Poor Drilling Research Articles

Design and In Vitro Validation of an Orthopaedic Drill Guide for Femoral Stem Revision in Total Hip Arthroplasty.

Cemented total hip arthroplasty (THA) demonstrates superior survival rates compared to uncemented procedures. Nevertheless, most younger patients opt for uncemented THA, as removing well-fixed bone cement in the femur during revisions is complex, particularly the distal cement plug. This removal procedure often increases the risk of femoral fracture or perforation, haemorrhage and weakening bone due to poor drill control and positioning. Aim of this study was to design a novel drill guide to improve drill positioning. A novel orthopaedic drill guide was developed, featuring a compliant centralizer activated by a drill guide actuator. Bone models were prepared to assess centralizing performance. Three conditions were tested: drilling without guidance, guided drilling with centralizer activation held, and guided drilling with centralizer activation released. Deviations from the bone centre were measured at the entry and exit point of the drill. In the centralizing performance test, the drill guide significantly reduced drill hole deviations in both entry and exit points compared to the control ([Formula: see text]). The absolute deviation on the exit side of the cement plug was 10.59mm (SD 1.56) for the 'No drill guide' condition, 3.02mm (SD 2.09) for 'Drill guide - hold' and 2.12mm (SD 1.71) for 'Drill guide - release'. The compliant drill guide centralizer significantly lowered the risk of cortical bone perforation during intramedullary canal drilling in the bone models due to better control of the cement drill position. Clinical and Translational Impact Statement: The drill guide potentially reduces perioperative risks in cemented femoral stem revision. Future research should identify optimal scenarios for its application.

Analysis of drilling vibration characteristics of anchoring system in coal mine

A new type of parallel operation unit for excavating and supporting anchors is proposed to address the issue of imbalanced excavation anchor ratio in coal mines. By equipping a straddle type anchoring drilling rig group, the synchronous parallel and fast operation mode for excavating and supporting anchors is achieved; Consider the problem of poor drilling stability of drill pipes in coal mines due to the coupling vibration between surrounding rock and anchoring equipment. Firstly, taking the multi drilling rig anchoring system as the research object, considering the influence of the equipment itself as an influencing factor on the vibration of the drill pipe, a dynamic model of the system is constructed using Lagrangian equations, and analytical solutions for the vibration displacement of each mass block are obtained; In order to more intuitively represent the vibration process of the drill pipe, Ansys is used to conduct modal analysis on the key components of the anchoring drilling rig system, and obtain the natural frequencies and vibration modes of each order of the key components; Using Adams to solve the rigid flexible coupling dynamic model of the anchoring drilling rig system, the vibration response laws of the drill pipe under different operating states were obtained. Secondly, Abaqus was used to simulate the drilling process of the drill pipe and obtain the vibration response law generated by the interaction between the drill pipe and the surrounding rock; The results indicate that the anchoring equipment has a greater impact on the vibration of the drill pipe, and the surrounding rock has a more stable impact on the vibration of the drill pipe. Due to the short body and large span structure of the anchoring system crossbeam expansion frame, the vibration response of the drill pipe is significantly greater than that of the retracted state of the drilling rig due to being in an unstable cantilever state when the drilling rig is extended. The theoretical reliability of the vibration response law of the drill pipe under different states has been further verified through drilling experiments of the anchoring system prototype. The relevant theories can provide a theoretical basis for the implementation of automatic anchoring technology in the anchoring system.

Rate of Penetration Prediction Method for Ultra-Deep Wells Based on LSTM–FNN

The drilling process is complex, especially for ultra-deep wells, which face the problems of high temperature, high pressure and poor drilling resistance in their formation. In order to establish an ROP (the Rate of Penetration) prediction model for ultra-deep wells, the characteristics of ultra-deep well drilling operations, such as formation temperature and formation pressure, are fully considered in the process of parameter optimization. Combined with the drilling mechanism and mutual information correlation coefficient, the final input parameters are determined. The powerful nonlinear fitting ability of the artificial intelligence method is very suitable for predicting the ROP. Considering the time sequence of multi-source data, this paper combines the powerful timing information-based mining ability of the LSTM (Long Short-Term Memory Neural Network) with the nonlinear fitting ability of FNN (Fully Connected Neural Network), and establishes an intelligent prediction model of the ROP based on a LSTM–FNN. The results show that the average relative error and R2 of the LSTM–FNN model on the data of well 1 and well 2 are better than the FNN and LSTM models. In addition, the accuracy of the LSTM–FNN model on the data of adjacent wells is reduced by only 5%, which further verifies the good mobility of the model.

Characterization of machinability of sintered steel foams having different porosities during drilling operations

Steel foams are a new class of engineering materials with exceptional structure and properties. Foams produced by powder metallurgy generally have a near-net shape, however, sometimes machining operations may be required. The presence of porosity in steel foams significantly affects the cutting process and causes poor machinability. This study deals with the evaluation of the machinability of Cu-Ni-Mo-based steel foams having different porosity produced by powder metallurgy. High speed steel and carbide-tipped drills were used for the drilling. All tests were performed in dry condition with drill diameter of 3 mm. The drilling characteristics were evaluated in terms of the surface roughness, chip formation, drilling force, tool wear, microstructure and hardness change after drilling. The machinability was also evaluated by measuring average width of breakout and skewness values of the hole drilled. The results indicated that the increase of porosity negatively affected the drilling quality of high porous steels. Both drills broke the chips in powder form and produced discontinuous chips. High porous parts exhibited higher hardness change as compared to lower ones. The carbide drill showed acceptable drilling forces and surface quality. HSS drill is not suitable for drilling due to poor hole quality and high drill wear. Highlights Steel foams exhibit poor machinability due to highly porous structure. Porosity and tool type significantly affect the surface integrity of steel foams. Surface roughness and drill wear increased with increasing porosity; however, feed force decreased. Intense presence of pores decreases the tool life remarkably. The skewness values of hole are positive in all porosities. Carbide-tipped drill produced the finest hole quality. The larger damage was observed at the exit of the drilled holes with HSS drill.

Factors Influencing Ore Recovery and Unplanned Dilution in Sublevel Open Stopes. Case study of Shaft No.4 at Konkola Mine, Zambia

Konkola Copper Mine’s Number 4 Shaft is a trackless underground mine applying sublevel open stoping (SLOS) mining method. Number 4 shaft wants to increase ore production from 1 million metric tonnes per annum to 3 million metric tonnes per annum in the next 5 years but ore recovery is 70% or less and dilution is 20% or more. In order to achieve the desired annual target of 3 million metric tonnes ore recovery should be increased from70% to (≥85%) and dilution should be reduced from 20% to (≤10%). Despite being one of the most used underground mining methods, the current SLOS has a challenge of high unplanned dilution. This paper reviews and evaluates parameters that influence recovery and unplanned dilution in sublevel open stopes and applies numerical modelling using PHASE2 software to establish the influence of stress environment on unplanned dilution at the mine. The input parameters for numerical modelling were: Uniaxial Compressive strength (UCS=170MPa), Geological Strength Index (GSI) =55, Young’s Modulus (E) =26000MPa, Hoek-Brown constant (s) =0.0067, Hoek-Brown constant (mi) =20 and Poisson ratio (v) =0.2 major principal stress (σ1) 39MPa, intermediate stress (σ2= 18MPa) and the minor principal stress (σ3= 15MPa). Results obtained from review of mine production records indicate that the main factors that influence unplanned dilution at Number 4 shaft are: poor ground conditions, lack of compliance to recommended stope designs, poor drilling and blasting practices, presence of geological discontinuities, adopted mining sequence of extracting high ore grade first that leads to creation of high stress blocks within the orebody and delayed mucking practice. Results obtained from PHASE 2D model indicate that total displacement of 90mm is recorded in the hangingwall hence influencing stope wall instability that leads to increased unplanned dilution. After stope extraction, it was observed that 60MPa of induced stress developed at the top right corner and 45-50 MPa at the crown pillar and right bottom corner of the stope.

Cutting Mechanism Study of an Innovative Non-Planar Cutter PDC Bit and Its Field Application

Tarim Kuqa tight sandstone reservoir is overlaid with extreme thick conglomerate, which has high compressive strength, strong heterogeneity and poor drill ability, resulting in low drilling ROP and less bit drilling footage. Through research study and analysis of PDC bit failure and wear modes, this paper described the development of an innovative non-planar PDC bit through cutting mechanism study and lab testing verification. When drilling through the strong homogeneity formation, it will still be surface contact between the non-planar cutter and the rock and therefore the rock-breaking mechanism is still the conventional shearing fracturing; When drilling through the heterogeneity formation, the convex ridges will generate the linear contact with the hard rock and the mechanical stress will be accumulated at the conglomerate surface to initially create the cracking and then break the rock with composite cutting mechanism of shearing and crushing to improve the rock breaking efficiency. Experimental results also showed that the non-planar cutter delivers several folds of impact resistance improvement over conventional cutter. The bit was successfully field tested in ultra-thick conglomerate layer in the Kuqa foreland thrust belt of the Tarim basin. The field test tripled bit footage and doubled ROP comparing to same intervals and formation in offset wells. It demonstrated the broader prospect of the non-planar PDC technology in conglomerate and highly heterogeneous applications.

Sustained wood burial in the Bengal Fan over the last 19 My

The Ganges-Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world's largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO2 While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (∼8°N, ∼3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C4 plants, implying that coarse woody, lowland export continued after C4 grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (∼0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.

Performance Analysis of Drilling Test of Aramid Fiber Composite

Aramid fiber-reinforced polymer (AFRP) is a typical difficult material to machine. It is easy to occur defects such as ablation and burr in the drilling process due to the serious non-uniformity and heterotrophy of these material properties, as well as low heat transfer coefficient and high fibre toughness of the aramid fibre, which remarkable affects the machining quality and assembly accuracy. In this paper, three types of drills with different cutting edge shapes were compared to analyse the influence of drilling on cutting force, cutting temperature and machining quality. The results showed that the tool geometry has a great influence on the drilling performance of AFRP. Due to poor drilling quality, 8-face drill and twist drill are not suitable for drilling AFRP drilling tools. The machining quality of Brad & Spur drill is relatively good, which can meet the drilling requirements of AFRP.

Differences between reservoirs in the intra-platform and platform margin reef-shoal complexes of the Upper Ordovician Lianglitag Formation in the Tazhong oil field, NW China, and corresponding exploration strategies

Abstract The Upper Ordovician Lianglitag Formation in the Tazhong oil field, NW China, is dominantly composed of shallow marine carbonates, and it can be subdivided into five members lithologically. Unclear understanding of the reservoir evolution in the platform margin and intra-platform reef-shoal complexes resulted in difficulty in locating reservoirs and poor drilling success in the intra-platform. By comparing the basic characteristics, diagenesis, and porosity evolution of the two types of reservoirs, this study established their development patterns and proposed corresponding exploration strategies based on comprehensive analysis of core, thin-section, well-logging, three-dimensional seismic, and geochemistry data. The major difference between the platform margin and intra-platform reservoirs lied in their pore types. The platform margin reservoirs had fabric-selective intragranular dissolution pores, intergranular dissolution pores, moldic pores, and non-fabric-selective karst fractures and caves, and tectonic fractures, whereas the intra-platform ones only had tectonic fractures, intercrystalline dissolution pores, and intergranular vugs. In terms of distribution, the platform margin reservoirs were mainly distributed in the parasequence top and landform highlands of the highstand system tract in Members 3 to 1, appearing in two to six cycles, with large single layer and accumulative thicknesses and a quasi-bedded continuous distribution in the lateral. However, the distribution of the intra-platform ones was not obviously correlated with sedimentary facies and paleogeomorphology, with smaller single layer and accumulative thicknesses and poorer lateral continuity. The evolution and distribution of high-quality reservoirs in the platform margin were jointly controlled by eogenetic marine diagenetic and meteoric dissolution including karst, burial dissolution, and tectonic fractures. In comparison, eogenetic marine diagenetic and meteoric dissolution in the intra-platform reef-shoal complexes were weak, accompanied by persistent cementation. The favorable reservoirs were primarily controlled by fractures and later burial dissolution. Hence, for the exploration of the platform margin reef-shoal complex reservoirs, the priority should be given to the areas with the superimposition of eogenetic marine diagenetic and meteoric dissolution, burial dissolution, and tectonic fracturing. For the exploration of intra-platform reef-shoal complex reservoirs, more attention should be paid to areas with overlapped fractures and burial dissolution, especially where Hercynian strike-slip faults and early fractures were superimposed. Less attention should be paid to the areas with eogenetic marine diagenetic and meteoric dissolution.

Development of a Mole-Like Drilling Robot System for Shallow Drilling

Drilling systems are widely used today for various purposes, but in harsh environments, such as the Arctic or space, it is hard to utilize these conventional systems because they require large amounts of equipment and labor. Various research projects have attempted to resolve this issue, but they are still in development stages owing to poor drilling performance. To solve this problem, we exploit the digging habits of the mole that is one of the representative animals living underground. In this paper, we propose the excavation mechanism for an embedded drilling robot, including cutting removal and balancing in the hole, which is inspired by a type of a mole known as the African mole-rat. To find the rate of penetration (ROP) trends of the proposed drilling system, simple drilling experiments are performed on autoclaved lightweight concrete blocks with a drill bit that imitates the polycrystalline diamond compact bit. The maximum ROP is obtained with the experiments and finite-element modeling simulations.

Influence of lubrication modes on residual stresses generation in drilling of 316L, 15-5PH and Inconel 718 alloys

Drilling is a very old and very complex process. As the tool is embedded in the part, neither the material removal phenomena, nor the evacuation of chips are well understood. As a consequence a bad choice of drilling tool or poor drilling conditions may affect the surface integrity of the machined part. The aim of this article is to bring a contribution to the understanding of lubrication modes on cutting phenomena and surface integrity when drilling a 316L austenitic stainless steel, a 15-5PH martensitic stainless steel and an Inconel 718 nickel alloy. Residual stress states in the hole have been analysed after drilling with three lubrication modes (internal high pressure coolant, external low pressure coolant, dry). Results have been analysed with regard to the thermal and mechanical actions of the drill on parts, thanks to temperature sensors along the hole, and thrust force+torque measurements. First this work has highlighted that residual stress state varies along a hole. Second, it has been shown that lubrication is a critical parameter on surface integrity. Whereas efficient cooling conditions enable to obtain compressive residual stresses and a limited affected layer, a lack of lubrication generates tensile residual stresses, a larger deviation in the results and an increase in the thickness of the affected layer.

The evolution of the Huangling uplift and its control on the accumulation and preservation of shale gas

ABSTRACT There are plenty of Sinian and Cambrian potential shale gas resources in South China, which is characterized by high thermal evolution degrees, poor drilling performances and only occurs in local areas. Taking the principle “high to find low” is the key issue to achieving a breakthrough in older shale. China Geological Survey drilled in the periphery of the Proterozoic basement, i.e. the Huangling anticline, in the western Hubei, and Hannan paleocontinent in the southern Shanxi. It received high-quality gas-bearing shale with relatively low Ro in the in Lower Cambrian Niutitang formation and Sinian Doushantuo formation. Based on geological conditions of shale gas reservoirs in the Huangling anticline, this paper puts forward the new model named “Control over reservoirs by periphery of basement” about shale gas accumulation, suggesting that the shale deposited in a deepwater continental shelf in the periphery of the basement is characterized by shallow burial, a short burial time, stable tectonics, relatively low thermal evolution degrees, and shale gas reservoirs in a good condition. The shale of the Sinian-Cambrian strata deposited in deepwater continental shelves in the periphery of Chuanzhong paleo-uplift in Sichuan, Hannan paleocontinent in the southern Shanxi, Huangling anticline in western Hubei and Jiangnang-Xuefeng paleo-uplift in Hunan and Guizhou province have good shale gas exploration potential.

Preparation and performances of coated and aluminous entry boards with water-soluble resins for PCB drilling

Purpose This paper aims to provide a new drilling entry board for printed circuit board (PCB) process, superior in heat dissipation, lubrication, water solubility and hole location accuracy, achieving an excellent drilling process. Design/methodology/approach Using a mixture of polyethylene glycol (PEG) and water-soluble adhesives as hydrosoluble, endothermic and lubricant resins and aluminum foils as baseplates, a series of coated and aluminous entry boards (CABs) for PCB drilling was successfully prepared. The surface appearance of the entry boards was observed clearly by scanning electron microscopy (SEM). The endothermic and lubricant effects of the resins applied on the CABs was characterized by differential scanning calorimetry (DSC) and their water solubility was tested in the normal-temperature water (25°C). Moreover, the CABs’ good drilling properties were tested when they were used for PCB drilling. Findings The SEM analysis showed that the surfaces of the resin layers coated on the CABs whose coating thicknesses were less than 80 μm were smoother and flatter, which could improve hole location accuracy and reduce drill breakage ratio. By virtue of DSC, the endothermic and lubricant effects of the CABs were proven. The fusion of PEG in the resin layers could absorb the heat produced by drilling, restrain the temperature of the drill bit and hole rising and lubricate the drill bit efficiently when a hole was being drilled, which could achieve high-quality holes with good production efficiency. The water-soluble test showed that the prepared CABs had excellent water solubility at normal temperature, enabling the resin left on the hole walls and in the flute of the drill bit to be washed away easily and thereby improving the drilling efficiency and quality. The drilling tests showed that the increase in the thickness of the CABs’ coating could improve the hole location accuracy and alleviate the bit wear. In addition, the suitable coating thickness could ensure the firm adhering of the resin coating the aluminum foil, effectively avoid drill intertwist and prevent the resin debris from blocking the drilled holes on the surface of the entry board, which could hinder chip removal, resulting in poor hole wall quality and drill breakage. Originality/value This paper has a remarkably high industrial practicality in the PCB manufacture process.

Prediction of Crack for Drilling Process on Alumina Using Neural Network and Taguchi Method

This study analyzes a variety of significant drilling conditions on aluminum oxide (withL18orthogonal array) using a diamond drill. The drilling parameters evaluated are spindle speed, feed rate, depth of cut, and diamond abrasive size. An orthogonal array, signal-to-noise (S/N) ratio, and analysis of variance (ANOVA) are employed to analyze the effects of these drilling parameters. The results were confirmed by experiments, which indicated that the selected drilling parameters effectively reduce the crack. The neural network is applied to establish a model based on the relationship between input parameters (spindle speed, feed rate, depth of cut, and diamond abrasive size) and output parameter (cracking area percentage). The neural network can predict individual crack in terms of input parameters, which provides faster and more automated model synthesis. Accurate prediction of crack ensures that poor drilling parameters are not suitable for machining products, avoiding the fabrication of poor-quality products. Confirmation experiments showed that neural network precisely predicted the cracking area percentage in drilling of alumina.

The prospective and hypothetical areas of zinc and/or lead ores in different types of deposits beyond the Upper Silesia Zn-Pb Ore District in Poland

Streszczenie Największe szanse na udokumentowanie zasobów perspektywicznych złóż rud Zn-Pb w Polsce występują w obszarze o powierzchni około 2000 km2 usytuowanym na północ od udokumentowanych złóż siarczkowych Zn-Pb regionu zawierciańskiego. Wydzielone zostały tam cztery rejony perspektywiczne dla wystąpień złóż rud siarczkowych Zn-Pb typu Mississippi Valery Type (MVT) w utworach węglanowych triasu (wapień muszlowy) i dewonu. Za najbardziej obiecujący uznano obszar na NW od Myszkowa oraz obszar na SE od Koziegłowów. Jednak ze względu na słabe rozpoznanie wiertnicze zasoby md Zn-Pb są trudne do oszacowania. Celowe jest przeprowadzenie dalszych prac geofizycznych (np. metodą 1P), które w przypadku pozytywnych wyników należałoby rozpoznać wierceniami. W cechsztyńskiej formacji miedzionośnej na monoklinie przedsudeckiej (wokół obszaru złożowego Lubin- -Sieroszowice), na peryklinie Żar (na SW od Zielonej Góry) i w niecce północnosudeckiej (wokół złóż Konrad i Lena-Nowy Kościół oraz na N od Zgorzelca) znanych jest kilka obszarów występowania bogatej mineralizacji Pb-Zn. Jednak ze względu na dużą głębokość zalegania mineralizacji, okruszcowanie to może stanowić jedynie kopalinę towarzyszącą wydobywaną przy okazji eksploatacji rud Cu-Ag. Jednak pomimo znacznych zasobów cynk jak dotychczas nie jest odzyskiwany w procesach przeróbczych jak i metalurgicznych przez KGHM Polska Miedź S.A. Liczne drobne wystąpienia mineralizacji Zn-Pb i Pb w Sudetach, G. Świętokrzyskich oraz w strefie kontaktu bloku małopolskiego z górnośląskim nie mają znaczenia ekonomicznego jednak stanowią ważne przesłanki dla dalszych poszukiwań, które mogą doprowadzić do odkrycia złóż siarczkowych Zn i/lub Pb, różnorodnych pod względem genetycznym (stratoidalne, hydrotermalne żyłowe i/lub brekcje, kontaktowo-metasomatyczne, SEDEX) jak i zasobowym.

Titanium Integration With Bone, Welding, and Screw Head Destruction Complicating Hardware Removal of the Distal Radius: Report of 2 Cases

Increasingly, surgeons treat distal radius fractures with locking plate systems. Recent case reports have focused on technical insertion errors resulting in removal difficulties: poor drilling orientation or cross-threading, destruction of the screw head, and filling of the screw recess with tissue. We report 2 complications of titanium locked plate removal secondary to in vivo reactions including titanium integration with bone and mechanical binding between the titanium screw and plate. We clarify and discuss terminology relevant to implant removal, including cold-welding, galling, fretting, and anodization. Even with optimal technique, in situ reactions can complicate titanium implant removal.

Field-Development Case Study: Production Optimization Through Continuous Multidisciplinary Reservoir and Production Monitoring

Summary This paper presents a field-development case study of a low-permeability turbidite reservoir in Russia. The giant Priobskoye field contains 30°API crude in laminated sandstones of 0.1 to 20 md at a depth of approximately 2,500 m. The complex geology, lack of reservoir information and lack of technology availability caused a 20-year gap between discovery and development. The initial pilot development was halted after poor drilling success, thus the operator invested in 3D-seismic acquisition and an integrated, multidisciplinary reservoir modeling and simulation effort. The subsequent development was based on oriented water-flooding patterns and massive hydraulic fracturing, together with an artificial-lift system equipped with permanent pressure and rate monitoring for evaluation and real-time production enhancement. The optimization of operational practices and introduction of fit-for-purpose technologies enabled a production increase from an intermittent hundreds of BOPD to more than 75,000 BOPD in a period of 3.5 years. The exploitation strategy of this pilot area demonstrated commercially sustainable production from the reservoir and will form the basis for full field development.

Legal Consequences of Damages to Underground Facilities by Horizontal Directional Drilling

Horizontal directional drilling is rapidly becoming the method of choice for installing new underground systems including water, sewer, electrical, telephone, fiber-optic cables, and gas lines. Due to its minimal impact to surface activities and competitive cost, this technique is being utilized worldwide. Unfortunately, poor drilling practices by some contractors have caused utility strikes that have resulted in major legal ramifications and subsequent negative image of the technique. Just one incident alone can result in significant monetary judgments due not only to the reparation for repairing the damaged utility, but also for damages due to “loss of use.” This paper presents theories of legal liability and recoverable damages applied to incidents of damages to underground facilities by the contractor. Recommendations for preventing the repetition of these types of incidents through the discussion of prior identification of potential hazards and proper drilling practices are discussed.

Powder factors in asymmetric blast patterns

A cell powder factor defines the local powder factor in a simple geometric procedure that accounts for the charge in each blast hole and the triangulation formed by blast hole collars in a blast pattern. In the case of asymmetric blast patterns, the cell powder factor deviates from the global powder factor. Poor drilling of blast hole collars produces significant variation in the cell powder factor, more so, than does poor blast hole charging. The cell powder factor does not account for timing within a blast and does not easily handle non-parallel blast hole configurations. The cell powder factor is best used as a design or audit tool before blast holes are loaded. It gives the opportunity to correct for poor drilling and/or poor charging practices prior to firing a blast.

The normativity of artefacts

Part of the distinction between artefacts, objects made by humans for particular purposes, and natural objects is that artefacts are subject to normative judgements. A drill, say, can be a good drill or a poor drill, it can function well or correctly or it can malfunction. In this paper I investigate how such judgements fit into the domain of the normative in general and what the grounds for their normativity are. Taking as a starting point a general characterization of normativity proposed by Dancy, I argue how statements such as ‘this is a good drill’ or ‘this drill is malfunctioning’ can be seen to express normative facts, or the content of normative statements. What they say is that a user who has a desire to achieve a particular relevant outcome has a reason to use, or not to use, the artefact in question. Next this analysis is extended to show that not just statements that say that an artefact performs its function well or poorly, but all statements that ascribe a function to an artefact can be seen as expressing a normative fact. On this approach the normativity of artefacts is analyzed in terms of reasons on grounds of practical, and to a lesser extent theoretical, rationality. I close by investigating briefly to what extent reasons on moral grounds are, in the analysis adopted here, involved in the normativity of artefacts.