【正文】 于省錢途徑之一。 100%的生產(chǎn)率的提高意味著要做的模具就更少因此在生產(chǎn)程序中節(jié)省更多的錢。 這里是一些薄壁的工具設(shè)計上的技巧： 1. 對于主要薄壁工作的應(yīng)用，一般用硬度大于鋼 p20的材料，尤其是要求有大的磨損和腐蝕 的時候。 H13和 D2鋼就是最常用的兩棲種材料著之一。 2. 模具的鎖定有時是彎曲的不對齊。 3. 型腔孔的型心能有助于減少型心在轉(zhuǎn)換時的破損。 4. 在型腔和主流道下面用更重的支持板（通常是 2~3英寸厚）和較重的導(dǎo)柱（一般是增加 ） 5. 比傳統(tǒng)的模具使用更大更多的推桿，以減少推桿的壓力 6. 考慮滑塊和導(dǎo)套的放置。 注射模具避免在復(fù)合材料上的缺陷 兩鐘或更多材料的注射模需要一個兩個澆口澆鑄方式或同時技術(shù)。不管使用程序如何，造模者在達(dá)到高質(zhì)量塑件方面面對相同的挑戰(zhàn)。任何多種材料成型過程的三個共同的問題是不足的聚合體的 化學(xué)和機(jī)械結(jié)合，一個或更多成分的不完全填補(bǔ)，和一個更多的成分的“ flash”。 這些情況能發(fā)生是否材料組合加強(qiáng)的和沒被加強(qiáng)的，實(shí)心的和起泡的，剛硬的和軟的，原料和再研磨，有色素和無色素，等等。 多種材料模和它的問題及問題的解決是復(fù)雜的題目，不能在簡短的文章里徹底探討清楚，接下來說明相關(guān)變量的范圍，以及對一些比較重要 30 的問題作簡單的介紹。 時間和溫度 引起材料之間結(jié)合不足的原因與材料注射時間和第二材料熔合時第一材料的溫度有關(guān)。第一材料的過分冷卻往往使熔合變?nèi)?。另外，第一次注射必須足夠冷卻才能不使第二 次注射時不引起變形和錯位。如果第一次材料仍然很軟，而第二次注射來得太快，答二材料將在第一材料是形成縮孔和飛邊。引起“流涎”現(xiàn)象。 在兩個注射機(jī)上的流動材料（在一個注射機(jī)上第一次注射，接著把它插入到另一個注射機(jī)上）不易產(chǎn)生和旋轉(zhuǎn)桌面的兩個澆口的注射機(jī)上的流動材料一樣好的結(jié)合。甚至當(dāng)用相容材料時兩次注射之間延長的時間相對要長，并且地一槍可能會太冷。一般認(rèn)為一個比較高塑件溫度有更好的化學(xué) /機(jī)械結(jié)合。如果當(dāng)?shù)谝淮巫⑸滢D(zhuǎn)移到第二個模具上時吸附了一些灰塵，那么將會對結(jié)合有很大的影響。一些材料往往很自然比其它材料粘 貼的更好。為了 overmolding ,樹脂供應(yīng)者 — 特別是 TPES的制造者 —通過提高對其它聚合物的粘附范圍努力地將某一等級最佳化。 添加劑和色素也會影響結(jié)合。在第一材料里面的玻璃纖維能提高與第二材料的結(jié)合質(zhì)量。這些材料表面上的纖維能促進(jìn)與第二注射材料的機(jī)械結(jié)合。 注意包含有像滑石或碳酸鈣一樣的填充物的材料應(yīng)被足夠烘干，因?yàn)檫@些填充物含有很多能是結(jié)合減弱的濕氣。 質(zhì)量影響元素 為了防止任一材料的沒填充和裝得太多（和飛邊），機(jī)器的從注射到 31 注射的準(zhǔn)確性明顯的是一個關(guān)鍵的因素。一般建議注射量少于 %到%。有注射速度閉環(huán)控制的注射機(jī)是最好的選擇。 第二是選擇一個有多種材料塑件成型經(jīng)驗(yàn)的模具制造者。如果開始就有很好的模具設(shè)計，這樣能省掉很多花費(fèi)。例如，它有助于增加那些有通過用 undercuts或相似設(shè)計獲得 的機(jī)械結(jié)合的材料之間的熱化結(jié)合。 確保多孔模具平衡好，熱流動的 maniflod也必須平衡好，而且下降的數(shù)字和大小一定對低壓的填充物是充分的。 模具的溫度是另一個重要因素。當(dāng)有核心 lifter的移動模具的第二次注射時，溫度準(zhǔn)確控制是強(qiáng)制的。因?yàn)殇摶蜾摵辖鹩胁煌? 的熱膨脹，所以不正確的 溫度會引起 lifter的契入和堵塞。 為了獲得好的多種材料塑件成型，操作者必須有很好的訓(xùn)練。 當(dāng)塑件制造結(jié)果不好時，錯誤的制造環(huán)境經(jīng)常是罪魁禍?zhǔn)?。因?yàn)樗? 復(fù)雜性，所以如果當(dāng)事情出錯時，也只有懂得程序的人才被允許去糾正。 獲得材料間好的結(jié)合也經(jīng)常取決于當(dāng)?shù)诙牧献⑸鋾r第一材料的溫度 Secret of successful thinwall molding Demands to create smaller, lighter parts have made thinwall molding one of the most sought after capabilities for an injection molder. These days ,”thin wall” is generally defined by portable electronics parts 32 having a wall thickness less than 1mm . for large automotive parts , “thin” may mean 2 mm . In any case, thinner wall sections bring changes in processing requirements: higher pressure and speeds, faster cooling times, and modification to partejection and gating arrangements .These process changes have in turn prompted new considerations in mold ,machinery ,and part design Machinery considerations Standard molding machinery can be used for many thinwall applications. Capabilities built into newer standard machines go well beyond those of 10 years ago. Advances in materials, gating technology and design further expand the capabilities of a standard machine to fill thinner parts . But as wall thicknesses continue to shrink, a more specialized press with higher speed and pressure capabilities may be required. For example, with a portable electronics part less than 1 mm thick, fill times of less than sec and injection pressures greater than 30,000psi are not unmon. Hydraulic machines designed for thinwall molding frequently have accumulators driving both injection and clamping cycles. Allelectric and hybrid electric/hydraulic models with high speed and pressure capabilities are starting to appear as well. To stand up to the high pressures involved, clamp force should be a minimum of 57tons/sq in. of projected area. In addition,extraheavy platens help to reduce flexure as wall thicknesses drop and injection pressures rise. Thinwall machines monly have a 2:1 or lower ratio of tiebar distance to platen thickness. Also, with thinner walls, closedloop control of 33 injection speed, transfer pressure,and other process variables can help to control filling and packing at high speeds and pressures. When it es to shot capacity, large barrels tend to be too large. We suggest you aim for a shot size of 40% to 70%of barrels capacity . The greatly reduces total cycle time seen in thinwall applications may make it possible to reduce the minimum shot size to 20%30% of barrel capacity, but only if the parts are thoroughly tested for property loss possible material degradation. Users must be careful, as small shot sizes can mean longer barrel residence times for the material ,resulting in property degradation . Molds: make ‘em rugged Speed is one of the key attributes of successful thinwall molding. Faster filling and higher are required to drive molten thermoplastic material into thinner cavities at a sufficient rate to prevent freeze off. If a standard part is filled in 2 sec, then a reduction in thickness of 25%potentially can require a drop in fill time of 50%to just 1 sec. One benefit of thinwall molding is that as wall sections drop, there is less material to cool. Cycle times can drop by 50%with aggressive wallthickness reduction. Careful management of the meltdelivery system can keep runners and sprues from diminishing that cycletime advantage. Hot runners and heated sprue bushings are often used in thinwall molding to help minimize cycle time. Mold material should be reviewed too. P20 steel is used extensively in conventional applications, but due to the higher pressures of thinwall molding, molds must be built more robustly. H13 and other tough steels add an extra degree of safety for thinwall tools.[If possible, 34 you will also want to select a molding material that