| 摘要: | ECJM電化學精微噴流加工(ECJM, Electrochemical jet machining)是一種非傳統的加工技術，其技術是利用電化學反應所發生的金屬移除效應去加工，金屬解離後由電解液的噴射流動帶離加工區，而磨料混漿噴射加工(ASJM, Abrasive jet machining)過程則是由水柱夾帶著磨料粒子衝擊目標工件，進而沖蝕工件材料。電化學精微噴射加工具有電極不易耗損，以電解方式噴射去除被加工物、無加工應力及變質層、加工速度快及加工表面平滑度佳的優勢，
本文研究目標為結合ECJM電化學精微噴射加工與ASJM磨料混漿噴射加工。由於電化學加工技術具有獨特的加工特色，常被應用於他種機械難以加工之場合。但當電化學技術應用於碳鋼或熱處理過後材料加工時，其加工後表面會生成黑層(Black layer)即富碳層。此層非電化學反應析出之產物，而是靠周圍鐵以離子方式離開工件表面後脫落，但因碳活性大故容易積附在工件表面，且不易藉由一般電化學加工之電解液流動方式帶離工件表面，進而阻礙電化學加工導致加工速率降低以及加工後工件表面粗糙度增加。
有鑒於此，本文提出利用磨料漿體輔助電化學噴流加工對SKD11模具鋼進行微孔加工，利用物理性沖蝕和電化學腐蝕作用，來克服黑層阻礙加工之困難點，進而提升加工效率和降低表面粗糙度。
本文研究中使用500與700μm的中空管，電解液使用NaCl，探討不同電壓、電解液濃度、磨料濃度、加工間隙與流量對加工的影響性，並比較有效深度與深寬比，最後由有效深度與深寬比來選取最佳之加工參數。最後以最佳參數加工出一1000μm的孔徑，比對有無磨料輔助之電化學噴流加工之差異。
實驗結果顯示，電壓在70V，NaCl濃度在20%，磨料濃度在1%，加工間隙在1000μm，流量在340ml/min時有最佳的有效高度。而有磨料輔助之電化學噴流加工較無磨料輔助之電化學噴流加工在粗糙度與移除量上，效果都來得好。
;Electrochemical jet machining (ECJM) is one of the non-traditional machining technologies, the technology is by metal material removing through electrochemical reaction, the dissolved metal were carried away via jet flow from machining region. However, The process of abrasive slurry-jet machining (ASJM) is that erodes material using abrasive particles by a steam of fluid impinging on a target. ECJM has several advantages, such as difficult to wear electrode, removing part of workpiece by dissolved via jet, no residual stress and Metamorphic layer, high machining rate and good smoothness on machining surface.
In this thesis, the object of research is to combine ECJM and ASJM. Due to the unique technology of electrochemical machining, it is usually applied to other conditions which mechanics is hard to machine. However, when the electrochemical technology applies to machine carbon steel or the material which have been heat treatment, the black layer will be generated on the surface, that is Carbon-rich layer. This layer is not the products of the electrochemical reaction, but the iron in ions fall after leaves from the surface of workpiece. Because the carbon is active, it is easy to deposit to the surface of workpiece, and it is not easy to depart by electrolyte flow in general electrochemical machining method. Moreover, this layer will obstruct electrochemical machining, so it causes the lower rate of machining and more roughness on the surface after machining.
In view of these, we proposed a project that is to machine and clear burr on SKD11 by ASJM. We can overcome the obstruction of blacklayer in the physical erosion and electrochemical corrosion, so as to increase the efficiency of machining and decrease the roughness of the surface.
In this thesis, the hollow tube is used in 500 and 700μm, and the NaCl is chosen as the electrolyte to drill SKD11, and investigate the influence of different voltage, concentration, abrasive concentration, gap and flow. Moreover, we compare the effective height and aspect ratio to choose the best parameters, and make an object to machine a hole of 1000μm, and compare the difference if ECJM with abrasive or not.
The results show that the best effective occurs when voltage in 70V and NaCl concentration in 20%, gap in 1mm and the flow in 340ml/min. And no matter roughness or material removal, ECJM assisted with abrasive is better than ECJM only. |
