Selected problems of precision injection molding. Part II. Factors influencing the quality of precise moldings

Abstract

Streszczenie -W artykule o charakterze literaturowego przegl¹du monograficznego przedstawiono wtryskiwanie precyzyjne jako proces realizowany w uk³adzie roboczym obejmuj¹cym nastêpuj¹ce elementy: cz³owieka-wykonawcê, formê wtryskow¹, wtryskarkê, metodê wtryskiwania, warunki (parametry) wtryskiwania oraz rodzaj wtryskiwanego tworzywa. Szczegó³owo omówiono wp³yw ka¿dego z tych elementów na koñcow¹ jakooeae uzyskiwanych wyprasek i jej powtarzalnooeae, uwzglêd-niaj¹c przy tym strukturê materia³u, w³aoeciwooeci mechaniczne i inne cechy u¿ytkowe, masê, skurcz, stan naprê¿eñ oraz dok³adnooeae wymiarów. S³owa kluczowe: wtryskiwanie, wtryskarki precyzyjne, jakooeae wyprasek, wykonawca, forma wtryskowa, tworzywo przetwarzane, powtarzalnooeae wyników. SELECTED PROBLEMS OF PRECISION INJECTION MOLDING. PART II. FACTORS INFLUEN-CING THE QUALITY OF PRECISE MOLDINGSSummary -In the literature review the precise injection molding is presented (Fig. 6) as a process realized in a working system consisting of the following elements: man-operator, injection mold ( Fig. 1-3), injection molding machine, injection method, injection parameters (Table 1) and the type of polymer. The effects of all the factors on the final quality of moldings obtained and its repeatability were discussed in detail. The material structure, mechanical properties and other functional features, weight, shrinkage ( Fig. 4 and 5), stress state and accuracy of dimensions of molding were taken into account.

Polymers in gearbox production

“…In recent years, a dynamic development of polymeric materials that are used in the manufacture of machine elements, including toothed drive system components, has been observed. The components are manufactured on a large scale from engineering composite materials based on a PA, POM, PC or acrylonitrile-butadienestyrene (ABS) matrix using injection molding [15,16] or material removal (cutting, electrical discharge machining (EDM) on computerized numeral control (CNC) machines (gear hobbing, milling with an end mill or formed cutter, CNC milling by cutting out the tooth shape) [17][18][19]. Thanks to the injection molding technology, it is possi-ble to obtain up to several hundred pieces in one injection cycle, depending on the number of mold cavities (the higher the number, the more profitable the production).…”

“…Polyoxymethylene (POM) is one of the most popular polyacetals used in the production of machine elements (e.g. gears) [15]. As is commonly known, it is a thermoplastic polymer with a high degree of crystallinity (about 80%).…”

On-line temperature recording in a multi cooling channel injection molding tool

“…It has very big impact on many different properties of injection molded parts, e.g. : stiffness, impact strength, residual stresses, and deformation [1][2][3][4][5]. There are lots of methods to control the mold temperature but it is neither simple nor easy to measure it precisely.…”

The influence of injection time and holding time on the residual stress state in injection moulded parts

“…Scheme of venting channels in four-cavity mould for the production of optical elements from PMMA: 1 -ring channel for degassing the cavities. 2 -runner venting channel (according to [7]) sek precyzyjnych zalicza siê elementy optyczne, którym stawiane s¹ wysokie wymagania odnooenie dok³adnooeci kszta³tu i wymiaru, co mo¿liwe jest do uzyskania dziêki zastosowaniu ma³ych wartooeci cioenienia wtryskiwania [23], lecz nie wp³ywa korzystnie na w³aoeciwooeci optyczne wyrobu. Cioenienie tworzywa w gnieŸdzie w fazie docisku jest czynnikiem decyduj¹cym o wielkooeci skurczu wypraski.…”