提高级进模性能毕业论文外文翻译.docx

《提高级进模性能毕业论文外文翻译.docx》由会员分享，可在线阅读，更多相关《提高级进模性能毕业论文外文翻译.docx（11页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、外文资料翻译By Arnold MiedemaCapitol Concept & Engineering Corp., Wyoming, MIImproving Performance of Progressive DiesProgressive 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 s

2、eries 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

3、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 e

4、lements 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 Drawn shells.Interpreting the Part PrintThe first step in th

5、e 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, su

6、rface 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

7、 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 soli

8、d 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

9、 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 DieCare must be taken to e

10、nsure 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

11、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 posit

12、ion 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

13、 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 shi

14、ft 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 visu

15、al 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 switchPart Lifters and Part FeedingProgressive dies often require the

16、 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

17、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 l

18、ifter 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 followin

19、g 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 du

20、ring 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 st

21、roke. 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 repea

22、ted 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.Flexible Part CarriersTo transport the strip from one station to the next in a progressive die, some material must be left bet

23、ween 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 carr

24、ier 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.Another concern is the vertical breathing of parts in die stations during the clos

25、ing 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. Vertical breathing also occurs when a flange is formed up in a progressive die station that is adjacent to stations that u

26、se 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

27、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. These sheets then are moved down in relation to each other to simulate how the upper die would close during the press dow

28、nstroke. This will show the relative position of the part as the die closes and during the reverse action as the die ram opens.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 v

29、arious 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.Ce

30、nter 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, leavi

31、ng 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

32、 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 clo

33、sure 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 to

34、oling. 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 th

35、e 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 carri

36、er 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 o

37、ne-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.Edge camber of the material as it is delivered from the coil can ca

38、use 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.Anothe

39、r 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 ProfileThe optimum carrier profile is affected by some of the

40、 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

41、: 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 close

42、s 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

43、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 mater

44、ial, 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, carrierwidth is a best judgment call.Depending on all the die factors

45、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 thr

46、ough 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 stron

47、g 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 fra

48、cture during flexing of the carrier. Also avoid any steps or nicks in the edges of the carrier.Upper Pressure PadsBecause 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

49、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 pa