疊片在熱加壓下制造工藝的研究外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯,壓下,制造,工藝,研究,外文,文獻(xiàn),翻譯,中英文 外文翻譯 Study of laminated object manufacturing with separately applied heating and pressing Springer-Verlag Abstract To improve the hot-pressing process currently employed in laminated object manufacturing (LOM),an innovative heating-and-pressing separation system is proposed, and heat transfer problems of this system are investigated. A thermal model is first established. It is solved numerically by the finite element method (FEM) software ANSYS, and verified by experiments. Based on the numerical solution under various operating conditions, it is found that the operating temperature of an adhesive can be reached quickly when the heater is maintained at a higher temperature, corresponding to a deeper heat-affected zone. This shortcoming can be effectively reduced if the speed of the heater is increased. Hence, a higher heater temperature together with a higher moving speed is suggested to shorten processing time and promote manufacturing efficiency. Through analysis, the appropriate distance between the roller and the heater, so as to obtain finished parts of high quality, is determined. Keywords Heat affected layer. Laminated object manufacturing .Rapid prototyping . Thermal model 1 Introduction Rapid prototyping (RP) manufacturing technology has been highly valued and explored by manufacturing industries and scientific institutes worldwide in recent years. Laminated object manufacturing (LOM) is one of the RP techniques that principally adopts the process of laminated forming [1, 2]. The bonding process is accomplished by applying heat and pressure by way of rolling a heated metal cylinder across a paper sheet, which has a thin layer of thermoplastic adhesive on the bottom side. The iterative process of bonding and laser cutting is repeated until the construction of the final layer is completed. Pak and Nisnevich [3] proposed a formula for a thermal model of LOM to analyze the heat transmission while the hot roller, i.e., the heated metal cylinder, hot-presses on the workpiece. Sonmez and Hahn [4] later addressed some of the problems that occurred in the hot-pressing process by analyzing the effects caused by parameters like temperature and pressure upon the paper with the FEM. However, there are still several disadvantages and difficulties in the LOM process. For example, papers are easily to be peeled off at the adhesion layer, bubbles occur in the workpiece, and it is hard to control the parameters during the hot-pressing process. The workpiece can either be burnt due to overheating, or an integrating failure can occur due to insufficient temperature. Furthermore, improper pressure and speed are the major causes for poor quality of cohesion as well. To effectively reduce the disadvantages of LOM caused by the hot-pressing process, a process of heating-and-pressing separation to is proposed for better workpiece results. This method is in contrast to the joint approach of the LOM machine, in which heating and pressing are applied simultaneously. This paper studies the heat transfer problems of the proposed system. The effects of the operating parameters on the hot-pressing process and on the arrangement of the heating and pressing are investigated. 2 Thermal model 2.1 Conceptions for heating-and-pressing separation The heating-and-pressing separation process of this research involves isolating the operations of heating and pressing, as shown in Fig. 1, which gives a 2D demonstration of the hot-pressing process. The workpiece is 30 cm long and 1 cm thick, and the roller is made of brass, which has a 6 cm outer diameter and is 48 cm long. By utilizing the roller’s weight of about 98 N, the paper can be pressed smoothly and evenly onto the workpiece. The heating source is provided by an infrared radiant ceramic heater. The adhesive, ethylene-vinylacetate (EVA), is placed not as it is in traditional LOM, but on the top side of the paper. The paper, LPH 042 140-LOM manufactured by HELISYS, has a thickness of 0.01 cm, and its material properties are shown in Table 1. The surface of the workpiece is heated to a specific temperature. This is followed by the application of a new layer of paper and pressing by the roller. To make the new layer of paper underneath the roller adhere firmly onto the workpiece, the adhesive must maintain a good adhesion force at the point where the roller touches the workpiece. Proper thermal analysis of the hot-pressing process is carried out in order to understand the temperature distribution on surface of the workpiece 2.2 Thermal model The workpiece can be taken as a 2D non-homogeneous material in 2D heat transfer analysis. Figure 2 displays the control volume model, which includes the boundary conditions, S0 to S6,and the coordinate system used in the following analysis. The heater moves in the x-direction and transfers heat to the control volume through the S6 boundary. The following analysis excludes the heat transfer between the newly-added layer and the roller. Basic assumptions LPH042 LOM Paper Density 0.900 grams/m3 Thermal conductivity (in-plane) 0.117 W/m .C Thermal conductivity (transverse) 0.31 W/m .C Thermal expansion coefficient (in-plane) 178 ?á 10.6 /.C Thermal expansion coefficient (transverse-plane) 3.8 ?á 10.6 /.C Specific heat 1455 J/kg .C Deflection temperature 77 .C Glass transition temperature 30 .C a. The heating process is treated as a transient state. b. The compactly integrated paper layers and adhesive are treated as a single object. c. It is taken as a two-dimensional problem because of the uniform heat source along the paper width direction. d. The paper laminate is taken as a moving object. e. Before the new layer is paved on the previously-added layer, the workpiece has reached ambient temperature. Governing equation: Although various materials may be used in LOM, which means the thermal characteristics of the paper and the adhesive may be different in different cases, LOM is still simplified as an anisotropic but homogeneous continuum and a two-dimensional problem. The governing equation [8] is expressed as Eq. 1: In the equation, Kx and Ky are the thermal conductivity (W/m.k) of the paper workpiece, which are changeable with the variation of temperature along directions x and y, respectively; (kg/m3).is its density; Cp (J/kg.K).is its heat capacity, which is also varied with the change of temperature; and Vx (m/sec)is the velocity of the moving heater source. Boundary conditions: Disregarding the movement of the newly-added paper layers, the boundary conditions, S0, S1, S2, S3, S4, S5,and S6 are set as follows. Because it is surrounded by air, the paper sheet (S0)maintains a stable temperature. Also, since heat flux has not yet reach the end area S1 in Fig. 2, the temperature on S1 should be equal to the initial temperature. Hence, the boundary condition for S0 and S1 is where T0 = 28 is room temperature in our analysis. Beyond a certain workpiece depth, the heat transfer of the material is quite small along the y direction, so it can be taken as adiabatic, and for S2 In the thermal control volume model, most heat transfer is due to conduction; other heat transfer modes become relatively negligible. Hence, the thermal gradient along S3 in the x direction approaches zero; i.e., for S3 The boundaries, except the area in contact with the heater, are exposed to the surrounding air. Hence, the boundary conditions for S4 and S5 are described. by Eqs. 5 and 6, respectively, as follows where in Eq. 5, KT is the thermal conductivity (W/m ?¤ K) of the paper workpiece, and h is the convection heat-transfer coefficient. In Eq. 6, KT . and h. are the thermal conductivity of the paper workpiece and convection heat-transfer coefficient, respectively, at a particular temperature of the workpiece after heating. The boundary S6 is just beneath the heater. There are heat convection and radiation in this area, and hence where q0 is the total heat flux through the boundary, h is the convection heat-transfer coefficient, ε is the material film emission rate, σ is the Stefan-Boltzmann constant (σ= 5.67×W/m2.K4), Te is the surface temperature of the heater, and Tsur is the surface temperature of the laminates. 3 Numerical solutions and experimental results Because it is very time-consuming and tedious to obtain the temperature distribution on a workpiece by direct measurements, a commercially available FEM software, ANSYS, is adopted to solve the temperature distributions under various operating conditions in this paper. In the experiments, a the K-type thermocouple, which is embedded in the laminated workpiece as shown in Fig. 3, is used to measure the adhesive temperature. The voltage signal is transformed and passed to the PC with an A/D card. The numerical results are compared with the experimental data to verify the effectiveness of the FEM. One case of the numerical solution and the corresponding experimental results are plotted in Fig. 4. The numerical solution is obtained with the assumption of a fixed heat source and a moving workpiece. But for implementing the real measurement, the temperature variation of one fixed point is recorded with reference to different heating source positions. These two sets of temperature data are therefore matched in one graph with the same abscissa. It can be seen that the errors between numerical solutions and experimental results are quite small. The errors for all tested cases are within 10%. This suggests that the FEM approach is acceptable. . 4 Effects of operating parameters on hot-pressing process 4.1 Effects of operating parameters on layer surface temperature Figure 5 shows the estimated temperature of the workpiece with a heat source of 450 .C, but with different moving speeds of the heat source. In the figure, the abscissa and ordinate represent the horizontal position and surface temperature of the laminates, respectively. The descending rate of temperature becomes greater under lower moving speeds of the heater than that under higher ones. The temperature of the adhesive can be efficiently increased by lowering heater speed. However, on the other hand, this would lead to the rapid temperature decline. For the paper sheet as a working material, this produces higher thermal stress and is not good for the prototypes quality. This also increases the time cost and reduces manufacturing efficiency. It is shown in Fig. 6 that the higher the heater temperature under the same moving speed, the higher the paper surface temperature. The temperatures of the heater and the paper surface are almost linearly positively dependent. 4.2 Effects of operating parameters on temperature distribution along the layer thickness direction The temperature distributions under two sets of heater temperatures and moving speeds of T = 350 .C, V = 6cm/sand T = 450 .C, V = 12 cm/s, are shown in Fig. 7. The surface temperatures during the heat absorption process are the same, the temperature descending curves differ only a little bit for these two sets of parameters. However, it is more significant in the layer thickness direction, as shown in Fig. 8. When the heater with higher temperature moves at a higher speed, the temperature gradient at the layer surface is larger, which is revealed by the steeper slope of the curve in the figure. This implies that there are fewer heataffected layers, leading to a better pressing and bonding effect and results in a better manufacture quality. Therefore, although the layer surface temperatures are the same under two set heater temperatures and moving speeds of T = 350 .C, V = 6cm/sand T = 450 .C, V = 12 cm/s, the latter parameter set shows fewer heataffected layers. With respect to heat-affected layer thickness, the higher heater temperature together with higher moving speed ensure lower heat-affected thickness and a shorter working time, which proves manufacturing process efficiency. 4.3 Relation between operating parameters and the hot-pressing process The adhesive on the paper obtains sufficient adhesion force at 80 .C and above, and the paper can stand up to a temperature as high as 200 .C. Beyond this temperature, coking of the paper occurs and adhesive becomes ineffective as well. Hence the layer surface should remain between 80 .C and 200 .C to ensure workpiece quality。 Figure 9 shows the configuration of the heater and roller superimposed on a typical surface temperature vs. position diagram of the workpiece. The heater is just above the layer material and it is 7 cm long. Within this range, the layer plays the role of heat absorber. At a position of 7 cm, which marks the rear edge of the heater, the layer reaches the highest temperature. The area from a position of 7 cm to 18 cm retains effective adhesion because of a proper temperature between 80 .C and 200 .C. The real pressing action starts from 7 cm plus the roller radius, since the roller diameter should be brought into consideration. Assuming the roller radius is 3 cm, the roller can be arranged to a position between 10 cm and 18 cm. This range is suitable for the pressing and adhesion processes, and it is indicated by the solid line rectangle in Fig. 9. Figure 10 shows the surface temperature of the workpiece under three sets of operating parameters. The maximum tem perature at the layer surface reaches 210 .C, a temperature higher than the paper coking temperature, under parameters of T = 450 .Cand V = 3cm/s. This set of parameters cannot be used for the heating-and-pressing separation procedure. If the parameters are set to T = 300 .C and V = 12 cm/s, the temperature of the effective pressing area (beyond position 10 cm) is only 65 .C. No efficient pressing effects can be accomplished under such an insufficient temperature. If the parameters are set to T = 450 .Cand V = 12 cm/s, the maximum layer surface temperature is around 120 .C, which is between the minimum agglutinating temperature and the coking temperature of the paper. The temperature is maintained at 90 .C at the location nearest the adhesion position and gradually descends to 80 .C at a position of 12 cm. The stretched area of about 2 cm in width is apt for adhesive sticking. Hence, this set of operating parameters is appropriate as far as the roller arrangement and hot-pressing are concerned. 5 Conclusion To rectify some problems of the current LOM apparatus with the combined heating and pressing operations, a heating-andpressing separation mechanism is proposed. The FEM is carried out to solve heat transfer problems, and the numerical solution of the temperature field is used for inference. The conclusions are described as follows: 1. The heating-and-pressing separation apparatus in this research can obtain a steeper temperature gradient in the heating process by elevating both the heater temperature and its moving speed. By the same strategy, a milder temperature variation curve can similarly be obtained in the heatreleasing process. This contributes to a larger pressing and sticking area and better sticking effects. 2. For the proposed heating-and-pressing separation process, the heat-affected layer thickness can be reduced with a higher heater temperature and a higher moving speed. This also ensures that the surface paper layer can be maintained at a stable temperature much lower than the paper coking temperature, and will lead to lower manufacturing time and cost, and promote efficiency of the whole process. 3. The proper sticking temperature and the sustainable coking temperature limit of the adhesive on the paper layer are observed through FEM analysis and experiments. With these characteristics of the adhesive, if a proper roller diameter is given, a suitable pressing and sticking area can be arranged to obtain well-operated effects. In addition, the optimum pressing and sticking position can be obtained by adjusting the distance between the heater and the roller to generate good workpiece quality. 疊片在熱加壓下制造工藝的研究 跳躍的人 摘要 當(dāng)前，為了改進(jìn)疊片物體在造業(yè)普遍使用的加熱步驟，一個創(chuàng)新的加壓分離系統(tǒng)被提出。并且這個系統(tǒng)的熱傳遞問題被調(diào)查 。一個熱量模型首先建立。它由有限元素方法(FEM) ANSYS軟件數(shù)字上解決，并且由實驗核實。根據(jù)數(shù)字解答在各種各樣的操作條件下，當(dāng)加熱器維持在一個較高溫度的時候，黏著劑的操作溫度能很快地被到達(dá), 對一個較深的受熱變質(zhì)。 如果增加加熱器的加熱速度，這個缺點(diǎn)可能能有效地減少變質(zhì)。因此，建議一個比較高的加熱器溫度和一個比較高的加熱速度以縮短處理時間和促進(jìn)制造業(yè)效率。透過分析, 滾筒和加熱器之間適當(dāng)?shù)木嚯x, 決定了高質(zhì)量的零配件的完成。 關(guān)鍵字： 熱影響了層數(shù)。疊片制造 快速的原型設(shè)計. 熱量模式 1 簡介 快速原型制造技術(shù)(其它)一直被高度重視。近年來全世界的科研院所和制造行業(yè)都在探究。疊片的制造，主要采取了焊接的溫度和壓力用滾動的方式在熱的金屬圓柱體表面, 在這一層薄薄的熱塑性粘合劑的底部. 用激光切割與焊接反復(fù)多次,直到完成。 Pak 和 Nisnevich[3]為一個 LOM 的熱模型計劃了一個公式分析熱傳導(dǎo), 即加熱壓平加工件。Sonmez 和哈恩 [4] 稍后通過分析在FEM 的溫度和壓力由叁數(shù)所引起的效果提出了在加熱和壓平程序中發(fā)生了的一些問題。 然而, 仍然有 LOM 程序上的一些缺點(diǎn)和困難。舉例來說, 文件容易在黏著性層被剝落 , 泡沫在工件中發(fā)生，而且在加熱壓平程序期間控制叁數(shù)是困難的。加熱件可能由于過熱被燃燒, 或一個整合損壞由于不夠的溫度能發(fā)生。 此外, 不合適的壓力和速度也是結(jié)合的不佳的主要因素。 為了有效地減少加熱壓平程序給LOM帶來的不利, 為了得到較好的工件，一個加熱的程序-和-壓平分離工序被計劃。 這一個方法是與 LOM 機(jī)器的聯(lián)合方式相反, 在哪加熱和壓入同時地被應(yīng)用。 這一張紙學(xué)習(xí)被提議系統(tǒng)的熱傳遞問題。對加熱和壓平程序和加熱和壓平上配置操作叁數(shù)被調(diào)查。 圖1。加熱燒結(jié)分離的示意圖 2 熱量模型 加熱燒結(jié)分離的概念 加熱-和加壓分離程序包括隔離加熱的操作和壓平,如圖 1 所示, 加熱熱-壓平程序的 2D 示范。工作件長30cm厚1cm ，而且滾筒是用黃銅做成的,這是一個外直徑 為6 cm 長48 cm 的滾筒。 利用筒自身大約 98 N 的重量，紙能被平滑地而且均勻地加壓在工作件上 加熱來源是由一個紅外線發(fā)光的陶瓷加熱器提供。 黏著劑, 乙烯-vinylacetate(伊娃), 被放置不當(dāng)做它在傳統(tǒng)的 LOM 中, 但是在紙的最上面的邊上。 紙, LPH 042140 LOM 的被 HELISYS 制作, 有一厚度的 0.01 cm,其材料特性見表1. 工作件的表面被加熱到一個特定的溫度。 紙和壓力通過滾子，這一應(yīng)用上了一個新臺階 . 表1 LPH042 激光光學(xué)調(diào)制器紙 密度 0.900 克/m 3 熱傳導(dǎo)性 (在-刨)0.117 W/m 。C 熱傳導(dǎo)性 (橫斷物)0.31 W/m 。C 熱膨脹系數(shù) (在-平面)178?á 10.6/.C 熱膨脹系數(shù) (橫斷物-平面)3.8?á 10.6/.C 比熱 1455 J/公斤。C 撓度溫度 77.C 玻璃變態(tài)溫度 30.C 圖 2.控制容積模型 A. 加熱過程被視為一個短暫的狀態(tài). B. 緊密層的綜合性文件和粘合劑被當(dāng)作一個對象. C. 這是作為一個平面的問題,因為在統(tǒng)一的熱源紙寬度方向. D. 頁的文件是作為移動物體. E. 在新的層鋪前增加一層,氣溫已達(dá)到。 管理原則； 雖然各種不同的材料可能被用于激光光學(xué)調(diào)制器，但是這意謂紙的熱特性和黏著劑可能在不同的情況是不同的,激光光學(xué)調(diào)制器仍然除了同種的連續(xù)性和一個二維的問題之外被單一化如一個各向異性。管理原則[8] 被表示成情緒商數(shù)。 在方程序, Kx 和 Ky 中是紙工作件的熱傳導(dǎo)性 (W/m.K), 沿著方向 x 和 y 對溫度的變動感到可改變, 分別地; (公斤/m 3).它的密度是; Cp(J/kg.K).是它的熱容量, 也被因溫度的變化而改變 ; 而且 Vx(m/sec) 是加熱器的速度。 接口條件: 忽視最近紙層的運(yùn)動, 接口條件， S0 ， S1 ， S2 ， S3 ， S4 ， S5 和 S6 依下列各項被設(shè)定. 因為它被包圍以空運(yùn)方式,紙張 (S0) 維持一個穩(wěn)定的溫度。 同時, ，因為熱熔劑有尚未在圖 2 中到達(dá)端面積 S1,溫度在 S1 上應(yīng)該和初次的溫度相等。 因此, 給 S0 和 S1 的接口條件是 T = T0 . 在 T0=28 是我們的分析的室溫的地方.| 一個特定的工作件深度，材料的熱傳遞沿著 y 方向相當(dāng)小，因此，它能絕熱, 對于 S2 在熱的控制容積模型, 大多數(shù)的熱傳遞是由于傳導(dǎo); 其他的熱傳遞模態(tài)相對地可以忽略。 因此, 熱升降率沿著在 S3在x的零點(diǎn)方向; 也就是, 對于 S3 接口,除與加熱器的接觸的面積, 遭受周圍的空氣。 因此，給 S4 和 S5 的接口條件被描述。 由情緒商數(shù)。 5 和 6, 分別地, 依下列各項 而在EQ. 5、是導(dǎo)熱(W/M.K)的文件,熱對流的H轉(zhuǎn)移系數(shù). 在EQ. 6、這份文件是導(dǎo)熱、對流裝置熱系數(shù)將分別在特定溫度下加熱裝置之后. 接口 S6 剛好在加熱器之下。 那里是在這一個面積中加熱對流和輻射,因此 q 0總熱通量,是通過邊界,熱對流的H轉(zhuǎn)移系數(shù).ε是物質(zhì)薄膜的發(fā)射率 σ是常數(shù)，Te 是加熱器的表面溫度，Tsur 是積層塑料板的表面溫度。 3 數(shù)字的溶液和實驗的結(jié)果 因為在直接測量，一個商業(yè)可得的 FEM 軟件的一個工作件上獲得溫度分布是非常耗時,ANSYS,被采用在這一張紙在各種不同的操作狀態(tài)之下解決溫度分布。 在正在如圖 3 所顯示的疊片工作件中埋入的實驗,一個 K-型的熱電偶, 用來測量相聚為伍的溫度。 電壓信號被轉(zhuǎn)換而且通過到和 A/D 卡片的個人計算機(jī)。 數(shù)字的結(jié)果被與實驗的數(shù)據(jù)相較查證 FEM 的熱交換率。 數(shù)字溶液和對應(yīng)的實驗結(jié)果的一個箱在圖 4 被計劃翻譯。 數(shù)字獲得解決擔(dān)任固定和移動裝置熱源. 但實際執(zhí)行測量、定點(diǎn)溫度變化之一就是針對不同的供熱源記錄位置. 這兩組數(shù)據(jù),因此溫度與abscissa同一個圖表. 可以看出,數(shù)值解和實驗結(jié)果之間的誤差很小. 所有的錯誤都在10%測試案例. 這表明,FEM方法是可以接受的. 圖 3. 測量裝置的示意圖 圖 4. 沿著加熱器和滾筒間移動的工作件的表面溫度的數(shù)值解和實驗結(jié)果 4.操作參數(shù)影響熱壓機(jī)的過程 4.1影響操作的表面溫度參數(shù) 圖 5場表演上的叁數(shù)和一個 450 度的熱源工作件的被估計的溫度效果 .C, 但是由于熱源的不同感人速度。 在身材，分別地,橫標(biāo)和縱標(biāo)表現(xiàn)水平的位置和積層塑料板的表面溫度。 溫度的降率超過在較高的一些下面的那在加熱器的低感人速度之下變得更棒。 黏著劑的溫度能有效率地被藉由降低加熱器速度增加。 然而, 另一方面，這會導(dǎo)致迅速的溫度衰微。 為如一個工作材料的紙張，這產(chǎn)生較高的熱應(yīng)力和對原尺是不好 。 這也增加時間成本而且減少制造效率。 它在圖 6 被顯示那更高地加熱器溫度在相同的加熱速度之下, 可以使升至更高的溫度。 加熱器的溫度和紙表面的線性可以依賴 圖 5. 沿著和一個 450 的熱源加熱器的加熱組合和滾子，除了熱源的不同加熱速度之外工作件的表面溫度。 圖 6. 沿著和以 12 cm/s 的速度移動的二者不同的熱源加熱器的加熱組合和滾筒的表面溫度 4.2 沿著層厚度方向操作在溫度分布上的叁數(shù)的效果 加熱器溫度的在二之下的溫度分布組而且移動 t=350 的速度 .C ， V=6 cm/砂 t=450.C, V=12 cm/s,在圖 7 被顯示。 在熱吸收處理期間的表面溫度是一樣的,只降曲線規(guī)的溫度為這些二組叁數(shù)差異一個小刀尖塊。 然而，它在層厚度方向更重要,如圖 8 所示。 當(dāng)有著比較高的溫度移動的加熱器以一個比較高的速度，溫度傾斜度在層表面比較大, 哪一個被身材的曲線的較險竣的斜度顯示。這暗示有較少的 heataffected 層,對一個更壓迫和會接帶領(lǐng)影響而且造成一個較好的制造性質(zhì)。因此，雖然層表面溫度是相同的在二個 t=350 的固定加熱器溫度和感人速度之下 .C ， V=6 cm/砂 t=450.C ， V=12 cm/s, 后者叁數(shù)設(shè)定表演較少的 heataffected 層。 有關(guān)于熱影響的層厚度，比較高的加熱器溫度連同比較高的移動速度一起確定比較低的熱影響的厚度和一個較短的工作時間,這證明制造業(yè)的處理效率。 圖7。操作叁數(shù)在加熱器的加熱組合和滾筒組之下，工作件的溫度 圖 8. 操作叁數(shù)的溫度在二之下的厚度組的方向的變化 4.3操作叁數(shù)和熱壓機(jī)處理之間的關(guān)系 在紙上的黏著劑獲得充份的黏著性力在 80.C 和上方, 和紙能經(jīng)得起一個溫度當(dāng)做高的當(dāng)做 200.C. 超過這一個溫度，紙的使成焦煤發(fā)生，而且黏著劑也變成無效。 因此層表面應(yīng)該保持在 80之間 .C 和 200.C 確定工作件性質(zhì)。 圖 9 表示加熱器的結(jié)構(gòu)