【正文】 1．加熱沖裁 材料在加熱狀態(tài)下剪切強度大大下降，因而可以降低沖裁力。閉合高度等） 選擇壓力機時，壓力機的公你壓力 (N)必須大干或等于沖裁時的總壓力 一、 沖裁力的計算 生產中常用平刀口模具沖裁，其沖裁力可按下式計算； K 安全系數，一般取皮＝ 1． 3。同樣、廢料〔或工件〕上沖出的孔會因彈性收縮而箍緊在凸模上。日前一般工廠都采用這種加上方法。此方法是先加工基準件 (落料時為凹模，沖孔時為凸模 )，然后根據基淮件的實際尺寸，來配做另一件 (落料時為凸模、沖孔時為凸模 )，然后根據基淮件的實際尺寸，來配做另一件 (落料時為凸模、沖孔時為凹模 )，在另一件上修出最小合理間 隙值。 沖孔徑的刃口尺寸計算公式如下： 符號意義： x公差帶偏移系數，目的是為避免多數沖裁件都偏向極限尺寸 (其他略 ) 其值與工件精度有關。刀口部分各尺寸關聯(lián)圖如圖所示。 按模具加工方法的不同，刃口計算方法分為兩種 1．凸模與凹模分開加工 分開加工：是指凸模與凹模分別按各自的圖紙單獨加工，模具間隙靠加工出的尺寸保證。（斷面 是有錐度的，落料件大端尺寸 =凹模尺寸，沖空件小端尺寸 =凸模尺寸） 2．考慮到磨損會使凹模尺個增大、凸模尺寸減小，為保證模具的壽命，落料凹模的基本尺寸應取靠近或等于工件的最小極限尺寸；沖孔凸模的基本尺寸應取靠近或等于工件的最大極限尺寸，并采用最小合理間隙值。 18 (6)凸凹模壁薄時．為防止?jié)q裂，應放大沖孔的 z。 (2)沖小孔時 z 值取大些，以防凸模折斷。原因之一是這種間隙沒有根據生產特點分類選用，其二是只以沖裁件精度作為主要依據，而沒有考慮斷面質景及棋具壽命等其他重要因素，所以在生產中存在不少問題。 t—— 材料厚度。／ t 與β的近似值。／ t愈小。 一、理論確定法 理論確定法的主要依據是要保證裂紋重合，以便獲得良好的斷面。在最小合理隙 Z Mi n 時可以得到與板面垂直的斷面，而不產生顯著的毛刺。工件形狀越復雜，模具創(chuàng)造及調整時就越難保證間隙勻，故尺寸偏差也越大。軟綱的彈性變形量較小，沖裁后的彈性恢復量也就小，故工件精度較高。 沖裁件與凸、凹模尺寸的偏差主要是由于： 制件（廢料）從凹模內推出，由于材料的彈性恢復造成的。 當間隙過大時 ， 裂紋也不重合 。間隙就是一個。 第二節(jié) 模具間隙 沖裁時不僅要求次沖出符合圖紙形狀叫零件，還應有一定質量要求，沖裁件質量是指切斷面質量、尺寸精度及形狀誤差。隨材料機械性 能，間隙，模具結構變化。當材料內應力達到抗剪強度時材料開始產生裂紋， CD 段為裂紋擴展直至材料分離的斷型階隊 ,DE 段位推出材料件推出凹?？?。 上述沖裁變形過程還可通過沖裁力的變化曲線圖中得到確認。在凹模和凸模刃口的聯(lián)線上取’單元體“，其應力應變圖如圖 1— 3 所示。 斷裂分離階段 外力繼續(xù)增加材料內應力不斷增大，在凸、凹模刀口處由于應力集中，內應力首先越過抗剪強度，出現微裂。 彈性變形階段 13 凸模接觸材隊由于凸模加壓，材料發(fā)生彈性壓縮與彎曲并擠入凹模洞口。下面就沖裁變形過程、沖裁件質量、沖裁模刀口尺寸設計及沖裁模結構設計等問題進行分析討論。 從板科上沖下所需形狀的零件 (或毛坯 )叫落科。? Called push material (pieces of) force. The purpose of calculating power stamping process is it? Reasonable choice is to press tonnage. (Of course choose not to consider the tonnage presses, as well as tables, press structure... Shut height, etc.) Select press when you press and public pressure (N) must make a big or equal to the total pressure during blanking First, the calculation of punching force Flat blade used in production Die Blanking, the blanking force can be calculated as follows。 too small. And to die is difficult to mold manufacturing costs. Accuracy and precision blanking dies relationship table Special Note: If the size of the workpiece is not marked tolerance. I T14 without tolerances according to class to deal with, and die according to I D 11 manufacturing (nongraphic parts). Or by I T 67 class manufacturing (for round parts). Mold processing method according to the different calculation methods are 8 divided into two kinds of edge 1. Separate punch and die machining Separate processing: refers to the punch and die are processed separately by the respective drawings, mold the size of the gap processed by guarantee. Therefore, to calculate and mark out the punch and die dimensions and tolerances. This method is suitable for round or shape of a simple piece. (1) Blanking Die Blanking piece size based degree d, according to the above principles, first determine the small scale and then reduce the die size in order to ensure a reasonable punch clearance. Knifeedge part of the incidence graph of the size shown. Edge blanking die size is calculated as follows: (2) The punching die set punching size of d. (Standard tolerance) calculated according to the principles of the punch first determine the size. Further increasing the die size in order to ensure a reasonable minimum edge clearance associated with some of the dimensions in Figure 213 (b) below. Red edge aperture size is calculated as follows: Symbol meaning: Xtolerance zone offset factor, the purpose is to avoid all bias limit most blanking size (other omitted) Its value and accuracy of the workpiece. Tolerance band offset coefficient of 27 x to be investigated, or obtained by the following relations Workpiece accuracy of IT10 above: x = 1 Workpiece accuracy of IT11 ~ 13: x = Fine piece head IT14: x = In order to ensure a reasonable space, mold manufacturing tolerances must meet the following conditions Convex, concave mold separate processing advantages are: convex, concave 9 mold with interchangeable, easy to mold batch processing. Convex, concave mold separate processing disadvantage: in order to ensure a reasonable gap. Require higher levels of mold manufacturing tolerances, mold making more difficult. (Based on the use of examples to explain 6,27 table) 2. Punch and die with the processing For plex shapes or thin material workpiece. In order to facilitate mold, should be used with the process. This method is first processed basis documents (when blanking die, punch when the punch), and then base the actual size of the Huai items to do with the other documents (when blanking punch, punch when punch), and then base the actual size of the Huai items to do with the other documents (when blanking punch, punch die when), in another space on the revised smallest reasonable value. Therefore, when used with the process, simply reference documents marked size and tolerance, another mark only basic dimensions. And marked punchfoot small scale only by the actual preparation of the die to ensure the single gap (blanking time)。 Can be seen from the above formula, gap z and the material thickness t, the relative cut into the depth h. / T and the crack orientation day. Relevant, but to another with the material properties and β is related to the more rigid material, h. / T smaller. Therefore, we can see from the style, the main factors affecting the 6 value gap is the material properties and thickness. The more rigid material more thick, the necessary and reasonable value of the larger gap. Table 13 for the popular press materials, h. / T and β approximation. A variety of materials h. / T and β value is still no accurate determination of value, and. Production is not