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Study of the impact of injection molding conditions on the properties and the accuracy of the microelements made of metal and ceramic powders

Andrzej Skalski

Abstract

The thesis concerns the technology of products manufactured from metal and ceramic powders by means of micro forming injection moulding method (µPIM). PIM technology is well known and well recognized in macro scale. However, in micro scale it is still in research phase. Results obtained so far show that this technology can successfully compete with other, popular methods of manufacturing microelements (such elements that their sizes or their structural details are expressed in tens or hundreds of micrometres). The thesis is written from the technological perspective and all aspects are considered with such approach. All phases of research correspond with product manufacturing stages. At the very beginning materials (powders and binders) are characterised. In case of binders the most appropriate composition was selected in the aspect of the injection moulding and debinderisation. In research iron, stainless steel and ceramic micropowders were applied. From the powders and binders the injection mass was prepared in the hot mixing operation. The obtained injection masses were examined to determine viscosity, thermal conductivity and thermal decomposition of the binder (DTA). The greater attention was focused on the injection moulding. The special experimental set-up was designed in which the crucial role played the micro injection moulding machine. The original testing procedure was proposed to analyse the flow of injection mass in microchannels that corresponds with the popular spiral test in macro scale. The analysis of influence of individual parameters (injection pressures p, temperature of injection mass Tw, temperature of the form Tf, granularity z, filling with powder of injection mass Vp and the cross-section of microchannels S) on the micro injection moulding was performed. The results shows that the great influence on the flow of injection mass have the cross-section of the microchannel S, Vp filling and the temperature of the form Tf. The filling of microchannels is also influenced by the granularity of powders. It has been shown that in case of masses with metal powders the finer the powder, the more difficult is to fill the microchannels and microchambers of the form. The pressure p and temperatures of injection mass Tw have a smaller influence on the flow of the mass in microchannels. Research findings are presented in graphical form and in the generalized statements allowing easily to predict the behaviour of the given injection mass with given parameters of microforming. The last part of the research was the manufacturing process of microsamples for bending and for tensile tests and the model microproducts (gears, tubes, complex gears). The final research stage of the process was the debinding and sintering. Debinding was performed as a thermal decomposition and a solvent elution. It has been demonstrated that the best way of debinding of microelements was scouring in solvent because it removes the binder in the most effective way and it did not damage the samples. The sintering process was performed in the laboratory as well as in the industrial conditions. After sintering process all the physical properties of the specimens were analysed and the accuracy of manufacturing process was examined. The microstructure of samples was presented for the different kinds of debinding and for different atmospheres of the sintering. The advantages and disadvantages of these operations were indicated. The density and the porosity of microproducts were determined. It has been found that in the samples a few or even dozen the percentage of porosity occurs that can have the significant impact on the mechanical properties and the surface roughness. The measurements of final samples and microproducts were performed and on basis of them the accuracy of the manufacturing and the shrinkage were determined. The last part of the thesis describes the conclusions drawn from the performed research and the technological recommendations for conducting the process of microinjection moulding of the elements from powders and micropowders. The thesis provides a comprehensive approach to the issues related to microinjection moulding of microelements from powders. The influence of the materials (binders, powders and micropowders) as well as of the technological parameters (microforming process, debindering conditions and sintering) on the properties and the accuracy of manufactured mikroelements was determined.
Record ID
WUTd4dfd82fc67a4ba3afedd568b956226c
Diploma type
Doctor of Philosophy
Author
Title in Polish
Badanie wpływu warunków formowania wtryskowego na właściwości i dokładność wykonania mikroelementów z proszków metalowych i ceramicznych
Title in English
Study of the impact of injection molding conditions on the properties and the accuracy of the microelements made of metal and ceramic powders
Language
(pl) Polish
Certifying Unit
Faculty of Mechatronics (FM)
Discipline
mechanical engineering / (technology domain) / (technological sciences)
Status
Finished
Defense Date
07-05-2014
Title date
21-05-2014
Supervisor
Dionizy Biało Dionizy Biało,, The Institute of Metrology and Biomedical Engineering (FM/IMBE)Faculty of Mechatronics (FM)
Internal reviewers
Leszek Kudła Leszek Kudła,, The Institute of Metrology and Biomedical Engineering (FM/IMBE)Faculty of Mechatronics (FM)
External reviewers
Barbara Ślusarek Barbara Ślusarek,, External affiliation of publication: Instytut Tele- i Radiotechniczny Warszawa
Pages
171
Keywords in English
metal powders; injection moulding; microelements; dimensional accuracy
Abstract in English
The thesis concerns the technology of products manufactured from metal and ceramic powders by means of micro forming injection moulding method (µPIM). PIM technology is well known and well recognized in macro scale. However, in micro scale it is still in research phase. Results obtained so far show that this technology can successfully compete with other, popular methods of manufacturing microelements (such elements that their sizes or their structural details are expressed in tens or hundreds of micrometres). The thesis is written from the technological perspective and all aspects are considered with such approach. All phases of research correspond with product manufacturing stages. At the very beginning materials (powders and binders) are characterised. In case of binders the most appropriate composition was selected in the aspect of the injection moulding and debinderisation. In research iron, stainless steel and ceramic micropowders were applied. From the powders and binders the injection mass was prepared in the hot mixing operation. The obtained injection masses were examined to determine viscosity, thermal conductivity and thermal decomposition of the binder (DTA). The greater attention was focused on the injection moulding. The special experimental set-up was designed in which the crucial role played the micro injection moulding machine. The original testing procedure was proposed to analyse the flow of injection mass in microchannels that corresponds with the popular spiral test in macro scale. The analysis of influence of individual parameters (injection pressures p, temperature of injection mass Tw, temperature of the form Tf, granularity z, filling with powder of injection mass Vp and the cross-section of microchannels S) on the micro injection moulding was performed. The results shows that the great influence on the flow of injection mass have the cross-section of the microchannel S, Vp filling and the temperature of the form Tf. The filling of microchannels is also influenced by the granularity of powders. It has been shown that in case of masses with metal powders the finer the powder, the more difficult is to fill the microchannels and microchambers of the form. The pressure p and temperatures of injection mass Tw have a smaller influence on the flow of the mass in microchannels. Research findings are presented in graphical form and in the generalized statements allowing easily to predict the behaviour of the given injection mass with given parameters of microforming. The last part of the research was the manufacturing process of microsamples for bending and for tensile tests and the model microproducts (gears, tubes, complex gears). The final research stage of the process was the debinding and sintering. Debinding was performed as a thermal decomposition and a solvent elution. It has been demonstrated that the best way of debinding of microelements was scouring in solvent because it removes the binder in the most effective way and it did not damage the samples. The sintering process was performed in the laboratory as well as in the industrial conditions. After sintering process all the physical properties of the specimens were analysed and the accuracy of manufacturing process was examined. The microstructure of samples was presented for the different kinds of debinding and for different atmospheres of the sintering. The advantages and disadvantages of these operations were indicated. The density and the porosity of microproducts were determined. It has been found that in the samples a few or even dozen the percentage of porosity occurs that can have the significant impact on the mechanical properties and the surface roughness. The measurements of final samples and microproducts were performed and on basis of them the accuracy of the manufacturing and the shrinkage were determined. The last part of the thesis describes the conclusions drawn from the performed research and the technological recommendations for conducting the process of microinjection moulding of the elements from powders and micropowders. The thesis provides a comprehensive approach to the issues related to microinjection moulding of microelements from powders. The influence of the materials (binders, powders and micropowders) as well as of the technological parameters (microforming process, debindering conditions and sintering) on the properties and the accuracy of manufactured mikroelements was determined.
KBN classification
44
Thesis file
  • File: 1
    Rozprawa doktorska.pdf
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Uniform Resource Identifier
https://repo.pw.edu.pl/info/phd/WUTd4dfd82fc67a4ba3afedd568b956226c/
URN
urn:pw-repo:WUTd4dfd82fc67a4ba3afedd568b956226c

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