模具基本结构-外文翻译.doc

毕业设计(论文)外文资料翻译

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外文出处： Basic Underfeed Mould

附 件： 1.外文资料翻译译文；2.外文原文。

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附件1：外文资料翻译译文

模具基本结构

模具由三个基本部分组成，分别是动模部分、浮动型腔板和定模板，如图1所示。动模部分包括动模板组件，支撑块，支撑板，推出机构和顶杆推出系统。这样设计的动模部分与最基本的模具结构中的动模部分相同。

浮动型腔板通过导柱(图1中没有示出)固定在定模板上，设计形式可以是整体式，也可以是嵌入式。导柱必须有足够的长度，(以便模具工作时)支撑浮动型腔板完成开合动作，并在模具合模时完成对型腔和型芯的找正作用。导套分别安排在动模板和浮动型腔板上。
浮动型腔板的最大运动距离由限位钉或类似装置控制。在动模板的适当位置钻孔，以便安装限位钉。限位钉必须有足够的长度，为定模板和浮动型腔板之间提供足够的空间，从而使浇注系统凝料顺利脱落。如果必须使用手动方式取出凝料，开模时凝料所需的最小距离应为65mm。
模具的开模顺序是：浮动型腔板和定模板先分开，确保模具打开时浇注系统凝料立即从浇口套中脱出。为实现这样的顺序，定模板和浮动型腔板之间装有弹簧。弹簧的弹力必须是够大，确保在初始推力的作用下浮动型腔板跟随动模部分一起运动。弹簧套在导柱上，一同装在浮动型腔板上相应的弹簧座处(如图2所示)，这种形式在弹簧装配中十分常见。

浇注系统的主要部分(分流道和主流道)开设在定模板上，为便于自动操作，分流道应采用梯形截面，以便脱出系统凝料。注意，如果采用圆形分流道，分流道的一半开设在浮动型腔板上，开模时，分流道可能留在浮动型腔板，并阻碍凝料的脱落或去除。
现在，我们将详细讨论模具装配，先看这类模具的生产循环过程。
熔体经过浇注系统充满型腔后(如图1(a)所示)，经过适当的保压过程，注塑机带动，模具开模。压缩弹簧的弹力立即释放出来，推动浮动型腔板和动模部分一起移动，如同前面论述的一样。主流道凝料被拉料杆从浇口套中拉出。浮动型腔板移动预定距离后，被限位钉限位。动模部分继续后移，塑件由于收缩作用包裹在型芯上从型腔中脱出(跟随动模一同移动)。点交口在结合处拉断，与分流道脱离(如图1(b)所示)。
安装在动模部分的拉料杆脱离浮动型腔板，浇注系统凝料由此脱下，然后在浮动型腔板和定模板之间自由落下。动模部分继续后退，知道推出机构开始运动，推出塑件(如图1(c)所示)。合模时，模具的各模板回到成型位置，重复下一个注塑循环。
前面的章节讨论了基本的两板式模具，其注塑成型的原理是，在压力作用下，熔体通过浇注系统注入模具型腔形成塑件。然而，两块模板本身并不构成模具的全部设计内容，因为塑件成形后没有办法取出塑件，(要想生产塑件)因为必须手动脱模。
此外，所有热塑性熔体凝固时都会收缩，这意味着塑件将包罩在型芯上。收缩作用使塑件脱模(存在)困难。生产中，为使塑件脱离型芯，必须使用某种脱模方式。下面将讨论不同的脱模方式。
注塑机为推出系统提供了自动推出力，其推出动力装置安装在注塑机移动板的后面。因此，模具的推出系统安装在动模部分将获得最大效率。例如，这部分(可以)安装在移动模板上。我们在前面章节中论述了需要从型芯上推下塑件，因此，塑件必须跟随型芯(一同移动)，推出系统装在动模部分最为告适。
模具的推出系统将在以下三个标题中讨论，即：(i)推出直架；(ii)推板装配机构；(iii)推出方式。
推出支架
推出支架是模具的一部分，用来主撑模板，并为推板的装配和运动提供空间。推出支架通常由动模座板和几块支撑块组成，支撑块安装在动模座板上，且便于加工成型。
推出支架有三种设计形式：
(i) 同轴的推出支架；
(ii) 框状推出支架；
(iii) 圆形支架。
推板装配机构
推板装配机构也是模具的一部分，用来安装推出零件。推板提配机构安装在推极支撑架内，直接披在模板后面。装配机构由推板、推板固定饭和注塑机顶出杆组成。注塑机顶出杆一端带有螺纹。通过螺纹紧固在推板上。在这种结构中，顶出杆的作用不仅是推出零件，而且顶杆上直径相等的部分通过顶出杆套筒，套筒去藐在模具座板上。
在更详细讨论模具推出方式之前，我们了解一下推出机构是如何工作的。模具安装在注塑机的移动台板上。台板左侧是注塑机推动杆。推动抖的位置是可以调整的，以适应不同的“推出力”。当移动台极向左移动时，开模，在推动的作用下模具推杆运动。 整个模具推件装配机构的装配如图1(b)所示。动模的其余部分(例如推板和推出支架)继续向左运动，直到模具完全打开(如图1(c)所示)。为使推出元件起作用，推板装配板和模板之间必须存在相对运动。
推出方式
塑件冷却后，其收缩状态取决于塑料熔体的成型过程。例如，对于内部不带有其他形状的塑件和实芯矩形件，塑件的收缩作用使其脱离型腔壁，因此，可以采用简单的脱模方式(推出塑件) 。
然而，若塑件具有内部形状，冷却收缩时塑件将包紧在型芯上，因此，有必要采用一些适当的方式推出塑件。
设计时有几种方式可供选择，但是，总的说来，选择哪种推出形式取决于塑件的形状。基本的推出方式有以下几种：(i)推杆脱模；(ii)推管脱模；(iii)推件板脱模；(iv)气动脱模。
定模部分的推出机构
尽管推出机构通安装在在模具的动模部分，但这种方式并不总是可行的。考虑到箱形塑件的表面质量，浇口必须设置在塑件内部。这种情况下，型芯和推出系统安装在定模部分，模具具有一定的复杂性。
首先，推出支架和推板装配板安装在定模板后面，这将极大地增加模具高度。 因此，熔体从喷嘴射出后要经过较长的距离(才能进入型腔)。然而，为缩短这段长度，浇口套(必须)较深地进入模板内，装配结构如图例，这就必须使用特殊的延伸式喷嘴。
其次，注塑机的定模部分并不能提供任何驱动推出系统工作的动力装置，这就意味着动力机构必须与模具设计成一体。尽管在上面“推出方式”中讨论的所有推出方式都能安装在模具的定模部分，但是在设计时应根据具体情况选择适合的方式。
拉料杆
开模时，流道凝料必然从浇口套中拉出。对于单腔模具，熔体沿着主流道直接进入模具型腔。开模时，塑件脱离型腔，浇道凝料也一同脱出。
对于带有基本浇注系统的的多腔模具，每次开模时浇道凝料很可能滞留在浇口套中，必须用手工去除熔体凝料。为避免这种情况，设计时总会考虑安装浇道凝料拉出机构。
普通的拉料方式是利用推杆顶部加工的凹陷拉料或者利用主流道入口处的凹陷拉料，该处凹陷与主流道的(锥度)方向相反。熔体进入凹陷后，(冷却)凝固，开模时，(这部分凝料)能够提供足够大的阻力以拉出浇道凝料。
拉料杆有两种基本形式。一种是在冷料井递补加工出空间，这种方式适合在分型面下部使用。另一种是在拉料装置的顶部加工出适当的形状，该方式适合在分型面上部使用。为区分两种基本拉料方式，我们分别用方式A和方式B表示。
整体式型腔和型芯板
当型脏就型芯由-块大的钢扳或钢块加工而成，或者铸成一体，不需使用主撒件而形成一块模板时，就构成整体式型腔板或型芯板。这种设计因具有强度高，尺寸小和成本低的特性，而主要应用在单型腔模具中。整体式型腔和型芯一般不用在多型腔模具中，因为(多型腔模具)设计时必须考虑一些其他因素，例如安装组合镶件等。
在模具制造的众多方法中，用于加工整体式型腔就型芯板的方法主要有两种：(a)使用传统机床对粗锻钢材坯料直接加工，(b)利用精确的熔模铸造技术将坯料加工成型腔和型芯。用于制造型腔和型芯的坯料经常需要特殊工艺的处理。通常，4.25%的镍铬合金钢(BS970-835M30)是生产整体式模板的指定材抖，这时采用直接的机加方式。精确的熔模铸造常常用来加工高铬钢。
镶拼式型腔和型芯
对于成型部位复杂的模具和多腔模具，也像整体式模具那样用一块钢材加工型腔和型芯并不容易。(如果采用整体式结构)加工顺序和操作过程将变的非常复杂，成本也高。因此镶拼式装配方式替代了整体式。
镶拼式型腔是用小钢块加工而成。加工后的小钢块作为镶件，形成公模(型芯)部分的称为型芯嵌件，相反的，形成母模(型腔)部分的称为型腔嵌件。然后，把这些镶件牢固地安装在被称为垫板的孔中，垫板由实心钢板或钢块加工而成。这些安装孔有的是由垫板的局部凹陷形成，有的是垫板直接加工而成。在后一种方式中，点半后部还要增加一块模板，起加固作用，确保镶件安装到位。

附件2：外文原文

Basic Underfeed Mould
A simple mould of this type is shown in Figure 3-1, the mould consists of three basic parts, namely: the moving half. The floating cavity plate and the feed plate, respectively.

The moving half consists of the moving mould plate assembly, support blocks, backing plate, ejector assembly and the pin ejection system. Thus the moving half in this design is identical with the moving half of basic moulds.
The floating cavity plate, which may be of the integer or insert-bolster design, is located on substantial guide pillars (not shown) fitted in the feed plate. These guide pillars must be of sufficient length to support floating cavity over its full movement and still project to perform the function of alignment between the cavity and core when the mould is being closed. Guide bushes are fitted into the moving mould plate and the floating cavity plate respectively.
The maximum movement of the floating cavity plate is controlled by stop bolts or similar devices. The moving mould plate is suitably bored to provide a clearance for the stop bolt assembly. The stop bolts must be long enough to provide sufficient space between the feed plate and the floating cavity plate easy removal of the feed system. The minimum space provided for should be 65mm just sufficient for an operator to remove the feed system by hand if necessary.
The desired operating sequence is for the first daylight to occur between the floating cavity plate and the feed plate. This ensures the sprue is pulled from the sprue bush immediately the mould is opened. To achieve this sequence, springs may be incorporated between the feed p1ate and the floating cavity plate. The springs should be strong enough to give an initial impetus to the floating cavity plate to ensure it moves away with moving half. It is normal practice to mount the springs on the guide pillars (Figure 3-2) and accommodate them in suitable pockets in the floating cavity plate.

The major part of the feed system (runners and sprue) is accommodated in the feed plate and to facilitate automatic operation the runner should be of a trapezoidal form so that once it is pulled from the feed plate is can easily be extracted. Note that if a round runner is used, half the runner ìs formed in the floating cavity plate, where it would remain, and be prevented from falling or being wiped clear when the mould is opened.
Now that we have considered the mould assembly in some detail, we look at the cycle of operation for this type of mould.
The impressions are filled via the feed system (Figure 3-1 (a)) and, after a suitable dwell period, the machine platens commence to open. A force is immediately exerted by the compression springs, which cause the floating cavity plate to move away with the moving half as previous discussed. The sprue is pulled from the sprue bush by the sprue puller. After the floating cavity plate has moved a predetermined distance it is arrested by the stop bolts. The moving half continues to move back and the moldings having shrunk on to the cores, are withdrawn from the cavities. The pin gate breaks at its junction with the runner (Figure 3-1 (b)).
The sprue puller, being attached to the moving half, is pulled through the floating cavity plate and thereby releases the feed system which is then free to fall between the floating cavity plate and the feed plate. The moving half continues to move back until the ejector system is operated and the moldings are ejected (Figure 3-1 (c)). When the mould is close the respective plates are returned to their molding position and the cycle is repeated.
The previous chapter dealt with the two-part mould in which a molding is formed by injecting a plastics melt, under pressure, into an impression via a feed system. The two parts by themselves, however, do not constitute an efficient design as no means are incorporated for removing the molding once it is made. It must therefore be removed manfully.
Furthermore, all thermoplastics materials contracts as they solidify, which means that the molding will shrink on to the core which forms it. This shrinkage makes the molding difficult to remove.
It is normal practice, therefore to provide some means by which the molded part can be positively ejected from the core, and this chapter deals with the various methods which are used.
Facilities are provided on the injection machine for automatic actuation of an ejector system, and this is situated behind the moving platen. Because of this, the mould’s ejector system will be most effectively operated if placed in the moving half of the mould, i.e the half attached to the moving platen. We have stated previously that we need to eject the molding from the core and it therefore follows that the core too, will most satisfactorily be located in the moving half.
The ejector system in a mould will be discuss under three headings, namely: (i)the ejector grid; (ii) the ejector plate assembly; and (iii) the method of ejection.
Ejector grid
The ejector grid is that part of the mould which support the mould plat and provides a space into which the ejector plate assembly can be fitted and operated. The grid norma1ly consists of a back plate (clamp plate ) on to which is mounted a number of conveniently shaped ‘support blocks’.
There are three alternative designs:
(i) The in-line ejector grid;
(ii) The frame-type ejector grid;
(iii)The circular support block grid.
Ejector plate assembly
The ejector plate assembly is that part of the mould to which the ejector element is attached. The assembly is contained in a pocket, formed by the ejector grid, directly behind the mould plate. The assembly consists of an ejector plate a retaining plate and ejector rod. One end of this, latter member is threaded and it is screwed into the ejector plate (see cross-section view). In this particular design the ejector the functions not only as an actuating member but also as an ejector rod passes through an ejector rod bush fitted in the back plate of the mould.
Before proceeding to discuss the undivided parts in more detail, let us consider how this assembly is actuated. The mould is mounted on the moving platen of the injection machine. To the left of the moving platen is the machine's actuating rod. This member can be adjusted to allow for various alternative ‘ejector strokes’. When the moving platen is caused to move to the left, and the mould opens, the mould's ejector rod at some point of the stroke strikes actuating rod. The entire ejector plate assembly is arrested as shown at (b). The remainder of the moving half (i.e the mould plate and the ejector grid) continue to move to the left until the opening stroke is complete (c). This relative movement between the ejector plate assembly and the mould plate is necessary to operate the ejector element.
Ejection techniques
When a molding cools, it contracts by an amount depending on the material being processed. For a molding which has no internal form, for example a solid rectangular block, the molding will shrink away from the cavity walls a shown , thereby permitting a simple ejection technique to be adopted.
However , when the molding has intema1 form, the molding, as it cools , will shrink onto the core and some positive type of ejection is necessary.
The designer has several ejection techniques from which to chose, but in general, the choice will be restricted depending upon the shape of the molding. The basic ejection techniques are as follows :(i) pin ejection; (ii)sleeve ejection;(iii) bar ejection; (iv)blade ejection; (v)air ejection; and (vi)stripper plate ejection.
Ejection from fixed half
While it is generally desirable to situate the ejector system in the moving half of the mould this is not always practicable. Consider the case of a box-type comment which must, for reasons of appearance, be gated from the inside. In this case the core and the ejector system are mounted on the fixed mould half. Now this presents certain complications.
First, to incorporate an ejector grid and ejector assembly behind the fixed mould plate causes this mould half to be excessively deep. Because of this the melt has to travel a long distance from machine's nozzle. This distance can be minimized, however, by sinking the sprue bush deep into the mould plate assembly as illustrated, though this necessitates using an apical extension nozzle.
Second facilities are not normally provided on the machine for actuating any type of ejector system from the fixed mould half side. This means that the actuating mechanism must be incorporated in the mould design.
While any of the ejection techniques discussed in section 3.4 can be incorporated in the fixed half, certain of these techniques are more easily incorporated than others.
Sprue pullers
When the mould opens it is essential that the sprue is pulled positively from the sprue bush. With single-impression moulds the sprue feeds directly into the base of the component and the sprue is pulled at the same time as the molding is pulled from the cavity.
For multi-impression moulds using a basic feed system the sprue would probably be left in the sprue bush each time the mould was opened. This would necessitate a manual operation to remove the unwanted sprue. To avoid this undesirable feature, an arrangement for pulling the sprue should always be incorporated in the design.
The common sprue pulling methods utilize undercut pin or an undercut recess situated direct1y opposite the sprue entry. The plastics material which flows into the undercut, upon solidifying , provides sufficient adhesion to pull the sprue as the mould is opened.
There are two basic designs of sprue puller in one the undercut is produced within the cold slug well region, and is situated below the parting surface the second design, the undercut portion of the sprue pul1ing device is situated above the parting surface. To differentiate between these two basic types, we designate them type A and type B respectively.
Integer cavity and core plates
When the cavity or core is machined from a large plate or block of steel, or is cast in one piece, and used without bolstering as one of the mould plates, it is termed an integer cavity plate or integer core plate. This design is preferred for single-impression moulds because of the strength, smaller size and lower cost characteristics. It is not used as much for multi-impression moulds as there are other factors such as alignment which must be taken into consideration.
Of the many manufacturing process available for preparing moulds only two are normally used in this case. These are (a) a direct machining operation on a rough steel forging or blank using the conventional machine tools, or (b) the 'precision' investment casting technique in which a master pattern is made of the cavity and core. The pattern is then used to prepare a casting of the cavity or core by a special process. A 4.25% nickel-chrome-molybdenum steel (BS970-835M30) is normally specified for integer mould plates which are to be made by the direct machining method. The precision inve