| 摘要: | SKD11經熱處理後，硬度達HRC58至60，係屬於難切削材料，利用傳統機械加工方法不易對其進行切削加工，容易使刀具產生磨耗而鈍化，致使切削力上升，本研究藉由超音波振動輔助液中銑削方式針對熱處理後的SKD11進行開槽銑削之研究，探討不同輔助方式與參數如超音波功率等級、主軸轉速、進給速率及切削深度對加工品質特性之影響，加工品質特性包括有表面粗糙度、刀具磨耗與加工深度、刀腹磨耗現象與加工後表面形貌，藉由表面粗糙度量測儀量測加工後工件表面粗糙度，透過千分錶量測加工後工件加工深度，另透過雷射共軛焦暨白光干涉顯微鏡(LSCM)、光學顯微影像量測儀(OM)及場發射掃描式電子顯微儀(SEM)觀察加工後刀腹磨耗現象與表面形貌分析。
實驗結果顯示，藉由超音波振動輔助與於切削液中加工之方式，透過超音波高頻振動刀具，可使連續性切削轉變為間歇性切削，且因刀尖與材料之間產生間歇性分離作用，使切削液更容易進入刀具尖端，能降低切削區域中的切削力，並同時藉由將刀具及工件浸沒於切削液中，降低切削中之溫度，減少刀具磨耗情形，從而改善加工後的表面品質，根據實驗結果，於超音波功率等級 Level 1 (Amplitude：1.9 μm)、進給速率為100 mm/min、主軸轉速 6000 rpm及切削深度為0.01 mm下，可得到較佳的表面粗糙度0.070 μmRa、加工深度0.023 mm及較小之刀具磨耗量0.034 mm，使用液中輔助方法相較於未使用液中輔助，表面粗糙度下降約4.87%，而刀具磨耗量下降了13.1%。
;SKD11, with a hardness of HRC58 to 60 after heat treatment, is difficult to be cut using traditional machining methods. The tool is likely to be worn and passivated, so that the cutting force increases. This study used the ultrasonic vibration assisted submerged-milling for slotting milling of SKD11 after heat treatment, and discussed the influence of different assistant methods and parameters such as ultrasonic power level, spindle speed, feed rate and cutting depth on machining quality characteristics. The machining quality characteristics included surface roughness, tool wear and machining depth, flank wear phenomenon and surface morphology after machining. The workpiece surface roughness after machining was measured by a surface roughness measuring instrument, and the workpiece machining depth after machining was measured by a dial gauge. The flank wear phenomenon after machining was observed and the surface morphology was analyzed using a LSCM, an OM and a SEM.
The experimental results show that by the ultrasonic vibration assist and submerged-milling, continuous cutting can be transformed into intermittent cutting through ultrasonic high-frequency vibration of the tool. Due to the intermittent separation between the tool tip and the material, the cutting fluid is easier to enter the tool tip. The cutting force in the cutting area can thus be reduced. The tool and workpiece were immersed in the cutting fluid, the cutting temperature was lowered, and the tool wear was reduced, thereby improving the surface quality after machining. According to experimental results, in the conditions of ultrasonic power Level 1 (Amplitude: 1.9 μm), feed rate 100 mm/min, spindle speed 6000 rpm and cutting depth 0.01 mm, a better surface roughness of 0.070 μmRa, machining depth of 0.023 mm and less tool wear of 0.034 mm can be obtained. In comparison to the method without submerged-milling, the surface roughness of the method with submerged-milling was reduced by about 4.87%, and the tool wear was reduced by 13.1%. |
