過電墊片級進模具設計

過電墊片級進模具設計,過電,墊片,模具設計 Improving Performance of Progressive Dies Progressive die stamping is a cost-effective and safe method of producing components. Careful design and construction of dies will ensure optimum performance. A progressive die performs a series of fundamental sheet metal operations at two or more stations in the die during each press stroke. These simultaneous operations produce a part from a strip of material that moves through the die. Each working station performs one or more die operations, but the strip must move from the first station through each succeeding station to produce a complete part. Carriers, consisting of one or more strips of material left between the parts, provide movement of the parts from one die station to the next. These carrier strips are separated from the parts in the last die station. There are six elements that should be addressed when designing and building a progressive die to maximize its performance: · Interpreting the part print, · Starting material into the die, · Part lifters and part feeding, · Flexible part carriers, · Upper pressure pads, and · Drawn shells. Interpreting the Part Print The first step in the proper design of a progressive die is to correctly analyze the part print. The tool designer must interpret the print to determine the function of the part by looking for such things as the type of material, critical surfaces, hole size and location, burr location, grain direction requirements, surface finish and other factors. The die designer must understand the part well, particularly if it has irregular shapes and contours. However, modern computer-drawn prints make this more difficult because computer-drawn part data can be downloaded directly to the die-design computer. As a result, the designer may not become thoroughly familiar with important part features. Also, many computer-drawn parts are more difficult to understand, because often, only one surface is shown and it may be the inside or outside surface. Computer drawings often show all lines, including hidden features, as solid lines instead of dotted lines. This leads to interpretation errors, which in turn leads to errors in the building of the die. To better understand complex part shapes, it is helpful to build a "sight" model of the part using sheet wax, rubber skins or wood models. Dimensional accuracy is not critical for these models, as they are used primarily to visualize the part. Rubber skins and sheet wax also can be used to develop preform shapes and to develop the best positions for the part as it passes through each die operation in the progressive die. Starting Material in the Die Care must be taken to ensure that the strip is started correctly into the die. Improper location of the lead end of the strip will do more damage to the die in the first 10 strokes of the press than the next 100,000 strokes. "Lead-in" gauges must have large leads and a ledge to support the lead end of the coil strip when it is inserted into the die. Large leads on the gauges are important so that the die setup person does not have to reach into the die, as well as for minimizing the time required to start a new strip into the die. Also, one gauge should be adjustable to compensate for variation in strip width,. The position of the lead edge of the strip is critical for the first press stroke, and must be determined for every die station to ensure that piercing punches do not cut partial holes in the lead edge. This could cause punch deflection or result in a partial cut with trimming punches, which can result in an unbalanced side load as the strip passes through the die. Any of these conditions can result in a shift of the punch-to-die relationship that may cause shearing of the punches. Improper location of the lead edge of the strip also can result in an unbalanced forming or flanging condition that can shift the upper die in relation to the lower die. Heels should be required to absorb this side load, particularly when forming thick materials. A pitch notch and pitch stop can provide a physical point to locate and control the lead edge of the strip. Brass tags or marker grooves also can provide a visual location, but these are not as accurate or as effective as a pitch notch stop. The press can be prevented from operating with either a short feed or over feed by mounting the pitch stop on a pivot and monitoring it with a limit switch. Part Lifters and Part Feeding Progressive dies often require the strip to be lifted from the normal die work level to the feed level before strip feeding takes place. This can vary from a small amount--to clear trim and punching burrs--to several inches to allow part shapes to clear the die. Normally, all lifters should rise to the same height so that the strip is supported in a level plane during forward feed. The strip must not sag between lifters; otherwise parts will be pulled out of their correct station location spacing. Bar lifters provide good support and are better than spring pins or round lifters notched on one side of the strip. Often, a good bar lifter system allows higher press speeds because feed problems are eliminated. Although the initial cost is more than round lifters, performance is better and setup time is reduced. As the strip is started into the lead-in gauges, the strip should be able to feed automatically through all the following die stations without requiring manual alignment in each set of gauges and lifters. The strip also must be balanced on the lifters so that it does not fall to one side during feed. A retainer cap can be mounted on the top of the outside bar lifters. This produces a groove that captures the strip during feed and prevents strip buckling. Gauging and lifter conditions can be simulated during die design by cutting a piece of transparent paper to the width of the strip. The lead edge of the paper is placed over the plan view of the die design at the location the strip will be for the first press stroke. Then the paper is marked with all of the operations that will be performed at the first die station--for example, notching and punching. The paper strip then is moved to the second station on the drawing and the operations for both the first and second stations are marked. This process is repeated through all the die stations to illustrate what the real part strip will look like when it is started into the die and helps determine the adequacy of gauges and lifters. To transport the strip from one station to the next in a progressive die, some material must be left between the parts on the strip. This carrier material may be solid across the width of the strip, or may be one or more narrow ribbons of material, see part carriers sidebar. Many parts require the edge of the blank to flow inward during flanging, forming or drawing operations. This may require the carrier to move sideways or flex vertically, or both, during the die operation. A flexible loop must be provided in the carrier to allow flexing and movement of the blank without pulling the adjacent parts out of position, Fig. 2. Another concern is the vertical "breathing" of parts in die stations during the closing and opening of the die in the press stroke. For example, vertical breathing takes place between the draw stations of parts requiring more than one draw to complete the part, Fig. 3. Vertical breathing also occurs when a flange is formed "up" in a progressive die station that is adjacent to stations that use upper pressure pads to hold the adjacent parts down. It is important to consider the flexing of the carrier during the upstroke of the press as well as during the downstroke because the action may be different. This can be simulated in the design stage by making an outline of the cross-section of the part, the pressure pads and the stationary-mounted steels on separate sheets of paper and then placing these sheets on top of each other in layers over the die section views. This will show the relative position of the part as the die closes and during the reverse action as the die ram opens Part Carriers A common feature in all progressive stamping dies is the material that transports the parts from station-to-station as it passes through the die. This material is known by various terms, such as carrier, web, strip, tie, attachment, etc. In this instance, we will use the term carrier, of which there are five basic styles: Solid carrier--All required work can be accomplished on the part without preliminary trimming. The part is cut off or blanked in the final operation. Center carrier--The periphery of the part is trimmed; leaving only a narrow tie near the middle of the part. This permits work to be performed all around the part. A wide center carrier permits trimming only at the sides of the part. Lance and carry at the center--The strip is lanced between parts, leaving a narrow area near the center to carry the parts. This eliminates scrap material between parts. Outside carriers--The carriers are attached to the sides of the part so that work can be done to the center of the part. One side carrier--The part is carried all the way or part of the way through the die with the carrier on one side only. This permits work on three sides of the part. The type or shape of the carrier will vary depending on what the part requires as it progresses from station to station in the die. The stock width may be left solid if no part material motion is required during die closure or it can be notched to create one, two or even three carriers between the parts The carriers can be straight, form a zig-zag pattern or have loops between the parts depending on where attachment points to the part are available or to accommodate whatever clearance may be required by the die tooling. As the part is formed, flanged or drawn into a shell, the carrier may have to move sideways or up and down as the die closes and opens. When die operations cause the carrier to move, it usually will be required to flex or stretch. Regardless of carrier flexing, their key function is to move the parts close enough to the next station so that pilots, gauges and locators can put the parts into their precise location as the die closes. If the carrier acquires a permanent stretch, the parts may progress too far to fit on the next station, or in the case that the die has two carriers, one carrier may develop permanent stretch with no stretch in the other carrier. This will create edge camber in the strip, causing it to veer to one side. This results in poor part location. A stretched carrier can be shortened to its correct length by putting a dimple in the carrier. If a center carrier or one-sided carrier develops camber, the strip can be straightened by dimpling or scoring one side of the carrier. Construct the dimple and scoring punches so that they are easily adjusted sideways for position and vertically for depth. as it is delivered from the coil can cause the strip to bind in the running gauges that guide the material during the feed cycle. This binding may cause the carriers to buckle, which results in short feeds. It often helps to relieve the guide edge of the gauges in between stations and have tighter gauge control at the work station. Another option is to eliminate camber by trimming both sides of the material in the beginning of the die. By adding stops at the end of these trim notches they can be used as pitch control notches to prevent progression overfeed. Optimum Carrier Profile The optimum carrier profile is affected by some of the following conditions: · Space available between parts: Try to keep the carriers within the stock width and pitch required for the blank. If this is not possible then the designer must add to the width and/or the progression of the material to provide adequate carrier room. · Attachment points to the part: If two carriers are used, try to keep the profile and length of the carriers somewhat the same so that any effect of carrier flexing is close to being balanced. · Clearance for punch and die blocks: Punch blocks that extend below the stock or die blocks that extend above the stock when the die closes will require clearance in relation to the parts and the carriers. If a loop of the carrier interferes with blocks it may be possible to form the loop vertical to provide clearance. · Thickness of the material: Large parts with thin material may require stiffener beads to add strength to the carrier for stock feeding. Another stiffening and strip guiding method is to lance and flange the edge of the stock, which also can be used as a progression notch. · The total of the strip: Heavy parts in long dies require more force to push the strip through the die. However, the weight is usually thick material, and thick material is stiffer than thin material. As a rule of thumb, flexible carriers for materials of 0.020 in. to 0.060 in. are about 3/16 in. to 5/16 in. wide. For stock thicknesses above and below this thickness range, carrier width is a "best judgment call." Depending on all the die factors involved, under normal conditions the carriers should be a consistent width for their full length, but especially in the area of flexing. Since nearly every stock feeder pushes material through the die rather than pull the material, the carrier must be strong enough to push the parts all the way through the die. A detection switch actuated by a complete feed of the strip at the exit of the die can detect buckling. If action of the die during closure or opening of the press requires the carriers to flex, design the carrier with loops that are long enough to flex without breaking, but still strong enough to feed all the parts to their full progression. If two flex carriers are not strong enough to feed the strip, consider three carriers. Try to make the radii in flex loops as large as practical. Sharp corners or small radii will concentrate stress of flexing, making it the first point to fracture during flexing of the carrier. Also avoid any steps or nicks in the edges of the carrier. Upper Pressure Pads Because of size or function, many progressive dies require two or more pressure pads in the upper die. Each may require a different travel distance to perform the work in the individual die station, such as trimming or forming or drawing. However, the upper pressure pads often are used to push the material lifters down by pressing against the strip, which pushes the lifters down. In this situation, all of the pressure pads that push material lifters down should have the same travel distance. If the upper pressure pads travel different distances, the strip will not be pushed down evenly. This can pull adjacent parts out of the progression, making it difficult to locate the parts in their proper station position after the feed cycle. If the part requires a flange to be formed up, the part carrier must have a flex loop to allow for vertical breathing of the part or provide a pressurized punch/pad with the same travel as the other pressure pads. The force required by the pressurized punch/pad has to be adequate to form the flanges up during the downstroke while the punch/ pad is in the extended position. This keeps the strip from breathing vertically as it is pushed down from the feed level to the normal work level. When the strip reaches the work level, the pressurized punch/pad stops its downward motion while the upper die continues down for punching, trimming, down flanging and other operations. Springs or nitrogen cylinders can be used for pressure in these pressurized punch/ pad stations, but they must have enough preload force to form the flanges up and to collapse the lower gripper pad before the upper punch/ pad recedes. 級進模穩(wěn)態(tài)運行能力的提升 級進模是一種成本低廉且安全的零件制造方法,. 精心設計模具結構可確保最佳性能。一副級進模在一次沖壓動作中可在模具不同工位進行不同的沖壓操作。這些在通過模具的帶料上同時進行的沖壓動作制造出零件。每個工位可進行一個或多個操作，但要生產出完整的零件條料必須經過每一個工位。而零件依靠零件之間的載體輸送到各個工位，并在最后一個工位進行切除。 為了使模具性能最佳，在設計和制造級進模具時，必須考慮以下五個方面： · 研究零件 · 送料方式 · 零件頂出和送進 · 設計零件載體 · 壓料裝置 零件排樣 設計級進模首先必須正確地理解零件圖，必須考慮材料、重要表面、孔的尺寸和和位置、毛刺方向、材料纖維方向、表面粗糙度和其他因素。 模具設計要求設計者必須對零件有透澈的了解，特別是對形狀和輪廓不規(guī)則的零件。然而，現(xiàn)代計算機繪圖使得零件數據可以直接下載到設計者的電腦上，使得設計者可能不熟悉零件重要特性。 另外,因為計算機繪圖經常出現(xiàn)這種情況，圖上只顯示一個面，可能是內表面也可能是外表面，使得很多計算機繪制的圖形難以看懂。電腦繪圖經常顯示所有的線條，包括隱藏部分，為實線而非虛線，這導致錯誤，進而導致模具結構錯誤。 為了更好地看懂復雜零件外形，可用蠟板，橡膠皮或者木板做成具有零件某個視圖方向上的外形的模型。模型不要求精確的尺寸，其主要是用來形象地表示零件形狀。也可以用這些模型來決定應該在級進模的哪個工位成形零件哪個部分的外形。 材料送進 必須確保條料準確地進入模具。如果條料導向錯誤，那么最初的10次沖壓動作對模具造成的損傷可能比接下來的100000次沖裁還大。當卷料送進入模具時必須順利導向且有限位裝置。良好的導向能力時非常重要的，因為這樣操作人員就不必將手伸入模具，而且可以縮短接上下一卷材料所需的時間。除此之外，導向裝置必須時可調的以適應條料寬度的變化。對第一次沖裁而言條料送進位置非常重要，必須確定條料在每個工位的送進位置的以保證凸模不沖偏，會導致沖頭變形或切不完整，可能造成條料不平衡送進時單側受力。任一種可能都會造成凸凹模錯位使得沖頭受剪切損壞。 條料送進不當成形時可能導致偏載或者邊緣卷起，影響上下模之間的相對位置。墊塊必須能夠承受這些載荷，特別是成形較厚材料時更應如此。 一個步距的凹口或止動銷可作為定位點控制條料送進位置，黃銅標簽或標記槽也提供了視覺定位 ，但是這些都不夠準確，不夠有效。通過在將步距限位銷安裝在支點上，并用限位開關監(jiān)控以防止條料送進不到位或送進過多以保護壓力機。 零件頂出和送進 級進模通常要求將條料抬高到距模具工作位置一定高度水平線上，使得條料送進到指定位置，而與清理廢料和毛刺或者利用制件外形清理模具無關。 正常情況下，所有抬高裝置必須上升到同一高度使條料在送進過程中保持水平。條料不能由凹陷，否則零件會被從正確位置拔出。相對于安排在條料側面的彈簧銷和球頭抬料銷，桿式抬料裝置效果更好。 多數時候一旦材料送進問題解決，則要求桿式抬料裝置可以承受較高的沖壓速率。雖然成本比球頭抬料裝置高，但性能要好的多，而且安裝時間也縮短了。 一旦條料進入導料槽，條料就必須能夠自動送進到所有后續(xù)工位而不需要人工在每個導向位置或抬料處對準導向。而且條料在抬料桿上應該保持平衡不在送進是偏向一側。在抬料桿頭部應裝上一個金屬帽蓋，形成一個凹槽，在條料送進時拖住條料不使其彎曲變形。 送進步距測量和抬料裝置的設置方案可通過在模具設計時用一塊與條料等寬度的透明紙板模擬條料來確定。紙板邊緣位于根據模具設計方案確定的第一工位沖裁時條料應送進的位置，然后在紙板上標示模具第一個工位所要進行的－的所有操作－比如：切槽和沖孔。接著將紙帶移動到第二個拉深工位，并在紙板上標示該工位進行的操作。在每個工位重復該操作則可在紙帶上顯示出送到最后工位時條料的形狀，在根據條料形狀設置定距和抬料裝置。 為將條料從一個工位運送到下一個工位，必須在條料上的零件之間留下部分材料作為運送條料前進的載體。這些載體可以是條料條料間的十字形部分或者由幾條窄條帶，如邊側載體。 零件在進行翻邊，成形或者拉深操作時要求邊緣材料向內流動，這就需要載體在模具工作期間能夠橫向移動或垂直收縮，或兩者都有。需要給載體提供足夠的活動空間，使得載體收縮和移動時不會將相鄰的零件拽離原來位置 另一個需要關注的問題是材料在壓力機開合模具期間的垂直運動。如，有的零件需要幾次才能拉深成形，在這些工位之間材料就發(fā)生垂直流動。 與壓力機下行時相同，必須注意壓力機上行時要保證載體運動靈活，因為載體向上運動可能會與向下運動有所不同?？稍谀＞咴O計階段做零件輪廓，壓邊圈和固定鋼板的輪廓，然后按順序放在模具斷面視圖之上，將這些零件根據相對之間的關系向下運動就可以模擬沖壓過程中上模是怎樣合模的，可顯示出開合模時零件之間的相對位置。 零件載體 所有級進模的共同點是零件靠坯料上的材料運送到模具中的各個工位，這些材料有各種不同的術語稱呼，如載體，筋，條帶，連接帶等等。在本例中，我們一概稱之為載體，其主要有以下五種形式： 原載體－所有操作可在零件上完成，不需要事先切出載體。 中間載體－先切出零件形狀，留下靠近中間的一段條帶。適用與在周邊進行切除工序的零件。如果載體寬度較大，允許在單側切出零件。 等寬雙側載體－條帶對稱分布在零件兩側，用一段窄長的條料運送零件，適用于須切除零件之間材料的零件。 邊料載體－載體在零件的邊緣，適用于在中間成形的零件。 單側載體－載體位于零件一側，運送零件到最后一個工位或中間工位，可在零件三個方向上成形。 根據零件在級進工位中成形的不同要求，載體有各種不同的類型。可在模具閉合期間沒有運動的坯料邊緣留余料或在做一個或兩個甚至三個缺口作為載體。 根據載體在零件上的連接點的位置和易于模具廢料切除，載體可以是直的或者有弧度的環(huán)形。在成形，翻邊或拉深杯筒形零件時，模具開合時載體還可以橫向或向上和向下移動。 模具工作時可能使得載體移動，要求載體具有伸縮性。撇開載體伸縮性不論，載體的主要功能是將零件盡可能地運送到離模具下個工位的定距、定位裝置盡可能近的位置，以便進行精確定位。 最佳載體形狀 載體形狀是否合理由以下決定： · 零件之間的空位部分： 盡量使載體在坯料橫向寬度和縱向步距之內，如果不能滿足這個條件，則設計人員需要考慮是否增加條料寬度或步距以保證載體的尺寸。 · 載體與零件連接部分：如果由兩個載體，盡量使兩個載體的形狀和長度大小一致，以使兩個載體韌性和靈活性相同。 · 凸凹模的清理：模具閉合時凸模進入坯料以下或者凹模升到坯料之上，要求開模時將相應的零件或廢料推出。如果載體與模塊相干涉，可將載體縱向設置以便清理。 · 材料厚度： 大型薄壁零件需要需要設加強筋以加強載體強度，方便條料送進。另一加強剛度和導向能力的方式是在坯料上開一缺口或將邊緣折起，這也可以作為定距。 如果載體伸長過多則下一個工位零件無法準確定位，而如果有兩個載體，一個伸長而另一個沒伸長，也會導致定位不好。 在載體上打一個凹坑可防止載體伸長。如果中心載體或單側載體拱起變形，可用壓痕進行矯正。設計凹痕結構并在凸模上打上相同形狀的印記，則可以很容易地進行側向和垂直方向定位。 條料邊緣翹曲是由于卷片筒使得條料與模具的導料裝置相碰而引起的，使得條料邊緣卷起，并最終導致條料送進不到位。對此經常在相應工位上改善導料板邊緣和設置更精確的導向裝置來解決。 另外一種解決邊緣卷起的方法是在第一個工位裁去兩邊的材料。在側刃處設擋料塊作為定距裝置以防止材料的過送進。 大零件在長的級進模中制造時要有足夠大的推力送進帶料。但是厚的材料通常較重，也比薄的材料剛度大得多。根據經驗可知，運送0.020英寸到0.060英寸厚得材料需要3/16英寸到5/16英寸寬的載體。對于厚度高于或低于這個范圍的坯料，載體寬度可很容易確定。 根據影響模具的各種因素來看，正常情況下載體全長的寬度應當一致，在需要材料移動的特殊區(qū)域可以不一致。大多數的自動送料機構都是以推的形式送料而不是拉料，這就要求載體有足夠的強度 。 條料送進完成后會出動裝在模具出口位置的檢測開關。如果模具打開或閉合時需要載體彎曲而不破裂，且有足夠得強度送進零件，載體必須設計得足夠長。如果兩個彎曲載體強度不夠可以考慮設置三個。 設計時彎曲半徑要盡可能大。尖角處或者彎曲半徑太小的地方載體彎曲時會應力集中會使材料破裂。而且要載體邊緣不要有階梯和斷口。 壓料裝置 由于體積或功能的需要，很多級進模需要在上模設置兩個或三個壓料裝置。不同工位的壓料裝置的工作行程可能都不相同，如沖裁或成形和拉深 然而，壓料裝置經常要通過作用在帶料上使頂料銷下沉。在這種情況下，所有壓料裝置的移動距離必須相同。如果工作行程不相同，則有些位置條料不會被完全壓住，會使附近的零件離開原來位置，送進時條料定位變得困難。 如果要求在零件翻邊，零件載體必須有一個伸縮回路，以便零件移動或者使凸模/壓邊圈擁有和其他壓邊裝置一樣的行程。而凸模或壓邊圈在極限位置時要有足夠的力完成翻邊蘭。在這過程中條料相應部分的材料垂直流動。 當條料下降到工作位置，施壓凸模或壓邊圈停止向下運動，而上模繼續(xù)向下沖孔，切邊，向下翻邊或其他成形操作?？捎脧娏椈苫驓馄孔鳛闆_壓凸模和壓邊圈的動力源，但要保證它們要有足夠的預緊力以完成翻邊或在凸模與壓邊圈后退前壓住下模頂料裝置。 拉深殼體 殼體拉深是將板料拉深成圓柱瓶形零件。在拉深操作中，坯料直徑受殼體周長的影響。而周長又受到材料的流動性和外圍材料向內流動阻力和邊緣阻力。 當邊緣材料受到的阻力超過極限值后邊緣就會起皺失穩(wěn)。為了避免出現(xiàn)起皺，必須時材料可以在凸模和壓邊圈之間順利流動。造成拉深破裂的兩個主意原因是拉深件直徑與坯料直徑比值超過極限值和拉深半徑太小。 從平整的坯料拉深成殼體和將殼體拉深為直徑更小的殼體時材料向內流動距離