1畢業(yè)設計（論文）外文翻譯所在學院： 機械與電氣工程學院 班 級： 學生姓名： 指導導師： 合作老師： 日期： 年 11 月 4 日2GRINGING TECHNOLOGY -磨削技術(shù), 1994 - Stephen Malkin 原文：題目 Automated surface finishing of plastic injection mold steelwith spherical grinding and ball burnishing processesAbstract:This study investigates the possibilities of automated spherical grinding and ball burnishing surface finishing processes in a freeform surface plastic injection mold steel PDS5 on a CNC machining center. The design and manufacture of a grinding tool holder has been accomplished in this study. The optimal surface grinding parameters were determined using Taguchi’s orthogonal array method for plastic injection molding steel PDS5 on a machining center. The optimal surface grinding parameters for the plastic injection mold steel PDS5 were the combination of an abrasive material of PA Al2O3, a grinding speed of 18 000 rpm, a grinding depth of 20 μm, and a feed of 50 mm/min. The surface roughness Ra of the specimen can be improved from about 1.60 μm to 0.35 μm by using the optimal parameters for surface grinding. Surface roughness Ra can be further improved from about 0.343 μm to 0.06 μm by using the ball burnishing process with the optimal burnishing parameters. Applying the optimal surface grinding and burnishing parameters sequentially to a fine-milled freeform surface mold insert, the surface roughness Ra of freeform surface region on the tested part can be improved from about 2.15 μm to 0.07 μm.Keywords :Automated surface finishing · Ball burnishing process · Grinding process · Surface roughness · Taguchi’s method1 IntroductionPlastics are important engineering materials due to their specific characteristics, such as corrosion resistance, resistance to chemicals, low density, and ease of manufacture, and have increasingly replaced metallic components in industrial applications. Injection molding is one of the important forming processes for plastic products. The surface finish quality of the plastic injection mold is an essential requirement due to its direct effects on the appearance of the plastic product. Finishing processes such as 3grinding, polishing and lapping are commonly used to improve the surface finish.The mounted grinding tools (wheels) have been widely used in conventional mold and die finishing industries. The geometric model of mounted grinding tools for automated surface finishing processes was introduced in [1]. A finishing process model of spherical grinding tools for automated surface finishing systems was developed in [2]. Grinding speed, depth of cut, feed rate, and wheel properties such as abrasive material and abrasive grain size, are the dominant parameters for the spherical grinding process, as shown in Fig. 1. The optimal spherical grinding parameters for the injection mold steel have not yet been investigated based in the literature.In recent years, some research has been carried out in determining the optimal parameters of the ball burnishing process (Fig. 2). For instance, it has been found that plastic deformation on the workpiece surface can be reduced by using a tungsten carbide ball or a roller, thus improving the surface roughness, surface hardness, and fatigue resistance [3–6]. The burnishing process is accomplished by machining centers [3, 4] and lathes [5, 6]. The main burnishing parameters having significant effects on the surface roughness are ball or roller material, burnishing force, feed rate, burnishing speed, lubrication, and number of burnishing passes, among others [3]. The optimal surface burnishing parameters for the plastic injection mold steel PDS5 were a combination of grease lubricant, the tungsten carbide ball, a burnishing speed of 200 mm/min, a burnishing force of 300 N, and a feed of 40 μm [7]. The depth of penetration of the burnished surface using the optimal ball burnishing parameters was about 2.5 microns. The improvement of the surface roughness through burnishing process generally ranged between 40% and 90% [3–7].The aim of this study was to develop spherical grinding and ball burnishing surface finish processes of a freeform surface plastic injection mold on a machining center. The flowchart of automated surface finish using spherical grinding and ball burnishing processes is shown in Fig. 3. We began by designing and manufacturing the spherical grinding tool and its alignment device for use on a machining center. The optimal surface spherical grinding parameters were determined by utilizing a 4Taguchi’s orthogonal array method. Four factors and three corresponding levels were then chosen for the Taguchi’s L18 matrix experiment. The optimal mounted spherical grinding parameters for surface grinding were then applied to the surface finish of a freeform surface carrier. To improve the surface roughness, the ground surface was further burnished, using the optimal ball burnishing parameters.2 Design of the spherical grinding tool and its alignment deviceTo carry out the possible spherical grinding process of a freeform surface, the center of the ball grinder should coincide with the z-axis of the machining center. The mounted spherical grinding tool and its adjustment device was designed, as shown in Fig. 4. The electric grinder was mounted in a tool holder with two adjustable pivot screws. The center of the grinder ball was well aligned with the help of the conic groove of the alignment components. Having aligned the grinder ball, two adjustable pivot screws were tightened; after which, the alignment components could be removed. The deviation between the center coordinates of the ball grinder and that of the shank was about 5 μm, which was measured by a CNC coordinate measuring machine. The force induced by the vibration of the machine bed is absorbed by a helical spring. The manufactured spherical grinding tool and ball-burnishing tool were mounted, as shown in Fig. 5. The spindle was locked for both the spherical grinding process and the ball burnishing process by a spindle-locking mechanism.3 Planning of the matrix experiment3.1 Configuration of Taguchi’s orthogonal arrayThe effects of several parameters can be determined efficiently by conducting matrix experiments using Taguchi’s orthogonal array [8]. To match the aforementioned spherical grinding parameters, the abrasive material of the grinder ball (with the diameter of 10 mm), the feed rate, the depth of grinding, and the revolution of the electric grinder were selected as the four experimental factors (parameters) and designated as factor A to D (see Table 1) in this research. Three levels (settings) for each factor were configured to cover the range of interest, and were identi- fied by the 5digits 1, 2, and 3. Three types of abrasive materials, namely silicon carbide (SiC), white aluminum oxide (Al2O3,WA), and pink aluminum oxide (Al2O3, PA), were selected and studied. Three numerical values of each factor were determined based on the pre-study results. The L18 orthogonal array was selected to conduct the matrix experiment for four 3-level factors of the spherical grinding process.3.2 Definition of the data analysisEngineering design problems can be divided into smaller-thebetter types, nominal-the-best types, larger-the-better types, signed-target types, among others [8]. The signal-to-noise (S/N) ratio is used as the objective function for optimizing a product or process design. The surface roughness value of the ground surface via an adequate combination of grinding parameters should be smaller than that of the original surface. Consequently, the spherical grinding process is an example of a smaller-the-better type problem. The S/N ratio, η, is defined by the following equation [8]:where:yi : observations of the quality characteristic under different noiseconditionsn: number of experiment After the S/N ratio from the experimental data of each L18 orthogonal array is calculated, the main effect of each factor was determined by using an analysis of variance (ANOVA) technique and an F-ratio test [8]. The optimization strategy of the smaller-the better problem is to maximize η, as defined by Eq. 1. Levels that maximize η will be selected for the factors that have a significant effect on η. The optimal conditions for spherical grinding can then be determined.4 Experimental work and resultsThe material used in this study was PDS5 tool steel (equivalent to AISI P20) [9], which is commonly used for the molds of large plastic injection products in the field of automobile components and domestic appliances. The hardness of this material is about HRC33 (HS46) [9]. One specific advantage of this material is that after machining, the mold can be directly used for further finishing processes without heat treatment due to its special pre-treatment. The specimens were designed and 6manufactured so that they could be mounted on a dynamometer to measure the reaction force. The PDS5 specimen was roughly machined and then mounted on the dynamometer to carry out the fine milling on a three-axis machining center made by Yang- Iron Company (type MV-3A), equipped with a FUNUC Company NC-controller (type 0M) [10]. The pre-machined surface roughness was measured, using Hommelwerke T4000 equipment, to be about 1.6 μm. Figure 6 shows the experimental set-up of the spherical grinding process. A MP10 touch-trigger probe made by the Renishaw Company was also integrated with the machining center tool magazine to measure and determinethe coordinated origin of the specimen to be ground. The NC codes needed for the ball-burnishing path were generated by PowerMILL CAM software. These codes can be transmitted to the CNC controller of the machining center via RS232 serial interface.The goal in the spherical grinding process is to minimize the surface roughness value of the ground specimen by determining the optimal level of each factor. Since ?log is a monotone decreasing function, we should maximize the S/N ratio. Consequently, we can determine the optimal level for each factor asbeing the level that has the highest value of η. Therefore, based on the matrix experiment, the optimal abrasive material was pink aluminum oxide; the optimal feed was 50 mm/min; the optimal depth of grinding was 20 μm; and the optimal revolution was 18 000 rpm, as shown in Table 4.The main effect of each factor was further determined by using an analysis of variance (ANOVA) technique and an F ratio test in order to determine their significance (see Table 5). The F0.10,2,13 is 2.76 for a level of significance equal to 0.10 (or 90% confidence level); the factor’s degree of freedom is 2 and the degree of freedom for the pooled error is 13, according to F-distribution table [11]. An F ratio value greater than 2.76 can be concluded as having a significant effect on surface roughness and is identified by an asterisk. As a result, the feed and the depth of grinding have a significant effect on surface roughness.Five verification experiments were carried out to observe the repeatability of using the optimal combination of grinding parameters, as shown in Table 6. The obtainable surface roughness value Ra of such specimen was measured to be about 0.35 μm. 7Surface roughness was improved by about 78% in using the op- timal combination of spherical grinding parameters. The ground surface was further burnished using the optimal ball burnishing parameters. A surface roughness value of Ra = 0.06 μm was obtainable after ball burnishing. Improvement of the burnished surface roughness observed with a 30× optical microscope is shown in Fig. 8. The improvement of pre-machined surfaces roughness was about 95% after the burnishing process.The optimal parameters for surface spherical grinding obtained from the Taguchi’s matrix experiments were applied to the surface finish of the freeform surface mold insert to evaluate the surface roughness improvement. A perfume bottle was selected as the tested carrier. The CNCmachining of the mold insert for the tested object was simulated with PowerMILL CAM software. After fine milling, the mold insert was further ground with the optimal spherical grinding parameters obtained from the Taguchi’s matrix experiment. Shortly afterwards, the ground surface was burnished with the optimal ball burnishing parameters to further improve the surface roughness of the tested object (see Fig. 9). The surface roughness of the mold insert was measured with Hommelwerke T4000 equipment. The average surface roughness value Ra on a fine-milled surface of the mold insert was 2.15 μm on average; that on the ground surface was 0.45 μm on average; and that on burnished surface was 0.07 μm on average. The surface roughness improvement of the tested object on ground surface was about (2.15?0.45)/2.15 = 79.1%, and that on the burnished surface was about (2.15?0.07)/2.15 = 96.7%.5 ConclusionIn this work, the optimal parameters of automated spherical grinding and ball-burnishing surface finishing processes in a freeform surface plastic injection mold were developed successfully on a machining center. The mounted spherical grinding tool (and its alignment components) was designed and manufactured. The optimal spherical grinding parameters for surface grinding were determined by conducting a Taguchi L18 matrix experiments. The optimal spherical grinding parameters for the plastic injection mold steel PDS5 were the combination of the abrasive material of 8pink aluminum oxide (Al2O3, PA), a feed of 50 mm/min, a depth of grinding 20 μm, and a revolution of 18 000 rpm. The surface roughness Ra of the specimen can be improved from about 1.6 μm to 0.35 μm by using the optimal spherical grinding conditions for surface grinding. By applying the optimal surface grinding and burnishing parameters to the surface finish of the freeform surface mold insert, the surface roughness improvements were measured to be ground surface was about 79.1% in terms of ground surfaces, and about 96.7% in terms of burnished surfaces.References1. Chen CCA, Yan WS (2000) Geometric model of mounted grindingtools for automated surface finishing processes. In: Proceedings of the6th International Conference on Automation Technology, Taipei, May9–11, pp 43–472. 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Wiley,New York原文：題目 球形研磨和拋光注塑模具鋼的自動化表面精加工工藝10摘要：本研究討論在數(shù)控加工中心注塑模具鋼 PDS5 在自由曲面下進行自動化球形研磨和拋光球的表面處理工藝的可行性。研磨工具持有人的設計和制造已經(jīng)完成了這項研究。在加工中心中，表面的最佳磨削參數(shù)采用田口直交法來進行塑料注射成型鋼 PDS5 而確定。塑料注塑模具鋼 PDS5 表面最佳磨削參數(shù)是，一種 pa 的氧化鋁磨削材料組合，以 18000rpm 的速度，20μm 的磨削深度，以及50 毫米/分鐘的進給速度磨削。試樣的表面粗糙度 Ra 可以通過使用最佳的表面磨削參數(shù)來從 1.60 微米大約提高至 0.35 微米。表面粗糙度 Ra 還可通過使用最佳拋光參數(shù)的球拋光這一過程進一步改善至約 0.343 微米至 0.06 微米。應用表面打磨和拋光最佳參數(shù)，依次細研磨自由曲面模仁，自由曲面上測試區(qū)的表面粗糙度 Ra 部分可提高到約 2.15 微米至 0.07 微米。關(guān)鍵詞：自動化表面精加工·球打磨過程··表面粗糙度磨削工藝·田口方法。1．簡介塑料是重要的工程材料，由于其特性，如耐腐蝕，耐化學品，密度低，易于制造，并已在工業(yè)應用中越來越多地取代金屬部件。注塑成型是一種重要的塑料產(chǎn)品成型工藝，塑料模具表面光潔度是一個直接影響塑料產(chǎn)品外觀的必要條件。如磨削，拋光和研磨這樣的整理程序常用來改善表面光潔度。研磨工具砂輪的裝入已經(jīng)廣泛使用的傳統(tǒng)模具，模具加工等行業(yè)。為了自動化表面精加工進程，安裝了磨削工具的幾何磨具在（1）中引入。在自動化表面精加工系統(tǒng)中，球形研磨的球形研磨工具的加工進程模型在（2）中闡述。磨削速度，切削深度，進給速度，研磨材料，磨料，料度等砂輪特性都為球面磨削過程的影響參數(shù)，如圖 1 所示。注塑模具鋼的最佳球面磨削參數(shù)尚未在文獻中調(diào)查發(fā)現(xiàn)。近年來，正在開展一些研究來確定球擠光過程的最佳參數(shù)（圖 2）。據(jù)說使用碳化鎢球或滾子可減小工件表面的塑性變形，因而改善表面粗糙度，表面硬度和抗疲勞性能[3-6]。打磨過程是由加工中心[3，4]和車床[5，6]完成。對表面粗糙度有顯著影響的主要拋光參數(shù)是滾珠或滾子的材料，打磨力，進給速度，拋光速度，潤滑，打磨通過次數(shù)，等等[3]。塑料模具鋼 PDS5 的最佳表面打磨參數(shù)是混合油脂潤滑劑，碳化鎢球，200 毫米/分鐘的磨削速度，300N 的擠11壓力，40μm 打磨速度。使用最佳擠光參數(shù)的表面拋光穿透深度約為 2.5 微米。通過擠光工藝改善表面粗糙度后，介于 40％到 90％之間。這項研究的目的是在加工中心中塑料注塑磨具自由曲面的球形研磨和表面拋光加工程序的開發(fā)。使用球形表面研磨和拋光程序的自動化表面加工流程圖在圖 3 中展示。我們以設計和制造在機械加工中心中使用的球形研磨工具以及其定位裝置為開始。 球形表面的最佳磨削工藝參數(shù)通過利用田口直交方法來確定。在田口的 18課矩陣實驗中，4 因素 3 相應水平被選擇。表面磨削的最佳安裝球面磨削參數(shù)被應用到自由曲面載體的表面光潔度加工中。為了改善表面粗糙度，使用最佳擠光參數(shù)來對工件表面進行進一步打磨。2．設計了球形研磨工具及其定位裝置為了使在自由曲面中進行球研磨加工工藝成為可能，球磨床中心應該和 Z軸的加工中心形成配合，球面磨削工具的安裝以及他的設備調(diào)整設計如 4 圖所示。電動砂輪機用兩個兩個可調(diào)整支點螺釘安裝在刀架上。在圓錐槽對齊組件的幫助下，該磨具球中心配合一致。對齊磨床球，兩個可調(diào)整支點螺釘擰緊；之后，校準組件可以被移除。球磨床中心坐標之前的偏差，連桿有約 5 微米，這是由數(shù)控三坐標測量機測量。由機床振動引起的力被螺旋彈簧吸收。生產(chǎn)出來的球研磨工具和拋光球被安裝如圖 5 所示。為了球研磨過程和球擠光過程，主軸被一個主軸鎖定機制鎖定。3.矩陣實驗的規(guī)劃3．1．田口直交的配置通過進行田口直交[8]矩陣實驗，幾個參數(shù)的影響可以達到有效的使用。為配合上述球面磨削參數(shù)，該磨床球研磨材料（10 毫米直徑），進料速度，磨削深度,并且電動砂輪機的換擋被 4 個實驗因素所選擇，本實驗中指定由因素 A 到因素 D（見表 1）。每個因素的三個等級（設置）配置包括感興趣的區(qū)域，并定義為數(shù)字 1，2 和 3。研磨材料的三種類型，即碳化硅（SiC），白鋁氧化物（Al2O3，華盛頓州），粉紅色氧化鋁（Al2O3，賓夕法尼亞州）分別選用和研究。每個因素三個數(shù)值乃根據(jù)預先研究結(jié)果決定。L18 的直交選擇由矩陣實驗中球形研磨工藝的 4 個 3 級因素決定。123.2 數(shù)據(jù)分析的定義工程設計問題可以劃分為較小的較好類型，標準的最佳類型，較大的較好類型，簽訂目標類型，還有其他的（8）。該信號與信噪比（S/ N）比作為目標函數(shù)用于優(yōu)化產(chǎn)品或過程設計。工件表面的表面粗糙度值通過適當?shù)哪ハ鲄?shù)組合值應當比原表面的更小。因此，球形研磨過程是一個較小較好類型問題的例子。S / N比，η，是由以下方程定義[8]：yi：在不同條件下，觀測噪聲質(zhì)量特性。n：實驗次數(shù)。S / N比從L18直交實驗數(shù)據(jù)中獲取計算，各因素的主要作用是通過使用方差（ANOVA）技術(shù)分析和F-比測試決定（8），較小較好問題的優(yōu)化策略是最大化η，由1式定義。最大化η的水平選擇是由顯著影響η的因素負責選擇得。球形研磨的最佳條件可以被確定。4.實驗工作和結(jié)果 在這項研究中所使用的材料是PDS5工具鋼（相當于采用AISI P20的）[9]，常用在在汽車零部件和家用電器領(lǐng)域中的大型注塑產(chǎn)品模型中。這種材料的硬度為HRC33（HS46）[9]。這個材料的優(yōu)勢是加工后，由于其特殊的前處理，不需要熱處理，可直接用于進一步加工過程。該工件被設計制造用來安裝在測力計中測試反應力。PDS5工件大多被加工而后安裝在測功機上用于Yang- Iron Company ( MV-3A類型)的三軸加工中心上面的精銑，以及配備在FANUC Company的數(shù)控控制器( 0M10型)上。預加工表面粗糙度的測量，使用Hommelwerke T4000設備，約1.6微米。圖6顯示了球形研磨進程的實驗裝置。由雷尼紹公司生產(chǎn)的MP10觸摸觸發(fā)式探頭還集成了加工中心刀庫來測量和確定切削工件同步。擠光加工路徑的數(shù)控代碼可用在PowerMILL CAM軟件上。這些代碼可以通過RS232串行接口控制器傳輸?shù)綌?shù)控加工中心。在球面磨削過程的目標是通過確定各因素的最佳水平來盡量減小切削工件表面粗糙度的值。由于對數(shù)函數(shù)是一個單調(diào)遞減函數(shù)，我們應該最大化S / N比。因此，我們可以判斷每個因素的最佳水平，因為該水平擁有η的最大值。因此，基于矩陣實驗，最佳的研磨材料呈粉紅色氧化鋁;最佳的進給速度為50毫米/分鐘;最佳的磨削深度為20微米;公轉(zhuǎn)的最佳轉(zhuǎn)速為18000個.通過使用方差（ANOVA）技術(shù)分析和F比檢驗，各因素的主要作用的進一步確定是用來確定13其意義（見表5） 。根據(jù)F-分布表（11） ，F(xiàn)0.10,2,13是2.76的顯著性水平等于0.10（或90%的置信水平） ，因素的自由度為2，合并誤差自由度為13。大于2.76 F比率值可歸納為對表面粗糙度的顯著影響，并由星號標識。因此，進給速度和磨削深度對表面粗糙度有顯著影響。設定樣品的表面粗糙度值Ra經(jīng)測量大約為0.35 μm，在使用球面磨削參數(shù)的最佳組合后表面粗糙度提高約78％。切削表面使用拋光球最佳參數(shù)進一步打磨。擠光之后，設表面粗糙度Ra的值為0.6微米。圖8所示 30倍光學顯微鏡觀察拋光表面粗糙度的改善。經(jīng)過拋光之后，預加工表面粗糙度改善95%左右。由田口式矩陣實驗獲得的表面磨削球最佳工藝參數(shù)應用于內(nèi)膜自由曲面的表面加工以評估表面光潔度的改善。香水瓶被選定為測試載體。該測試對象的內(nèi)膜數(shù)控加工用PowerMILL CAM軟件模擬。經(jīng)過精細加工，內(nèi)膜將用從田口矩陣實驗中獲得的最佳球研磨參數(shù)進行進一步磨削。此后不久，切削表面用最佳擠光參數(shù)進行拋光，以進一步提高被測物體的表面粗糙度（見圖.9） 。磨具內(nèi)膜表面粗糙度用Hommelwerke T4000設備測量，精細研磨后磨具內(nèi)膜的表面平均粗糙度Ra平均為2.15微米；切削表面的為0.45微米；表面拋光的平均為0.07微米。被測對象切削表面的表面粗糙度大約改善為（2.15-0.45）/2.15=79.1％，而拋光表面的為（2.15-0.07） /2.15=96.7％。5 結(jié)論 在這項工作中，注塑模具自由曲面的表面加工處理中自動化球研磨和擠光的最佳參數(shù)在加工中心成功的開發(fā)了。球面磨削工具的安裝（及其排列組成部分）被設計和制造。最佳球面研磨磨削表面參數(shù)通過田口L18的矩陣實驗被測定。注塑模具鋼PDS5的最佳表面研磨參數(shù)分別是粉紅色鋁氧化合物（Al2O3, PA）的混合研磨材料，50毫米/分鐘的進給速度，20微米的磨削深度，18 000轉(zhuǎn)的公轉(zhuǎn)。試樣的表面粗糙度Ra通過使用最佳球研磨條件進行表面磨削可以大概從1.6微米提高至0.35微米。通過應用最佳表面打磨和拋光參數(shù)對磨具內(nèi)膜自由曲面進行表面加工。改善表面粗糙度后，在切削表面中，切削表面大概是79.1%，在拋光表面上大約是96.7%。14