塑料模具设计中英文翻译

1、常州工学院毕业设计(论文外文文献学院机电学院专业班级10成型一学生姓名高丽君指导教师陈怀国A.Mold ComponetsMolds used in injection molding consist of two halves;one stationary and one movable.The stationary half is fastened directly to the stationary platen and is in direct contact with the nozzle of the injection unit during operation.The mova

2、ble half of the mold is secured to the movable platen and usually contains the ejector mechanism.There are many possible mold designa,including multiple piece molds for complicated parts.On production molding equipment many articles may be shot at the same time by the use of multiple cavity molds.Th

3、e use of a balanced runner system carries the plastic from the sprue to each individual cavity.At this poin the material passes through a gate into the cavity.The gate is a restriction,smaller then the runner,to provide for even filling of the mold cavity and to allow the products to be easily remov

4、ed form the runner system.With most injection molding system,the articles can be snapped away from the runner or sprue without additional trimming.Prouducts that have been injection molded can usually be identified by finding where the gate was broken off.The gate will usually be located at the edge

5、 or parting line of an object or in the center of cylindrical product.Molds are expensive,as are the machines.Yet,once the product has been designed, molds made,and production stared,articles can be produced in quantity at low cost.Virtually all thermoplastics can be injection molded through variati

6、ons in mold and machine design.Mold(and dieparts that are mass-produced and standardized in shape and dimension are referred to as“standards”(or“standard parts”.Specialized operators of milling machines, lathes,lathes,electronic discharge machining(EDNequipment and grinders produce mold components i

7、ndependently of each other,following detaied mold part drawings.Finally,all these items come together with the standard mold base and hardware and are assembled by the mold maker.Today,standard components for the moldmaking industry are marketed by a number of companies.Fig.3.1.1illustrate the stand

8、ard components for Molds.Table3.1.1Status of standardization(1998components forCompression,Injection,and Die-Cast MoldPos. No.Denomination StandardDIN ISO1Plate,plain16760-16753-22Plat,drilled V16760-2/3Support pillar DIN ISO1007310073 4Centring sleeve1675994495Locating guide pillar1676180176Locatin

9、g guide busch1671680187Ejector pin,cylindrical head1530-A67518Shouldered ejector pin,cylindrical head1530-C8694 9Ejector pin,conical head1530-D/10Flat ejector pin1530-F869311Ejector sleeve16756840512Sprue puller insert16757/13Sprue bushing16752-11007214Angle pin/840415Locating unit,round and falt/84

10、0616Locating ring1676310907-110907-2 17Thermal insulating sheet167131560018Cooling connectors16766/B Mold ConstructionThe construction of the mold for injection molding begins with the working drawing. From it the tequirements for the mold can be specified.These would include the material from which

11、 the mold should be made,the availability of equipment for machining the mold,and the mold capacity of the die set on the machine.Cold rolled steel is an ideal material for laboratory molds,since it machines well,is fairly inexpensive,and holds up well for nozzle pressure and wear.Its major disadvan

12、tage is that it will rust quickly unless protected by mold telease or wax during storage.Complicated常州工学院mold cavities need specialized machining and polishing,therefore,circular cavities which can be turned and polished on the lathe require less equipment and machining skill.Similar molds may also

13、be machined from aluminum,and they have the advantage of not rusting.Excessive wear develops on the sprue due to the high nozzle pressure on the soft aluminum,but this can be overcome by the use of a steel cover plate on the top of the mold.Another method of mold construction is by the casting proce

14、ss using an aluminum filled epoxy resin.This type of mold is particularly suited to products of intricate design and products that are difficult to machine.The cast epoxy is strong and gives good surface detail, however,it is brittle and should have a steel top plate attached to absorb the wear of t

15、he nozzle.A pattern of the product must be secured or made and placed on a mold plate.The drag of a small steel flask is placed around the pattern and the epoxy resin is poured to fill the mold half.When this half of the mold has been cured,the cope is placed over it and the remainder of the mold po

16、ured.Upon curing,the flask is removed,all surfaces machined smooth,dowel pinholes drilled,and dowels inserted.A steel cap plate should be bolted to the top halves and the sprue,runners,and gates machined.Instructions for mixing,pouring,and curing the aluminum filled epoxy should be followed accordin

17、g to the manufacturers specifications.2.Hot Runner SystemsHot runners are classified according as they are heated:insulated-runner systems(it is not described in this articleand genuine hot-runner systems.The latter can be further sub-classified according to the type of heating:internal heating,and

18、external heating.Heating is basically performed electrically by cartridge heaters,heating rods,band heaters,heating pipes and coils,etc.To ensure uniform flow and distribution of the melt, usually a relatively elaborate aontrol system comprising several heating circuits and an appropriate number of

19、sensors is needed.The operating voltage is usually220V to240V,but small nozzles frequently have a low voltage of5V,and also15V and24V operating voltage.Runner systems in conventional molds have the same temperature level as the rest of the mold because they are in the same mold block.If,however,the

20、runner system is located in a special manifold that is heated to the temperature of the melt,all the advantages listed below accrue.Runner manifolds heated to melt temperature have the task of distributing the malt as far as the gates without damage.They are used for all injectionmolded thermoplasti

21、cs as well as for crosslinking plastics,such as elastomers and thermosets.常州工学院In the case of thermoplastics,these manifolds are usually referred to as the hot-runner system,the hot manifold,or simply as hot runners.For crosslinking plastics,they are known as cold runners.A.Hot-Runner SystemsHot-run

22、ner systems have more or less become established for highly-automated production of molded thermoplatic parts that are produced in large numbers.The decision to use them is almost always based on economics,duction size.Quality considerations, which played a major role in the past,are very rar

23、e now because thermoplastics employed today are almost all so that they can be processed without difficulty with hot-tunner systems that have been adapted accordingly.Hot-tunner systems are available as standard units and it is hardly worthwhile having them made.The relevant suppliers offer not only

24、 proven parts but also complete systems tailored to specific needs.The choice of individual parts is large.B.Economic Advantages and Disadvantages of Hot-Runner Systems1.Economic AdvantagesSavings in materials and costs for regrind.Shorter cycles;cooling time no longer determined by the slowly solid

25、ifying runners; no nozzle retraction required.Machines can be smaller because the shot volume-around the runners-is reduced,and the clamping forces are smaller because the runners do not generate reactive forces since the blocks and the manifold block are closed.2.Economic DisadvantagesMuch more com

26、plicated and considerably more expensive.More work involved in running the mold for the first time.More susceptible to breakdowns,higher maintenance costs(leakage,failure of heating elements,and wear caused by filled materials.3.Technological AdvantagesProcess can be automated(demoldingbecause do no

27、t need to be demolded.Gates at the best position;thanks to uniform,precisely controlled cooling of the gate system,long tlow paths are possible.Pressure losses minimized,since the diameter of the runners is not restricted.Artificial balancing of the gate system;balancing can be performed during runn

28、ing production by means of temperature control or special mechanical system(e.g.adjustment of the gap in a ring-shaped die or use of plates in flow channel.Natural balancing is better.Selective influencing of mold filling;needle valve nozzles and selective actuation ofthem pave the way for new techn

29、ology(cascade gate system:avoidance of flow lines,in-mold decoration.Shorter opening stroke needed compared with competing,conventional three-platen molds.Longer holding pressure,which leads to less shrinkage.4.Technological DisadvantagesRisk of thermal damage to sensitive materials because of long

30、flow paths and dwell times,especially on long cycles.Elaborate temperature control required because non-uniform temperature control would cause different melt temperatures and thus non-uniform filling.C.Design of a Hot-Runner System and its ComponentsHot-runner molds are ambitious systems in a techn

31、ological sense that involve high technical and financial outlay for meeting their main function of conveying melt to the gate without damage to the material.D.Externally/Internally Heated SystemsThe major advantages and disadvantages of the two types.E.Externally Heated System1.AdvantageLarge flow c

32、hannel cause low flow rare and uniform temperature distribution.2.DisadvantageThe temperatures required for external heating have to be very much higher.For PA66, for example,the mold temperature is approximately100and the manifold temperature is at a temperature difference of approximately170from t

33、he mold block,which means.Special measures required for fixing the hot-runner nozzles to the gates because of the considerable themal expansion.Risk of disruption if this is not adepantely resolved.Higher heating power(over500W per100mm line for a typical cross-section measuring40·7mm2.Insulati

34、on from the mold block.Large,unsupported ateas and therefore,with large-surface molds,risk of bowing of the mold platen on the feed side if this has not been designed thick enough and thus,as a direct consequence,the mold becomes very heavy.F.Internally Heated SystemA frozen layer of plastic forms o

35、n the inner surface of the channel and functions as aninsulation layer.The heat requirement of the system is much lower(toughly55W per100mm length of inside tube.The temperature differences between mold and manifold blocks are negligible; therefore measures that would have been necessary for large h

36、eat expansion are not needed.The hot manifold of an internally heated system if a compact block that is bolted tightly to mold.Consequently,the mold is very rigid and no measures are required for centering the nozzles and gates.This also allows the plate on the machine side to be manufactured as one

37、 block consisting of fixed mold with inbuilt manifold and corresponding rigidity.The melt volume is small and so the dwell times of the flowing melt are short.On the other hand,the flow rates are very much greater and this can damage the material.It is not advisable to use internally heated systems

38、for sensitive materials.When deciding on a certain system,advice can be obtained from suppliers.3.Forming TheoryThe confidence level in successfully forming a sheetmetal stamping increases as the simplicity of the part's topography increases.The goal of forming with stamping technologies is to p

39、roduce stampings with complexgeometric surfaces that are dimensionally accurate and repeatable with a certain straindistribution,yet free from wrinkles and splits.Stampings have one or more forming modes that create the desired geometries.These modes are bending, stretch forming and drawing.Stretchi

40、ng the sheetmetal forms depressions or embossments. Drawing compresses material circumferentially to create stampings such as beer cans.As the surfaces of the stamping become more complex,more than one mode of forming will be required.In fact,many stampings have bend,stretch and draw features produc

41、ed in the form die.The common types of dies that shape material are solid form,stretch form and draw.Solid Form The most basic type of die used to shape material is the solid form die.This tool simply displaces material via a solid punch"crashing"the material into a solid die steel on the

42、press downstroke.The result is a stamping with uncontrolled material flow in terms of strain distribution.Since"loose metal"is present on the stamping,caused by uncontrolled material flow,the part tends to be dimensionally and structurally unstable.Stretch Form Forming operations that prov

43、ide for material flow control do so with a blankholder.The blankholder is a pressurized device that is guided and retained within the dieset.Stampings formed with a blankholder may bedescribed as having three parts,shown in Fig.1.Theyaretheproductsurface(shown in red,blankholder surface(flat area sh

44、own in blueand a wall that bridges the two together. The theoretical corner on the wall at the punch is called the punch break.The punch opening is the theoretical intersection at the bottom of the draw wall with the blankholder.The male punch is housed inside the punch opening,whereas the blankhold

45、er is located around the punch outside the punch opening.These tools have a one-piece upper member that contacts both the b-lankholder and punch surfaces.A blank or strip of material is fed onto the blankholder and into location gauges.On the press downstroke,the upper die member contacts the sheet

46、and forms a lock step or bead around the outside perimeter of the punch opening on the blankholder surface to prevent material flow off the blankholder into the punch.The blankholder then begins to collapse and material stretches and compresses until it takes the shape of the lower punch.The die act

47、ions reverse on the press upstroke,and the formed stamping is removed from the die.Draw The draw die has earned its name not from the mode of deformation,but from the fact that the material runs in or draws off the blankholder surface and into the punch. Although the draw mode of deformation is pres

48、ent in draw dies,some degree of the stretch forming and bending modes generally also are present.The architecture and operational sequence for draw dies is the same as stretch-form dies with one exception.Material flow off the blankholder in draw dies needs to be restrained more in some areas than o

49、thers to prevent wrinkling.This is achieved by forming halfmoon-shaped beads instead of lock steps or beads found in stretch-form dies.The first stage of drawing sheetmetal,after the blank or strip stock has been loaded into the die,is initial contact of the die steel with the blank and blankholder.

50、 The blank,round for cylindrical shells to allow for a circumferential reduction in diameter,is firmly gripped all around its perimeter prior to any material flow.As the press ram continues downward,the sheetmetal bends over the die radius and around the punch radius.The sheetmetal begins to conform

51、 to the geometry of the punch.Very little movement or compression at the blank edge has occurred to this point in the drawing operation.Air trapped in the pockets on the die steel is released on the press downstroke through air vents.The die radius should be between four and10times sheet thickness t

52、o prevent wrinkles and splits.Straightening of sheetmetal occurs next as the die continues to close.Material that was bent over the die radius is straightened to form the draw wall.Material on the blankholder now is fed into the cavity and bent over the die radius to allow for straightening without

53、fracture.The die radius should be between four and10times sheet thickness to preventwrinkles and splits.The compressive feeding or pulling of the blank circumferentially toward the punch and die cavity is called drawing.The draw action involves friction,compression and tension.Enough force must be p

54、resent in drawing to overcome the static friction between the blank and blankholder surfaces.Additional force is necessary during the drawing stage to overcome sliding or dynamic friction and to bend and unbend the sheet from the blankholder surface to the draw wall.As the blank is drawn into the pu

55、nch,the sheetmetal bends around the die radius and straightens at the draw wall.To allow for the flow of material,the blank is compressed.Compressionincreases away from the die radius in the direction of material flow because there is more surface area of sheetmetal to be squeezed.Consequently,the m

56、aterial on the blankholder surface becomes thicker.The tension causes the draw wall to become thinner.In some cases, the tension causes the draw wall to curl or bow outward.The thinnest area of the sheet is at the punch radius,and gradually tapers thicker from the shock line to the die radius.This i

57、s a probable failure site because the material on the punch has been work-hardened the least, making it weaker than the strain hardened material.The drawing stage continues until the press is at bottom dead center.With the operation now complete,the die opens and the blankholder travels upward to st

58、rip the drawn stamping off of the punch.Air vents provided inflat or female cavities of the punch allow air to travel under the material asit is lifted by the blankholder.The stamping will have a tendency to turn inside out due to vacuum in the absenceof air vents.4.Injection mold designThe plastic

59、injection mold is in the present all plastics mold,uses the broadest mold,can take shape the complex high accuracy,plastic product.Under only is sketchily introduces.The design plastic injection mold first must have the certain,understanding to the plastic, the plastic principal constituent is a polymer.Like we often said the ABS plastic then is the propylene nitrile,the pyprolylene,the styrene three kind of monomers uses