电火花加工变质层对模具成形表面的影响

电火花加工是模具制造的主要加工手段之一,其物理本质决定了用该手段加工的模具成形表面存在表面变质层.分析表面变质层的形成机理、变质层对模具质量和寿命的影响,并提出对策.     

关于线切割加工的变质层

目前线切割加工已广泛应用于模具制造行业中,但线切割加工的工件表面硬度低、磨损快,有时还出现碎裂现象。根据近几年国外对这一问题的探索,发现造成上述现象的主要原因是由于在线切割加工的工件表面形成了“电加工变质层”。下面将电加工变质层的组织状况以及防止和去除变质层的方法作一介绍。 1.变质层的组织状况线切割加工是利用放电发出的高热和电解作用使金属熔融或气化来进行加工的。加工后工件加工表面因急速冷却使熔融状态的金属再凝固而形成了“电加     

基于线切割加工中模具表面变质层的分析

介绍了线切割加工中模具表面变质层的形成及影响因素，并对模具表面所形成的显微裂纹提出了预防措施。     

电火花线切割后抛光工艺对钢表面质量的影响

<正> 一、前言线切割是一种广泛使用的模具加工方法,它使模具加工工序简化,生产周期缩短而受到大家的欢迎。但由于加工表面存在着变质层,常常导致模具早期疲劳开裂,影响了模具的使用寿命。为改善电加工变质层这     

型腔模化学抛光技术

化学铣削(简称化铣)就是用化学方法切削金属,化学抛光属于化学铣削的范畴。工件经过化学抛光能达到理想的表面粗糙度,在模具制造中我们应用了化学抛光工艺。我国的型腔模和热锻模都采用电火花加工。加工后模具型腔表面形成一层白亮变质层,该层有较大的残余拉应力,硬度高,粗糙度差,有时还有裂纹,影响寿命,为此需要抛光。以前用手工抛光,劳动强度大,费时间。现     

利用ANSYS的模具线切割加工表面变质层分析

分析了线切割(WEDM)加工表面变质层的影响因素,根据DK7732机床在模具加工中的应用,用有限元软件AN-SYS对线切割加工过程进行温度分布计算,在采用与真实加工相类似的边界条件下,模拟电参数(脉冲宽度)的变化对线切割加工工件表面变质层的影响,得出在实验条件下,按DK7732机床各档脉冲宽度加工时变质层的分布数据,以及其高温层和低温层区域相对较宽、中温区域很窄的结论,有利于后续的工艺探究。同时提出了减少变质层的相应措施。     

7CrSiMnMoV钢电火花线切割电参数优化及变质层研究

通过电火花线切割加工7CrSiMnMoV模具钢,对线切割加工电参数和工件表面的变质层进行了研究。利用正交试验的方法对加工电参数进行了优化,电参数优化后的工件表面质量得到提高。在此基础上观察分析了7CrSiMnMoV模具钢线切割后变质层的微观形貌和显微组织,并利用X射线衍射仪对线切割加工试样表面变质层的物相进行了分析。     

电火花线切割后抛光工艺对钢表面质量的影响

一、前言线切割是一种广泛使用的模具加工方法,它使模具加工工序简化,生产周期缩短而受到大家的欢迎。但由于加工表面存在着变质层,常常导致模具早期疲劳开裂,影响了模具的使用寿命。为改善电加工变质层这一不利影响,本文总结了用喷丸抛光、超声抛光、电化学—机械修磨抛光,使原始的线切割加工表面层去除或变质,形成新的表面层。用对比的方法分析 Cr12钢抛光前后金相组织,显微硬度、残余应力、表面粗糙度     

模具电加工的后续工序——新兴抛光方法的加工原理及其应用

电火花线切割加工后的模具表面上存在一层厚薄不均的变质层,若在其后采用手工抛光,既费工耗时又难保质量。七十年代以来,新型的模具抛光方法,相继问世,按其原理分为三类:     

线切割加工表面的玻璃珠喷丸抛光

线切割加工大多被用于冲模制造中。但是线切割加工表面会产生加工变质层形成与母体材料不同的组织,它是引起模具迅速磨损与鳞片状剥落的原因,所以,对于精密模具在线切割加工后需要进行研磨抛光加工。 本文介绍玻璃珠喷丸在线切割加工表面研磨抛光中的应用及其对冲模表面性能的影响。玻璃珠喷丸加工在日本的应用普及率还很低,但这一工艺在欧洲已得到广泛使用。 一、玻璃珠喷丸法 玻璃珠喷丸是喷丸加工法中的一种,多用来清除零件表面的毛刺、氧化皮锈斑和进行无光泽处理。 玻璃珠喷丸法的原理与传统的喷砂法相同,即利用压缩空气把颗粒很细小的…     

Electrical discharge abrasive drilling of hard materials using a metal matrix composite electrode

The main object of the present work was to develop an electrical discharge abrasive drilling (EDAD) methodology to remove the re-solidified layer through the grinding induced by a metal matrix composite electrode prior to the re-solidification of molten material. A metal matrix composite (Cu/SiC_p) electrode, with an electroless pretreatment of Cu coating on SiC_p to enhance bonding status between Cu and SiC_p, was made with a rotating device and this was employed to study the EDAD technology. The machinability of the mold steel HPM50 and tungsten carbide P20 was investigated by the combined technologies of EDAD. The machined surfaces of these materials were examined by scanning electron microscopy (SEM) and their surface roughness measured by a profilemeter. From the experimental results, it was found that the EDAD machining efficiency was three to seven times than that of normal EDM operation for mold steel. However, the efficiency improvement is hardly detectable for tungsten carbide. In addition, the surface roughness of both materials could be improved in comparison with that achieved after EDM.     

线切割加工条件对模具零件表面粗糙度的影响

为改善快走丝电火花线切割加工的表面粗糙度,提高模具加工的质量和使用寿命,分析了快走丝电火花线切割加工条件中放电参数、工作液和电极丝对零件表面粗糙度的影响,并在此基础上提出了改善零件表面粗糙度的相应措施和方法。     

浅析模具制造中电火花技术的应用

通过电火花加工原理和加工过程,对模具加工精度的有关影响因素进行了分析,介绍了电火花加工工艺流程的有关应用技术,并有效提高了电火花加工后的模具精度。     

基于电火花加工方法的表面改性技术研究

研究了一种在普通电火花加工机床上实现金属工件表面改性的新方法。它是在传统电火花加工方法的基础上，采用TiC-Co半烧结体电极和普通煤油工作液，在工件表面形成一层硬质陶瓷层，从而达到改善工件表面性能的目的，这种新方法被称之为放电沉积。对放电沉积原理进行了探讨，在大量试验的基础上，总结了放电沉积的工艺方法。通过扫描电镜、电子探针、X射线衍射分析、摩擦磨损等试验，对形成的沉积层特性进行了定量和定性分析。最后利用该方法在普通的高速钢车刀上进行了初步应用。试验与分析表明，该方法是一种极具潜力的金属表面改性方法。     

模具高速切削关键技术研究进展

通过对高速切削技术(HSM)含义的描述,详细介绍了高速切削加工技术的特点、先进性及其在模具加工行业中的应用。与传统的模具加工工艺(普通放电加工EDM)相比较,详细分析了高速切削技术应用于模具加工制造业中的优势,并重点从高速切削机床、加工刀具、加工工艺技术及策略等方面,对高速切削技术应用于模具制造中的关键技术进行了分析探讨。最后综述了模具高速加工中存在的问题并对模具高速切削加工技术在我国的前景进行了展望。     

Investigation of the relationship between the white layer thickness and 3D surface texture parameters in the die sinking EDM process

It is a well known fact that the EDM process results in the formation of a hard, brittle recast layer on the component's surface. Several investigations have been carried out in order to assess the nature of the recast layer in terms of its phase structure, the microhardness, presence and the density of cracks, and other surface features. Some researchers [Barash, Delpretti] have reported mathematical relationships between the thickness of the white layer and 2D amplitude surface roughness parameters (such as R_a and R_t). But so far no investigation has been reported which correlates the thickness of the white layer with 3D surface roughness parameters, especially those related to spatial parameters. This paper presents an experimental investigation of the effect of the EDM process factors (current and pulse on-time) on the thickness of the white layer. Empirical equations relating the thickness of the white layer with 3D surface texture amplitude, spatial and volume parameters are presented and their physical basis is discussed. The results of this study show that a better correlation can be obtained between the average thickness of the white layer (AWLT) and the spatial parameter, S_ds as compared to other 3D surface texture parameters. This is believed to be mainly due to the similar effect of the current and pulse on-time on both AWLT and S_ds. The possible effect of surface tension between the solid and liquid phases on the thickness of the white layer during erosion is also discussed.     

Effect of silicon particles on the rapidly resolidified layer of Al-Si alloys in the electro discharge machining process

The rapidly resolidified layer is formed by the re-solidification of residual molten materials on the machined surface during the electric discharge machining (EDM) process. This study adopts a range of 4–29 wt% to change the silicon content in Al-Si alloy specimens to clarify the effect of silicon particles including the content, area fraction and intercept length of primary silicon particles on the performance of the rapidly resolidified layer during the EDM process. The layer thickness, surface roughness and ridge density on the rapidly resolidified layer are considered in the performance evaluation and explored by experiment. Experimental results indicate that the EDMed surface has a continuous ridge appearance and the effect of silicon particles including the content, area fraction and intercept length of primary silicon particles has the advantage of more ridge density. The rapidly resolidified layer thickness and surface roughness on the EDMed surface tend to increase with increasing the content and area fraction of the silicon particles.     

进电端放电法对单晶硅电火花加工接触电阻的影响研究

为改善高电阻率硅的电火花线切割可加工性,提出了一种在半导体电镀金属薄膜表面放电的方法（简称进电端放电法）。首先在硅(电阻率为2.1Ω·cm)表面电镀一层铜膜,然后利用铜刷作电极,在铜膜表面进行放电,利用放电形成的高温在硅表面形成重掺杂层,以降低接触势垒。分析了表面重掺杂层的形成机理,制备了硅试件并得到了伏安曲线,结果表明,试件的进电端接触电阻明显减小。最后采用进电端放电法对电阻率为2.1Ω·cm、直径为100mm的硅锭进行电火花线切割试验,加工效率可由12mm2/min提高至30mm2/min。     

Surface microstructure replication in injection molding

In recent years, polymer components with surface microstructures have been in rising demand for applications such as lab-on-a-chip and optical components. Injection molding has proven to be a feasible and efficient way to manufacture such components. In injection molding, the mold surface topography is transcribed onto the plastic part through complex mechanisms. This replication, however, is not perfect, and the replication quality depends on the plastic material properties, the topography itself, and the process conditions. This paper describes and discusses an investigation of injection molding of surface microstructures. The fundamental problem of surface microstructure replication has been studied. The research is based on specific microstructures as found in lab-on-a-chip products and on rough surfaces generated from EDM (electro discharge machining) mold cavities. Emphasis is put on the ability to replicate surface microstructures under normal injection-molding conditions, i.e., with commodity materials within typical process windows. It was found that within typical process windows the replication quality depends significantly on several process parameters, and especially the mold temperature. For the specific microstructures, evidence suggests that step-height replication quality depends linearly on structure width in a certain range.     

INVESTIGATING THE EFFECTS OF EDM PARAMETERS ON SURFACE INTEGRITY,MRR AND TWR IN MACHINING OF Ti–6Al–4V

Ti–6Al–4V is a kind of difficult-to-cut material with poor machinability by traditional machining methods, while electrical discharge machining (EDM) is suitable for machining titanium alloys. In this paper, three input machining parameters including pulse current, pulse on time and open circuit voltage were changed during EDM tests. To investigate the output characteristics; material removal rate (MRR), tool wear ratio (TWR) and different aspects of surface integrity for Ti–6Al–4V samples such as topography of machined surface, crack formation, white layer (recast layer) thickness and microhardness were considered as performance criteria. The variations of MRR and TWR versus input machining parameters were investigated by means of main and interaction effect plots and also verified by ANOVA results. The effect of pulse energy based on pulse on time and pulse current variations against recast layer thickness and microhardness was studied. The possibility of forming different chemical elements and compounds on the work surface after EDM process was investigated by EDS and XRD analyses. The experimental results revealed that general aspects of surface integrity for machined samples are mostly affected by pulse current and pulse on time. The approximate density of cracks, micro holes and pits on the work surface is intensively dependent on pulse energy variations. Although increase of pulse energy improves the material removal efficiency but leads to increase of average thickness and microhardness of recast layer.