PRODUCTION ENGINEERING ARCHIVES. Chip breaking phenomenon during cutting steel and polymer materials. 1. Introduction.

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1 PROUTION ENGINEERING RHIVES 16 (2017) PROUTION ENGINEERING RHIVES ISSN (print) ISSN (online) Exist since 4 th quarter 2013 vailable online at János Líska 1 hip breaking phenomenon during cutting steel and polymer materials 1 John Von Neumann University, GMF Faculty o Engineering and omputer Science, Kecskemét H-6000, Izsáki út 10, liska.janos@gam.uni-neumann.hu rticle history Received ccepted vailable online Keywords utting orces utting temperature High Speed amera Polymer Turning bstract Research in 60s and 70s started to deal with the shape o the chip characterization. It was possible then to do a limited study by means o measuring tool park. uring such a study, dierent models or chip ormation became amiliar, such as the Time or Merchant model. The aim o article is to gain insight into some accompanying phenomena, occurring while cutting o dierent materials and with various tools. uring an experimental design, the possible eects o dierent variables on each other and individually were considered. Two work-pieces (45, POM) with two inserts (with two dierent edge design) were tested while changing o cutting speed and eed. uring measurements cutting orces at 5000 Hz signal reception were tested or the evolution o cutting temperature at dierent experimental settings was evaluated. The chip characteristics are measured by a high speed camera. The camera is connected with P or recording and controlling the experimental procedure in real-time. The requency o High Speed amera was similar than the requency o the cutting orce measuring system. This similarity is provided with the system set-up synchronization. 1. Introduction chip low in all wedged-tool machining processes can be described, in theory, in a common way, by means o two dierent cutting schemes termed orthogonal cutting. In orthogonal cutting (Fig. 1) a cutting edge o the tool is perpendicular to the direction o relative work-piece cutting tool motion and also to the side ace o the work-piece. From the relative movement o work-piece and cutting tool, a layer o material in the orm o chip is removed. In order to continue removing the material in the second stage, the tool is taken back to its starting position and ed downwards by the amount, the eed o the process. Perpendicular to, h is the depth o cut, which is smaller than or equal to the width o the tool edge. The surace along which the chip lows is the rake ace o the tool. The angle between the rake ace and a line perpendicular to the machined surace is called rake angle β. The ace o the tool that is near the machined surace o the work-piece is the lank ace. The angle between the lank ace o the tool and the work-piece is called clearance angle a. The angle between the rake ace and the lank ace is the wedge angle b. The sum o the three angles is always equal to 90, thus: α+β+γ=90 (1) Orthogonal cutting represents a two-dimensional mechanical problem with no side curling o the chip considered. It represents only a small ragment o machining processes, i.e. planning or end turning o a thin-walled tube. However, it is widely used in theoretical and experimental work due to its simplicity. ecause o its 2 nature many independent variables are eliminated, e.g. two cutting orces are only identiied to orthogonal cutting problems. (MRKOPOULOS.P. 2013). Fig. 1. Merchant model o orthogonal cutting Source: U J., ÉKÉS J RHIWUM INŻYNIERII PROUKJI

2 JÁNOS LÍSK / PROUTION ENGINEERING RHIVES 16 (2017) II. Sandvik oromant Q NH TM 1125 Fig. 3. asics o Experimental esign Source: LÍSK J., GÁL The orces at machining by dynamometer KISTLER 625 7/ were measured. n inrared camera Flir T360 and High Speed amera Olympus or the high speed pictures were also used. The zone o machining rom distance 800mm (Fig. 2) was observed. The work-piece was a 45 steel and POM (polioximethilen) in diameters 101mm and 135mm. oth inserts (Fig. 4) was PV coat (Ti,r,l)N+(Ti,l)N. The cutting inserts o dierent geometry can be seen in ig. 3. It is also noticeable that the chip breakers are dierent. uring the OE (esign o Experiments) the statistical sotware MINIT was used. n experimental table was generated by means o sotware ater inputting the primary data. Fig. 2. Experimental set-up 2. esign o Experiments Experiments in mechanical engineering are planned by the help o ull-actorial design o experiment, which states, that or investigation o machining process the black box is applicable (Fig. 3). The outgoing arrow on the right side is the dependent variable, which is marked as ỹ. The value o the dependent variable has to be impressible. The inluencing actors are reerred as independent variables (actors) and are marked as Xi. The black box can have more ỹi outputs. Factors can include more values, these values are levels. The experimental settings can be created by the combination o actor levels. These settings are variable values o ỹ. In the so called active experiments all actors were set on 2 or 3 level and their values were changed in a predetermined order. This method ensures reliable variations with limited settings (LÍSK J., GÁL. 2013). n experiment with combination o our variables o minimum and maximum values was designed. The variables are: cutting speed v c ; (v cmin = m/min; v cmax = m/min), eed ; ( min = 0.05 mm/rev.; max = 0.1 mm/rev.), work-piece material: ; (45; POM.), utting inserts: (I.; II.) The inserts are: I. Sandvik oromant Q NH TF 1125 Fig. 4. utting inserts a) -., b) -. Source: SNVIK OROMNT 3. Results and discussion The measurement o tool geometry is very important during the experiments. esides two dierent tools, a contour and surace measurement system was used or measuring the cutting tool geometry (Fig. 5). Fig. 5. Tool geometries RHIWUM INŻYNIERII PROUKJI 38

3 JÁNOS LÍSK / PROUTION ENGINEERING RHIVES 16 (2017) eore the cutting orce measurements, the measurement goodness was supposed to be checked. In Fig.6 the evaluation o main cutting orces without cutting can be seen. t the beginning it can be observed that the orces are very closed to zero (the small tail swing is only the error o the measurement card o dynometer). ter turning on the spindle clearly shows relatively higher tail swing. I the spindle is turned o, the orces are similar to those at the initial phase o the measurement. turning o work-piece was light cutter. ter ew milliseconds the cutting temperature increased aster. Fig. 6. hecking o measurement goodness ter checking the accuracy, the main cutting orces were measured. For better understanding, one measurement can be presented as an example. The work-piece material was 45, the cutting tool material was no. II, and the cutting parameters were: v c = m/min, = 0,1 mm/rev. In the Fig. 7, the evaluation o main cutting orces can be observed. The diagram clearly shows, that two dierent type o results occur: - the indent area o cutting orces - the area o cutting orces The attribution o the curve is a standard. Fig. 8. Evaluation o indent o the tool to the work-piece The third diagram (Fig. 9) shows the irst contact area o the tool with the work-piece. It is a very ast area (it is around 26 ms), and 210 measured points or better results were obtained. The trend o the curve was very similar to the one in Fig. 6, but here the slop was not very gentle. Moreover, the accuracy o a curve was evaluated. It was about 82%, which is a very good value or such a ast area. Fig. 9. The irst contact o the tool with the work-piece The characteristic areas, which can be seen in Fig. 6, are also shown in Fig. 10. The picture, presents the evaluation o cutting temperature at the indent area. Firstly (on the let), it can be observed that the chip has no colour. Later, however, i looked at rom the let to the right, one can notice dierent colours; yellow, brown and purple. Fig. 7. Evaluation o main cutting orces However, the closer the indent is, the more interesting phenomena can be observed. In Fig. 8 a very ast area o cutting can be seen. The duration time was only 0.17 s. This small area is not characteristic or the exponential trend. The best trend line was 5 th degree polinom. On the diagram it can be noticed that curve in the middle part was gently sloping which happened because, owing to cutting temperature, the Fig. 10. hip coloured due to cutting temperature 39 RHIWUM INŻYNIERII PROUKJI

4 JÁNOS LÍSK / PROUTION ENGINEERING RHIVES 16 (2017) The results are shown in 2 diagram (but the results which could be seen on the diagrams was three-dimensional F c,, v c ), in Figure Main cutting orces (F c ) were ormed by the known proessional literature at material 45. y increasing o eed () the chip cross section and orces also increases. Thereore, while increasing cutting speed (v c ), a small decrease is detected. The cutting temperature is established similarly, like in the literature. It varies in using the II. tool, where cutting temperature increased greatly with increasing o cross section. ue to the chip breaker o II. tool which has another design, the chip goes longer section on the insert. Thereore, it will have a higher riction. It conirms temperature recordings. Forces were inversely proportional as compared to 45, at material POM. This is because the material has a worse thermal conductivity. The material sotens quickly and energy o chip removal will be smaller. It shows itsel at evolution o cutting temperatures, too. In this case higher eed and lower cutting speed has a better impact at using o II. tool. It means, that higher technological parameters had a beneicial impact on cutting temperature. It also resulted in orces, which decreased at using o bigger parameters. It has a positive impact on the economy o cutting. Supervising o critical cutting temperature (which is dierent in all materials), because i it reaches this temperature at plastics, it can result in damage o material. ontour Plot o vs ; < > 550 Material 45 ontour Plot o vs ; Fig. 13. Main cutting orce () evaluation with two variables ( and ) at machining POM material and. Fig. 14. Main cutting orce () evaluation with two variables ( and ) at machining POM material and. ontour Plot o vs ; ontour Plot o vs ; Material 45 < > 50 < 50,0 50,0 52,5 52,5 55,0 55,0 57,5 > 57,5 < 270, , , , , , ,000 > 340,000 Fig. 11. Main cutting orce () evaluation with two variables ( and ) at machining 45 material and. Fig. 15. utting temperature evaluation with two variables ( and ) at machining 45 material and. ontour Plot o vs ; < > 550 Material 45 ontour Plot o vs ; < > 325 Material 45 Fig. 12. Main cutting orce () evaluation with two variables ( and ) at machining 45 material and. Fig. 16. utting temperature evaluation with two variables ( and ) at machining 45 material and. RHIWUM INŻYNIERII PROUKJI 40

5 JÁNOS LÍSK / PROUTION ENGINEERING RHIVES 16 (2017) ontour Plot o vs ; < > 102 also uncertain, and here was the biggest prospect o the tool crash. Fig. 17. utting temperature evaluation with two variables ( and ) at machining POM material and. ontour Plot o vs ; Fig. 20. First contact o the tool with the work-piece < > 115 Fig. 18. utting temperature evaluation with two variables ( and ) at machining POM material and. uring the measurement the High Speed amera (HS) system can be used. The base o HS in this article was a better understanding o the indent area zone. Fig. 8 shows the indent area and its size. On the other hand, there were our dierent zones in the indent area, which can be seen in Fig. 19. The irst was the irst contact o the tool with the work-piece (Fig. 20). ter that, in the second zone there is no cutting area, this is the plastic deormation burnishing zone (Fig. 21). In Fig. 22 the hal cutting area can be seen, which can represent o the transition rom the deormation zone to the cutting zone. t the end, in Fig. 23 the area where the tool is working with ull chip area can be seen. Fig presents cutting polymer material. While cutting steel similar situations and indent area zones occur. Fig. 21. No cutting zone Fig. 22. Hal cutting zone Fig. 19. The indent are zones t the time o the irst contact, the material has a signiicant resistance at the ront o the tool. This area was Fig. 23. utting zone In the second zone we have burnishing occurs. Fig. 19 we shows a signiicant increase o the orce rom point 1 to 2, which is typical or this area. onsequently, the cutting temperatures also increased here. 41 RHIWUM INŻYNIERII PROUKJI

6 JÁNOS LÍSK / PROUTION ENGINEERING RHIVES 16 (2017) ter the increase o orce and cutting temperature gently sloped area occurs. Here, the material was soter and the cutting is easier than in the case o the previous part. Finally, in the ourth zone there is a ull chip area cutting zone, and here the cutting orce reaches the maximum value. From this point the orces did not increase, it rather stagnated around a value. This area is called cutting zone, and values rom this sector we can be used or standard evaluations. In every experiments, it is very important to obtain eect o the cutting parameters and their response to attendants. In this article, the MINIT statistical sotware can be used. With the help o this sotware, the ull actorial experiments were planned, and some crucial things were also evaluated. Fig present the Pareto charts o the main eects. Firstly, the main eects o cutting orces. Term 0 28,9 Lenth's PSE = 11,25 Term Pareto hart o the Eects (response is, lpha = ) 200 Eect Fig. 24 Pareto chart o main cutting orce 0 19,3 Lenth's PSE = 7,5 50 Fig. 25. Pareto chart o cutting temperature 300 Pareto hart o the Eects (response is, lpha = ) Eect Factor Factor Name Tool Material Name Tool Material The chart clearly shows the main eect was the material, eed-material, eed and cutting speed-material. It was very interesting, because i the material is let, the main eect was the eed and cutting speed, and the eed had a bigger eect (one o the chip are actor) than the cutting speed. Fig. 25 shows a similar situation, but there is an additional eect, i.e., the tool. Thereore, it can be deinitely stated that the tool and its conductivity have a big impact on the evaluation o cutting temperatures. 4. Summary and conclusion This article is an introduction to the research o chip removal mechanism. The goal is to explore chip removal mechanism o more plastic or composite material. Modern statistical sotware o today and dierent simulation sotware and measuring tools aid in exploring o never phenomena and mechanisms. In the uture, the experiment has been planned to be repeated with the use o other materials, tools, or cutting parameters. cknowledgements This research is supported by EFOP project. The Project is supported by the Hungarian Government and coinanced by the European Social Fund. Reerence VILLE ON: productdetails.aspx?c=q-nh tf%201125#query=%7% 22n%22:%22Insert%22,%22l%22:%22%22,%22r%22:%5%5,%22c %22:%5 U J., I ÉKÉS J Teoretické základy obrábania kovov. la, ratislava. ZVR M., UK E Multi-dimensional chatter stability or enhanced productivity in dierent parallel turning strategies, In International Journal o Machine Tools and Manuacture, Volume 123, LÍSK J., GÁL Turning o omposites. Factory utomation, Veszprém, MRKOPOULOS.P Finite element methods in manuacturing processes. Sotcover, 关键词切割力切割温度高速相机聚合物车削 抽象 切割钢和聚合物材料时的切屑现象 60 年代和 70 年代的研究开始处理芯片特性的形状 然后可以通过测量工具园进行有限的研究 在这样的研究中, 不同的芯片形成模型变得很熟悉, 例如 Time 或 Merchant 模型 文章的目的是深入了解一些伴随的现象, 同时切割不同的材料和各种工具 在实验设计中, 考虑了不同变量对于每个变量的可能影响 在改变切割速度和进给的同时, 测试了具有两个刀片 ( 两个不同边缘设计 ) 的两个工件 (45,POM) 在测量期间, 测试了在 5000Hz 信号接收处的切割力, 或者评估了不同实验设置下切割温度的演变 芯片特性由高速摄像机测量 相机与 P 连接, 用于实时记录和控制实验程序 高速摄像机的频率与切割力测量系统的频率相似 系统设置同步提供了这种相似性 RHIWUM INŻYNIERII PROUKJI 42