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Lin Li - One of the best experts on this subject based on the ideXlab platform.
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influence of ultrasonic vibration on Percussion Drilling performance for millisecond pulsed nd yag laser
Optics and Laser Technology, 2018Co-Authors: Houxiao Wang, Lin Li, Guoxiang Xu, Wei Zhou, Dao Hua ZhangAbstract:Abstract The ultrasonic vibration-assisted laser Drilling is a recently emerging/growing new technique, especially in laser Drilling. Differently from the previous work reported, this paper proposed to use the ultrasonic vibration (25 kHz) for assisting the millisecond pulsed Nd:YAG laser Percussion Drilling process to improve the Drilling performance. Through comparing the drilled microholes without/using ultrasonic assistance, the influence of ultrasonic vibration on the drilled blind hole morphology/geometry, the hole wall surface roughness, the recast layer microstructure, and the hardness distribution of the heat affected zone for the drilled microhole was analyzed by altering laser pulse energy and/or laser pulse number. It was shown that the ultrasonic vibration incorporated into the laser Drilling process might enhance the Drilling efficiency in terms of the increase of hole depth and width. However, the drilled hole taper might be decreased via using ultrasonic assistance. Moreover, the ultrasonic vibration might clean the inner hole wall surface, and the microhole morphology/geometry could be improved through using ultrasonic assistance, resulting in a relatively clean and better-profiled hole wall with less defects and smaller taper due to the contribution of ultrasonic assistance. In addition, it was indicated that ultrasonic vibration might also improve the microhole heat affected zone hardness and reduce the inner hole wall surface roughness.
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sequential laser and mechanical micro Drilling of ni superalloy for aerospace application
Cirp Annals-manufacturing Technology, 2010Co-Authors: M M Okasha, Paul Mativenga, N Driver, Lin LiAbstract:Laser Percussion Drilling is inherently associated with poor geometry and thermal defects. While mechanical micro-Drilling produces good quality holes, premature drill breakage often occurs and it is difficult to drill holes at acute angles. This paper presents the feasibility and basic characteristics of a new approach for micro-Drilling In718 alloy sheets at an acute angle, using sequential laser and mechanical Drilling. The results demonstrate that sequential laser-mechanical micro-Drilling alleviates the defects associated with laser-drilled holes, reduces burr size and machining time and increases the tool life compared with mechanical Drilling.
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comparative statistical analysis of hole taper and circularity in laser Percussion Drilling
International Journal of Machine Tools & Manufacture, 2002Co-Authors: Mehrdad Ghoreishi, Lin LiAbstract:Abstract The present study investigates the relationships and parameter interactions between six controllable variables on the hole taper and circularity in laser Percussion Drilling. Experiments have been conducted on stainless steel workpieces and a comparison was made between stainless steel and mild steel (IMechE Part B: J. Eng. Manufact. (in press)). Laser peak power, laser pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position were selected as independent process variables. The central composite design (CCD) was employed to plan the experiments in order to achieve required information with reduced number of experiments. The process performance was evaluated in terms of equivalent entrance diameter, hole taper and hole entrance circularity. The ratio of minimum to maximum Feret’s diameter was considered as circularity characteristic of the hole. The models of these three process characteristics were developed by linear multiple regression technique. The initial models were computed according to the least squares procedure and were finalised by stepwise regression method. The significant coefficients were obtained by performing analysis of variance (ANOVA) at 1, 5 and 7% levels of significance. The final models were checked by complete residual analysis and finally were experimentally verified. It was found that the pulse frequency had a significant effect on the hole entrance diameter and hole circularity in Drilling stainless steel unlike the Drilling of mild steel where the pulse frequency had no significant effect on the hole characteristics.
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an investigation into the role of melt ejection in repeatability of entrance and exit hole diameters in laser Percussion Drilling
In: International Congress on Application of Lasers and Opto-electronics (ICALEO?01) Jacksonville Florida USA: International Congress on Application o, 2001Co-Authors: Gary K L Ng, Lin LiAbstract:Laser Percussion Drilling is a well-established industrial tool for the fabrication of small holes in aerospace components. Yet the process is inherently variable and the hole geometry can not be precisely predicted by the processing parameters. It is well known that melt ejection has a significant influence on the hole geometry. Therefore, an investigation into the role of melt ejection on the entrance and exit hole geometry repeatability is carried out for laser Percussion Drilling. This work intends to study the melt ejection process by the variation of operating parameters and seeks to identify a relationship with the resulting hole geometry.Laser Percussion Drilling is a well-established industrial tool for the fabrication of small holes in aerospace components. Yet the process is inherently variable and the hole geometry can not be precisely predicted by the processing parameters. It is well known that melt ejection has a significant influence on the hole geometry. Therefore, an investigation into the role of melt ejection on the entrance and exit hole geometry repeatability is carried out for laser Percussion Drilling. This work intends to study the melt ejection process by the variation of operating parameters and seeks to identify a relationship with the resulting hole geometry.
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Effect of processing parameters on hole circularity in laser Percussion Drilling – a statistical model
International Congress on Applications of Lasers & Electro-Optics, 2001Co-Authors: Mehrdad Ghoreishi, Lin LiAbstract:In laser Percussion Drilling, holes are produced mainly by melt ejection with a series of laser pulses. The circularity of the holes not only depends on various laser-processing parameters but also their interactions that influence the characteristics of melt ejection. In this work a statistical modelling approach was used to study the effects of six processing variables (peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position) and their interactions on the hole circularity. Response surface method was used to statistically analyse the process. For each variable five levels were considered and the experiments were conducted based on a Central Composite Design (CCD). The experiments were performed using an optical fibre delivered Nd:YAG laser Drilling on mild steel sheets of 2.5 mm thickness. An analysis of variance (ANOVA) was performed to test the significance of the variables at 1% and 7% levels. It was found that pulse width has a significant effect on the hole entrance circularity. Pulse frequency and number of pulses have very little effect on the hole entrance circularity.In laser Percussion Drilling, holes are produced mainly by melt ejection with a series of laser pulses. The circularity of the holes not only depends on various laser-processing parameters but also their interactions that influence the characteristics of melt ejection. In this work a statistical modelling approach was used to study the effects of six processing variables (peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position) and their interactions on the hole circularity. Response surface method was used to statistically analyse the process. For each variable five levels were considered and the experiments were conducted based on a Central Composite Design (CCD). The experiments were performed using an optical fibre delivered Nd:YAG laser Drilling on mild steel sheets of 2.5 mm thickness. An analysis of variance (ANOVA) was performed to test the significance of the variables at 1% and 7% levels. It was found that pulse width has a significant effect on t...
P. J. Byrd - One of the best experts on this subject based on the ideXlab platform.
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the influence of temporal pulse train modulation during laser Percussion Drilling
Optics and Lasers in Engineering, 2001Co-Authors: D. K. Y. Low, P. J. ByrdAbstract:Abstract The temporal pulse train modulation during laser Percussion Drilling was found to effect significant changes to the material ejection processes. In particular, distinct differences in the material ejection processes have been observed between a temporal pulse train shaping technique termed as sequential pulse delivery pattern control (SPDPC) and the normal delivery pattern (NDP), wherein the parameters of successive laser pulses were constant. Due to the reduced upward material removal fractions in SPDPC Drilling, the spatter deposition area was reduced from approximately 6.7 to 2.7 mm 2 . In addition, the melt layer thicknesses at the hole bottom were significantly increased from 11–61 to 18– 369 μm . Such changes were identified as being due to the low laser pulse intensities before beam breakthrough associated with the SPDPC method. It was observed that the use of the linearly increasing SPDPC method increased the downward material removal fractions, from 20% to 28% observed in NDP Drilling, to 34%–39%. Such an increase in the downward material ejection mechanism in SPDPC Drilling was identified as being primarily due to the pointed blind-hole profile generated before the onset of beam breakthrough. The work has shown that modulating the entire pulse train in laser Percussion Drilling could control the material ejection processes. Furthermore, the fundamental elements of the SPDPC technique are given in terms of the rate of energy deposition and total pulse train energy.
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spatter free laser Percussion Drilling of closely spaced array holes
International Journal of Machine Tools & Manufacture, 2001Co-Authors: Lin Li, A G Corfe, P. J. ByrdAbstract:Abstract Spatter is one of the inherent defects commonly associated with holes produced with laser Drilling. This work reports on a method of spatter prevention, workable for a wide range of process parameters. The method is based on the application of a specially developed anti-spatter composite coating (ASCC), containing a mixture of ceramic filler particles embedded in a silicone elastomer matrix, on the workpiece surface prior to laser Percussion Drilling. Experiments were conducted using a fibre-optic delivered 400 W Nd:YAG laser for the Drilling of closely spaced through holes (2 mm hole pitch) in Nimonic 263 alloy sheets. The work revealed that the ASCC effectively prevented the deposition of spatter such that laser drilled holes were produced whilst maintaining the as-received surface characteristics of the Nimonic 263 alloy for all the assist gases tested (O 2 , air, N 2 and Ar). The process characteristics and spatter prevention mechanism associated with the use of the ASCC have been investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, contact angle analysis and high-speed photographic imaging. Comparative studies were also made with the case of uncoated laser Drilling.
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Combined spatter and hole taper control in Nd:YAG laser Percussion Drilling
International Congress on Applications of Lasers & Electro-Optics, 2000Co-Authors: D. K. Y. Low, P. J. ByrdAbstract:Spatter and hole taper formations are two quality problems often encountered during laser Percussion Drilling of metallic materials. Researchers and manufacturers alike are actively seeking ways to either prevent or control these two inherent defects. This current work presents the combined use of a specially developed anti-spatter composite coating (ASCC) and a hole taper control method termed as Sequential Pulse Delivery Pattern Control (SPDPC). The ASCC is based on a mixture of ceramic particles and silicone elastomer, applied on the workpiece surface prior to laser Drilling. The SPDPC involves the alteration of the overall delivery pattern during a pulse train required to drill a through-hole. This work has shown that the combined use of the ASCC and SPDPC was successful in preventing spatter whilst generating through-holes with good overall parallelism in Ni alloy sheet during Nd:YAG laser Percussion Drilling. The fundamental effects and mechanisms involved in the ASCC and SPDPC techniques are also discussed.Spatter and hole taper formations are two quality problems often encountered during laser Percussion Drilling of metallic materials. Researchers and manufacturers alike are actively seeking ways to either prevent or control these two inherent defects. This current work presents the combined use of a specially developed anti-spatter composite coating (ASCC) and a hole taper control method termed as Sequential Pulse Delivery Pattern Control (SPDPC). The ASCC is based on a mixture of ceramic particles and silicone elastomer, applied on the workpiece surface prior to laser Drilling. The SPDPC involves the alteration of the overall delivery pattern during a pulse train required to drill a through-hole. This work has shown that the combined use of the ASCC and SPDPC was successful in preventing spatter whilst generating through-holes with good overall parallelism in Ni alloy sheet during Nd:YAG laser Percussion Drilling. The fundamental effects and mechanisms involved in the ASCC and SPDPC techniques are also d...
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taper formation mechanisms and taper control during laser Percussion Drilling of ni alloy
2000Co-Authors: D. K. Y. Low, P. J. ByrdAbstract:This paper reports a novel technique for controlling hole taper in laser Percussion Drilling. The method is termed Sequential Pulse Delivery Pattern Control (SPDPC) and it is based on the alteration of the overall laser pulse pattern during a pulse train required to drill a hole. The work has shown that SPDPC is effective in producing through holes with good overall parallelism in Ni alloy (2.65 mm thick), giving an average hole taper of 12 μm for 0.55 mm holes. Experiments were conducted to understand the taper formation mechanisms. The effectiveness of the SPDPC method in reducing hole taper has been identified as being primarily due to the reduction of upward liquid melt ejection which in turn reduced the erosion of hole due to melt ejection, as well as the optimisation of the laser pulse intensity distribution during hole propagation.
D. K. Y. Low - One of the best experts on this subject based on the ideXlab platform.
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hole taper
2016Co-Authors: M Ghoreishi, D. K. Y. LowAbstract:modelling of laser Percussion Drilling fo
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Statistical modelling of laser Percussion Drilling for hole taper and circularity control
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2002Co-Authors: Mehrdad Ghoreishi, D. K. Y. LowAbstract:AbstractThe aim of the present work is to investigate the effects of different variables and their interactions in laser Percussion Drilling and to understand the possibility of controlling simultaneously the two important characteristics of a laser drilled hole: taper and circularity. Six variables, namely the peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position, were selected as independent controllable factors. The response surface method was used to statistically analyse the process. For each variable, five levels were considered and the experiments were performed based on a central composite design. A fibre-optic delivered neodymium-doped yttrium aluminium garnet laser was used to laser Percussion drill mild steel sheets with a thickness of 2.5mm. The entrance diameter, the taper and the ratio of maximum to minimum Feret diameter for the hole entrance (circularity) were considered as responses/outputs in order to evaluate the process performance in ...
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hole taper characterisation and control in laser Percussion Drilling
CIRP Annals, 2002Co-Authors: D. K. Y. Low, M Ghoreshi, J R CrookallAbstract:Small hole (< 1 mm diameter) Drilling by lasers is widely applied in various manufacturing processes. Hole tapering is one of the inherent manufacturing problems associated with laser Percussion Drilling (multiple pulse Drilling) whereby material is ejected in the form of molten droplets when a series of laser pulses are delivered to a point on a workpiece. This paper reports an investigation into the mechanisms of hole taper formation, its characteristics and the development of a taper control technique. A statistical modelling technique is used to characterise the parameter relationships during hole-taper formation. Laser beam inter-pulse shaping is used to control the hole-taper. Parallel holes are produced as a result of this new development.
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the influence of temporal pulse train modulation during laser Percussion Drilling
Optics and Lasers in Engineering, 2001Co-Authors: D. K. Y. Low, P. J. ByrdAbstract:Abstract The temporal pulse train modulation during laser Percussion Drilling was found to effect significant changes to the material ejection processes. In particular, distinct differences in the material ejection processes have been observed between a temporal pulse train shaping technique termed as sequential pulse delivery pattern control (SPDPC) and the normal delivery pattern (NDP), wherein the parameters of successive laser pulses were constant. Due to the reduced upward material removal fractions in SPDPC Drilling, the spatter deposition area was reduced from approximately 6.7 to 2.7 mm 2 . In addition, the melt layer thicknesses at the hole bottom were significantly increased from 11–61 to 18– 369 μm . Such changes were identified as being due to the low laser pulse intensities before beam breakthrough associated with the SPDPC method. It was observed that the use of the linearly increasing SPDPC method increased the downward material removal fractions, from 20% to 28% observed in NDP Drilling, to 34%–39%. Such an increase in the downward material ejection mechanism in SPDPC Drilling was identified as being primarily due to the pointed blind-hole profile generated before the onset of beam breakthrough. The work has shown that modulating the entire pulse train in laser Percussion Drilling could control the material ejection processes. Furthermore, the fundamental elements of the SPDPC technique are given in terms of the rate of energy deposition and total pulse train energy.
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Combined spatter and hole taper control in Nd:YAG laser Percussion Drilling
International Congress on Applications of Lasers & Electro-Optics, 2000Co-Authors: D. K. Y. Low, P. J. ByrdAbstract:Spatter and hole taper formations are two quality problems often encountered during laser Percussion Drilling of metallic materials. Researchers and manufacturers alike are actively seeking ways to either prevent or control these two inherent defects. This current work presents the combined use of a specially developed anti-spatter composite coating (ASCC) and a hole taper control method termed as Sequential Pulse Delivery Pattern Control (SPDPC). The ASCC is based on a mixture of ceramic particles and silicone elastomer, applied on the workpiece surface prior to laser Drilling. The SPDPC involves the alteration of the overall delivery pattern during a pulse train required to drill a through-hole. This work has shown that the combined use of the ASCC and SPDPC was successful in preventing spatter whilst generating through-holes with good overall parallelism in Ni alloy sheet during Nd:YAG laser Percussion Drilling. The fundamental effects and mechanisms involved in the ASCC and SPDPC techniques are also discussed.Spatter and hole taper formations are two quality problems often encountered during laser Percussion Drilling of metallic materials. Researchers and manufacturers alike are actively seeking ways to either prevent or control these two inherent defects. This current work presents the combined use of a specially developed anti-spatter composite coating (ASCC) and a hole taper control method termed as Sequential Pulse Delivery Pattern Control (SPDPC). The ASCC is based on a mixture of ceramic particles and silicone elastomer, applied on the workpiece surface prior to laser Drilling. The SPDPC involves the alteration of the overall delivery pattern during a pulse train required to drill a through-hole. This work has shown that the combined use of the ASCC and SPDPC was successful in preventing spatter whilst generating through-holes with good overall parallelism in Ni alloy sheet during Nd:YAG laser Percussion Drilling. The fundamental effects and mechanisms involved in the ASCC and SPDPC techniques are also d...
Mehrdad Ghoreishi - One of the best experts on this subject based on the ideXlab platform.
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statistical analysis of repeatability in laser Percussion Drilling
The International Journal of Advanced Manufacturing Technology, 2006Co-Authors: Mehrdad GhoreishiAbstract:This study investigates the effect of six parameters in the repeatability of drilled holes in laser Percussion Drilling process by means of statistical techniques. Peak power, pulse width, pulse frequency, number of pulses, gas pressure and focal plane position were considered as independent process parameters. Experiments were designed with the aim of reducing the number of required experiments. The response surface method was used to develop the models for required responses. The significant factors in the process were selected based on the analysis of the variance (ANOVA). The experiments were conducted in mild steel sheet with a thickness of 2 mm. Each experiment was repeated 35 times in order to investigate the repeatability of the process. The equivalent entrance diameter, percentage of standard deviation of entrance diameter (%STD Eq Dia), circularity (ratio of minimum to maximum Feret’s diameter) and its standard deviation (STD circularity) were selected as process characteristics. The %STD Eq Dia and STD circularity, respectively, show the repeatability of equivalent diameter and circularity in the process.
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multi criteria optimization of laser Percussion Drilling process using artificial neural network model combined with genetic algorithm
Materials and Manufacturing Processes, 2006Co-Authors: O B Nakhjavani, Mehrdad GhoreishiAbstract:ABSTRACT This is a study of laser Percussion Drilling optimization by combining the neural network method with the genetic algorithm. First, optimum input parameters of the process were obtained in order to optimize every single output parameter (response) of the zprocess regardless of their effect on each other (single criterion optimization). Then, optimum input parameters were obtained in order to optimize the effect of all output parameters in a multicriteria manner. Artificial neural network (ANN) method was employed to develop an experimental model of the process according to the experimental results. Then optimum input parameters (peak power, pulse width, pulse frequency, number of pulses, assist gas pressure, and focal plane position) were specified by using the genetic algorithm (GA). The output parameters include the hole entrance diameter, circularity of hole entrance and hole exit, and hole taper. The tests were carried out on mild steel EN3 sheets, with 2.5 mm thickness. The sheets were drill...
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comparative statistical analysis of hole taper and circularity in laser Percussion Drilling
International Journal of Machine Tools & Manufacture, 2002Co-Authors: Mehrdad Ghoreishi, Lin LiAbstract:Abstract The present study investigates the relationships and parameter interactions between six controllable variables on the hole taper and circularity in laser Percussion Drilling. Experiments have been conducted on stainless steel workpieces and a comparison was made between stainless steel and mild steel (IMechE Part B: J. Eng. Manufact. (in press)). Laser peak power, laser pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position were selected as independent process variables. The central composite design (CCD) was employed to plan the experiments in order to achieve required information with reduced number of experiments. The process performance was evaluated in terms of equivalent entrance diameter, hole taper and hole entrance circularity. The ratio of minimum to maximum Feret’s diameter was considered as circularity characteristic of the hole. The models of these three process characteristics were developed by linear multiple regression technique. The initial models were computed according to the least squares procedure and were finalised by stepwise regression method. The significant coefficients were obtained by performing analysis of variance (ANOVA) at 1, 5 and 7% levels of significance. The final models were checked by complete residual analysis and finally were experimentally verified. It was found that the pulse frequency had a significant effect on the hole entrance diameter and hole circularity in Drilling stainless steel unlike the Drilling of mild steel where the pulse frequency had no significant effect on the hole characteristics.
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Statistical modelling of laser Percussion Drilling for hole taper and circularity control
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2002Co-Authors: Mehrdad Ghoreishi, D. K. Y. LowAbstract:AbstractThe aim of the present work is to investigate the effects of different variables and their interactions in laser Percussion Drilling and to understand the possibility of controlling simultaneously the two important characteristics of a laser drilled hole: taper and circularity. Six variables, namely the peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position, were selected as independent controllable factors. The response surface method was used to statistically analyse the process. For each variable, five levels were considered and the experiments were performed based on a central composite design. A fibre-optic delivered neodymium-doped yttrium aluminium garnet laser was used to laser Percussion drill mild steel sheets with a thickness of 2.5mm. The entrance diameter, the taper and the ratio of maximum to minimum Feret diameter for the hole entrance (circularity) were considered as responses/outputs in order to evaluate the process performance in ...
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Effect of processing parameters on hole circularity in laser Percussion Drilling – a statistical model
International Congress on Applications of Lasers & Electro-Optics, 2001Co-Authors: Mehrdad Ghoreishi, Lin LiAbstract:In laser Percussion Drilling, holes are produced mainly by melt ejection with a series of laser pulses. The circularity of the holes not only depends on various laser-processing parameters but also their interactions that influence the characteristics of melt ejection. In this work a statistical modelling approach was used to study the effects of six processing variables (peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position) and their interactions on the hole circularity. Response surface method was used to statistically analyse the process. For each variable five levels were considered and the experiments were conducted based on a Central Composite Design (CCD). The experiments were performed using an optical fibre delivered Nd:YAG laser Drilling on mild steel sheets of 2.5 mm thickness. An analysis of variance (ANOVA) was performed to test the significance of the variables at 1% and 7% levels. It was found that pulse width has a significant effect on the hole entrance circularity. Pulse frequency and number of pulses have very little effect on the hole entrance circularity.In laser Percussion Drilling, holes are produced mainly by melt ejection with a series of laser pulses. The circularity of the holes not only depends on various laser-processing parameters but also their interactions that influence the characteristics of melt ejection. In this work a statistical modelling approach was used to study the effects of six processing variables (peak power, pulse width, pulse frequency, number of pulses, assist gas pressure and focal plane position) and their interactions on the hole circularity. Response surface method was used to statistically analyse the process. For each variable five levels were considered and the experiments were conducted based on a Central Composite Design (CCD). The experiments were performed using an optical fibre delivered Nd:YAG laser Drilling on mild steel sheets of 2.5 mm thickness. An analysis of variance (ANOVA) was performed to test the significance of the variables at 1% and 7% levels. It was found that pulse width has a significant effect on t...
B. N. Smolyanitsky - One of the best experts on this subject based on the ideXlab platform.
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Energy-Based Volumetric Rock Destruction Criterion in the Rotary–Percussion Drilling Technology Improvement
Journal of Mining Science, 2017Co-Authors: V. N. Oparin, Vn Karpov, Vv Timonin, B. N. SmolyanitskyAbstract:Efficiency of energy-based criterion of volumetric rock destruction in estimation of Drilling technology is theoretically validated and experimentally proved in in-situ rotary–Percussion Drilling in mines in Russia. The criterion is adapted to the performance of various Drilling units by means of introduction of empirical coefficients for transformation of Drilling energy intake to the relevant energy characteristics of stress rock fracture in face zone. The mathematical description of the criterion of minimum energy intake of rotary–Percussion Drilling depending on stress state and physical properties of rocks, and on force of rotary–feed mechanism is presented. The authors introduce a new geomechanical notion—factor of topological connection of rocks and give its analytical expression using experimental uniaxial compression and uniaxial tension strength of rocks, required in the design and improvement of rotary–Percussion Drilling in different geological and geotechnical conditions of mining.
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energy based volumetric rock destruction criterion in the rotary Percussion Drilling technology improvement
Journal of Mining Science, 2017Co-Authors: V. N. Oparin, Vn Karpov, Vv Timonin, B. N. SmolyanitskyAbstract:Efficiency of energy-based criterion of volumetric rock destruction in estimation of Drilling technology is theoretically validated and experimentally proved in in-situ rotary–Percussion Drilling in mines in Russia. The criterion is adapted to the performance of various Drilling units by means of introduction of empirical coefficients for transformation of Drilling energy intake to the relevant energy characteristics of stress rock fracture in face zone. The mathematical description of the criterion of minimum energy intake of rotary–Percussion Drilling depending on stress state and physical properties of rocks, and on force of rotary–feed mechanism is presented. The authors introduce a new geomechanical notion—factor of topological connection of rocks and give its analytical expression using experimental uniaxial compression and uniaxial tension strength of rocks, required in the design and improvement of rotary–Percussion Drilling in different geological and geotechnical conditions of mining.