| 摘要: | 現今工業產品中，利用模具生產產品的比例愈來愈高，加上市場競爭的激烈化，模具的加工速度和精度之要求愈來愈嚴格，合金工具鋼(SKD11)具有高硬度、高強度、高韌性和耐磨耗等良好的機械性質，目前已廣泛被使用於模具材料。小徑深孔加工為模具加工中一項非常重要的加工過程，小徑深孔加工雖有很多方法(如傳統的切削加工、非傳統的雷射加工)，非傳統的放電加工(Electrical discharge manufacture)由於機器設備簡單，加工成本低廉，加工精度及表面狀態皆可達所需的規格，利用放電加工作小徑深孔加工是值得推薦的一種加工方法，對合金工具鋼材料(SKD11)作小徑深孔加工值得深入研究。 本研究利用國產快速穿孔放電加工機為實驗機器，以外徑3mm，內徑1mm的黃銅管為電極，添加粒徑25μm石墨粉末水溶液為加工液，對合金工具鋼(SKD11)材料進行快速穿孔放電加工，探討放電脈衝電流、脈衝時間、電容、加工液噴流壓力、加工液濃度以及主軸進給速度等六組各種不同參數值對快速穿孔放電加工的材料去除率、電極消耗率、表面粗糙度以及入口孔徑和出口孔徑的孔徑差異量等特性的影響。 實驗結果顯示脈衝電流、脈衝時間、電容、噴流壓力以及主軸進給速度等越大時，輸入的能量也較大或加工速度較大，電極消耗率和材料去除率皆越大；加工液濃度愈大時，工具和材料二電極的碳素保護層增加，電極消耗率和材料去除率有降低的趨勢；脈衝電流和脈衝時間參數值越大時，輸入的放電能量增加，放電痕直徑會變大、放電痕深度會加深，工件加工面的表面粗糙度值有增大的趨勢；主軸進給速度大時，去除加工面融熔材料較均勻，加工面的表面粗糙度值有稍許降低的趨勢；加工液的噴流壓力、放電電容值參數對表面粗糙度值的影響不大；加工液石墨濃度增加有分散放電效果，表面粗度有變好的趨勢；脈衝時間、電容、脈衝電流以及主軸進給速度等參數值較大時，輸入的能量較大，加工速度增加，相對的縮短了穿孔加工時間，減少二次放電次數，入口孔徑和出口孔徑的孔徑差異量有變小的趨勢；加工液的石墨濃度越大，工具和材料二電極的碳素保護層增加，入口孔徑和出口孔徑的孔徑差異量有降低的趨勢。 Today, using die products is increasing in industry. Alloy tool steel SKD11 has the excellent mechanical properties of high hardness, high strength, high toughness and abrasion-proof, so it is using generally as die material. This study use local fast drilling discharge machine with brass tube electrode of 3 mm outer diameter and 1 mm inner diameter and working liquid by adding graphite particles of particle diameter 25 micro-meter. By doing fast drilling discharge to alloy tool steel SKD11, we study six different parameters as pulse current, pulse duration, capacity, liquid pressure, concentration and feed speed having the effect on material removal rate, electrode wear rate, surface roughness, inlet diameter, variation between entrance and exit of fast drilling discharge. By experimental results we realize the increase of pulse current, pulse duration, capacity, liquid pressure and feed speed, also the increase of input energy or working speed, electrode wear rate and material removal rate will increase, too. The increase of concentration of working liquid will increase the coated carbine of tool and material electrode, so electrode wear rate and material removal rate will decrease. The increase of pulse current and pulse duration will increase input discharge energy, hole diameter, hole depth and surface roughness. The increase of feed speed will decrease surface roughness. The parameters as liquid pressure, capacity and concentration will not have obvious effect on surface roughness. The increase of pulse duration, capacity, pulse current and feed will increase input energy and working speed, so it will decrease drilling time and secondary discharge times and variation between entrance and exit. The increase of graphite concentration will decrease variation between entrance and exit. |
