Pocket milling of composite fibre-reinforced polymer using industrial robot

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2nd CIRP Conference on Composite Material Parts Manufacturing 2nd CIRP on Conference onMaterial Composite Material Parts Manufacturing 2nd CIRP Conference Composite Parts Manufacturing (CIRP-CCMPM 2019)

Pocket composite fibre-reinforced polymer using Pocket milling milling of of28th composite fibre-reinforced polymer using industrial industrial robot robot CIRP Design Conference, May 2018, Nantes, France Ever Grisol de Meloa,b*, Tiago Borsoi Kleinb, Sascha Reinkoberb,

b Ever Grisolto deanalyze Meloa,b*, Tiago Borsoia Kleinband , Sascha Reinkober , A new methodology the functional physical architecture of b Jefferson de Oliveira Gomes a, Eckart Uhlmannb Jefferson de Oliveira Gomes , Eckart Uhlmann existing products for an assembly oriented product family identification Department of Mechanical Engineering, Aeronautics Institute of Technology (ITA), Marechal Eduardo Gomes 50, São José dos Campos, 12228-900, Brazil a a

Department of Mechanical Engineering, Aeronautics Technology (ITA), Marechal Gomes São José dos Germany Campos, 12228-900, Brazil b Fraunhofer Institute for ProductionInstitute Systemsofand Design Technology (IPK), Eduardo Pascalstraße 8-9,50, Berlin, 10587, b Fraunhofer Institute for Production Systems and Design Technology (IPK), Pascalstraße 8-9, Berlin, 10587, Germany

Paul Stief *, Jean-Yves Dantan, Alain Etienne, Ali Siadat

* Corresponding author. Tel.: +49-303-900-6245. E-mail address: [email protected] or [email protected] * Corresponding Tel.:Supérieure +49-303-900-6245. E-mail address: [email protected] or [email protected] Écoleauthor. Nationale d’Arts et Métiers, Arts et Métiers ParisTech, LCFC EA 4495, 4 Rue Augustin Fresnel, Metz 57078, France

* Corresponding author. Tel.: +33 3 87 37 54 30; E-mail address: [email protected]

Abstract Abstract

In the recent decades, aerospace and automotive industry are replacing metal materials by carbon fibre-reinforced polymer (CFRP). The In the recent decades, aerospace and automotive industry are replacing metal materials by carbon fibre-reinforced polymer (CFRP). The Abstract mechanical properties of CFRP materials are very attractive due to high mechanical strength and low weight. However, there are technological mechanical properties of CFRP materials are very attractive due to high mechanical strength and low weight. However, there are technological challenges in the machining process for this type of material. The anisotropy and inhomogeneity of the CFRP cause high wear of the cutting tool, in the machining process thistowards type of more material. The anisotropy and inhomogeneity of the CFRP cause high wear of the cutting Inchallenges today’s delamination, business environment, the for trend product variety and customization is unbroken. Due to this the needtool, of spalling, fuzzing, fibre pull-out, matrix cracking, thermal degradation and resulting in poor quality ofdevelopment, the part. In addition, the spalling, delamination, fuzzing, fibre pull-out, matrix cracking, thermal degradation and resulting in poor quality of the part. In addition, the agile and reconfigurable production systems emerged to cope with various products and product families. To design and optimize production requirement for processes that are more flexible within a larger work area makes the use of industrial robot (IR) a promising alternative. The requirement for processes that are more flexible within a larger work area makes the use of industrial robot (IR) a promising alternative. The systems wellevaluated as to choose the optimal product matches, product analysis methods are influences needed. Indeed, most conditions of the known methods aimThe to present as work the performance of the IR regarding motion accuracy, which machining of composites. present work evaluated the performance of the IR regarding motion accuracy, which influences machining conditions of composites. The analyze a product or one product onout theusing physical level. Different product families, however, may differ largely terms of factors. the number trimming in a pocket milling wasfamily carried the factional replication of the 3k factorial design, with three levelsinand three The and tool trimming in a pocket milling was carried out using the factional replication of the 3k factorial design, with three levels and three factors. The tool nature of components. Thisspindle fact impedes efficient comparison and choiceInoforder appropriate product family machining combinations for the production speed nanwere selected as input parameters. to evaluate the robotic performance, resultant geometry, feed rate fz and geometry, feed rate fz and spindle speed n were selected as input parameters. In order to evaluate the robotic machining performance, resultant cutting A force dimensional were selected as output parameters be assessed. After obtaining the force equations system. newFmethodology proposed toquality analyze existing products in view of their to functional and physical architecture. Theresults, aim is to cluster r, surface andis cutting force Fr, surface and dimensional quality were selected as output parameters to be assessed. After obtaining the force results, equations these infor neweach assembly product families for the optimization of existing assembly andshow the creation wereproducts generated cuttingoriented tools and Response Surface Methodology (RSM) was applied. Thelines results that the of usefuture of IRreconfigurable is a promising were generated for each cutting tools and Response Surface Methodology (RSM) was applied. The results show that the use of IR is a promising alternative for the Based CFRP on machining of large aeronautical components. assembly systems. Datum Flow Chain, the physical structure of the products is analyzed. Functional subassemblies are identified, and alternative for the CFRP machining of large aeronautical components. a functional analysis is performed. Moreover, a hybrid functional and physical architecture graph (HyFPAG) is the output which depicts the © 2020 Authors. Published by B.V. similarity between product families by providing 2019 The Authors. Published by Elsevier Elsevier B.V. design support to both, production system planners and product designers. An illustrative © 2019 The Authors. Published by Elsevier B.V. This is an access article under the BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) example of open a nail-clipper is used toofexplain the proposed methodology. industrial case on study on two product of steering columns of Peer-review under responsibility the CC scientific committee of the 2nd An CIRP Conference Composite Materialfamilies Parts Manufacturing. scientific committee committee of of the the 2nd 2nd CIRP CIRP Conference Conference on on Composite Composite Material Material Parts Parts Manufacturing. Manufacturing. Peer-review under responsibility of the scientific thyssenkrupp Presta France is then carried out to give a first industrial evaluation of the proposed approach. polymer (CFRP); ©Keywords: 2017 Thecarbon-fibre-reinforced Authors. Published by Elsevier B.V.industrial robot (IR); machining process; high speed cutting (HSC) Keywords: carbon-fibre-reinforced polymer (CFRP); industrial robot (IR); machining process; high speed cutting (HSC) Peer-review under responsibility of the scientific committee of the 28th CIRP Design Conference 2018. Keywords: Assembly; Design method; Family identification

reduce resultant cutting force (Fr) [1,5]. According to Korn reduce resultant cutting force (Fr) [1,5]. According to Korn (apud Wu [6]), in the production of aerospace components, the (apud Wu [6]), in the production of aerospace components, the best machining strategy is the combination of HSC and (High Over the last decades, the usage of lightweight materials, best strategy the combination of HSC andand/or (High Over the last decades, the usage of lightweight materials, of 1.mainly Introduction themachining productMachining) range andisHPM. characteristics Performance The HPMmanufactured focuses to maximize carbon fibre–reinforced polymer (CFRP), continually Performance Machining) HPM. The HPM focuses to maximize mainly carbon fibre–reinforced polymer (CFRP), continually assembled in this system. In this context, the main challenge in the material removal rate. In addition, a surface with better grew in the aerospace, naval, sport, construction and medical the material removal rate. In addition, atosurface with single better grew in to the aerospace, naval, sport, construction and medical Due the fast development in the domain of modelling and analysis is now not only cope with quality due to the multi-tooth cutting of the milling can be industry [1]. An aircraft can have up to 50% of its structural quality due to the product multi-tooth of the millingfamilies, can be industry [1]. Anand aircraft can have trend up to of 50% of its structural communication an and ongoing digitization products, limited rangecutting or existing product generateda[7]. weight in composite [2] automobiles, around 8.5% [3].and [3] . generated [7]. weight in composite [2] and automobiles, around 8.5% digitalization, enterpriseswith are greater facing important also main to be challenges able to analyze and tomilling compare productsarise to define The use of manufacturing IR becomes an alternative flexibility, but The in pocket of CFRP’s from The use of IR becomes an alternative with greater flexibility, newThe mainfamilies. challenges in pocket millingthat of CFRP’s arise from challenges in today’s market environments: a continuing product It can be observed classical lower cost and larger work area to CFRP machining. the anisotropy and inhomogenity of the composite,existing which lower cost and larger work area to CFRP machining. the anisotropy and inhomogenity of the composite, which tendency product development families are regrouped in function of clients features. However,towards IR’s arereduction exposed of to high mechanical loads times duringand the product generates spalling, delamination, fuzzing, fibreorpull-outs, However,product IR’s arelifecycles. exposed toInhigh mechanical loads during the However, generates assembly spalling,oriented delamination, fuzzing,arefibre pull-outs, shortened addition, there is an increasing product families hardly to find. CFRP machining, which can cause dimensional errors in the matrix cracking, thermal degradation [8,9]. The damages CFRP machining, which can cause dimensional errors in the matrix cracking, thermallevel, degradation [8,9]. The damages demand of customization, being at the same time in a global On the product family products differ mainly in twoa caused in the machining process of the CFRP may have workpiece. The correct adjustment of the cutting parameters can caused in the machining process of the CFRP may have a workpiece. The correct adjustment of thethe cutting parameters can main competition with competitors all over world. This trend, characteristics: (i) the number of components and (ii) negative impact on the surface and dimensional quality and the can help to reduce efforts and therefore improve IR stability during negative impact on the surface and dimensional quality and can help to reduce efforts and therefore improve IR stability during which is inducing the development from macro micro type of components (e.g. mechanical, electrical,Furthermore, electronical).the therefore cause the rejection of the workpiece. machining. Furthermore, according to Klocke [4] it istorequired therefore cause the rejectionconsidering of the workpiece. Furthermore, the machining. Furthermore, according to Klocke [4] itaugmenting is required markets, results in diminished lot sizes due to Classical methodologies mainly single products cutting force is an important indicator of machinability for to consider all relevant machining parameters. Many works cutting force is an important indicator of machinability for to consider all relevant machining parameters. Many works product varieties low-volume [1]. or solitary, already existing product families analyze the (HSC) production) can significantly milling of CFRP [10]. The control of the cutting force may show that the use(high-volume of high-speedtocutting cutting (HSC) can significantly milling of CFRP [10]. The control of the cutting force may show that the use of high-speed To cope with this augmenting variety as well as to be able to product structure on a physical level (components level) which identify possible optimization potentials in the existing causes difficulties regarding an efficient definition and 2212-8271 © 2019 The Authors. Published by Elsevier B.V. 2212-8271 2019 responsibility TheitAuthors. Published Elsevier B.V. ofknowledge production system, is important to by have a precise comparison of different families. Addressing this Peer-review©under of the scientific committee the 2nd CIRP Conference on Composite Material product Parts Manufacturing. 1. Introduction 1. Introduction

Peer-review under responsibility of the scientific committee of the 2nd CIRP Conference on Composite Material Parts Manufacturing.

2212-8271 © 2020 The Authors. Published by Elsevier B.V. This is an©open article Published under theby CC BY-NC-ND 2212-8271 2017access The Authors. Elsevier B.V. license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of scientific the scientific committee theCIRP 2nd Design CIRP Conference on Composite Material Parts Manufacturing. Peer-review under responsibility of the committee of the of 28th Conference 2018. 10.1016/j.procir.2019.09.006

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eliminate the delamination in the milling process [5]. In addition, robotic machining processes can be limited by low stiffness compared to CNC machine tools [11]. Despite the research published in the last decades on the process of machining CFRP, this theme is still in early stages of development, since this material is heterogeneous and is composed of strong and brittle reinforcing fibres, which make it difficult to machine. According to Iglesias et al. [12], the manufacturing process using IR is constantly increasing around the world and forecasts indicate that it will continue to rise. According to DePree et al. [13], milling, cutting, and drilling operations using industrial robots are only applied to low-hardness materials such as wood, plastic and foams, Fig. 1. Materials such as aluminum, copper and some types of composites for the drilling and deburring processes are currently being tested and applied. However, milling operations still present technical challenges that must be addressed. Furthermore, IR presents low precision and sensitivity to process loads[14]. Due to constant modernization and automation, IR functions are being used in all industrial branches, with demands for a permanent change in manufacturing lines [15]. The use of IR in production cells is recognized as a considerable gain in terms of flexibility [16,17]. Abeliansky et al. and Graetz et al. [18,19] said that the use of IR increased productivity and added value. In addition, the use of the IR in the machining process of CFRP can provide a reduction in the costs. However, Reinkober [20] said that currently most installed robotic cells are only used for finishing processes because of lower applied forces. This is a reason to believe that IR will continue to increase productivity as their applications are further developed.

IR LDS RSM ae ap Fr fz n vf

of the IR in milling of CFRP. In addition, the analysis of the Fr was carried out to assess this application. The machining tests were carried on a 6-axis KUKA IR type KR60 HA. The IR is equipped with the application module Milling ES350L 4P nominal power 8kW – HSD SPA, and an auxiliary system for suctioning the particulates, manufactured in department production system of the Fraunhofer IPK, Fig.2a. The selected machining operation to be analyzed in this study was full slotting, Fig. 2b. The CFRP workpieces were 4 mm thick with 11 inner layers of unidirectional fibre. The composite is type SGL CARBON SIGRAFIL C30 T050 and epoxy resin content of 35 %. The cutting tools used in these tests were prepared by Hufschmied Zerspanungssysteme. GmbH. The cutting tool geometry F0–068HO080-E has 4 cutting teeth, 4 secondary teeth, and right cutting. The cutting tool geometry F1–068ECOL080 has 9 teeth in right helix, with right cutting and optimized chip breaker division; and the cutting tool geometry F2–108H080080 has 2 teeth, narrow-toothed with pyramidal edge, with grinding functionality to the matrix of the composite, Fig.2c. All tool has coating material C type and coating process with PVD. Prototyping

Component

Final Product

Plastic Copper Aluminum Cast Iron Steel Glass

Nomenclature ANOVA CFRP CNC DOE HPM HSC IPK

181

Analysis of Variance Carbon-Fibre-Reinforced Polymer Computer Numeric Control Design of Experiment High Performance Machining High Speed Cutting Institute for Production Systems and Design Technology Industrial Robot Least Significant Difference Response Surface Methodology width of cut depth of cut Resultant cutting force feed for tooth spindle speed (rotation per minute) feed rate

2. Materials and Methods This work evaluated the machinability through dimensional and surface quality analyses, in order to study the performance

Titanium Composite

All

Milling

Drilling

Cutting

Fig. 1. Application of industrial robots: material and process. Adapted from [13].

Pockets length of 115 mm were full slotting milled during the experimental procedure. The tests were performed 3 times for each combination of parameters, to ensure repeatability of tests. In order to allow an analysis of the machining processes for the CFRP material using IR the aimed dimensional quality had to be defined as a first step. Hashish [21]], affirmed that manufacturer’s specifications identify the tolerances, surface finish, and composite integrity allowances. The accuracy requirement was defined according to information from companies in the aeronautical sector: 0.15 mm for high precision parts. Another requirement was used: fibre protrusion and fibre pull-out. According to Ulhmann et al. [22], fibre protrusion is less important for assembly activities, but becomes relevant in the varnishing of the workpieces. Fibre pull-out can reduce the workpiece thickness and therefore influence the strength and parallelism of parts for subsequent riveting and assembly processes. A combination of cutting parameters typically employed in industrial applications and

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found in literature were chosen in these experiments. The ae = 8 and ap = 4 mm were kept at a constant.

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the piezoelectric platform, the data is converted into force and analyzed through software using Python language. Analysis of variance (ANOVA), Shapiro - Wilk and Tukey Test were used to evaluate the Fr. Three levels were specified for each factor as showed in Table 1. Table 1. Summary of process parameters. Parameters designation

Tool

Feed rate vf (mm/min)

Spindle speed n (rpm)

A

B

C

1

F0

1000

12000

2

F1

2000

24000

3

F2

4000

36000

Factor

Level

3. Results and Discussions

Fig. 2. Setup – (a) robotic cell with the suction system, (b-1) CFRP machining geometry, (b-2) layers of CFRP workpiece and (c) cutting tools.

In order to improve the existing machining process, the relationship between the inputs and outputs should be evaluated. Design of Experiment (DOE) is a statistical formal methodology that allows to establish statistical correlations between a set of inputs variables with chosen outcomes of the process under certain uncertainties [23]. This study used the 3k factorial design i.e. a factorial arrangement with k factors, each at three levels. This system of notation was specified because it facilitates the geometric view of the design and because it is directly applicable to regression model, blocking, the construction of fractional factorials. In addition, the Taguchi method was used, in order to overcome numerous experiments associated [24]. However, Plackett and Burman [25] showed that the full factorial design can be fractionalized, where the standard error is a multiple of 4. Thus, this study used Taguchi robust design methods – Plackett-Burman designs, in particular. The study of process parameters (factor and level) is shown in Table 1. The outputs to evaluate the performance of IR in pocket milling, as previously mentioned, are Fr and surface quality. The analysis of the surface quality – topic 3.1 – is measured using a Conrad Electronics SE optical microscope whose USB camera has an optical resolution of 6.0 million pixels. The camera's magnification range varies from 10 to 200 times. The analysis of surface quality was carried out qualitatively. The Fr were measured by fixing the CFRP plates on a support directly attached to a Kistler type 9257B, force measurement piezoelectric platform, with the acquisition of Fx, Fy and Fz forces. The voltages signals were exported to Labview for further analysis. After collecting the voltages signals from

The described tests were conducted in order to evaluate the performance of the IR in CFRP machining. The use of HSC besides decreasing the Fr also contributes to a better stability of the IR. Additionally, as observed by Uhlmann et al. [26] in composite machining tests with CNC machine, the HSC processes showed better surface qualities, with no delamination, fibre protrusion or thermal effects on the workpiece surface. However, the intensity of fluffing/delamination damage increases with increasing speed, if the feed per tooth remains fixed [10]. In the next sections, data will be presented on the surface and dimensional quality, of Fr and statistical analysis for the parameters presented in Table 1. 3.1. Surface and dimensional quality of CFRP The quality of the CFRP machined part is assessed with respect to delamination and fibre protrusion, and this is particularly crucial to avoid parts rejection. Unfortunately, currently there is no standardized method for CFRP quality control, what makes the analyses strongly conditioned to each end user. According to Bolar et al. [27], good surface finish is an important requirement for components used in the aerospace and automobile industries. The poor surface finish may lead to the development of residual stress and component rejection. The surface and dimensional quality of the part is influenced by the cutting parameters, cutting tool, and process stability. In order to analyse the effectiveness of the HSC process with IR, the quality criteria fibre pull-out and fibre protrusion were investigated via microscope. Also, some authors show that a higher vf affects the surface quality, causing local cracks and delamination[28]. However, other works showed that n ≤ 12000 rpm tend to generate better surface qualities, with no delamination, fibre protrusion or thermal effects on the workpiece [1,5,22]. The influence of the cutting parameters and tool cutting geometry on the quality in terms of fibre pull-out and cracks was investigated to classify the best machining combinations using the IR. Fig.3 shows the machined surface quality arising from combinations of the cutting parameters: vf =1 and 4 m/min and 12000 and 36000 rpm, for the three cutting tools of

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different geometries used in these experiments. Cutting tools F0 and F1 presented a lower formation of fibre pull-out and cracks as spindle speed increases, compared to cutting tool F2, regardless of the selected cutting parameters. This confirms the efficiency of HSC technology applied in CFRP machining. The cutting tool F2 performed well only for low feed rate. Cutting tools F0 and F1 provide better performance in machined surface qualities, possibly due to their geometries with cutting edges. This geometry was able to cut the matrix and fibres. However, the cutting tool F2, with narrow-toothed geometry, crushes the material causing, in general, a poor surface machined quality for the tested cutting parameters. However, the correct application of cutting parameters can provide a better IR stability during CFRP milling.

183

Table 1. Interactions of vf and tool obtained the greatest values when compared in pairs, Table 2. A second analysis was performed for each cutting tool. The cutting tool F1 presented the highest values of Fr for all tested conditions. The cutting tool F2, which had the poor surface quality performance, showed lower values of Fr.

3.2. Resultant cutting force of CFRP machining The use of HSC in the CFRP milling causes a reduction of Fr, a better part quality and provides greater productivity. It should be remembered that Fr are higher with the increase in feed rate vf. However, high spindle speeds help reduce Fr, Fig.4, present the results obtained for the cutting tools F0, F1, and F2, respectively. The cutting tool F0 produced forces Fr ≤ 200N for n = 12000 rpm and vf = 2m/min. During milling with a feed rate of vf = 4 m/min and n = 12000 rpm the resultant cutting force was Fr = 159 N. For the same feed rate and higher spindle speed the Fr is 80 N. Increasing the feed rate from 1 to 4 m/min resulted in a 100% increase in Fr for the cutting tool F0 at constant spindle speed. The cutting tool F1 presented for all conditions the highest values of Fr compared and the cutting tool F2 obtained the lowest Fr values. The F2 cutting tool geometry provided less effort for the IR, which assists in greater IR stability. However, as seen in the previous topic, the cutting tool F2 did not present good performance in terms of machined surface quality for these cutting parameters. The F2 tool have narrow-toothed with pyramidal edge, with grinding functionality to the matrix of the composite. However, for cutting speed tested, the F2 tool geometry increases the cracks. Regarding the surface quality criteria, no significant influence of the cutting direction (up/down-milling) could be identified. 3.3. Statistical analysis to experimental validation of resultant cutting force Although the fact that innumerable empirical models have already been suggested and validated for the resultant cutting force Fr, experimentally measured data are always necessary. Thus, a statistical analysis was done to validate the experimental tests. The adequacy of the tests was checked with the help of analysis of variance (ANOVA) and further confirmed by evaluating the values of F-ratio. This analysis was conducted under consideration of a 95% confidence level for each performance characteristic. Through ANOVA, it was observed that the geometry of the cutting tool had a 60.20% influence on the resultant Fr, followed by the vf and n, 17.84% and 13.12% respectively,

Fig. 3. Top view of the slot to comparison of surface quality criteria for workpiece – cutting parameters and cutting tool geometries.

The statistical analysis for cutting tool F0 showed that the feed rate has a 63.94% influence on the resulting Fr and the cutting speed has 31.81% influence, Table 3. These data are in accordance with the literature. The feed rate is the main factor influencing the Fr [40] and the cutting speed assists in reducing the Fr [9]. However, tests with cutting tool F1 showed that the cutting speed had a slightly greater influence on the Fr. The LSD showed that n and vf parameters have independent behaviour. The data for cutting tool F1 presented a balance on the influence of the Fr for n and vf, 53.22% and 48.16% respectively. The vf = 2 and 4 m/min showed similar characteristics, as well as n = 12000 and 24000 rpm. This can be observed in the RSM because the cutting tool F1 has a larger area in this range. The cutting tool F2 also presents a balance in the influence on the Fr for the variables n and vf, 44.37% and 49.76%, Table 3. The statistical analysis was possible to generate equations of cutting forces and also RSM. Fig. 5 shows the surface response

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184

(RSM) of the forces for the three cutting tools. The cutting tool F2 showed a larger area for lower cutting force values (0-80 N). Only the cutting tool F1 had a cutting force higher than 240 N, mainly for higher feed rates.

5

respectively. This describes that more 95% of the total variability is validated by the proposed quadratic model. For Equations 1, 2 and 3, the values of determination coefficient R2 are 99.99%, 95.15%, and 98.31%, respectively. This shows that more 95% of the total variability is validated by the proposed quadratic model.

Fig. 4. Results of resultant cutting force. Table 2. ANOVA – S/N ratio. Factor

Sum Sq

Mean Sq

P value

Influence%

n

19700

9850

0.00

13.12

vf

26800

26800

0.00

17.84

Cutting tool

90415

45208

0.00

60.20

n : vf

48

48

0.04

0.03

n : Tool

6658

1664

0.01

4.43

vf : Tool

965

483

0.02

0.64

n : vf : Tool

5602

2801

0.00

3.73

Table 3. ANOVA – Tool. Factor

Sum Sq

Mean Sq

P value

Influence %

F0 vc

6289

3144

0.00

31.81

vf

12641

12641

0.00

63.94

vc : vf

841

841

0.00

4.25

Fig. 5. Response Surface Methodology for tools.

Fr(F0)=56.4–5.4*e-2*n*40.2*vf +1.7*e-2*n2–2.3*e-2*n*vf

(1)

Fr(F1)=63.9–0.7*n–9.3*vf –7.6*e *n +0.1*n*vf

(2) (3)

-4

F1

2

vc

16187

8096

0.00

53.22

Fr(F2)=55.7–0.1*n+27.8*vf +8.6*e-5*n2–1.9*e-2*n*vf

vf

9522

9522

0.00

48.16

vc : vf

4705

4705

0.01

23.80

4. Conclusions

F2 vc

4370

2185

0.00

44.37

vf

4901

4901

0.00

49.76

vc : vf

578

578

0.01

5.87

The Equations (1, 2 and 3), it is shown that the value of determination coefficient R2 is 99.99%, 95.15%, and 98.31%,

This work presents a study on the effects of feed rate vf, cutting speed n and cutting tool geometry in CFRP milling using IR. The surface and dimensional quality were used as performance criteria. The following conclusions have been drawn from the present experimental investigation:



HSC application provides a better surface finish in terms of fibre pull-out. However, it is important to remark that high values of the cutting speed can cause delamination.



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



 

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Ever Grisol de Melo et al. / Procedia CIRP 85 (2019) 180–185 Author name / Procedia CIRP 00 (2019) 000–000

The geometry of the tool have influence in this application in both surface quality and resultant cutting force Fr. As stated earlier, it is critical to reduce the effort during machining using IR. Therefore, the choice of cutting tool geometry must be carefully made. There were no failures by delamination for any of the tests performed. However, fibre pull-out was noted. The cutting tools F0 and F1 presented a better performance for surface quality. The cutting tool F2 gives better Fr performance when compared to cutting tools F0 and F1. The cutting tool F2 for maximum vf = 4 m/min showed Fr of 113 N (n = 12000 rpm) and 52 N (n = 36000 rpm). Via ANOVA, it was observed that the cutting tool geometry had an influence of 60.5% on the resulting Fr. The F1 cutting tool presented the highest values of Fr. The LSD showed that n and vf behave independently. It is known that vf is mainly the parameter that influences the Fr. However, n has proven to be an alternative to reduce shear forces. By means of the statistical analysis, it was possible to generate force equations for each cutting tool which resulted in one RMS. The use of commercial IR becomes a promising technology to meet the demands of Industry 4.0. The IR showed an excellent performance to the CFRP machining process

Acknowledgements This work was supported by the Coordination for the Improvement of Higher Education Personnel – CAPES (grant number 88882.180844/2018-01); German Academic Exchange Service – DAAD (grant number 91744162); Institute for Production Systems and Design Technology – IPK ; and Aeronautics Institute of Technology – ITA. References [1] Lopresto V, Caggiano A, Teti R. High Performance Cutting of Fibre Reinforced Plastic Composite Materials. Procedia CIRP 2016;46. p.71–82. [2] Hiken A. The Evolution of the Composite Fuselage: A Manufacturing Perspective. In: Aerospace Engineering: IntechOpen; 2019. [3] Ahmad J. Machining of Polymer Composites. Boston, MA: Springer US; 2009. [4] Klocke F, Kuchle A. Manufacturing processes. Berlin: Springer; 2009. [5] M'Saoubi R, Axinte D, Soo SL, et al. High performance cutting of advanced aerospace alloys and composite materials. CIRP Annals 2015;64-(2). p.557–80. [6] Yier Wu. Optimal Pose Selection for the Identification of Geometric and Elastostatic Parameters of Machining Robots 2014. p.230. [7] Youssef HA, El-Hofy H. Machining technology: Machine tools and operations. CRC Press; 2008. [8] Hejjaji A, Zitoune R, Crouzeix L, Le Roux S, Collombet F. Surface and machining induced damage characterization of abrasive water jet milled carbon/epoxy composite specimens and their impact on tensile behavior. Wear 2017;376-377.

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