Development of the Optimal Feed Value Selection for Milling Process
Supat Ieamsupapong*
บทคัดย่อ
จุดประสงค์หลักของงานวิจัยชิ้นนี้คือการพัฒนากลศาสตร์ของขั้นตอนการตัดเฉือนโดยใช้งานร่วมกับต้นแบบของดอกกัดที่สามารถเชื่อถือได้และต้นแบบของแรงตัดทางกลที่เป็นที่ยอมรับในความเที่ยงตรงของแรงที่คำนวณได้ สำหรับใช้เลือกค่าพารามิเตอร์ต่างๆ ของกระบวนการกัด โดยจะเน้นที่การค้นหาค่าที่เหมาะสมที่สุดของระยะป้อน ภายใต้สมมุติฐานที่ว่า เราทราบค่าที่เหมาะสมที่สุดของความเร็วตัดและระยะตั้งลึกของกระบวนการกัดดังกล่าวล่วงหน้าก่อนแล้ว เนื่องจากในปัจจุบันนี้มีการพัฒนาเทคโนโลยีของเครื่องตัดความเร็วสูงไปได้ไกลมากจากอดีตจึงทำให้มีเทคโนโลยีกระบวนการกัดที่ดีขึ้นประกอบกับมีความต้องการที่จะลดเวลาในการผลิตและค่าใช้จ่ายที่เกิดขึ้นในกระบวนการผลิต ด้วยเหตุนี้เองจึงทำให้มีช่องว่างที่สามารถจะปรับปรุงพัฒนากระบวนการกัดในปัจจุบัน ซึ่งจะได้กล่าวในรายละเอียดและแสดงผลของงานวิจัยในบทความชิ้นนี้
Abstract
The overall goal for this work was to develop a mechanics of cutting based procedure coupled with a dependable cutter model and reliable mechanistic cutting force model for selecting the appropriate cutting conditions, particularly, the optimal feed value selection under the assumption that optimal values of cutting speed and depth of cut were known for milling process. With the availability of today’s high speed machining technology and the requirement for reducing machining time and cost, there is potential for improvement in the current milling process which will be described and shown in this work.
Keywords: cutter model, mechanistic force model, optimal feed value selection
1. Introduction
The “rule of thumb” or intuitive techniques commonly used to determine suitable values for the cutting parameters rely on trial and error and/or experience of the process engineer/machinist. Clearly, this is a very costly and time-consuming approach which is not desirable. Consequently, the development of approaches for predicting cutting forces and feed values have become the interest of the recent industrial and academic research. There were a lot of efforts to investigate the prediction of milling force. W. Kline [1], P. Lee and Y. Altintas [2] were among the first who developed the milling force prediction from orthogonal cutting. In a few years later, S. Engin and Y. Altintas [3] extended their work to come up with general cutter model which are widely used on these days. However, these researches focused on cutting force, mechanics, and dynamics of cutting process which
* Lecturer, Department of Production Engineering, King Mongkut’s University of Technology North Bangkok, Phone 0-2913-2500 Ext.8215, Fax 0-2587-0029, E-Mail: supat_272@yahoo.com
วารสารวิชาการพระจอมเกล้าพระนครเหนือ ปีที่ 18 ฉบับที่ 2 พ.ค. - ส.ค. 2551
The Journal of KMUTNB., Vol. 18, No. 2, May - Aug. 2008
makes a missing link from cutting force to optimal cutting parameters and consequently manufacturing cost. Therefore, this research work was developed from S. Ieamsupapong [4] which presented a simple model to represent a work piece surface and combine with reliable well-established mechanistic cutting force model by S. Engin and Y. Altintas [3] to come up with the optimal feed value selection strategy for milling process.
2. Methodology
2.1 Assumptions
Some assumptions were applied to the reliable mechanistic cutting force model by S. Engin and Y. Altintas [3] and Y. Altintas [5] and the feed selection algorithm for the milling process. Since there are many of factors in dynamics of milling process therefore some effects are still not well-understood and have not been included in the model. This phenomenon will be shown later in this work that the simulated force profiles, which are nice and smooth while the real cutting force profiles fluctuate because of some dynamic effects that exist. These assumptions can be summarized as follows:
• The mechanistic force model does not account for tool wear.
• The mechanistic force model assumes no chatter in cutting process.
• The mechanistic force model only accounts for the static part of the cutting process but not the dynamic part.
• The specified tolerance is entirely due to tool deflection.
2.2 Overall Approach
The overall approach used in developing the optimal feed selection strategy is illustrated in Figure 1. The goal of this strategy is to determine the maximum allowable feed value that yields a resultant cutting force which is less than or equal to
Figure 1 Overall methodology used in this work.
on cutting force, mechanics, and dynamics of cutting process which makes a missing link from cutting force to optimal cutting parameters and consequently manufacturing cost. Therefore, this research work was developed from S. Ieamsupapong [4] which presented a simple model to represent a work piece surface and combine with reliable well-established mechanistic cutting force model by S. Engin and Y. Altintas [3] to come up with the optimal feed value selection strategy for milling process. 2. Methodology 2.1 Assumptions Some assumptions were applied to the reliable mechanistic cutting force model by S. Engin and Y. Altintas [3] and Y. Altintas [5] and the feed selection algorithm for the milling process. Since there aremany of factors in dynamics of milling process therefore some effects are still not well-understood and have not been included in the model. This phenomenon will be shown later in this work that the simulated force profiles, which are nice and smooth while the real cutting force profiles fluctuate because of some dynamic effects that exist. These assumptions can be summarized as follows: