EXPERIMENTAL CHOICE OF SUITABLE CUTTING TOOL FOR MACHINING OF PLASTIC

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1 TECHNOLOGICAL ENGINEERING volume XI, number 1/2014 DOI: /teen EXPERIMENTAL CHOICE OF SUITABLE CUTTING TOOL FOR MACHINING OF PLASTIC Dagmar Sokova, Robert Cep, Lenka Cepova, Simona Kociajova Department o Working and Assembly, Faculty o Mechanical Engineering VŠB-Technical University o Ostrava, Czech Republic Article history: Received 10 september 2014 Accepted 7 november 2014 Available online Abstract In today's competitive times overall development o the technology is moving somewhere urther, including automotive industry, which went toward relieving material. One o the many materials which are applied in the automotive industry, are polymers. The aim o the article was to test three dierent types o cutters or machining material group N - nonerrous metals. The article was tested three dierent types o cutters rom dierent vendors on electro material SKLOTEXTIT G 11 and samples size 12x100x500mm. The entire experiment was conducted in a company Slavík- Technické plasty on the machine tool SCM RECORD 220. In the conclusion are technical-evaluation, experimental results and conclusions or company. Keywords Machining; Plastic; Experiment; Cutting Tool 1 INTRODUCTION Development o technologies is speeding up in the current quickly evolving and competitive world. The automotive industry, which has taken steps towards lightweight materials, is no exception. Polymers are one o the types o materials which have been applied in this industry. They are used in all areas including machining, orming, and others. Machining o polymers is diicult and requires the use o appropriate tools, proper selected procedure and care. Cutting, turning, milling and drilling are among the most widespread machining processes considering these materials. (making holes or various joining devices) [1]. It is milling that is playing an important role in the ield o machining. Currently, it is the most eicient and the most lexible available machining method, which is being constantly developed and sophisticated. The uture o machining belongs to modern ways o machining and machining technologies above all - HSC (High Speed Cutting), HFC (High Cutting) and HPC (High Perormance Cutting). Apart rom the machine and the tool itsel, cutting conditions have the major inluence on the quality o laminate machining. It depends on the proper selected procedure, operating speed and on ensuring the utter cut, which means avoiding riction o the tool with the surace o the workpiece. I the tool does not cut properly, delamination o the material and/or iber raction occur [1]. One can come across with many kinds o polymer materials in their engineering practice but also with the materials reinorced with iberglass and/or carbon ibers. In spite o the act that the issues o machining o polymers reinorced with iberglass are very actual, only a ew experts and production companies concentrate on this ield. Electroinsulating materials are widely used in engineering practice, the aviation industry and in addition, they can be also ound in the ield o medicine. [2] 2 EXPERIMENT The whole experiment took place in Slavik - Technicke plasty Company on a Three Axis Machine tools, SCM RECORDS 220, see Figure 1, with the support o aluminum vacuum table, where electroinsulating material and some samples, measuring 12x100x 500mm, were ixed. The machine tools were equipped with the control system Alpha CAM. Please, see the parameters in Table 1. Figure 1 Three axis machining centre SCM RECORD 220 Table 1 Parameters o machine tool Dimensions o the machine tool 225x1250x3050 Weight o the machine tools 7200Kg Working dimensions 320x1300x3250 Distance spindle to table 320 Rapid shit eed 45 m.min -1 Table size 1200x3120 Working eed 18 m.min -1 Spindle ISO 30 Spindle revolutions Max min -1 Engine perormance 7,5 kw Tools magazine 12 Max. cutting tool diameter 80 mm Max. cutting tool length 200 mm 32

2 The name o the machined electroinsulating material is SKLOTEXTIT G 11- ČSN EN , see Figure 2. It is a lamellar material, which is produced rom adjusted glass abric and epoxy resin with addition o illers. The material is characterized by excellent mechanical (see Table 2) and electroinsulating characteristics, which are maintained even at high temperature. The table ranges rom light yellowish to light greenish. It is used to produce components with good mechanical and electroinsulating characteristics, electrical equipment at high temperature or humid environment, or to produce electroinsulating components that are resistant to stress on material, such as rames, machine bodies, distributing box, transormers, instrumental panels and/or electrical machines. [3] Table 4 25mm 70 mm Number o teeth 2 Angle o the helix 55 Type 2 - DOUBLE-EDGED CYLINDRICAL MILLING CUTTER WITH DIAMOND COATING MADE BY ARNO Another hard metal cutter comes to comparison. It is suitable or machining aluminum and aluminum alloys (see igure 4). The rest o the parameters can be seen in table 5. Figure 2 Rough material SKLOTEXTIT G11 Table 2 Mechanical characteristics o SKLOTEXTIT G11 Density [g/cm 3 ] Bending strength [Mpa] Tensile strength [MPa] Resistance to splitting [N] 1,65-1, The electroinsulating material was milled only by climb eed method. Thus, extraction o ibers rom the matrix was avoided. Three milling cutters rom dierent manuacturers were used. See the results in Table 3: Type Table 3 Comparison o 3 types o milling cutters Double-edged cylindrical cutter Company Angle o the helix 1. no coating WNT diamond coating ARNO straight edges HOFFMANN GROUP - Figure 4 Cylindrical milling cutter with diamond coating made by ARNO Table 5 13 mm 50 mm Number o teeth 2 Angle o the helix 45 Type 3 - DOUBLE-EDGED CYLINDRICAL MILLING CUTTER WITH STRAIGHT EDGES MADE BY HOFFMAN GROUP A hard metal cutter again, however this one comes with diamond coating and straight edges. It is suitable or machining materials containing glass or carbon ibers (see igure 5). The rest o the parameters can be seen in table 6. Type 1 - DOUBLE-EDGED CYLINDRICAL MILLING CUTTER WITH OUT COATING MADE BY WNT This cutter is suitable or machining o brass as well as plastic (see igure 3). It is a hard metal cutter with the helix angle o 55. The rest o the parameters can be seen in table 4. Figure 5 Cylindrical milling cutter with straight edges made by Homan Group Table 6 3 mm 60 mm Number o teeth (Cutting edges count) 2 Angle o the helix - Figure 3 Cylindrical milling cutter with no coating made by WNT TECHNOLOGICAL ENGINEERING, Volume XI, number 1/2014, Unauthenticated 33

3 The tested tools were inserted into a reducing bush and placed in a tool tray. The cutters were measured using an indicator (see igure 6). The measured value was written in the table o tools. b) Figure 8 View o the machined material: a) the end o the machined groove, b) ibers ripped o rom the groove Figure 6 Measuring a tool using a indicator A program was created in control sotware Alpha CAM, once the milling cutters were measured. It simulates cutting a simple slot and setting up the cutting conditions. The operating speed was set to n = 13,000 min -1. The reason or this setting was the limited speed o the machine. The speed was then decreased manually i it was needed. The inal program was loaded into the machine and the production started. 3 RESULTS OF THE EXPERIMENT The irst tested miller/cutter was the double-edged cylindrical cutter with no coating made by WNT; see Figure 7. During the irst phase o milling, it was visible that gradual dulling occurred. As you can see in Figure 8, machining under the conditions that are stated in Table 7 caused that at the end o the milled grooves, ibers were burnt and/ or ripped o rom the material. The cutter ater the machining can be seen in Figure 9. Table 7 Cutting parameters o the double-edged cylindrical cutter Double-edged cylindrical cutter without coating, made by WNT Revolution n = 7600 min -1 Cutting speed vc = 120 m.min -1 = 0,032 mm Milling lenght L = 500 mm Cutting depth ap = 3 mm Figure 9 The appearance o the cylindric mill, produced by WNT ater machining the material The second machine, which was tested, was the double-edged cylindrical cutter with diamond coating, produced by ARNO. Diamond coating should ensure minimal blunting o the machine. According to Figure 10 it is clear that no material was burnt in the milled groove in comparison with the previous cutter without coating. Nevertheless, the appearance o the machined groove did not look well again. There were ibers that got o rom the material. Such eect is either the result o blunting o the machine, or wrongly set cutting conditions. See Table 8. For the appearance o the cutter ater machining, see Figure 11. Table 8 Cutting parameters o the double-edged cylindrical cutter Double-edged cylindrical cutter with diamond coating, produced by ARNO Revolution n = min -1 Cutting speed vc = 200 m.min -1 = 0,08 mm Milling length L = 500 mm Cutting depth ap = 3 mm Figure 7 Machined material cutter rom WNT a) a) 34

4 b) Figure 10 The view o the machined material ater it was machined by the cutter, produced by ARNO: a) ront view o the machined groove, b) side view o the groove and its torn out ibers Figure 13 The appearance o the cylindric mill, produced by HOFFMAN GROUP ater machining the material 4 TECHNICAL AND ECONOMIC EVALUATION Three kinds o millers had been bought or the machining o electroinsulating material. In Table 10, see the prices o each o them. Prices or instruments Table 10 Figure 11 The appearance o the cylindrical mill, produced by ARNO ater machining the material The third and the last tested one was a double-edged cylindrical cutter with diamond coating, produced by Homann Group, which has straight edge where together with climb milling the work piece was clinged slightly to the table, thus avoiding ibers being torn out. In Figure 12 we can see the milled groove and some ibers. However, the appearance is cleaner and smoother. For the appearance o the machined groove, see Fig. 13. Table 9 Cutting parameters o the double-edged cylindrical cutter WNT CZK ARNO AFD DLC 591CZK HOFFMANN GROUP CZK Calculation o unit machining time : Double-edged cylindrical cutter with diamond coating, produced by Homann Group Revolution n = min -1 Cutting speed vc = 200 m.min -1 = 0,04 mm Milling length L = 500 mm Cutting depth ap = 3 mm where: L t AS /1/ v v z n /2/ z L cutting length [mm], v - eed speed [mm.min -1 ], tas machining time [min], z - number o teeth, n revolution [m.min -1 ]. For milling [4,5,6] : L l ln l p ln /3/ Figure 12 The appearance o the milled groove, by Homan group. l n H ( D H) /4/ TECHNOLOGICAL ENGINEERING, Volume XI, number 1/2014, Unauthenticated 35

5 Table 11 The calculated machining time or each cutter WNT ARNO HOFFMANN GROUP 2,2 min 0,5 min 0,5 min From the economic point o view, our aim is to choose a tool while taking into account its quality and price. On the basis o the tests it can be concluded that the doubleedged cylindrical cutter, made by Homann Group achieved the best results. Due to the minimal volume o orders o electroinsulating material at Slavik- Technicke plasty company, the high price is the cutter`s disadvantage. However, or uture i we take into consideration the advantages o the cutter, which is high-quality machined surace and shorter production time, I recommend this cutter or a small butch production and large lot productions, where the proportion o quality/price will be applied. In the case o piece production, as it is in our case, I would recommend double-edged cylindrical cutter, made by ARNO. Having taken into account its low price and the quality o machined material, the cutter is suicient enough or machining o electroinsulating materials. Provided using the cutter, it will be needed to adjust cutting conditions in order to avoid torn out ibers rom the material. 5 CONCLUSIONS We used three dierent kinds o cutters rom dierent producers or machining o the N- non-errous group metal materials in the experiment. The cutters were tested on electroinsulating material SKLOTEXTIT G11, on the samples with parameters o 12x100x500 mm. Speciic parameters based on producer`s recommendations were set or individual cutters. The experiment took place in the company Slavik- Technicke plasty on SCM RECORD 220 machine. The cutters were machining the materials under given conditions along their whole length, which means 500 mm. The length was set according to commonly machined sizes in the company. The irst cutter to be assessed was the one made by WNT. It was the cylindrical double-edged cutter without coating with helix rising o 55%. This cutter is suitable or machining o yellow copper and plastic. The results o the cutter were the worst ones, because speedy blunting and subsequent burning o the material occurred under recommended cutting conditions. Another tested cutter was the cylindrical doubleedged cutter with diamond coating and helix angle o inclination o 45%, made by ARNO. This cutter is suitable or machining aluminum and aluminum alloys. The results o the cutter in the tests were quite avorable; ater the groove was milled no burnt surace occurred, compared to the previously mentioned cutter. However, ater machining the groove torn out ibers remained, which does not correspond with our needs. The last tested cutter was the double-edged cutter with straight edges, made by HOFFMANN GROUP. The cutter is suitable or machining composite materials which contain carbon and iberglass. The test`s results were excellent. Not only was no burnt surace but there occurred no visibly torn out ibers, too. The machining was proceeding with no diiculties or complications. Unortunately, taking into account its price, the cutter is not adequate or us because o minimal volume o orders o cultivated material. From the point o view o the price, the best cutter is the second one, made by Arno. Provided the cutting conditions are reconditioned or electroinsulating material machining, the cutter will be convenient and suicient rom both technical and economic point o views. [7,8] ACKNOWLEDGEMENT Article has been done in connection with projects Practical Competence and Proessional Qualiications Improvement in the Area o Technical Education, reg. no. CZ.1.07/2.4.00/ , Education system or personal resource o development and research in ield o modern trend o surace engineering - surace integrity, reg. no. CZ.1.07/2.3.00/ inanced by Structural Founds o Europe Union and rom the means o state budget o the Czech Republic and by project Students Grant Competition inanced by the Ministry o Education, Youth and Sports and Faculty o Mechanical Engineering VŠB- TUO. LITERATURE [1] Cited [2] Kříž, A.; Kožmín, P. Tenké vrstvy na řezných nástrojích v aplikaci obrábění plastů. Plzeň, r.2006 [3] Loyda, M.; Šponer, V.; Ondráček, L.; Bareš, A, a kolektiv. Svařování termoplastů, Aktualizované druhé vydání, 2011, PRAHA, ISBN [4] Kocman, K. ; Prokop, J. Technologie obrábění. 1.vyd. Brno: Akademické nakladatelství CERM, s. ISBN [5] Kocman, K; Prokop, J. Technologie obrábění. 2. vydání. Brno: Akademické nakladatelství CERM, s.r.o., s. ISBN [6] Humár, A. Technologie I : Technologie obrábění - 1. část [online].brno : Ústav strojírenské technologie (Vysoké učení technické v Brně,Fakulta strojního inženýrství), 2003 [cit ]. Dostupné z WWW:< [7] Kociajová, S. Testování řezné geometrie nástrojů na obrábění polymerů: Dipolomová práce, 2014, VŠB TU Ostrava, 45 s. [8] Košút, M. Rakoci, J. - Czán, A. Ďurech, L.: Studying o Interaction o Cutting Tool and Workpiece at High Production Turning. In. Technological engineering 2013/1, 36