{"id":17394,"date":"2021-07-21T15:29:22","date_gmt":"2021-07-21T13:29:22","guid":{"rendered":"http:\/\/s522541291.online.de\/?p=17394"},"modified":"2024-10-25T15:01:14","modified_gmt":"2024-10-25T13:01:14","slug":"europlast-in-plastverarbeiter-ausgabe-10-98","status":"publish","type":"post","link":"https:\/\/ep-kunststofftechnik.de\/en\/europlast-in-plastverarbeiter-ausgabe-10-98\/","title":{"rendered":"EUROplast in plastic proces\u00adsors edition 09\/01"},"content":{"rendered":"

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Tips for practitioners
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Print version in Acrobat Reader format<\/strong><\/u><\/a>

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The material matrix is intended to help developers who are not native to the plastics industry narrow down the right material. The matrix is deliberately kept simple, but is intended to help avoid major wrong decisions.<\/h5>\n\n\n\n

Practice has shown that new develo\u00adp\u00adments often take wrong paths when it comes to material selec\u00adtion, which are diffi\u00adcult to correct later. If a new product is created, the materials must be largely narrowed down at an early stage of construc\u00adtion, on which, for example, strength calcu\u00adla\u00adtions or shrin\u00adkage are based. Some proper\u00adties are provided with averaged real values, others only with school grades in order to be able to compare (1: high value \/ 6: lowest value)<\/p>\n\n\n\n

If the raw material price is considered too late because the material was selected based on purely technical aspects, this can endanger an entire project or at least delay it enorm\u00adously. However, prices are subject to a wide range of fluctua\u00adtions, especi\u00adally for standard plastics. Shown here is a snapshot of medium quality, with purchase quanti\u00adties of around 1000 kg (as of September 2001).<\/p>\n\n\n\n

In addition to calcu\u00adla\u00adting its own weight, the density of the material is also included in the calcu\u00adla\u00adtion, since the volume of a plastic part is prede\u00adter\u00admined and the weight is only calcu\u00adlated using the specific weight. Here, looking at the volume price is an interes\u00adting state\u00adment.<\/p>\n\n\n\n

Strength here means the tensile strength, knowing the fact that plastic compon\u00adents are prima\u00adrily calcu\u00adlated accor\u00adding to the maximum elonga\u00adtion. This means that you define the environ\u00admental influences and then look in the tables for the strengths that you can expect the compo\u00adnent to have in order not to exceed the maximum limit elonga\u00adtion.<\/p>\n\n\n\n

The level of stress to which a compo\u00adnent is exposed is crucial for its tempe\u00adra\u00adture resis\u00adtance. It is also important how long a compo\u00adnent is exposed to high tempe\u00adra\u00adtures. The values given here are average values of the usage tempe\u00adra\u00adture over a medium exposure time and serve as a guide only.<\/p>\n\n\n\n

It is important for the designer to know how far the material flows in the mold. Average flow lengths with 2 mm compo\u00adnent thick\u00adnesses are mentioned here. It is important to know that the flow paths increase dispro\u00adpor\u00adtio\u00adna\u00adtely with thicker walls. Further\u00admore, in every material group there are also types with better and worse flow proper\u00adties. And lastly, it must be mentioned that hot runner techno\u00adlogy with multiple connec\u00adtions makes it possible to produce parts with a high wall thick\u00adness-flow path ratio.<\/p>\n\n\n\n

For proces\u00adsing shrin\u00adkage during injec\u00adtion molding, only average values are given for a wall thick\u00adness of 2 \u2014 3 mm and optimal part proces\u00adsing, which are based on years of experi\u00adence. Due to tool tempe\u00adra\u00adtures that deviate from the manufacturer\u2019s speci\u00adfi\u00adca\u00adtions, as well as inade\u00adquate tempe\u00adra\u00adture control channels in the tool and extreme cycle times, the real shrin\u00adkage values can deviate signi\u00adfi\u00adcantly from the values stated here. For this reason, the infor\u00adma\u00adtion provided by raw material manufac\u00adtu\u00adrers often covers a wide range.<\/p>\n\n\n\n

The draft angles are important for removing the compon\u00adents from the mold without drawing marks. Due to the diffe\u00adrent shrin\u00adkage of the materials, the required demoul\u00adding angles also vary. Further\u00admore, thin walls require larger demol\u00adding trays than thicker walls. VDI level 30 corre\u00adsponds to a medium struc\u00adture with a roughing depth of 3.5 \u03bcm, although the tool should be designed with VDI level 33 due to the somewhat reduced image.<\/p>\n\n\n\n

The average cavity pressure is, on the one hand, a calcu\u00adla\u00adtion variable for the design of the injec\u00adtion molding machine, where strong fluctua\u00adtions can occur depen\u00adding on the geometry of the compo\u00adnent, and on the other hand, the demol\u00adding forces also increase as the cavity pressure increases. The number and design of the ejectors must be adapted to these forces.<\/p>\n\n\n\n

Impact strength is an important aspect for the suita\u00adbi\u00adlity of plastic compon\u00adents for everyday use. In addition, the struc\u00adtural design contri\u00adbutes signi\u00adfi\u00adcantly to the durabi\u00adlity of a compo\u00adnent after impact stress. The influence of water absorp\u00adtion in polyamide and the general possi\u00adbi\u00adlity of impact modifi\u00adca\u00adtion with, for example, elastomer modifiers should be mentioned here.<\/p>\n\n\n\n

The chemical resis\u00adtance of a plastic is a very complex topic because, in addition to the large number of chemical substances, their concen\u00adtra\u00adtion and the ambient tempe\u00adra\u00adture also play a major role. In addition, most common chemi\u00adcals are mixtures of a variety of indivi\u00addual substances. This means that when asses\u00adsing chemical resis\u00adtance you have to go through long lists of substances and the substances with which the compo\u00adnent later comes into contact are often not tested or these substances are diffi\u00adcult to deter\u00admine. In general and very simply, one can say: Amorphous plastics (mostly trans\u00adpa\u00adrent plastics, if not colored) have poor chemical resis\u00adtance. Parti\u00adally crystal\u00adline plastics (mostly opaque plastics, if not colored) have good chemical resis\u00adtance.<\/p>\n\n\n\n

Apart from special proces\u00adsing processes (with very fast cooling speeds), all amorphous plastics are more or less trans\u00adpa\u00adrent and all semi-crystal\u00adline plastics are opaque and trans\u00adlu\u00adcent if the wall thick\u00adness is small. An excep\u00adtion here, however, is ABS, which is opaque although amorphous because it has been copoly\u00adme\u00adrized from diffe\u00adrent raw materials, which influences the refrac\u00adtion of light. Basically, it should be noted that the dimen\u00adsional requi\u00adre\u00adments are often too high for plastic parts. However, it is often possible to cope with larger tolerances through a plastic-friendly design.<\/p>\n\n\n\n

Property matrix of the most common thermoplastics<\/h5>\n\n\n\n
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Our specia\u00adlist article on optimal material selec\u00adtion, inclu\u00adding a practical material matrix, was published in the specia\u00adlist magazine Plast\u00adver\u00adar\u00adbeiter (issue 09\/01).<\/p>","protected":false},"author":1,"featured_media":17391,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"brizy-blank-template.php","format":"standard","meta":{"wp_typography_post_enhancements_disabled":false,"footnotes":""},"categories":[10,8],"tags":[15,17,16],"class_list":["post-17394","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aktuelles","category-presse","tag-events-2","tag-innovation-2","tag-technologie-2"],"brizy_media":[],"_links":{"self":[{"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/posts\/17394","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/comments?post=17394"}],"version-history":[{"count":15,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/posts\/17394\/revisions"}],"predecessor-version":[{"id":24451,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/posts\/17394\/revisions\/24451"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/media\/17391"}],"wp:attachment":[{"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/media?parent=17394"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/categories?post=17394"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ep-kunststofftechnik.de\/en\/wp-json\/wp\/v2\/tags?post=17394"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}