微型成型 | 5分钟阅读

利用超声波技术成型微零件

特写:微成型

新机器利用超声波熔化塑料以进行微成型,这与标准工艺中使用的剪切加热和传导加热相反。

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Back in 2007, researchers at the 阿斯卡姆 技术 Centre in Barcelona, Spain, started investigating melting thermoplastics with ultrasonic 恩ergy. After proving out the process, the researchers considered possible commercial applications, according to Enric Sirera, who ultimately became sales director at 超音波, the commercial venture spun off in 2010 from 阿斯卡姆  使本发明商业化。

“研究人员看到了市场对小零件,微型零件(包括高纵横比的零件)的需求,” Sirera explains. 超音波 成立于2010年“设计,开发和工业化围绕此超声成型工艺的机器。”

超音波’s vision is to use ultrasonic waves to melt plastics prior to molding, as opposed to the shear and conductive heating used in the normal combination of heater bands and reciprocating screw for 注射 molding. By doing so, the researchers believed they could prepare only the required amount of material for each part versus bringing an 恩tire barrel of material up to temperature, with the subsequent residence time and potential for degradation.

In their first crack at an ultrasonic-centered machine, the researchers constructed a prototype press by taking a standard 注射 molding machine, removing the 恩tire 注射 unit, and substituting one of their design.

“It worked perfectly,” Sirera recalls. “这是伟大的一步。然而,到那时,我们意识到液压和夹紧力已超出了我们的需求。所以,我们说,‘Hey, let’s考虑根据此过程重新设计一台新机器。’”
With the first prototype machine completed in 2010, the company hit the show circuit to begin promoting the technology, including stops in Germany at Fakuma and Orlando, Fla., at NPE2012. Last year, 超音波 participated in the K 2013 show in Germany as commercial sales began in earnest.

如今,该领域共有12台机器,其中7台正在进行生产,其余的则在大学和R&D中心。这些机器遍及美国,英国,波兰,荷兰和西班牙,用于医疗,航空航天和精密机械应用。

关键区别
Sirera指出,超音波的一个关键差异化因素’s成型技术(将术语“injection”),是颗粒的超声波熔化如何降低材料’s viscosity. “这意味着在相同的熔化温度下,超声波加热的粘度会降低,从而导致在更低的压力下成型,内部应力更少的成型可能性,以及使材料流向以前更薄,更细小的几何形状的能力。未能被填补。”

Instead of a hopper-fed barrel and screw, 超音波 machines feature a dosing unit that dispenses only the amount of material to be melted for each cycle. Once inside the dosing chamber, the resin is heated via ultrasonic waves, vibrating the plastic and creating spaces within its molecular structure. “当您在分子周围创建更多空间时,” Sirera explains, “您可以降低粘度。随着自由体积的增加,粘度下降。”

In micro 注射 molding, Sirera notes that pressures can rise easily to 1200 bar and over. With ultrasonic melting, however, those pressures drop down to the 300 to 500 bar range.
The 超音波 machine is technically rated with a clamping force of 3 metric tons, but even that would be overkill, according to Sirera. In production, he says the 超音波 machine typically uses from 1.5 to 2.2 m.t. of clamping force. As an added bonus, the elimination of heater bands, as well as hydraulic pumps and motors normally used to keep the clamp shut under high pressure, means that 恩ergy consumption for the 超音波 is reduced by 85-90% compared with a standard 注射 machine.

没有停留时间
在标准的微成型设置中,零件可能利用0.1g的料量,而机器的料筒容量为100g,那么模塑商必须经过1000次的料量才能清除料筒。“这会导致大问题,” Sirera notes. In the 超音波 design, the dosing unit handles the material at room temperature, and only as needed.

“想象一个装有室温物料的料斗,” Sirera explains. “机器保持在室温下。一旦我们想要成型零件,我们就关闭模具,将材料粒料注入模具中,仅使用该注射的材料量,然后喇叭就掉下来,振动并熔化,只将所计量的材料量熔化那个镜头。”一旦熔化,柱塞便以低得多的压力将熔化的塑料推入工具腔中。

“There’根本没有停留时间,这意味着可以随时启动和停止机器,”Sirera说,并补充说,也没有清除操作。如果需要更换物料,则只需清空料斗并重新填充即可。

Sirera says parts still have a runner and sprue, which can become outsized in micromolding, but here he notes that 超音波 still saves 40-70% of the equivalent cold-runner volume compared with standard micro 注射 molding. For the material, eliminating the dual stresses of thermal degradation caused by long residence times and by 注射 under high pressure has had some interesting results.

超音波 has seen less change in the polymer’的分子量,有助于材料保持机械性能,而该过程还意味着聚合物链“refreeze nicely,”根据Sirera的说法,产生了更坚固,更均匀的熔体和零件。

Sirera notes that the technology is suitable for all types of thermoplastics, including high-temperature materials like PEEK, polysulfone, and liquid-crystal polymers (LCP). In filled materials, or ones with additives, 超音波 has also seen better dispersion and more homogeneity in the finished compounds and parts. Maximum overall shot size currently is around 1.5 to 2 g, but could go somewhat larger.

“如果您问我是否有一天我们会使用超声波成型制作保险杠面板,我不会’t think so,”Sirera说,在添加之前。“It’s too soon to tell.”

那不’t mean there aren’小部分机会多。“以前证明不可能的模具几何形状现在可以实现,” Sirera says. “当我们谈论制造设计时,现在您有了一种新的制造技术,可以让您尝试新的几何形状。我们不’虽然尚不知道极限,但我们预见了巨大的机会。 ” 

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