New-style thermoplastic powder is used at alternative laser agglomeration
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source:AVELLINO CNC Machining
Resemble alternative laser agglomeration (Selective Laser Sinterin, SLS) such compensatory sex machines a method, allow to pass CAD data directly statified build three-dimensional part. With the tradition shape for instance Injection Molding photograph compares the method, this kind of method that dismisses a tool offerred infinite geometrical freedom to spend almost. Thanksed to new technology develops, this technology already surmounted the applied domain of established archetypal technique, the function that it can apply to one fraction now make. Adopt this kind of method, new product can be come out by independent production with inferior economic risk, this reduced a product to turn the time to the market greatly. Although a lot of different compensatory sexes machine a method, but they cannot be achieved a breakthrough with the block up of a few elements related material in manufacturing application however. Want special requirement to be added on component and its function only, machine a method often must " compromise " . However, give the archetypal product with mechanical good stress for production, alternative laser agglomeration is can satisfactory. To gain the most auspicious point from inside this kind of processing technique, be necessary to enlarge the limits of usable material. The latent capacity of this technology exceeds pure archetypal production technology greatly. A precondition of alternative laser agglomeration is, material must can obtain with the form of subtle powder. Up to now, half crystallization PA12 basically is used at the production of the part with mechanical large stress. Although resemble polystyrene (PS) , polycarbonate (PC) etc thermoplastic material can be obtained with pulverous form, but the result is production gotten product is the poriferous part that has very poor mechanical performance. These material are used at nicety to cast production of medium the core that break a pattern normally. In addition, thermoplastic elastomer applies inside narrow range. The polymer technology institute that is in German Erlangen-Nuremberg university (Lehrstuhl F R Kunststofftechnik, LKT) in the research job that has, a variety of limitation that the focus concerns at removing these and material centrally. Because machined a process to put forward to material a series of requirement, because this material is characteristic,had conclusive effect to the successful treatment of new material. In plastic treatment process, normally the function of these material must agree with well and truly the requirement of alternative laser agglomeration. The modification ability that this asks to be able to pass factory and manufacturing process to undertake is aimed at material only is contented. The character of the part of requirement laser agglomeration that limits to plastic powder and quantity of heat, be like degree of structure of density, surface, detail, and outline precision, affirmatory through machining the interaction between parameter and material. Consider to make clear, the geometrical configuration of pulverous grain affected the exterior surface roughness of the component. Similar, pulverous melt behavior and sex of come down in torrents, and its application decided component density. The dimension of PA12 pulverous grain distributings to be affected to the porosity of agglomeration component with geometrical configuration very big, because land of this very old rate gets,pulverous layer piles up the influence of density. Result, of the intensity that jumps over tall pulverous layer to pile density to cause agglomeration part, density and dimension precision rise. The laser agglomeration powder that city makes work distributings by 60m left and right sides, dimension even globose particle is comprised (graph 1) . Those who use is plastic must be opposite pyrolysis is particularly stable, because they must be below adjacent and crystal temperature,hold a few hours. In final phase of production, not melt but the powder of already hot ageing and part are detached. Good case is, after the final phase that establishs a procedure in compose piling collect, powder won't agglomerate, such, in final detached phase, powder can pass gravitational method to part very simply with the component. Besides the application of material, the character of finished product component still suffers compose to build the influence of accurate control place of process temperature. Mix to half crystallization amorphous thermoplastic plastic temperature is different. Amorphous plastic in the bate inside wider temperature range, and the melting point range with half plastic crystallization is narrow much, and, the range that its viscosity curve drops after exceeding crystallization melt temperature is bigger. Here, critical factor is melt particle formed agglomeration layer, this is why melt viscosity should as far as possible low. Good form establishs a procedure is the paradigmatic status that achieves agglomeration of accurate isothermal laser. So laser is offerred only surmount change the additional energy of a need. Accordingly, the temperature of the layer increases all round should as far as possible low. In control of standard isothermal procedure, fuse-element and powder can appear concomitant, also can say so, compose builds a process to appear in the condition with a concomitant two-phase. This discovery is derivative another precondition related to material: Plastic recrystallization temperature should greatly under crystallization melt temperature. Quantity of the scanning that show difference heats up a law (DSC) make the difference between two temperature is expressed (graph 2) . This is the one big characteristic of window of laser agglomeration treatment: If temperature exceeds the temperature limitation of upper part, fuse pulverously will not control; If temperature is restricted under lower part, so before generated polymer fuse-element begins crystallization, and the component can narrow (be out of shape as a result of internal stress, "Warp " ) . After building a process to finish when compose only, powder and component ability cool gradually with temperature gradient of lowest, the result gets the part of low stress and better measure precision. Compose builds the warp in the process to be able to bring about pulverous layer irregular, this establishs harm compose the procedure. The appearance that Nextpage laser causes changes carbon dioxide laser basically is used at processing, because a lot of plastic very tall absorption was shown to spend inside its wavelengh limits. According to lambert - Bill is mensurable and mensurable, the absorptivity inside infra-red limits can pass disappear smooth law to decide directly. Gotten result is relative value, they suffer the geometrical configuration of temperature, grain and the effect that check a method greatly. The basis is measured, each complete frit receives requires energy to be able to be calculated to come out. The research that different to 3 kinds material has shows, they are absorbing characteristic respect to show very different behaviour (graph 3) . Polyformaldehyde absorbs maximum laser amount, and polyethylene drew one fraction energy only. Such, can get a lot of craft parameter that are aimed at material. The PA2200 of laser agglomeration powder that between these two kinds of systems fixed position gets city makes work (manufacturer: German EOS GmbH) , it is had absorb mediumly degree. Accordingly, geometry, stream change to establish a procedure with compose with the interaction between thermodynamic influence relevant. Besides treatment window and absorptivity, basic process model also must include to study affirmatory parameter through the system. The laser agglomeration of polyformaldehyde powder is not all and plastic can obtain globose particle through direct polymerization. Accordingly, through cooperating with Neue Materialien Frth GmbH, evaluated the different method that achieves granular powder end. Be controlled about the process and but repeatability, broken law photograph compares microtherm at other optional method, be like melt whitewashing, showed very large dominant position, although manufacturing particle is not bulbiform (graph 1) . The first research crystallizes partly through different grain account thermoplastic plastic undertake, these material come from company of German BASF, Evonik, Essen, Basell Polyolefine, and Ems-Chemie company of Switzerland. The purpose of this research is to obtain a diameter under the 100m, grain that has high yield. A disadvantage of broken law is mechanical catenary suffer concussion to smash and produce remarkable polymer degradation. This also can happen below microtherm. To a lot of application domains, polyformaldehyde is a kind of interesting stuff, because it behaved very good physical characteristic, do not have a harm to human body physiology, and have be able to bear or endure very well chemical sex. Before having a test to pretreatment polyformaldehyde powder, the related to treatment process character that afore-mentioned mentioning has been decided and check. Measure according to DSC and infra-red law, can estimate density of the treatment temperature that laser agglomeration place requires and energy. Agglomeration shapes lever of a kind of drawing, with serve as pair of physical characteristic to use drawing to check (DIN EN ISO 527) , and the sample of the microcosmic evaluation of the felt to the layer and configuration. Compare with photograph of Injection Molding component, the component that machines methodological production through a kind of compensatory sex behaved inferior intensity and taller brittleness normally. In producing the reason of this kind of circumstance to depend on often controlling agglomeration process, what this caused a part is porous. In agglomeration process, period of time holds in crystallization temperature upper part as a result of fuse-element temperature, subsequently slow refrigeration comes room temperature, accordingly, can reach tall crystallization level (CPOM is the biggest ~ 85% ) the high strenth with the product, borrow this, rupture percentage elongation is reduced (graph 4) . Inside a longer time, the motion of molecular catenary is ensured, can develop tall crystal structure so. In the microscope image of section of lever of the drawing in polarized light, POM showed fewerer than PA 2200 administrative levels and more apparent and orderly ball are graininess exceed crystal lattice (graph 5) . The crystallization structure with a certain number of successive layers decided accurate isothermal condition is temporary existence at least. Can go up in what POM drawing lever detects attrib border area sees horizontal brilliant area, this arises in attrib border place normally. Of the component go up the surface is border of such a photograph, the cooling phase after because pulverous layer is built in compose,be being finished still is increasing. If the process is not stable, so different horizontal brilliant face also meets origin arise in component interior. A of agglomeration of POM component laser outstanding characteristic is, they are even and the outside area with same quality. Before this, so high surface quality is not typical to laser agglomeration, constant what process of depressive laser agglomeration gets normally is the rough surface that contains break. In alternative laser agglomeration use POM makes clear, it is likely that economic ground produces plastic powder from the grain that has second birth property. Because material is had,be able to bear or endure very well chemical sex, dimension precision is tall, bibulous rate is low, and the mechanical function of the laser agglomeration part that gets from this, these treatment processes will expand greatly broader product range. The potential application domain of this kind of new laser agglomeration has a car to make, family expenses product and medical treatment technology. Current research job basically is centered in the geometrical configuration that optimizes particle, and form part with what enhance material modified powder through globose filling. Pass modified, enhanced sex of pulverous come down in torrents and density, also enhanced component function sex. CNC Milling