HUNGARIAN JOURNAL OF INDUSTRY AND CHEMISTRY Vol. 49 pp. 71–75 (2021) hjic.mk.uni-pannon.hu DOI: 10.33927/hjic-2021-25 ANALYSIS OF FORMED CHIPS IN THE CASE OF TURNING DIFFERENT POLYMER MATERIALS ÁDÁM SARANKÓ*1 , GÁBOR KALÁCSKA1 , AND RÓBERT ZSOLT KERESZTES1 1Institute of Technology, Hungarian University of Agriculture and Life Sciences, Páter Károly u. 1, Gödöllő, 2100, HUNGARY In this paper, turning input parameters were defined for 12 different polymer materials that can be used in technical practices. Our goal was to determine turning input parameters where chip formation is favourable or continuous chips do not cause any problems. Our tests included the examination of detached chips and the values of the average surface roughness of the machined surfaces. Keywords: chip formation, polymer materials, turning 1. Introduction Nowadays, in addition to the 3D printing of polymers, the machining of polymer and polymer composite mate- rials still plays an important role. Turning is one of the most productive machining technologies used to make cylindrical products. Polymers that exhibit good levels of machinability favour the development of chip formation. However, technical practices often use polymer materials that exhibit favourable properties (hardness, toughness, flexibility) but are difficult to machine. The most com- mon problem is continuously flowing chips. In this case, rather than the chip being moved away from the material, it is pushed in front of the tool. As a result, the heat can- not dissipate from the chips and the detached chips are in constant contact with the tool, which generates additional heat. Since polymers tend to withstand high temperatures less than metals, their machined surfaces melt and their surface roughness becomes unacceptable. Researchers have already studied the shape of de- tached chips. The literature is mainly concerned with the study of types of chips generated during the machining of metallic materials such as C45 [1, 2], Al/SiCp [3] and AISI D2 tool steel [4]. Kharlevich and Venuvinod anal- ysed the formation of 3D chips in general as a result of metal cutting [5,6], while others have researched methods of chip breaking for machining tools [7, 8]. Although chip detachment and formation are very im- portant aspects in machining, in the case of polymers, this area has not yet been investigated. *Correspondence: saranko.adam@uni-mate.hu 2. Experimental methods 12 different polymer materials were tested, namely PA6 G-H, PA66 GF30, PET TF, PET, POM-C, POM-GF25, POM-H, PP, PTFE, PVC, textile bakelite and UHMWPE. Accord- ing to a manufacturer of polymer materials, the aforemen- tioned materials are the most commonly used, excluding the so-called high-performance ones. In this research, turning tests were performed to de- termine input parameters that can be used in practice to avoid such problems, e.g. melted surfaces, caused by continuously flowing chips. The turning tests were run on an E 400 conventional lathe machine and an NCT EUROturn-12B CNC lathe machine. Both devices are lo- cated in the workshop of the Institute of Technology. In all the experiments, a SCLCR 20.20 K09 tool shank and a CCGT 09T304-AS IC20 polished turning insert were used. After each test, a close-up photo of the surface was taken and the average surface roughness measured. For surface measurements, a Mitutoyo Surftest SJ-201P sur- face roughness tester was used. Furthermore, the formed chips were collected before being analysed. The input parameters of all the tests are shown in Ta- ble 1. In the case of roughing, the depth of cut was 3 mm, while a depth of cut of 0.25 mm was used for finishing. The air-cooled solution was mainly suitable for blow- ing off the detached chips. At first, all the experiments were tried without implementing any cooling methods. However, in the case of certain materials, flowing chips were formed in all cases, so chip blowing was used for these materials. https://doi.org/10.33927/hjic-2021-25 mailto:saranko.adam@uni-mate.hu 72 SARANKÓ, KALÁCSKA, AND KERESZTES Table 1: Input parameters of all tests Input parameters for roughing on a CNC lathe machine (NCT EUROturn-12B) PA6 G-H PA66 GF30 PET TF PET POM C POM GF25 vc (m/min) 250 250 250 250 250 250 f (mm/rot.) 0.2 0.2 0.15 0.15 0.2 0.2 Cooling - - - - - - POM H PP PTFE PVC Textile bakelite UHMW-PE vc (m/min) 250 250 250 250 250 250 f (mm/rot.) 0.2 0.2 0.2 0.1 0.2 0.15 Cooling - - - - - - Input parameters for finishing on a CNC lathe machine (NCT EUROturn-12B) PA-6 G-H PA-66 GF-30 PET TF PET POM C POM GF-25 vc (m/min) 300 300 300 300 300 300 f (mm/rot.) 0.1 0.1 0.1 0. 1 0.1 0.1 Cooling air air air air air air POM H PP PTFE PVC Textile bakelite UHMW-PE vc (m/min) 300 300 300 300 300 300 f (mm/rot.) 0.1 0.1 0.1 0.1 0.08 0.1 Cooling air air air air - air Input parameters for roughing on a conventional lathe machine (E 400) PA-6 G-H PA-66 GF-30 PET TF PET POM C POM GF-25 vc (m/min) 61 52 59 75 58 52 f (mm/rot.) 0.75 0.75 0.4 0.4 0.6 0.6 Cooling - - - - - - POM H PP PTFE PVC Textile bakelite UHMW-PE vc (m/min) 66 76 58 58 59 58 f (mm/rot.) 0.6 0.75 0.6 0.2 0.75 0.4 Cooling - - - - - - Input parameters for finishing on a conventional lathe machine (E 400) PA-6 G-H PA-66 GF-30 PET TF PET POM C POM GF-25 vc (m/min) 65 62 63 79 62 62 f (mm/rot.) 0.1 0.1 0.1 0.1 0.1 0.1 Cooling - air air air - air POM H PP PTFE PVC Textile bakelite UHMW-PE vc (m/min) 71 80 57 63 63 62 f (mm/rot.) 0.1 0.1 0.1 0.1 0.1 0.1 Cooling - air air air - air 3. Results The input parameters shown in Table 1 can also be con- sidered as results. These parameters were determined ex- perimentally. In other aspects, however, the main results are the av- erage surface roughness of the machined surfaces and the properties of the detached chips. Table 2 shows the results of the average surface roughness measurements. Although other setups can be used, by applying the parameters described above, safe and productive machin- ing can be achieved by avoiding problems caused by con- tinuously flowing chips. The detached chips were examined subjectively rather than by making specific measurements. However, the re- sults obtained in this way can be used in practice and pro- vide a suitable point of reference. Photos of the detached chips in all cases are presented in Fig. 1, while the properties of these chips are shown in Table 3. 4. Conclusions In general, the turning of tough polymeric materials re- sults in the formation of continuous chips. Due to the big Hungarian Journal of Industry and Chemistry ANALYSIS OF FORMED CHIPS IN THE CASE OF TURNING DIFFERENT POLYMER MATERIALS 73 Table 2: Average surface roughness values Material Average surface roughness (µm) NCT EUROturn-12B E 400 Roughing Finishing Roughing Finishing PA6 G-H 4.06 1.18 12.95 1.58 PA66 GF30 3.12 1.27 12.32 1.55 PET TF 1.73 0.95 5.24 1.47 PET 1.75 0.9 5.18 1.13 POM-C 3.48 0.66 8.62 1.14 POM-GF25 3.75 1.2 8.56 1.43 POM-H 3.44 0.68 8.72 1.14 PP 3.38 0.89 12.72 1.45 PTFE 5.01 1.77 18.44 1.93 PVC 1.01 0.78 2.35 0.87 Textile bakelite 6.81 3.15 10.30 1.59 UHMWPE 2.53 1.81 11.27 1.67 Table 3: Properties of the detached chips Properties of the detached chips NCT EUROturn-12B E 400 Roughing Finishing Roughing Finishing PA6 G-H 5, 6, 7, 8 5, 6, 9 5, 6, 8 3, 4, 7 PA66 GF30 3, 4 4, 5 3, 4 3, 4 PET TF 4, 5 4, 5 3, 10 4, 5 PET 4, 5 4, 5 5, 10 4, 5 POM-C 1, 2 3, 4 1, 2 3, 4 POM-GF25 1, 2 1, 2 1, 2 3, 4 POM-H 1, 2 3, 4 1, 2 3, 4 PP 4, 5, 6 4, 5 3, 8 4, 5 PTFE 3, 4 3, 4 3, 4 3, 4 PVC 4, 5 4, 5 4, 5 3, 4 Textile bakelite 4, 11 11 1, 4, 11 11 UHMWPE 3, 6, 7, 10 3, 6, 9 3, 6, 7, 8 3, 6, 7 1: elemental, 2: rigid, 3: curved, continuously flowing, 4: easy to tear, 5: straight, continuously flowing, 6: tough, 7: stretches, 8: does not tear, 9: tears after being stretched, 10: hard to tear, 11: dust-like cross-section of chips during the roughing operation, the mass of individual detached chips influences in which di- rection they start to flow. This is less of a problem because the ventilation effect of the chuck does not adversely af- fect the cooling of the chips. In the case of the finishing operation, the cooling of the chips is critical. It is recommended to use air cooling, although not specifically for the purpose of cooling, in order to blow chips away from the workpiece and tool. Even though the quality of the machined surfaces can be improved by tools with bigger radius, chips can still cause problems. During the experiments, chip blowing was worthwhile in all cases, especially during smoothing operations. Future research can be conducted by precisely defin- ing the air-cooling method, applying other tools and in- vestigating high-performance polymeric materials. In the case of chip blowing, the distance between the workpiece and the chuck, the weight of the detached chips as well as the ventilation effect of the chuck must be taken into ac- count. The direction and velocity of the air is also signif- icant. It was found that a strong airflow is not always the 49 pp. 71–75 (2021) 74 SARANKÓ, KALÁCSKA, AND KERESZTES Figure 1: Photos of the detached chips most desirable. The distance between the nozzle and the tool is limited by the geometries of the machine as well as the workpiece. By precisely defining these parameters, more practical information can be provided. Acknowledgement The authors would like to thank Quattroplast Kft. for pro- viding the engineering polymeric materials. Nomenclature vc cutting speed (m/min) f feed rate (mm/rotation) Ra average surface roughness (µm) PA6 G-H cast polyamide 6, Hungarian version PA66 GF30 polyamide 66 with 30 m/m% glass fiber PET TF polyethylene terephthalate with the ad- dition of PTFE Hungarian Journal of Industry and Chemistry ANALYSIS OF FORMED CHIPS IN THE CASE OF TURNING DIFFERENT POLYMER MATERIALS 75 PTFE polytetrafluoroethylene PET polyethylene terephthalate POM-GF25 polyoxymethylene with 25 m/m% glass fiber POM-C polyoxymethylene copolymer POM-H polyoxymethylene homopolymer PP polypropylene PVC polyvinyl chloride UHMWPE ultra-high molecular weight polyethy- lene REFERENCES [1] Segreto, T.; Simeone, A.; Teti, R.: Chip form Clas- sification in Carbon Steel Turning through Cut- ting Force Measurement and Principal Compo- nent Analysis Procedia CIRP, 2012, 2, 49–54 DOI: 10.1016/j.procir.2012.05.038 [2] Segreto, T.; Simeone, A.; Teti, R.: Principal com- ponent analysis for feature extraction and NN pat- tern recognition in sensor monitoring of chip form during turning. 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Proc. 2020, 49, 50–69 DOI: 10.1016/j.jmapro.2019.10.026 49 pp. 71–75 (2021) https://doi.org/10.1016/j.procir.2012.05.038 https://doi.org/10.1016/j.procir.2012.05.038 https://doi.org/10.1016/j.cirpj.2014.04.005 https://doi.org/10.1016/j.jmapro.2021.02.032 https://doi.org/10.1016/j.matpr.2021.01.137 https://doi.org/10.1016/j.matpr.2021.01.137 https://doi.org/10.1016/S0890-6955(98)00066-2 https://doi.org/10.1016/S0890-6955(01)00115-8 https://doi.org/10.1016/j.ijmecsci.2019.105411 https://doi.org/10.1016/j.jmapro.2019.10.026 https://doi.org/10.1016/j.jmapro.2019.10.026 Introduction Experimental methods Results Conclusions