【正文】 in MultiMaterial MoldingInjection molding with two or more materials requires either a twoshot molding approach or a simultaneous coinjection technique. Regardless of the process used, molders face the same challenges in achieving high part quality. Three mon problems with any multimaterial process are insufficient chemical or mechanical bonding of the polymers, inplete filling of one or more ponents, and flashing of one or more ponents. These conditions can occur whether the materials binations is reinforced and unreinforced ,solid and foamed, rigid and soft, virgin and regrind, pigmented and unpigmented , etc.Multimaterial molding and its problems and solutions is a plex subject that cannot be explored thoroughly in a short article . The acpanying 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 es too soon, while the first material is still soft, the second material can press 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 twoshot machine with rotating table. Even when using patible 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 remended 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 suppliersparticularly 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 qualityTo prevent underfilling or overfilling (and flashing)of either material, the shotto shot accuracy of the machine is obviously a critical factor. Shot variability of less than %to %is remended. A machine with closedloop injectionspeed control is the best choice. Next, pick a mold maker with experience in multimaterial 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 multicavity molds are well balanced . Hotrunner manifolds must be balanced too, and the number and size of drops must be sufficient for lowpressure 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 bination.Operators must be well trained for successful multimaterial molding . Wrong machine settings are often the culprits when parts don’t turn out right . Because of its plexities ,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. 總結近三個月的畢業(yè)設計終于結束了，通過這段日子的設計學習，自己的專業(yè)知識和獨立思考問題的能力有了很大的提高，對我走向社會從事本專業(yè)工作有著深遠的影響?，F(xiàn)在就此談談對本次畢業(yè)設計過程中的認識和體會。首先，我學會了查閱資料和獨立思考。我的課題是鋼筋彎曲機的設計。在設計過程中，真正體會到了實踐的重要性。我曾到建筑工地去參觀學習，了解現(xiàn)場環(huán)境和設備，真正從實際出發(fā)來考慮自己的設計。同時，廣泛深入圖書館，實事求是，認真查閱有關書籍資料，鍛煉了自己的分析問題、解決問題的能力。因是兩人合作項目，在設計時，也充分體會到了合作的重要性，培養(yǎng)了自己的團隊精神。不可否認，在這個過程中，也遇到不少困難，所幸的是得到了劉老師，招老師，陳老師的悉心指導，起到了點石成金的作用，大大啟發(fā)了我，使我能不斷前進。其次，認識到實踐的重要性。這次設計我做了很多重復工作、無用功，但是這些重復工作和無用功積累了設計經(jīng)驗。同時也認識到設計不能只在腦子里想其結構、原理，必須進行實際操作。另外，也應從多個角度來思考問題的所在，嘗試其它的方法，以求找到最佳方法，因為即使想的很完美，但到實際的設計時會遇到很多想不到的實際問題。在設計的過程中，也出現(xiàn)了一些客觀不足的問題，就是支架，減速器的箱蓋只能靠想象，不能根據(jù)實際的情況來作合適、客觀地修改，難免有些缺點和不足，由于諸多原因，本次設計存在一些不足和有待改善的地方，希望老師能夠看待。最后，衷心感謝劉老師，招老師，陳老師的細心指導和教導，使我在大學里的最后一段時間里，學到了更多的知識。衷 心 鳴 謝衷心感謝劉杰華老師，招惠玲老師，陳敏華老師對我的悉心指導參考文獻1. 吳宗澤主編。機械設計實用手冊。北京：化學工業(yè)出版社。2. 江耕華，陳啟松主編。機械傳動手冊。北京：煤炭工業(yè)出版社。3. 機械化科學研究院編。實用機械設計手冊。北京：中國農(nóng)業(yè)機械出版社。4. 西北工業(yè)大學機械原理及機械零件教研室編。機械設計。北京：高等教育出版社。5. 陳作模主編。機械原理。北京：高等教育出版社。6. 王光銓主編。機床電力拖動與控制。北京：機械工業(yè)出版社7. 馬曉湘，鐘均祥主編。畫法幾何及機械制圖。廣州：華南理工大學出版社。8. 廖念針主編。互換性與測量技術基礎。北京：中國計量出版社。9. 實用機械電氣技術手冊機械工業(yè)出版社 5 小 齒 輪圖 小 齒 輪鳴 謝（5 號，宋體，行距為固定值 20 磅）參考文獻（5 號，宋體，行距為固定值 20 磅） （參考文獻用“[” ， “]”括起，具體寫法參照學校有關畢業(yè)論文（設計）的撰寫