ZL50裝載機(jī)總體及工作裝置設(shè)計(jì)
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設(shè)計(jì)任務(wù)書
設(shè)計(jì)題目：
酒瓶蓋啟子級(jí)進(jìn)模設(shè)計(jì)與制造
設(shè)計(jì)要求：
1、設(shè)計(jì)思路明確，合理布置設(shè)計(jì)的先后次序
2、正確全面的分析沖件的工藝性
3、根據(jù)沖件的工藝性和結(jié)構(gòu)特點(diǎn)確定模具的類型與結(jié)構(gòu)
4、根據(jù)實(shí)際沖裁要求正確的計(jì)算出有關(guān)數(shù)據(jù)
5、認(rèn)真分析并確定主要零件的結(jié)構(gòu)尺寸
6、正確的選取有關(guān)標(biāo)準(zhǔn)件
7、根據(jù)機(jī)械制圖的要求正確的繪制出主要的零件圖和總裝配圖
設(shè)計(jì)進(jìn)度：
第一周 ：收集資料
第二周 ：整理設(shè)計(jì)思路
第三周 ：模具的工藝方案的確定
第四周 ：模具零部件的設(shè)計(jì)與計(jì)算
第五周 ：模具的總體設(shè)計(jì)及整理電子稿
第六周 ：修改設(shè)計(jì)及上交論文
第七周 ：論文答辯
指導(dǎo)教師（簽名）：
前 言
振興和發(fā)展我國的模具工業(yè)，日益受到人們的重視和關(guān)注?！澳＞呤枪I(yè)生產(chǎn)的基礎(chǔ)工藝裝備”也已經(jīng)取得了共識(shí)。在電子、汽車、電機(jī)、電器、儀器、儀表、家電和通信等產(chǎn)品中，60%～80%的零部件都要依靠模具成形。用模具生產(chǎn)制件所具備的高精度、高復(fù)雜程度、高一致性、高生產(chǎn)率和低消耗，是其他加工制造方法所不能比擬的。模具又是“效益放大器”，用模具生產(chǎn)的最終產(chǎn)品的價(jià)值，往往是模具自身價(jià)值的幾十倍、上百倍。目前全世界模具年產(chǎn)值約為600億美元，日、美等工業(yè)發(fā)達(dá)國家的模具工業(yè)產(chǎn)值已超過機(jī)床工業(yè)，從1997年開始，我國模具工業(yè)產(chǎn)值也超過了機(jī)床工業(yè)產(chǎn)值。
?? 模具生產(chǎn)技術(shù)水平的高低，已成為衡量一個(gè)國家產(chǎn)品制造水平高低的重要標(biāo)志，因?yàn)槟＞咴诤艽蟪潭壬蠜Q定著產(chǎn)品的質(zhì)量、效益和新產(chǎn)品的開發(fā)能力。鑒于模具工業(yè)的重要性，在1989年3月國務(wù)院頒布的《關(guān)于當(dāng)前產(chǎn)業(yè)政策要點(diǎn)的決定》中，把模具列為機(jī)械工業(yè)技術(shù)改造序列的第一位、生產(chǎn)和基本建設(shè)序列的第二位。1997年以來，又相繼把模具及其加工技術(shù)和設(shè)備列入了《當(dāng)前國家重點(diǎn)鼓勵(lì)發(fā)展的產(chǎn)業(yè)、產(chǎn)品和技術(shù)目錄》和《鼓勵(lì)外商投資產(chǎn)業(yè)目錄》。經(jīng)國務(wù)院批準(zhǔn)，從1997年到2000年，對(duì)80多家國有專業(yè)模具廠實(shí)行增值稅返還70%的優(yōu)惠政策，以扶植模具工業(yè)的發(fā)展。
?? 現(xiàn)在，應(yīng)該引起我們特別注意的是，1999年8月20日黨中央和國務(wù)院發(fā)布的《關(guān)于加強(qiáng)技術(shù)創(chuàng)新發(fā)展高科技實(shí)現(xiàn)產(chǎn)業(yè)化的決定》中，明確提出了高新技術(shù)產(chǎn)業(yè)領(lǐng)域?！稕Q定》指出：要在電子信息特別是集成電路設(shè)計(jì)與制造、網(wǎng)絡(luò)及通信、計(jì)算機(jī)及軟件、數(shù)字化電子產(chǎn)品等方面，加強(qiáng)技術(shù)創(chuàng)新，形成一大批擁有自主知識(shí)產(chǎn)權(quán)、具有競(jìng)爭(zhēng)優(yōu)勢(shì)的高新技術(shù)產(chǎn)業(yè)?！稕Q定》還指出：要加強(qiáng)傳統(tǒng)產(chǎn)業(yè)的技術(shù)升級(jí)，注重電子信息等技術(shù)與傳統(tǒng)產(chǎn)業(yè)的嫁接，大幅度提高國產(chǎn)技術(shù)裝備的水平。
近年許多模具企業(yè)加大了用于技術(shù)進(jìn)步的投資力量，將技術(shù)進(jìn)步視為企業(yè)發(fā)展的重要?jiǎng)恿?。一些國?nèi)模具企業(yè)已普及了二維CAD，并陸續(xù)開始使用UG、Pro/engineer、I-DEAS等國際通用軟件，個(gè)別廠家還引進(jìn)了Moldflow、C-Flow、DYNAFORM、等CAE軟件，并成功用于模的設(shè)計(jì)中。
2
摘 要
我國沖壓模具無論在數(shù)量上，還是在質(zhì)量、技術(shù)和能力等方面都已有了很大發(fā)展，但與國民經(jīng)濟(jì)需求和世界先進(jìn)水平相比，差距仍很大，一些大型、精密、復(fù)雜、長(zhǎng)壽命的高檔模具每年仍大量進(jìn)口，特別是中高檔轎車的覆蓋件模具，目前仍主要依靠進(jìn)口。因而只有培養(yǎng)模具人才才能縮小我國同發(fā)達(dá)國家之間的距離。
這次畢業(yè)設(shè)計(jì)我設(shè)計(jì)的是酒瓶蓋啟子沖裁模，利用的是級(jí)進(jìn)模生產(chǎn)的。級(jí)進(jìn)模，又稱為多工位級(jí)進(jìn)模、連續(xù)模、跳步模，它是在一副模具內(nèi)，按所加工的工作分為若干等距離的工位，在每個(gè)工位設(shè)置一個(gè)或幾個(gè)基本沖壓工序，來完成沖壓工作某部分的加工。被加工材料，事先加工成一定寬度的條料，采用某種送進(jìn)方法，每次送進(jìn)一個(gè)步距。經(jīng)逐個(gè)工位沖制后，便得到一個(gè)完整的沖壓工件。在一副級(jí)進(jìn)模中，可以連續(xù)完成沖裁、彎曲、拉深、成形等工序。一般來說，無論沖壓零件形狀怎么復(fù)雜，沖壓工序怎樣多，均可用一副級(jí)進(jìn)模沖成完成。
本設(shè)計(jì)重點(diǎn)是在分析沖裁變形過程及沖裁件質(zhì)量影響因素的基礎(chǔ)上，主要介紹沖裁件的工藝性分析、確定沖裁工藝方案、選擇模具的結(jié)構(gòu)形式、進(jìn)行必要的工藝計(jì)算、選擇與確定模具的主要零部件的結(jié)構(gòu)與尺寸、校核模具閉合高度及壓力機(jī)有關(guān)參數(shù)、繪制模具總裝圖及零件圖都是這次設(shè)計(jì)的主要內(nèi)容。
用于級(jí)進(jìn)模的材料，都是長(zhǎng)條狀的板材。材料較厚、生產(chǎn)批量較少時(shí)，可剪成條料；生產(chǎn)批量大時(shí)，應(yīng)選擇卷料。卷料可以自動(dòng)送料，自動(dòng)收料，可使用高速?zèng)_床自動(dòng)沖壓。級(jí)進(jìn)模對(duì)材料的厚度和寬度都有嚴(yán)格的要求。寬度過大，條料不能進(jìn)入模具的導(dǎo)料板或通行不暢；寬度過小則影響定位精度，還容易損壞側(cè)刃、凸模等零件。
本次設(shè)計(jì)不僅讓我熟悉了課本所學(xué)的知識(shí)，而且我做了把所學(xué)到的知識(shí)運(yùn)用到實(shí)踐當(dāng)中，更讓我了解了級(jí)進(jìn)模設(shè)計(jì)的全過程和加工實(shí)踐的各種要點(diǎn)。
關(guān)鍵詞 酒瓶蓋啟子，沖孔，落料，級(jí)進(jìn)模
目 錄
1 沖壓件工藝性分析及沖裁方案的確定 1
2主要設(shè)計(jì)計(jì)算 3
2.1 排樣方案的確定及計(jì)算 3
2.2 沖壓力的計(jì)算 4
2.3 壓力中心的確定及相關(guān)計(jì)算 5
2.4 工作零件刃口尺寸計(jì)算 7
2.5 卸料彈簧的設(shè)計(jì) 10
3模具總體設(shè)計(jì) 12
3.1 模具類型的選擇 12
3.2 定位方式的選擇 12
3.3 卸料﹑出件、導(dǎo)向方式的選擇 12
4 零件的結(jié)構(gòu)設(shè)計(jì) 14
4.1 落料凸模的設(shè)計(jì) 14
4.2 沖孔凸模的設(shè)計(jì) 15
4.3 凹模的設(shè)計(jì) 16
5模具材料的選用及其它零部件的設(shè)計(jì) 18
5.1 模具材料的選用 18
5.2 定位零件的設(shè)計(jì) 19
5.3 料板及卸料部件的設(shè)計(jì) 20
5.4 模架及其他零部件的設(shè)計(jì) 20
6 模具總裝圖及設(shè)備的選定 22
6.1模具的總裝圖 22
6.2 設(shè)備的選定 23
7 模具零件加工工藝 24
8 模具的裝配和沖裁模具的試沖 26
8.1 模具的裝配 26
8.2 沖裁模具的試沖 26
總結(jié)與致謝 29
參考文獻(xiàn) 30
1 沖壓件工藝性分析及沖裁方案的確定
工件名稱：酒瓶蓋起子
生產(chǎn)批量：大批量
材料：Error! No bookmark name given.
材料厚度：1.
工件簡(jiǎn)圖：如圖1.1所示。
圖1.1酒瓶蓋啟子零件圖
此工件只有落料和沖孔兩個(gè)工序。材料為，具有良好的沖壓性能，適合沖裁。工件結(jié)構(gòu)相對(duì)簡(jiǎn)單，有一個(gè)的孔和1個(gè)不規(guī)則的孔；孔與孔、孔與邊緣之間的距離也滿足要求，最小壁厚為4。工件的尺寸全部為自由公差，可看作IT13級(jí)，尺寸精度較低，普通沖裁完全能滿足要求。
沖裁工藝方案的確定：
該工件包括落料、沖孔兩個(gè)基本工序，可有以下三種工藝方案。
方案一：采用單工序模生產(chǎn)。
方案二：采用復(fù)合模生產(chǎn)。
方案三：采用級(jí)進(jìn)模生產(chǎn)。
方案一：?jiǎn)喂ば蚰Ｉa(chǎn)。模具結(jié)構(gòu)簡(jiǎn)單，但需要兩道工序兩副模具，成本較高而生產(chǎn)效率低，難以滿足中批量生產(chǎn)要求。
方案二：復(fù)合模生產(chǎn)。只需一副模具，工件的精度及生產(chǎn)效率都較高，但沖壓后成品保留在模具上，在清理模具上的物料時(shí)會(huì)影響沖壓速度，操作方便。
方案三：級(jí)進(jìn)模生產(chǎn)。也只需一副模具，生產(chǎn)效率高，操作方便，工件精度也能滿足要求。
通過對(duì)上述三種方案的分析比較，該件的沖壓生產(chǎn)采用方案三為佳。
1.在哪種情況下需對(duì)沖孔凸模采取保護(hù)措施？
沖小孔凸模是需對(duì)對(duì)沖孔凸模采取保護(hù)措施。小孔沖裁通常是指沖孔直徑小于板料厚度，凸模顯得很細(xì)長(zhǎng)，沖裁時(shí)容易彎曲而折斷。因此小孔沖裁結(jié)構(gòu)必須對(duì)凸模采取保護(hù)措施。但有時(shí)，雖沖孔直徑大于板厚，但由于凸模直徑較小，沖裁時(shí)稍受側(cè)向力，就可能引起凸模折斷，這時(shí)也應(yīng)對(duì)凸模采取保護(hù)措施。
2..怎樣安排排樣方法？
排樣方法分為有廢料、少廢料和無廢料排樣。有廢料排樣法：是沿制件的全部外形輪廓沖裁，在制件之間及制料側(cè)邊之間都有工藝余料（搭邊）。少廢料排樣方法：沿制件的部分外形輪廓切斷或沖裁，只在制件之間（或制件與條料側(cè)邊之間）留有搭邊。無廢料排樣法：無廢料排樣法就是無工藝搭邊的排樣，制件直接由切斷條料獲得。
3.怎樣確定沖裁模刃口尺寸？
落料尺寸由凹模尺寸決定，沖孔時(shí)孔的尺寸由凸模尺寸決定。設(shè)計(jì)落料模時(shí)，以凹模為基準(zhǔn)，間隙取在凸模上；設(shè)計(jì)沖孔模時(shí)，以凸模為基準(zhǔn)，間隙取在凹模上?？紤]到?jīng)_裁中凸模、凹模的磨損，設(shè)計(jì)落料模時(shí)，凹?；境叽鐟?yīng)取尺寸公差范圍較小；設(shè)計(jì)沖孔模時(shí)凸模基本尺寸應(yīng)取工件尺寸公差范圍內(nèi)較大尺寸；確定沖模刃口制造公差時(shí)應(yīng)考慮制件的公差要求。
4.設(shè)計(jì)排樣時(shí)應(yīng)考慮哪些因素？
（1）提高材料的利用率；
（2）模具結(jié)構(gòu)簡(jiǎn)單，能提高模具壽命；
（3）排樣方法應(yīng)時(shí)沖壓操作方便，減小勞動(dòng)強(qiáng)度且保證安全；
（4）保證制件質(zhì)量和制件板料對(duì)纖維方向的要求。
5.怎樣降低沖裁力？
凸模的階梯布置：凸模階梯布置時(shí)由于凸模工作端面不在一個(gè)平面，各凸模沖裁力的最大值不同時(shí)出現(xiàn)，從而達(dá)到降低沖裁力的目的，凸模直徑有較大差異時(shí)，一般把小直徑凸模做短一些。斜刃沖裁：斜刃時(shí)將沖孔凸?；蚵淞习寄５墓ぷ魅锌谥瞥尚比校瑳_裁時(shí)刃口不是全部同時(shí)切入，而是逐步地將材料分離，能顯著降低沖裁力，但斜刃口制造和刃磨都比較困難，刃口容易磨損，沖裁也不夠平整，為了能得到較平整的工件，落料時(shí)斜刃做在凹模上；沖孔時(shí)斜刃做在凸模上。加熱沖裁使金屬抗剪強(qiáng)度，也能降低沖裁力。
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e pos 模具工業(yè)現(xiàn)狀Process simulation in stamping – recent
applications for product and process design
Abstract
Process simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of FE-simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts.
In industrial applications, there are two objectives for conducting FE-simulations of the stamping process; (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FE-simulations are applied. Pam-Stamp, an incremental dynamic-explicit FEM code released by Engineering Systems Int'l, matches the second objective well because it can deal with most of the practical stamping parameters. FAST_FORM3D, a one-step FEM code released by Forming Technologies, matches the first objective because it only requires the part geometry and not the complex process information.
In a previous study, these two FE codes were applied to complex-shaped parts used in manufacturing automobiles and construction machinery. Their capabilities in predicting formability issues in stamping were evaluated. This paper reviews the results of this study and summarizes the recommended procedures for obtaining accurate and reliable results from FE simulations.
In another study, the effect of controlling the blank holder force (BHF) during the deep drawing of hemispherical, dome-bottomed cups was investigated. The standard automotive aluminum-killed, drawing-quality (AKDQ) steel was used as well as high performance materials such as high strength steel, bake hard steel, and aluminum 6111. It was determined that varying the BHF as a function of stroke improved the strain distributions in the domed cups.
Keywords: Stamping; Process ;stimulation; Process design
1. Introduction
The design process of complex shaped sheet metal stampings such as automotive panels, consists of many stages of decision making and is a very expensive and time consuming process. Currently in industry, many engineering decisions are made based on the knowledge of experienced personnel and these decisions are typically validated during the soft tooling and prototyping stage and during hard die tryouts. Very often the soft and hard tools must be reworked or even redesigned and remanufactured to provide parts with acceptable levels of quality.
The best case scenario would consist of the process outlined in Fig. 1. In this design process, the experienced product designer would have immediate feedback using a specially design software called one-step FEM to estimate the formability of their design. This would allow the product designer to make necessary changes up front as opposed to down the line after expensive tooling has been manufactured. One-step FEM is particularly suited for product analysis since it does not require binder, addendum, or even most process conditions. Typically this information is not available during the product design phase. One-step FEM is also easy to use and computationally fast, which allows the designer to play “what if” without much time investment.
Fig. 1. Proposed design process for sheet metal stampings.
Once the product has been designed and validated, the development project would enter the “time zero” phase and be passed onto the die designer. The die designer would validate his/her design with an incremental FEM code and make necessary design changes and perhaps even optimize the process parameters to ensure not just minimum acceptability of part quality, but maximum achievable quality. This increases product quality but also increase process robustness. Incremental FEM is particularly suited for die design analysis since it does require binder, addendum, and process conditions which are either known during die design or desired to be known.
The validated die design would then be manufactured directly into the hard production tooling and be validated with physical tryouts during which the prototype parts would be made. Tryout time should be decreased due to the earlier numerical validations. Redesign and remanufacturing of the tooling due to unforeseen forming problems should be a thing of the past. The decrease in tryout time and elimination of redesign/remanufacturing should more than make up for the time used to numerically validate the part, die, and process.
Optimization of the stamping process is also of great importance to producers of sheet stampings. By modestly increasing one's investment in presses, equipment, and tooling used in sheet forming, one may increase one's control over the stamping process tremendously. It has been well documented that blank holder force is one of the most sensitive process parameters in sheet forming and therefore can be used to precisely control the deformation process.
By controlling the blank holder force as a function of press stroke AND position around the binder periphery, one can improve the strain distribution of the panel providing increased panel strength and stiffness, reduced springback and residual stresses, increased product quality and process robustness. An inexpensive, but industrial quality system is currently being developed at the ERC/NSM using a combination of hydraulics and nitrogen and is shown in Fig. 2. Using BHF control can also allow engineers to design more aggressive panels to take advantage the increased formability window provided by BHF control.
Fig. 2. Blank holder force control system and tooling being developed at the ERC/NSM labs.
Three separate studies were undertaken to study the various stages of the design process. The next section describes a study of the product design phase in which the one-step FEM code FAST_FORM3D (Forming Technologies) was validated with a laboratory and industrial part and used to predict optimal blank shapes. Section 4 summarizes a study of the die design stage in which an actual industrial panel was used to validate the incremental FEM code Pam-Stamp (Engineering Systems Int'l). Section 5 covers a laboratory study of the effect of blank holder force control on the strain distributions in deep drawn, hemispherical, dome-bottomed cups.
2. Product simulation – applications
The objective of this investigation was to validate FAST_FORM3D, to determine FAST_FORM3D's blank shape prediction capability, and to determine how one-step FEM can be implemented into the product design process. Forming Technologies has provided their one-step FEM code FAST_FORM3D and training to the ERC/NSM for the purpose of benchmarking and research. FAST_FORM3D does not simulate the deformation history. Instead it projects the final part geometry onto a flat plane or developable surface and repositions the nodes and elements until a minimum energy state is reached. This process is computationally faster than incremental simulations like Pam-Stamp, but also makes more assumptions. FAST_FORM3D can evaluate formability and estimate optimal blank geometries and is a strong tool for product designers due to its speed and ease of use particularly during the stage when the die geometry is not available.
In order to validate FAST_FORM3D, we compared its blank shape prediction with analytical blank shape prediction methods. The part geometry used was a 5?in. deep 12?in. by 15?in. rectangular pan with a 1?in. flange as shown in Fig. 3. Table 1 lists the process conditions used. Romanovski's empirical blank shape method and the slip line field method was used to predict blank shapes for this part which are shown in Fig. 4.
Fig. 3. Rectangular pan geometry used for FAST_FORM3D validation.
Table 1. Process parameters used for FAST_FORM3D rectangular pan validation
Fig. 4. Blank shape design for rectangular pans using hand calculations.
(a) Romanovski's empirical method; (b) slip line field analytical method.
Fig. 5(a) shows the predicted blank geometries from the Romanovski method, slip line field method, and FAST_FORM3D. The blank shapes agree in the corner area, but differ greatly in the side regions. Fig. 5(b)–(c) show the draw-in pattern after the drawing process of the rectangular pan as simulated by Pam-Stamp for each of the predicted blank shapes. The draw-in patterns for all three rectangular pans matched in the corners regions quite well. The slip line field method, though, did not achieve the objective 1?in. flange in the side region, while the Romanovski and FAST_FORM3D methods achieved the 1?in. flange in the side regions relatively well. Further, only the FAST_FORM3D blank agrees in the corner/side transition regions. Moreover, the FAST_FORM3D blank has a better strain distribution and lower peak strain than Romanovski as can be seen in Fig. 6.
Fig. 5. Various blank shape predictions and Pam-Stamp simulation results for the rectangular pan.
(a) Three predicted blank shapes; (b) deformed slip line field blank; (c) deformed Romanovski blank; (d) deformed FAST_FORM3D blank.
Fig. 6. Comparison of strain distribution of various blank shapes using Pam-Stamp for the rectangular pan.
(a) Deformed Romanovski blank; (b) deformed FAST_FORM3D blank.
To continue this validation study, an industrial part from the Komatsu Ltd. was chosen and is shown in Fig. 7(a). We predicted an optimal blank geometry with FAST_FORM3D and compared it with the experimentally developed blank shape as shown in Fig. 7(b). As seen, the blanks are similar but have some differences.
Fig. 7. FAST_FORM3D simulation results for instrument cover validation.
(a) FAST_FORM3D's formability evaluation; (b) comparison of predicted and experimental blank geometries.
Next we simulated the stamping of the FAST_FORM3D blank and the experimental blank using Pam-Stamp. We compared both predicted geometries to the nominal CAD geometry (Fig. 8) and found that the FAST_FORM3D geometry was much more accurate. A nice feature of FAST_FORM3D is that it can show a “failure” contour plot of the part with respect to a failure limit curve which is shown in Fig. 7(a). In conclusion, FAST_FORM3D was successful at predicting optimal blank shapes for a laboratory and industrial parts. This indicates that FAST_FORM3D can be successfully used to assess formability issues of product designs. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Fig. 8. Comparison of FAST_FORM3D and experimental blank shapes for the instrument cover.
(a) Experimentally developed blank shape and the nominal CAD geometry; (b) FAST_FORM3D optimal blank shape and the nominal CAD geometry.
3. Die and process simulation – applications
In order to study the die design process closely, a cooperative study was conducted by Komatsu Ltd. of Japan and the ERC/NSM. A production panel with forming problems was chosen by Komatsu. This panel was the excavator's cabin, left-hand inner panel shown in Fig. 9. The geometry was simplified into an experimental laboratory die, while maintaining the main features of the panel. Experiments were conducted at Komatsu using the process conditions shown in Table 2. A forming limit diagram (FLD) was developed for the drawing-quality steel using dome tests and a vision strain measurement system and is shown in Fig. 10. Three blank holder forces (10, 30, and 50?ton) were used in the experiments to determine its effect. Incremental simulations of each experimental condition was conducted at the ERC/NSM using Pam-Stamp.
Fig. 9. Actual product – cabin inner panel.
Table 2. Process conditions for the cabin inner investigation
Fig. 10. Forming limit diagram for the drawing-quality steel used in the cabin inner investigation.
At 10?ton, wrinkling occurred in the experimental parts as shown in Fig. 11. At 30?ton, the wrinkling was eliminated as shown in Fig. 12. These experimental observations were predicted with Pam-stamp simulations as shown in Fig. 13. The 30?ton panel was measured to determine the material draw-in pattern. These measurements are compared with the predicted material draw-in in Fig. 14. Agreement was very good, with a maximum error of only 10?mm. A slight neck was observed in the 30?ton panel as shown in Fig. 13. At 50?ton, an obvious fracture occurred in the panel.
Fig. 11. Wrinkling in laboratory cabin inner panel, BHF=10?ton.
Fig. 12. Deformation stages of the laboratory cabin inner and necking, BHF=30?ton.
(a) Experimental blank; (b) experimental panel, 60% formed; (c) experimental panel, fully formed; (d) experimental panel, necking detail.
Fig. 13. Predication and elimination of wrinkling in the laboratory cabin inner.
(a) Predicted geometry, BHF=10?ton; (b) predicted geometry, BHF=30?ton.
Fig. 14. Comparison of predicted and measured material draw-in for lab cabin inner, BHF=30?ton.
Strains were measured with the vision strain measurement system for each panel, and the results are shown in Fig. 15. The predicted strains from FEM simulations for each panel are shown in Fig. 16. The predictions and measurements agree well regarding the strain distributions, but differ slightly on the effect of BHF. Although the trends are represented, the BHF tends to effect the strains in a more localized manner in the simulations when compared to the measurements. Nevertheless, these strain prediction show that Pam-Stamp correctly predicted the necking and fracture which occurs at 30 and 50?ton. The effect of friction on strain distribution was also investigated with simulations and is shown in Fig. 17.
Fig. 15. Experimental strain measurements for the laboratory cabin inner.
(a) measured strain, BHF=10?ton (panel wrinkled); (b) measured strain, BHF=30?ton (panel necked); (c) measured strain, BHF =50?ton (panel fractured).
Fig. 16. FEM strain predictions for the laboratory cabin inner.
(a) Predicted strain, BHF=10?ton; (b) predicted strain, BHF=30?ton; (c) predicted strain, BHF=50?ton.
Fig. 17. Predicted effect of friction for the laboratory cabin inner, BHF=30?ton.
(a) Predicted strain, μ=0.06; (b) predicted strain, μ=0.10.
A summary of the results of the comparisons is included in Table 3. This table shows that the simulations predicted the experimental observations at least as well as the strain measurement system at each of the experimental conditions. This indicates that Pam-Stamp can be used to assess formability issues associated with the die design.
Table 3. Summary results of cabin inner study
4. Blank holder force control – applications
The objective of this investigation was to determine the drawability of various, high performance materials using a hemispherical, dome-bottomed, deep drawn cup (see Fig. 18) and to investigate various time variable blank holder force profiles. The materials that were investigated included AKDQ steel, high strength steel, bake hard steel, and aluminum 6111 (see Table 4). Tensile tests were performed on these materials to determine flow stress and anisotropy characteristics for analysis and for input into the simulations (see Fig. 19 and Table 5).
Fig. 18. Dome cup tooling geometry.
Table 4. Material used for the dome cup study
Fig. 19. Results of tensile tests of aluminum 6111, AKDQ, high strength, and bake hard steels.
(a) Fractured tensile specimens; (b) Stress/strain curves.
Table 5. Tensile test data for aluminum 6111, AKDQ, high strength, and bake hard steels
It is interesting to note that the flow stress curves for bake hard steel and AKDQ steel were very similar except for a 5% reduction in elongation for bake hard. Although, the elongations for high strength steel and aluminum 6111 were similar, the n-value for aluminum 6111 was twice as large. Also, the r-value for AKDQ was much bigger than 1, while bake hard was nearly 1, and aluminum 6111 was much less than 1.
The time variable BHF profiles used in this investigation included constant, linearly decreasing, and pulsating (see Fig. 20). The experimental conditions for AKDQ steel were simulated using the incremental code Pam-Stamp. Examples of wrinkled, fractured, and good laboratory cups are shown in Fig. 21 as well as an image of a simulated wrinkled cup.
Fig. 20. BHF time-profiles used for the dome cup study.
(a) Constant BHF; (b) ramp BHF; (c) pulsating BHF.
Fig. 21. Experimental and simulated dome cups.
(a) Experimental good cup; (b) experimental fractured cup; (c) experimental wrinkled cup; (d) simulated wrinkled cup.
Limits of drawability were experimentally investigated using constant BHF. The results of this study are shown in Table 6. This table indicates that AKDQ had the largest drawability window while aluminum had the smallest and bake hard and high strength steels were in the middle. The strain distributions for constant, ramp, and pulsating BHF are compared experimentally in Fig. 22 and are compared with simulations in Fig. 23 for AKDQ. In both simulations and experiments, it was found that the ramp BHF trajectory improved the strain distribution the best. Not only were peak strains reduced by up to 5% thereby reducing the possibility of fracture, but low strain regions were increased. This improvement in strain distribution can increase product stiffness and strength, decrease springback and residual stresses, increase product quality and process robustness.
Table 6. Limits of drawability for dome cup with constant BHF
Fig. 22. Experimental effect of time variable BHF on engineering strain in an AKDQ steel dome cup.
Fig. 23. Simulated effect of time variable BHF on true strain in an AKDQ steel dome cup.
Pulsating BHF, at the frequency range investigated, was not found to have an effect on strain distribution. This was likely due to the fact the frequency of pulsation that was tested was only 1?Hz. It is known from previous experiments of other researchers that proper frequencies range from 5 to 25?Hz [3]. A comparison of load-stroke curves from simulation and experiments are shown in Fig. 24 for AKDQ. Good agreement was found for the case where μ=0.08. This indicates that FEM simulations can be used to assess the formability improvements that can be obtained by using BHF control techniques.
Fig. 24. Comparison of experimental and simulated load-stroke curves for an AKDQ steel dome cup.
5 Conclusions and future work
In this paper, we evaluated an improved design process for complex stampings which involved eliminating the soft tooling phase and incorporated the validation of product and process using one-step and incremental FEM simulations. Also, process improvements were proposed consisting of the implementation of blank holder force control to increase product quality and process robustness.
Three separate investigations were summarized which analyzed various stages in the design process. First, the product design phase was investigated with a laboratory and industrial validation of the one-step FEM code FAST_FORM3D and its ability to assess formability issues involved in product design. FAST_FORM3D was successful at predicting optimal blank shapes for a rectangular pan and an industrial instrument cover. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Second, the die design