uncutting, "adjacent edge checking" and "rolling ball algorithm" are proposed to avoid overcutting, Using these methods to offset, quasi-offset- curves which are defined by this research can be found. If tool on these curves, there will not any uncutting and partial overcutting exist, but gouging. After trimming out the gouging of quasi-offset-curves, offset-curves which are defined by this research can be found out finally.If there exist self- interference in the raw offset curve, that means overcutting occure. Allan Hansen's discriminating overcutting method of interference index is not adopted here because of the difficulty to calculate the interference index for the split small segments when self-interference points concentrate in one offset segment element. In this research, Tiller and Suh's method of finding correct loop from the the whole raw offset curves is also discarded because of the unnecessary self-interferencial calculation and the difficulty of finding the correct loop.In the testing of three commerical CAD/CAM softwares, there also exist some uncutting and overcutting. But those mistakes do not occure in the testing using the methods proposed in this research. The methods proposed in this research to produce offset-curves will achieve the effect that interference index can't meet.Keywords:pocket, offset, CAD/CAM, tool path, overcut, AutoLISP The milling tool paths of pockets are derived from their

Topics: 袋形工件, 偏置, 刀具路徑, pocket, offset, tool path, [[classification]]53
Year: 2010
OAI identifier: oai:ir.lib.ntnu.edu.tw:309250000Q/6377
Download PDF:
Sorry, we are unable to provide the full text but you may find it at the following location(s):
  • http://ir.lib.ntnu.edu.tw/ir/h... (external link)
  • Suggested articles


    To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.