【導(dǎo)讀】1前言．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．1. 2總體設(shè)計(jì)方案．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．3. 3具體設(shè)計(jì)說明．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．4. 型腔數(shù)的確定．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．6. 同時(shí)，由于近年來進(jìn)口模。模具行業(yè)是制造業(yè)的重要組成部分，具有廣闊的市場前景。注塑模具的結(jié)構(gòu)是由塑件。凡注塑模具，均可分為動(dòng)模和定模兩大部分。因此，塑料注射模的數(shù)量為其它各類塑料模具之首，約占整個(gè)塑料模具總產(chǎn)量。水桶制品的幾何尺寸進(jìn)行測量

　　

【正文】 doesn’t accelerate mold wear when injected into the cavity at high speeds.] However, robust tools cost moneypossibly even 30% to 40%more than a standard mold. Yet the cost is often offset by increased productivity. In fact, the thinwall 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 thinwall applications, use steel harder than P20,especially when high wear and erosion are expected. H13 and D2 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 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 MultiMaterial Molding Injection 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 35 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. 36 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 quality To 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 37 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.