Odrezovalne razmere pri procesu kriogenega frezanja z uporabo tekočega CO2

Grguraš, Damir (author), Pušavec, Franci (mentor)

V doktorskem delu je predstavljeno kriogeno frezanje (ang. cryogenic milling) z uporabo tekočega ogljikovega dioksida (ang. Liquid Carbon Dioxide – LCO2). Način enokanalnega dovoda (ang. single-channel supply) kriogenega medija, t.j. mešanice (a) LCO2 in (b) olja v obliki oljne megle – MQL (ang. Minimum Quantity Lubrication – MQL) predstavlja pomemben napredek pri kriogenem odrezavanju (ang. cryogenic machining). Hladilna in mazalna sposobnost mešanice LCO2 + olje (MQL), ki neposredno vplivata na odrezovalne razmere, do sedaj nista bili individualno analizirani. V tem delu je zato hladilna sposobnost (ang. cooling capability) kriogenega medija določena s pomočjo nadzorovanega vira toplote za simulacijo procesa odrezavanja. Mazalna sposobnost (ang. lubrication capability) kriogenega medija pa je določena preko detajlne analize toka kriogenega medija. Rezultati kažejo, da ima kriogeni medij nižjo hladilno sposobnost, kot konvencionalna emulzija na bazi olja (ang. oil based emulsion). To se odraža v višji temperaturi odrezavanja (ang. cutting temperature) pri uporabi kriogenega medija. Kljub temu, najdaljšo obstojnost orodja dosežemo pri kriogenem odrezavanju, kar nakazuje na pomembnost zadostnega hlajenja. Hkrati je pomembno tudi mazanje, ki je najustreznejše ob uporabi nepolarnega olja v mešanici LCO2 + olje (MQL). Nadalje, ugotovljeno je, da uporaba mešanice LCO2 + olje (MQL) ne vpliva negativno na obliko odrezkov. Zaradi značilno daljše obstojnosti orodja pa je kriogeno odrezavanje stroškovno ugodnejše od konvencionalnega odrezavanja. Predstavlja tudi varno tehnologijo odrezavanja, saj koncentracija CO2 v zraku v bližini CNC stroja, ne presega dovoljenih vrednosti.

• Language: Slovenian
• Keywords: Odrezovalne razmere, kriogeno odrezavanje, kriogeno frezanje, tekoči ogljikov dioksid (LCO2), enokanalni dovod LCO2 + olje (MQL), hladilna sposobnost, temperatura odrezavanja, mazalna sposobnost, analiza toka
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: FS - Faculty of Mechanical Engineering
• Place of publishing: Ljubljana
• Publisher: [D. Grguraš]
• Year: 2020
• Number of pages: XXVI, 114 str.
• PID: 20.500.12556/RUL-113709
• UDC: 621.914:621.564:62-72(043.3)
• COBISS.SI-ID: 303760640
• Publication date in RUL: 29.01.2020

GRGURAŠ, Damir, 2020, Odrezovalne razmere pri procesu kriogenega frezanja z uporabo tekočega CO2 [online]. Doctoral dissertation. Ljubljana : D. Grguraš. [Accessed 26 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=113709

Secondary language

• Language: English
• Title: Machining conditions of cryogenic milling using liquid CO2

Abstract

In the following doctoral thesis, cryogenic milling using liquid carbon dioxide (LCO2) is presented. A novel single-channel supply of pre-mixed (a) LCO2 and (b) oil – delivered as a minimum quantity lubrication (MQL) – represents a significant advancement of cryogenic-machining technology. Cooling and lubrication capability of the mixture LCO2 + oil (MQL), which directly affects the machining conditions, have not been individually analyzed so far. Therefore, in this thesis, cooling capability of the cryogenic media was determined utilizing a controlled heat source for simulating the machining process. Lubrication capability of the cryogenic media was determined by advanced cryogenic media streamflow analysis. Results are showing that cryogenic media offers lower cooling capability than conventional oil based emulsion. This is further reflected in a higher cutting temperature, when the cryogenic media is employed. Nevertheless, the longest tool life is achieved in cryogenic machining, which indicates the importance of sufficient cooling. In addition, lubrication plays an important role; the most suitable lubrication provides nonpolar oil in the mixture of LCO2 + oil (MQL). Furthermore, the use of mixture LCO2 + oil (MQL) was found not to adversely affect the chip shapes. Moreover, due to the significantly longer tool life, cryogenic machining is more cost-effective than conventional machining. It is also a safe machining technology, since the CO2 concentration in the air near the CNC machine, does not exceed the permitted values.

• Keywords: Machining conditions, cryogenic machining, cryogenic milling, liquid carbon dioxide (LCO2), single-channel supply of LCO2 + oil (MQL), cooling capability, cutting temperature, lubrication capability, streamflow analysis