Hole Surface Roughness Research Articles

Effect of Tool Wear on Hole Quality in Drilling of Carbon Fiber Reinforced Plastic–Titanium Alloy Stacks Using Tungsten Carbide and Polycrystalline Diamond Tools

This paper reviews the nature of hole defects and postulates the cause of hole defects resulting from the drilling process of carbon fiber reinforced plastic–titanium alloy stacked panels (CFRP–Ti stacks) using tungsten carbide (WC) and polycrystalline diamond (PCD) twist drills. The parameters that describe the hole quality of the CFRP–Ti stacks include CFRP entry hole delamination, hole diameter and roundness, inner hole surface roughness, CFRP hole profile, CFRP–Ti interplate damage, and Ti exit burr. They are caused by heat generation during drilling as well as hot Ti chips and adhesion, Ti burr formation, tool instability, and tool geometry change due to tool wear. For the WC drills, large flank wear and margin wear occurred at the high spindle speed condition, resulting in a reduction of the hole size and an increase of the hole roundness and CFRP–Ti interface damage. At the low spindle speed condition, tool geometry was changed due to the large edge rounding. This resulted in large fiber pull-out at the CFRP hole surface. Ti entry burrs caused damage associated with fiber removal and matrix discoloring at the bottom of the CFRP panel and this interplate damage was observed to increase with tool wear. When compared with the WC tool at the same speed condition, the PCD drill maintained relatively small hole defects under all parameters.

Experimental Investigations on Drilling Characteristics of Cenosphere Reinforced Epoxy Composites

In the present paper, the experimental investigations on drilling characteristics of cenosphere reinforced epoxy composites with cemented carbide drill have been presented. The drilling aspects such as thrust and hole surface roughness have been performed as function of four process parameters, namely, spindle speed, feed rate, drill diameter and % weight of the filler. Composite specimens were prepared with 20%, 40% and 60% by weight of cenosphere filler in epoxy resin as the matrix. The full factorial design (FFD) has been employed for conducting drilling experiments and the proposed drilling characteristics were analysed using response surface methodology (RSM) based quadratic models. The response surface analysis reveals that the addition of cenosphere as filler in epoxy resin appreciably decreases with the thrust and hole surface roughness for the developed composites.

Loss reduction in few-mode photonic crystal fiber by reducing inner surface imperfections in air holes.

We studied both theoretically and experimentally the additional loss in photonic crystal fiber (PCF) that results from inner surface imperfections such as contamination and the surface roughness of air holes. We estimated the modal loss dependence of these imperfections using a model with a "defective layer" for the first time. The theoretical studies suggest that higher order modes have a larger loss due to imperfections in the air holes. By minimizing the inner surface imperfections of the six innermost air holes, we can theoretically expect any additional loss to be reduced to a negligible level. Moreover, we examined our theoretical prediction experimentally. We fabricated few-mode PCFs by employing a suitable inner surface treatment for just the six innermost holes. As expected theoretically, the transmission loss was greatly reduced by employing these processes. The lowest transmission losses in the 1550 nm band were 0.31 dB/km for the LP01 mode and 0.43 dB/km for the LP11 mode. Our theoretical model will be useful with a view to realizing few-mode PCF with a loss comparable to that of conventional fibers.

Machinability of drilling T700/LT-03A carbon fiber reinforced plastic (CFRP) composite laminates using candle stick drill and multi-facet drill

Carbon Fiber Reinforced Plastic (CFRP) composite laminates are widely used in aerospace and aircraft structural components due to their superior properties. However, they are regarded as difficult-to-cut materials because of bad surface quality and low productivity. Drilling is the most common hole making process for CFRP composite laminates and drilling induced delamination damage usually occurs severely at the exit side of drilling holes, which strongly deteriorate holes quality. In this work, the candle stick drill and multi-facet drill are employed to evaluate the machinability of drilling T700/LT-03A CFRP composite laminates in terms of thrust force, delamination, holes diameter and holes surface roughness. S/N ratio is used to characterize the thrust force while an ellipse-shaped delamination model is established to quantitatively analyze the delamination. The best combination of drilling parameters are determined by full consideration of S/N ratios of thrust force and the delamination. The results indicate that candle stick drill will induce the unexpected ellipse-shaped delamination even at its best drilling parameters of spindle speed of 10,000 rpm and feed rate of 0.004 mm/tooth. However, the multi-facet drill cutting at the relative lower feed rate of 0.004 mm/tooth and lower spindle speed of 6000 rpm can effectively prevent the delamination. Comprehensively, holes quality obtained by multi-facet drill is much more superior to those obtained by candle stick drill.

Surface precision and roughness of deep holes produced by small-diameter gun drills

Experimental data are presented regarding the influence of the cutting conditions and the working profile of the tool on the surface precision and roughness of deep holes produced by small-diameter (2.05 mm) gun drills with hard-alloy and steel shafts.

Tool life and hole surface integrity studies for hole-making of Ti6Al4V alloy

With a significant growth in the use of titanium alloys in the aviation manufacturing industry, the key challenge of making high-quality holes in the aircraft assembly process needs to be addressed. In this work, case studies deploying traditional drilling and helical milling technologies are carried out to investigate the tool life and hole surface integrity for hole-making of titanium alloy. Results show that the helical milling process leads to much longer tool life, generally lower hole surface roughness, and higher hole subsurface microhardness. In addition, no plastically deformed layer or white layer has been observed in holes produced by helical milling. In contrast, a slightly softened region was always present on the drilled surface. The residual stress distributions within the hole surface, including compressive and tensile residual stress, have also been investigated in detail.

Hole quality and cutting time evaluation in the interpolated helical milling

The interpolated helical milling (IHM) is considered a very flexible strategy which allows milling, instead of drilling, holes with more generic tools. However, despite of its dissemination in industry, it is currently known that few research works have been carried out about the influence of cutting condition on the quality of holes and their cutting time. In this study, the production of holes was investigated using the IHM technique for rough and finish machining conditions, and the process performance was evaluated by the cutting time, and the holes surface roughness and roundness. Fifty four holes were milled in AISI 1045 steel bars with end mill cutters in a vertical machining centre; following Taguchi (L9) experiments where the cutting speed, circular feed per tooth and axial feed per tooth were analysed for rough operations, and for the finish operations, the radial depth of cut was also investigated. From the results, it can be concluded that high quality surface can be achieved at the rough phase. In this case, the combination of lower axial feed rates (ƒz) and higher cutting speed (Vc) should be selected to guarantee a higher hole quality, without compromising the productivity. [Received 13 April 2015; Revised 06 August 2015; Accepted 06 September 2015]

Effect of Machining Parameters on Tool Wear and Hole Quality of AISI 316L Stainless Steel in Conventional Drilling

This paper focuses on the effect of drilling parameters on tool wear and hole quality in terms of diameter error, roundness, cylindricity, and surface roughness. In this work, the drilling was conducted using uncoated carbide tool with diameter of 4 ± 0.01mm with point angle of 135° and helix angle of 30°. The drilling was done at different levels of spindle speed (18 and 30 mmin-1) and feed rate (0.03, 0.045 and 0.06 mmrev-1). Austenitic stainless steel AISI 316L was the workpiece material. Comparatives analysis was done on hole diameter, roundness, cylindricity, and surface roughness of the drilled holes by experimentation. From the result, the hole quality characteristics are mostly influenced by cutting speed and feed rate. An exception was for circularity error where a two tail t-test for circularity error indicates that cutting speed and feed rate give no significant influence on circularity error. As the cutting speed increases, the surface roughness decreases (1.09μm). Contrary, when the feed rate increases, the surface roughness value increases as well. For cylindricity error, lower cutting speed and lower feed rate will give better result. In terms of diameter error, feed rate influences more than cutting speed. Minimum diameter error was achieved when low cutting speed and low feed rate were employed.

Whirling vibration of drilling shaft in minimal quantity lubrication deep hole drilling using theoretical and experimental investigation

Under the concept of safety, improving efficiency, or reducing costs in deep hole drilling, the effect of minimal quantity lubrication (MQL) on the dynamic characteristics of drilling shaft is analyzed. A model is presented to describe the pressure function of MQL cutting fluid during drilling process. This model is based on the compressible Reynolds equation in air/oil feature with nonlinearity, and the differential transformation theory is introduced to solve the time-dependent pressure equation satisfied with MQL cutting fluid. Further, with an emphasis on model development, experiments are performed to validate the correctness and effectiveness of the above methods. A series of experimental investigations are carried out on the whirling characteristics of drilling shaft when the rotational speed and drilling depth are changed. Additionally, the vibration trajectories of drilling shaft and the surface roughness of hole are detected under different experimental conditions such as MQL drilling or traditional drilling. The results show that the whirling trajectory of drilling shaft decreases significantly in MQL deep hole drilling but the surface roughness of machined hole is worse due to surface scratches or scales. Nevertheless, there exists an optimal rotational speed of drilling shaft to improve machining precision of hole surface. These results indicate that the MQL method has shown potential to be even more productive as compared to traditional drilling and that the proposed method in this paper can lay a foundation for investigating the dynamic stability of drilling shaft in MQL drilling.

Study of accuracy and surface roughness of holes in comparative testing of small diameters gun drills

The results of industrial tests of gun drills with the diameter of 2.05 mm with carbide and with steel stems are given. It is shown that the gun drills with cemented carbide stem and especially AlTiN coating have a greater resistance and greater accuracy diametrical holes sizes in comparison to gun drill with steel stem.

Investigation into effect of particle impact damping (PID) on surface topography in boring operation

This paper presents a novel method, based on the particle impact damping (PID), for the attenuation of regenerative vibration in boring operation. A specially designed boring bar having a cavity near machining-end for partial filling of spherical particles has been developed. Characteristics of boring bar with and without PID have been found from impact and shaker tests. After identifying appropriate particle size and filling volume, experiments are conducted to evaluate the performance in actual boring operations. Additional boring experiments are also conducted to confirm the performance by changing particle size and filling volumes. The collision of the particles in PID is found to attenuate regenerative vibration by the energy dissipation and thus effectively enhances stability of the boring operation. Analysis of effect of PID on surface topography in terms of chatter marks, surface roughness, and roundness of bored holes shows that the proposed method results in improvement of bore quality when compared with a boring bar without PID. It is also established that radial vibration of the boring bar has a significant influence on the surface topography obtained in boring operation.

Experimental studies on drilling tool load and machining quality of C/SiC composites in rotary ultrasonic machining

Carbon fiber reinforced silicon carbide matrix (C/SiC) composites have great potential in space applications because of their excellent properties such as low density, superior wear resistance and high temperature resistance. However, the use of C/SiC has been hindered seriously because of its poor machining characteristics. With an objective to improve the machining process of C/SiC composites, rotary ultrasonic machining (RUM) and conventional drilling (CD) tests with a diamond core drill were conducted. The effects of ultrasonic vibration on mechanical load and machining quality were studied by comparing the drilling force, torque, quality of holes exit and surface roughness of drilled holes between the two processes. The results showed that the drilling force and torque for RUM were reduced by 23% and 47.6%, respectively of those for CD. In addition, the reduction in drilling force and torque decreased gradually with increasing spindle speed, while they changed slightly with increasing feed rate. Under identical conditions, RUM gave better holes exit than CD. Moreover, because of the lower lamellar brittle fracture and pit originating from carbon fibers fracture, the roughness of surface of drilled holes obtained with RUM was lower than CD and the maximum reduction was 23%.

Optimization of the Cutting Parameters for Drilling Magnesium Alloy AZ 91

Abstract In this study, machinability of AZ 91D magnesium alloy, which has been widely used in automotive and aircraft industries, was investigated by using HSS and carbide tools at dry cutting conditions. Taguchi's L18 (2**1 3**2) mixed model was used for the experiments. Drilling parameters such as feed rate, spindle speed and cutting tool were optimized according to the multiple responses (diametral error, circularity and surface roughness) by grey relational analysis. The effects of machining parameters and their interactions on the hole diameter, circularity and surface roughness were determined. The analysis of Taguchi and ANOVA indicated that the influence of drill material on the surface roughness of the drilled hole was high, but on the hole diameter and circularity it was low. Furthermore, the results of grey relational analysis revealed that optimal combination of the drilling parameters (0.3 mm/rev feed rate, carbide tool and 3000 rpm spindle speed) can be used to obtain the minimum diametral error, circularity error and surface roughness.

The Effect of Cutting Speed and Feed Rate on Hole Surface Integrity in Single-shot Drilling of Metallic-Composite Stacks

Experimental work was carried out to evaluate the influence of cutting speed (Ti/CFRP/Al: 30/120/120 and 36/144/144m/min) and feed rate (0.05, 0.08, 0.12 and 0.15mm/rev) on workpiece surface integrity following single-shot drilling of multilayer metallic-composite stacks (Ti-6Al-4V/CFRP/Al-7050) using CVD diamond coated tooling. When operating with the lower cutting speed set of 30/120/120m/min and a feed rate of 0.08mm/rev, average hole surface roughness (Ra) was ∼ 0.60, 0.87 and 0.27μm in the Ti, CFRP and Al layers respectively after 30 holes. Roughness values in the stack increased to 0.84, 1.6 and 0.43μm Ra when employing the higher cutting speed of 36/144/144m/min, with the drill lasting only 20 holes. Microhardness depth profile evaluation of the machined surfaces showed no appreciable variation in both the Ti and Al material, irrespective of cutting conditions. Matrix cracking and burn were apparent in the CFRP layer as feed rate increased due to greater wear of the drill corner.

Experiment Investigation of Hole Accuracy and Surface Roughness in Femur Bone Drilling Using Different Parameters

Success indicators in bone drilling include clean, good accuracy drilled holes without damage at the surrounding tissue. This study investigates the influence of cutting parameters in bone drilling against hole accuracy (enlargement diameter, circularity error, and cylindricity error) and surface roughness (Ra). A series of bone drilling experiments was carried out using femur bovine bone and without irrigation. Variations of drill type (high speed steel and coated and uncoated carbide) and cutting speed (19 m/min and 94 m/min) were used as input variables, while the feed rate (0.025 mm/rev) was constant. It was found that coated carbide drill results minimum magnitude on all machining responses. Type of tool gives significant effect on diameter enlargement and surface roughness, yet not on circularity and cylindricity errors. The range of cutting speed evaluated does not give significant effect on any surface integrity measures.

Improvement of Surface Roughness of Inner Hole for Grinding Machine Using Adaptive Fuzzy Sliding Mode Controller

In industry, grinding is commonly used as a finishing or semi-finishing operation. The surface roughness is a variable often used to describe the quality of the overall grinding system. However, the traverse and longitudinal waviness are produced by the random nature of the grinding process and by machine vibration in surface. This paper presents an adaptive fuzzy sliding mode control (AFSMC) to improve surface roughness in inner hole machining using diamond grinding bar. The experimental results show that the AFSMC can reduce surface roughness (Ra).

Multi-Response Optimization in Drilling of Glass Epoxy Polymer Composites Using Simulated Annealing Approach

The glass epoxy polymer composites are broadly used in various engineering fields because of outstanding properties. Even if, these composites are produced as near net shapes, the machining has to be carried out in the last stage of manufacture. Drilling is used to install the fasteners for assembly of laminates, but drilling of composites is somewhat complex task owing to exceedingly abrasive nature of reinforcement. Hence the choice of optimal process parameters is essential for successful machining performance. This paper illustrates the application of simulated annealing (SA) approach for simultaneous minimization of various machinability aspects such as thrust force, hole surface roughness and specific cutting coefficient during drilling of glass epoxy polymer composites. The experiments were performed as per full factorial design (FFD) for glass epoxy composites (without filler) and silicon carbide (SiC) filled glass epoxy composites materials. The mathematical models of proposed machinability characteristics were constructed using response surface methodology (RSM) with spindle speed and feed as controllable factors. The experimental investigation indicates that the SiC filled glass epoxy composite provides better machinability compared to glass epoxy composite without the addition of filler. The proposed machinability models were then utilized with SA to select the optimal parameters such as spindle speed and feed, which results in minimal thrust force, hole surface roughness and specific cutting coefficient.

Vector modeling of robotic helical milling hole movement and theoretical analysis on roughness of hole surface

To avoid the machine problems of excessive axial force, complex process flow and frequent tool changing during robotic drilling holes, a new hole-making technology (i.e., helical milling hole) was introduced for designing a new robotic helical milling hole system, which could further improve robotic hole-making ability in airplane digital assembly. After analysis on the characteristics of helical milling hole, advantages and limitations of two typical robotic helical milling hole systems were summarized. Then, vector model of helical milling hole movement was built on vector analysis method. Finally, surface roughness calculation formula was deduced according to the movement principle of helical milling hole, then the influence of main technological parameters on surface roughness was analyzed. Analysis shows that theoretical surface roughness of hole becomes poor with the increase of tool speed ratio and revolution radius. Meanwhile, the roughness decreases according to the increase of tool teeth number. The research contributes greatly to the construction of roughness prediction model in helical milling hole.

INFLUENCE OF CUTTING PARAMETERS ON THE SURFACE ROUGHNESS AND HOLE DIAMETER OF DRILLING MAKING PARTS OF ALLUMINIUM ALLOY / PJOVIMO PARAMETRŲ ĮTAKA GRĘŽIAMŲ SKYLIŲ SKERSMENIMS IR PAVIRŠIŲ ŠIURKŠTUMUI GAMINANT DETALES IŠ ALIUMINIO

The article researches the drilling process of an aluminium alloy. The paper is aimed at analyzing the influence of cutting speed, feed and hole depth considering hole diameter and hole surface roughness of aluminum alloy 6082 in the dry drilling process and at making empirical formulas for cutting parameters. The article also describes experimental techniques and equipment, tools and measuring devices. Experimental studies have been carried out using different cutting parameters. The obtained results have been analyzed using computer software. According to the existing techniques for measuring, surface roughness and hole diameters have been measured, empirical models have been created and the results of the conducted experiments have been inspected. The findings and recommendations are presented at the end of the work. Santrauka Nagrinėjamas aliuminio gręžimo procesas. Darbo tikslai – išnagrinėti pjovimo greičio, pastūmos ir skylės gylio įtaką gręžiamų skylių skersmenims ir paviršių šiurkštumui aliuminio lydinio 6082 sausojo gręžimo proceso metu bei sudaryti empirines formules pjovimo parametrams nustatyti. Analizuojamas gręžimo procesas. Aprašyta eksperimento metodika, naudota įranga, įrankiai ir matavimo prietaisai. Naudojant skirtingus pjovimo parametrus buvo atlikti eksperimentiniai tyrimai. Gauti rezultatai buvo analizuojami pasitelkiant kompiuterinę programinę įrangą. Pagal jau sukurtas matavimo metodikas buvo matuojamas skylių paviršių šiurkštumas ir skersmenys. Sukurti empiriniai modeliai ir atlikti patvirtinamieji jų patikrinimo eksperimentai. Pateiktos išvados ir rekomendacijos.

Effect of Electrode Route Motion on Electrode Wear in EDM Machining of Mold Steel

In the electrical discharge machining (EDM) of deep holes, electrode wear may cause the dimensions of the finished holes to deviate from their design values. In practice, the extent of the electrode wear and the surface roughness of the machined holes depend not only on the EDM machining parameters (e.g., the pulse duration, the pulse current, and so on), but also on the electrode route motion. Accordingly, the present study performs an experimental investigation into the effects of three different electrode routes (straight dip, spiral attack hole, and awl free expand hole) on the electrode wear and surface roughness of the machined holes in the EDM machining of PDS5A and PDS-1 mold steel, respectively. Overall, the experimental results show that of the three electrode route motions, the awl free expand hole motion results in a more uniform wear of the electrode and a lower surface roughness of the machined hole.