This paper aims to quantitatively analyze the relationship between forces acting on the tool tip and tool movement during drilling operations. The study encompasses axial and lateral vibrations ...superimposed on the nominal tool movement, arising from rigid body motion (rotational and axial velocities). Specifically, only forces attributed to the cutting process are considered, excluding considerations of indentation forces around the chisel edge. The research adopts a generalized approach, spanning from tool measurements to establishing the force model. The investigation involves measuring cutting forces and correlating them with the varying rake and inclination angles of the drill’s cutting edges. An analytical model is proposed to describe the distribution of all local force components along drill edges, considering the evolution of forces and geometry. The dynamic coefficient matrix is evaluated by using the identified cutting coefficient and tool geometry. Validation of the proposed methodology is demonstrated through drilling experiments on Ti6Al4V alloy, utilizing three solid carbide drills with distinct geometries. The proposed procedure allows complete identification of the dynamic characteristics from the measurements taken at the entrance stage of hole drilling operation. Moreover, the influence of tool geometry on cutting coefficients and dynamic coefficient matrices are discussed.
•A novel method is developed to achieve minimized experimental effort to identify cutting coefficients in drilling process.•Experiments with industrially relevant tools validated the accurate predictions of transient drilling axial force and torque.•The method is extended to inversely obtain the dynamic coefficient matrix, for the first time, from experimentally measured forces.•Effects of geometry and dynamic interactions were demonstrated using three solid carbide drills with distinct geometries.
Tool wear of coated drills in drilling CFRP Wang, Xin; Kwon, Parick Y.; Sturtevant, Caleb ...
Journal of manufacturing processes,
January 2013, 2013-1-00, 20130101, Letnik:
15, Številka:
1
Journal Article
Recenzirano
This study aimed to investigate the wear of certain coated drills when drilling carbon fiber reinforced composites (CFRP). Three different drills were used in the drilling experiments: uncoated, ...diamond coated and AlTiN coated carbide (WC–Co) drills. The tool wear in CFRP machining was quite different from that in conventional metal machining. The primary wear type was a dulling or blunting of the cutting edge, which has been referred to as edge rounding wear or edge recession. In this paper, a hypothesis has been developed to explain the edge rounding wear in CFRP machining. Due to the fracture-based chip formation of CFRP, there is lack of the work material stagnation zone in front of the cutting edge, which normally prevents the edge wear in metal machining. Series of wear lead to rapid dulling of the cutting edge. The resistance to edge rounding wear on the coated as well as uncoated drills has been investigated. The diamond coating significantly reduces the edge rounding wear. However, AlTiN coated drills showed no visible improvement over the uncoated carbide drill, despite of their high hardness, thus not protecting the drill. The wear mechanisms of the uncoated carbide drill and coatings are discussed. It is believed that the 2-body and 3-body abrasive wear fail to explain the observed tool wear in CFRP drilling. However, the wear of the coatings and uncoated carbide substrate from tribo-meter tests correlated well with the tool wear in the CFRP drilling. Therefore, the tribo-meter test can be used to screen the prospective tool materials before carrying drilling experiment.
Natural fiber-reinforced composite materials are finding wide acceptability in various engineering applications. A substantial increase in the volume of production of these composites necessitates ...high-quality cost-effective manufacturing. Drilling of holes is an important machining operation required to ascertain the assembly operations of intricate composite products. In the present experimental investigation, natural fiber (sisal and Grewia optiva fiber)-reinforced polylactic acid-based green composite laminates were developed using hot compression through film stacking method. The drilling behavior of green composite laminates was evaluated in terms of drilling forces (thrust force and torque) and drilling-induced damage. The cutting speed, feed rate, and the drill geometry were taken as the input process parameters. It was concluded that all the three input process parameters affect the drilling behavior of green composite laminates. The drill geometry was established as an important input parameter that affects the drilling forces and subsequently the drilling-induced damage.
The new developed high-strength CFRP laminates are widely employed in varieties of applications and are mainly used in main loadbearing structural components of large commercial aircrafts. Drilling ...is one of the important operations in manufacturing composite structure, often a final operation during assembly. Defects such as burrs and delamination in drilling of CFRP are always serious problems and lead to rejection and impose heavy loss. In the present research, the machinability of a new developed high-strength T800S/250F CFRP laminate is evaluated by using CVD coated twist drill and CVD coated dagger drill. The machinability was investigated in terms of drilling forces, burr defect, hole wall surface morphology and delamination damage. The results indicate that feed rate is the most significant factor affecting the machined surface finish followed by the spindle speed. The dagger drill showed excellent drilling performance than the twist drill and was more suitable for drilling of T800S/250F CFRP laminate. The results also highlight the importance of employing the high speed drilling to minimize the drilling-induced defects.
State-of-the-art treatment of such orthopedic diseases as fracture and femoral head necrosis implies the installation of prosthesis or fixed equipment into patients’ injured parts using bone ...drilling. This study proposes an ultrasonic longitudinal torsion-assisted drilling (ULTAD) technique for biotic bone drilling. A comparative experiment was carried out between conventional drilling and ULTAD drilling in biotic bone, namely porcine femur. These tests proved that under the same drilling parameters, the ultrasonic component in bone drilling could reduce the drilling temperature and forces, improve the material removal by chip breaking, shorten the length of bone debris, and facilitate their discharge. Moreover, the proposed ULTAD technique reduced the number, length, and width of microcracks in the borehole wall, thus protecting the drilled biotic bone from internal damage.
Polyimide (PI) and polyetheretherketone (PEEK) are superior high‐performance thermoplastics being extensively used in the fields of fiber‐reinforced polymer composites. However, there is very limited ...literature addressing the machining behavior of the PI and PEEK composites. The present paper aims to conduct a comparative study into the machining characteristics of these two representative high‐performance thermoplastic matrix composites under varying cutting conditions. Machinability aspects of the carbon/PI and carbon/PEEK thermoplastic composites were evaluated in terms of drilling forces, machining temperatures, delamination damage, surface morphologies, hole dimensional accuracy and tool wear. The results indicate that the carbon/PEEK composites generally show a much poorer machinability than the carbon/PI composites in terms of higher drilling forces, higher cutting temperatures, larger delamination extents and excessive tool wear. Since the carbon/PEEK composites exhibit certain ductility leading to the continuous chip formation, the cut hole surface morphologies and dimensional accuracy are much better than those gained in the carbon/PI composites. Both the cutting speed and the feed rate affect significantly the drilling forces and the resulting delamination damage. The fundamental wear mechanisms of drilling carbon/PI composites are abrasion wear in the form of edge rounding and slight chip adhesion, while for the carbon/PEEK composites, they are abrasion, serious chip adhesion because of the high drilling temperatures promoted at the drill‐work interface and catastrophic failures of coating peeling and edge fracture.
High strength to weight ratio along with non-corrosive characteristics make glass fiber reinforced plastics (GFRPs) most promising material in aerospace, navel, automobile and construction sector. ...However its non-homogeneous and anisotropic nature leads to unfavorable hole quality when subjected to drilling. Among all the drilling induced defects delamination has received considerable attention. Delamination of the material at drill entry occurs above critical torque where as it occurs above critical thrust force at drill exit which adversely affect product quality and results into rejection. Paper presents, a mechanistic approach to develop cutting force models to predict thrust force and torque in GFRP drilling. The mechanistic approach exploits different set of fundamentals of the process including speed, feed rate and tool geometry. Tool point angle, diameter and primary cutting edge effects are mainly considered in this model to predict thrust forces and torque for cutting speed and feed rate combinations. Drilling experiments were conducted on unidirectional glass fiber with stacking sequence of (0/90) sheet with carbide drill to study the influence of various combinations of speed and feed on thrust force and torque. Proposed model is validated for the drill point angle, drill diameter and primary cutting edge of drill bit for GFRP drilling over a wide range of machining conditions.
Drilling is used in a very large variety of applications, which is one of the most complex manufacturing processes and is a semi-enclosed cutting process. The use of titanium alloy Ti6Al4V in ...engineering applications has increased in recent years, and in many of these applications drilling is one of the most critical stages in the manufacturing process. Critical issues in drilling of Ti6Al4V are often associated with large drilling forces and short life. Understanding and predicting the drilling forces occurring during drilling of Ti6Al4V would allow extending the currently used optimization methods and proposing new tool geometries and tool materials. The current paper introduces an improved mechanistic model for predicting the drilling force distribution along the main cutting edge and chisel edge of a drill, which considered the effect of feed rate. Based on the definitions of working angles, the equivalent model of drilling is developed. The effect of feed rate on the working rake angle was also investigated. Then, the drilling force model in the main cutting edge is developed based on the oblique cutting model. However, there are two different equivalent regions in chisel edge; here the drilling force model is developed based on orthogonal cutting model and plastic extrusion model, respectively. A special drilling forces distribution experiments are carried out in drilling Ti6Al4V. Good agreement between the measured and predicted drilling forces is found.
The abrasive reinforcement present in ‘Metal matrix composites’ (MMCs) is responsible for numerous machining challenges for the research fraternity. The increase in tool wear, burr formation, surface ...roughness, and increase in cutting forces are few of such machining challenges during the drilling of MMCs. The present research investigation explores the effect of change in drill point geometry on the drilling Quality characteristics (QCs) of the drilled hole wall. The drilling QCs under investigation are, Specific cutting pressure (SCP) and Surface roughness (SR) of the drilled hole wall. The levels of the input process parameters for optimum values of the output responses were established by Taguchi’s methodology. SEM images and contour plots of drilled hole wall have been used to qualitatively explain the drilling behavior of MMCs. The chip formation mechanism observed during drilling establishes the cutting behavior of the different cutting edges of the modified drill point geometry. It has been observed that the single conical chips were produced by primary cutting edge and single ring type chips were produced by secondary cutting edge. The step diameter is the main factor which influences the SCP followed by the feed and point angle. The surface roughness of the drilled hole wall has been governed by the cutting speed, feed and step diameter. Burnishing and honing effect were observed on the drilled hole wall surface because of entrapped free SiC particles using SEM.
Drilling is one of the most important method for hole making in composite materials. Drilling of polymer matrix composites causes substantial damage around the drilled hole. Damage free holes can be ...made using modified drill geometry. The present research investigation focuses on the drill geometry as candidate parameter that influence drilling forces and drilling-induced damage. The four different drill geometries (solid and hollow in shape) are used for drilling in composite materials. The cutting mechanism of these drill geometries is substantially different, and therefore influences the drilling-induced damage. The experimental results suggest a strong relationship between the drill point geometry and the drilling-induced damage.
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