水桶注塑模模具設計【含CAD圖紙和說明書】
水桶注塑模模具設計【含CAD圖紙和說明書】,含CAD圖紙和說明書,水桶,注塑,模具設計,cad,圖紙,以及,說明書,仿單
附錄：外文翻譯
薄壁模具成功的秘密
要求生產一種小的輕的零件,就要我們尋找一個能夠注出薄壁工件的注塑模具.現(xiàn)在,”薄壁”在微電子方面通常定義為少于1m壁厚.在大的自動化方面,”薄”可能意味是2mm左右.無論怎么樣,越薄壁的地方,在生產過程中要求的變化就越多:更高的壓力和速度,更短的冷卻時間,和改注射的方法和工作排列的方式.這些過程的改變在模具,機構和零件設計中要引起一系列的思考
機械方面的思考:
標準的注塑機都能夠應用于大多數(shù)的薄壁注射.新標準的注塑機的容量遠超過了十幾年前的機器.先進的材料和技術,高超過的設計水平大大的增加了薄壁零件對標準注塑機的要求.
但是當薄壁不斷的收縮,要求有更大的高速帶來的特殊壓力.例如微電子零件的壁厚少于1m,填充時間要少于0.5秒和注射壓力大于30000psi是不罕見的.為薄壁注射而設計的水力機械通常儲蓄的能量既用于注射又用于夾緊循環(huán).純電的和水電混合的機械的出現(xiàn)往往能夠提供更高的速度和更大的壓力.
為了抵抗高壓,在注射范圍內,夾緊里應該是在5-7噸每平方英寸.另外,連接桿到壓盤有助于減少彎曲,當墻壁厚度減少,注射壓力上升.薄壁注射機的連接桿到壓盤厚度的距離通常是2:1,或者是更低的比率.而且,隨著壁厚的變薄,注射速度的閉環(huán)的控制,轉移壓力和其他的過程變量能在高速度和壓力擁包的情況下幫助控制充滿型腔.
當它開始注射容量時，大量的塑料裝入型腔太多了。我們建議注射40%~70%的型腔容量到模的型腔里面。在薄壁注射的應用中經常能見到的大大地減少的總循環(huán)周期時間可以使把最小注射量降低到型腔容量的20%~30%成為可能，但是 ，只有在徹底了解零件因材料變化而引起的其特性的變化的情況下才能實現(xiàn)。用戶必須小心，小的注射量可能引起材料性能的降低，因此，意味著更長的只社時間。
模子：本身的精度
速度是薄壁模能否做成功的關鍵的因素之一。更快的折射速度和更高的注射壓力把溶解的熱塑性的材料在一個足夠的速度下注入狹窄的型腔以避免其凝固。如果標準零件注射時間在2sec內，如果它的厚度減少25%那么充型時間就能減少50%，即1sec鐘就能充滿型腔。
薄壁模具的好處之一是當壁厚減少時，需要冷卻的材料也相應的減少。隨著主要壁厚的減少，循環(huán)周期能減少50%，熔化狀態(tài)下的系統(tǒng)的小心的管理能使分流道和主流道縮小循環(huán)周期的時間。熱的分流道和主流道通常用于薄壁零件的注塑以利于把周期時間減少到最小。
模具的材料也應該被檢查。P20鋼在傳統(tǒng)的應用中廣大被使用，但是，由于薄壁注射的壓力不斷的增大，模具也必須做得更堅固。H-13鋼和其它的堅韌的鋼為薄壁的工具提供了額外的安全保證。（另外，如果可能，你也可以選用模具的材料這 可以使在高速度注入型腔的時候，不會加快模具的磨損。）
不過，比標準的零件來說精密的模具可能要多花費30%~40%?？墒?，生產率成倍提高可以彌補這多花費的部分。實際上，薄壁的注塑的方法是經常用于省錢途徑之一。100%的生產率的提高意味著要做的模具就更少因此在生產程序中節(jié)省更多的錢。
這里是一些薄壁的工具設計上的技巧：
1. 對于主要薄壁工作的應用，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。H-13和D-2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）和較重的導柱（一般是增加0.005英寸）
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. 考慮滑塊和導套的放置。
注射模具避免在復合材料上的缺陷
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。不管使用程序如何，造模者在達到高質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和機械結合，一個或更多成分的不完全填補，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的和沒被加強的，實心的和起泡的，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，接下來說明相關變量的范圍，以及對一些比較重要的問題作簡單的介紹。
時間和溫度
引起材料之間結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。第一材料的過分冷卻往往使熔合變弱。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。
在兩個注射機上的流動材料（在一個注射機上第一次注射，接著把它插入到另一個注射機上）不易產生和旋轉桌面的兩個澆口的注射機上的流動材料一樣好的結合。甚至當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。一般認為一個比較高塑件溫度有更好的化學/機械結合。如果當?shù)谝淮巫⑸滢D移到第二個模具上時吸附了一些灰塵，那么將會對結合有很大的影響。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合。在第一材料里面的玻璃纖維能提高與第二材料的結合質量。這些材料表面上的纖維能促進與第二注射材料的機械結合。
注意包含有像滑石或碳酸鈣一樣的填充物的材料應被足夠烘干，因為這些填充物含有很多能是結合減弱的濕氣。
質量影響元素
為了防止任一材料的沒填充和裝得太多（和飛邊），機器的從注射到 注射的準確性明顯的是一個關鍵的因素。一般建議注射量少于0.3%到0.5%。有注射速度閉環(huán)控制的注射機是最好的選擇。
第二是選擇一個有多種材料塑件成型經驗的模具制造者。如果開始就有很好的模具設計，這樣能省掉很多花費。例如，它有助于增加那些有通過用undercuts或相似設計獲得 的機械結合的材料之間的熱化結合。
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。當有核心lifter的移動模具的第二次注射時，溫度準確控制是強制的。因為鋼或鋼合金有不同 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練。 當塑件制造結果不好時，錯誤的制造環(huán)境經常是罪魁禍首。因為它的 復雜性，所以如果當事情出錯時，也只有懂得程序的人才被允許去糾正。
獲得材料間好的結合也經常取決于當?shù)诙牧献⑸鋾r第一材料的溫度
Secret of successful thin-wall molding
Demands to create smaller, lighter parts have made thin-wall molding one of the most sought after capabilities for an injection molder. These days ,”thin-wall” is generally defined by portable electronics parts 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 part-ejection 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 thin-wall 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 0.5 sec and injection pressures greater than 30,000psi are not uncommon. Hydraulic machines designed for thin-wall molding frequently have accumulators driving both injection and clamping cycles. All-electric 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 5-7tons/sq in. of projected area. In addition,extra-heavy platens help to reduce flexure as wall thicknesses drop and injection pressures rise. Thin-wall machines commonly have a 2:1 or lower ratio of tiebar distance to platen thickness. Also, with thinner walls, closed-loop control of injection speed, transfer pressure,and other process variables can help to control filling and packing at high speeds and pressures.
When it comes 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 thin-wall 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 thin-wall 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 thin-wall molding is that as wall sections drop, there is less material to cool. Cycle times can drop by 50%with aggressive wall-thickness reduction. Careful management of the melt-delivery system can keep runners and sprues from diminishing that cycle-time advantage. Hot runners and heated sprue bushings are often used in thin-wall 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 thin-wall molding, molds must be built more robustly. H-13 and other tough steels add an extra degree of safety for thin-wall tools.[If possible, you will also want to select a molding material that doesn’t accelerate mold wear when injected into the cavity at high speeds.]
However, robust tools cost money-possibly even 30% to 40%more than a standard mold. Yet the cost is often offset by increased productivity. In fact, the thin-wall approach is frequently used to save money on tooling. A 100% increase in productivity can mean that fewer molds to be built, thereby saving money over the life of a program.
Here are some more tips on tool design for thin walls:
For aggressive thin-wall applications, use steel harder than P20,especially when high wear and erosion are expected. H-13 and D-2 steels have been successful in gate inserts.
Mold interlocks sometimes can stave off flexing and misalignment.
Cores that telescope into the cavity can help reduce core shifting and breakage.
Use heavier support plates[often 2 to 3 in thick]with support pillars [typically preloaded 0.005 in]under the cavities and sprue.
Use more and large ejector pins than with conventional molds to reduce pin pushing.
Consider strategic placement of sleeve and blade knockouts.
Injection Molding Troubleshooter Avoid Pitfalls in Multi-Material Molding
Injection molding with two or more materials requires either a two-shot molding approach or a simultaneous coinjection technique. Regardless of the process used, molders face the same challenges in achieving high part quality. Three common problems with any multi-material process are insufficient chemical or mechanical bonding of the polymers, incomplete filling of one or more components, and flashing of one or more components. These conditions can occur whether the materials combinations is reinforced and unreinforced ,solid and foamed, rigid and soft, virgin and regrind, pigmented and unpigmented , etc.
Multi-material molding and its problems and solutions is a complex subject that cannot be explored thoroughly in a short article . The accompanying table indicates the range of variables involved. A few of the more important factors bear a brief discussion.
Time and temperature
One cause of insufficient bonding between materials relates to the timing of the injection of the materials and temperature of the first material when it is joined with the second . Too much cooling of the first material tends to weaken bonding. On the other hand, the first shot must be cooled enough not to be deformed or displace when you shoot the second one. If the second shot comes too soon, while the first material is still soft, the second material can compress and flash over the first one ,causing ”splash marks”.
When running parts on two injection machines(molding the first shot on machine one and inserting it into the mold of the second machine ),bonding is not apt to be as good ad on a two-shot machine with rotating table. Even when using compatible materials, the delay time between the two shots is relatively long and the first shot is likely to be too cold . A higher part temperature is recommended for better chemical /mechanical bonding. Also, if the first shot picks up dust while being transferred to the second mold , bonding will also be negatively affected.
Apart from process conditions, material choice can greatly affect bonding . Some materials naturally tend to adhere better than others, and resin suppliers-particularly makers of TPES—have been working hard to optimize certain gradesfor overmolding by increasing their range of adhesion to other polymers.
Additives and pigments can affect bonding. Glass fibers in one materials can enhance bonding with the second . Fibers on the surface of the material promote a mechanical bond with the second shot . Note that materials containing fillers like talc or calcium carbonate should be dried adequately . These fillers hold a hot of moisture, which can detract from bonding.
Elements of quality
To prevent underfilling or overfilling (and flashing)of either material, the shot-to -shot accuracy of the machine is obviously a critical factor. Shot variability of less than 0.3%to 0.5%is recommended. A machine with closed-loop injection-speed control is the best choice.
Next, pick a mold maker with experience in multi-material parts. You can save a lot of money if you have the mold designed well from the start . For example, it can be helpful to supplement the thermal/chemical bonding between two materials with a mechanical joint achieved by using undercuts or similar designs.
Make sure multi-cavity molds are well balanced . Hot-runner manifolds must be balanced too, and the number and size of drops must be sufficient for low-pressure filling.
Mold temperature is another important factor. Accurate control of the temperature is mandatory when running molds with core lifters for the second shot . Incorrect mold temperature can cause a lifter to wedge or jam, because of differential thermal expansion of the steel or steel/brass combination.
Operators must be well trained for successful multi-material molding . Wrong machine settings are often the culprits when parts don’t turn out right . Because of its complexities ,only people who understand the process should be allowed to attempt corrections if something goes wrong . Achieving a good bond between materials is often dependent on the temperature of the first material when the second is injected.
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