Keywords

1 Introduction

The need for adaptable mining systems with possibility of reconfiguration, to carter for ever changing production, demands is becoming more evident in the mining industries. In an environment where production targets are not constantly met, machine breakdowns due unforeseen circumstances and ever changing customer demands are of concern, adaptable beneficiation technologies promises to be a solution to address such challenges. Small to medium mining companies who cannot afford the luxury of buying big machines when demand of their products need to be scaled is another eminent challenge to be addressed. Considering the beneficiation machines especially Vibrating Screens (VS) that are used for separation of crushed mineral particles obtained from primary, secondary and tertiary crushers into different sizes. The different types of VS used in the mining industries are horizontal screens, linear screens, gyratory screens, vibrating screens, circular motion screens, elliptical motion screens and resonance screens. There are a variety of mining and processing equipment that are currently designed and manufactured all over the world, but the aforementioned type of screens are built using dedicated manufacturing systems, which thus makes this machine restricted to particular type, screen structure, efficiency and production target; which in the long run results in the aforementioned problem. In view of this, the RVS is the newly designed and developed beneficiation machine, with an adjustable screen structure to meet up with variance in mineral volume products demanded by customers at varying time at the production site. The machine is also of utmost importance to meet the varying design specifications needed by different mining companies. Nevertheless, there is no doubt that the Reconfigurable Manufacturing System (RMS) concept has been proposed to meet changes and uncertainties of manufacturing environment and this objective would be achieved by reconfiguring hardware or software resources [1]. The major uncertainty of reducing the efficiency of the conventional vibrating screen is downtime. Meanwhile some designers and manufactures are seeking alternative ways to come up with new innovative screening methods. Currently, in the mining and material processing industries, screens are installed for operation for certain number of years, later, the same screen will be replaced with a bigger or alternatively a smaller structure simply because it is not able to respond to new production demands. Also, when there is high mineral particle demand, most of these industries are forced to buy another screen to be able to meet up with the fluctuating demand, thus increasing the company’s operating cost and reducing the profits substantially. Due to the low efficiency from the conventional vibrating screen, this provide designers a leading edge for new innovative solutions that utilize the reconfigurability concept. Reconfigurability is a very valuable concept in responding to meet the highlighted challenges of mining and processing industry in the world. A RVS is an innovative solution that is designed to have a cost-efficient production, with a higher standardization level by modularizing the structural components.

This machine has been designed to ensure higher mineral concentrates productivity as well as meeting the company’s exact production target, which presently has been infeasible due to downtime, unscalable machinery, which has been seen as inevitable scenario in the mining industries. According to Vorster and De la Garza [2], the different types of downtime costs that contribute to high maintenance costs spent on mining machines are associated resource impact costs, lack of readiness costs, service level impact costs and alternative method impact costs. Associated resource impact costs concern the effects of the failure on other components of the team. Lack of readiness costs are penalty costs assessed when an item that should be constantly available is not. Service level impact costs measure the decreased productivity of a fleet of equipment when a portion of that fleet has failed. Alternative method impact costs occur when a different method of production must be used due to the failure of a given component of the original production team. Different research has been done to show the negative impacts of down time on the mining operations and profit of the company. Edwards et al. [3] used regression analysis to predict the expected downtime cost rate for tracked hydraulic excavators in opencast mining industry. Their model shows that, machine weight is an excellent predictor of downtime cost. Vorster and Sears [4] proposed failure cost profiles which measure the expected cost per unit time in terms of the duration of the interval out of service. For a fixed repair time, the work featured the introduction of a cost related criterion that also takes into account the relative productivity of equipment that may be assigned to different kind of works. By doing so, the authors were able to decide replacement and task assignments for a fleet of similar equipment.

Operator-induced consequential costs were studied by Edwards et al. [3]. The work includes skill level of operators, fatigue, morale, and motivation. The authors suggest that operator’s skill has the most important factor concerning the performance of the equipment. Considering operational poor practices, Pathmanathan [5] reported the increased frequency and cost of equipment downtime induced by the negligence of the operator and lack of proper training and knowhow on the part of the equipment supervisor. Arditi et al. [6] also consider operation uncertainty (i.e. different environmental conditions) as well as design complexity as the causes of greater risk for equipment downtime. Nepal and Park [7] explored the impact of downtime on construction projects duration and related costs. The analysis highlights how various factors and processes interact with each other to create downtime, and mitigate or exacerbate its impact on project performance.

Thus, effective machine maintenance is an inevitable function in a mining industry. The implementation of this type of vibrating screen will be advantageous in such a way to allow highly flexible and reconfigurable production on a very long term basis. Reconfigurable manufacturing system as designed by Koren et al. [8], is referred to as a manufacturing system designed from the outset for rapid change in structure, including software and hardware components, in order to adjust production capacity and functionality quickly, in response to uncertainty in customer requirements. In addition, reconfigurability concepts have been described by different researchers. Wiendahl et al. [9], defined reconfigurability as phenomenon which exhibits a switch or change in manufacturing systems or configurations with minimal effort and delay for achieving the desired adaptability to the set of subcomponents. Lee [10] also augmented Wiendahl et al. [9] by emphasizing that RMS is completely achieved on a manufacturing system, when it is been produced at optimum costs for its different configurations. In view of this, Setchi and Lagos [11], reported that the aim of reconfigurability is to achieve responsiveness in manufacturing systems with respect to changing market conditions. Daniyan et al. [12] stated that the essence of a reconfigurable fixture is to balances operator’s safety and comfort with cost effectiveness, accuracy and precision, as well as smart location. Furthermore, Galan et al. [13] highlighted that market or customer does not necessarily impact the need for reconfigurability, but its sometimes based on companies own preference or relevance.

Thus, the concept of reconfigurability and its application in manufacturing industries was explored and investigated to develop an RVS which will be beneficial to the mineral processing industries. The RVS is defined by the authors as newly improved beneficiation equipment for use in classifying materials such as bulk granular and particulate materials and wet slurries, through the theory of reconfigurability to increase or decrease its capacity as a result enhancing the productivity of the equipment in response to ever changing customer demands. The characteristics of RMS were meticulously explained by Mehrabi et al. [14]. Convertibility: is the ability to easily transform the functionality of existing systems and machines to suit new production requirements. Scalability: is the ability to easily modify production capacity by adding or subtracting manufacturing resources (e.g. machines) and/or changing components of the system. Modularity: is the compartmentalization of operational functions into units that can be manipulated between alternate production schemes for optimal arrangement. Integrability: is the ability to integrate modules rapidly and precisely by a set of mechanical, informational, and control interfaces that facilitate integration and communication. Customization: is the ability to produce a particular product based on the customers’ requirements, designs, specifications and configuration in order to ensure customers satisfaction. Diagnosability: is the ability to automatically read the current state of a system to detect and diagnose the root causes of output product defects, and quickly correct operational defects. These characteristics of RMS were utilized in the design and the development of RVS.

For the RVS operation, the crushed granite mineral particles obtained from the jaw crusher are processed using a RVS. The blasted mineral particles from the mine are fed through the hopper of the screen plant by means of Load Haul Dump (LHD) trucks and then transported to the crushing machines through a conveyor belt. The jaw crusher crushes the granite rocks into smaller sizes for further processing. The crushed mineral particles are transported by a conveyor belt to the screening section. The process is continuously repeated in order to compare subsequent processing variations as depicted in Fig. 1. The undersize mineral particles are stored in groups called stockpiles, while the oversized mineral particles are returned back to the crusher. Based on the inferred mineral resource generated throughout the process, industries establish their production targets based on the tonnage, mineral content and the grade of the mineral particles. When companies establish production targets it is mainly on reasonable grounds that are likely to be achieved. Change and uncertainty is a dominant factor affecting mining industries. The demand for processed mineral particles is increasing every day however in some instances they may be decrease in demand such as during the global recession. Regardless of increase or decrease in demand, costumers are still expecting to get mineral particles processed at an optimum cost and at the right time. The change, uncertainty and production targets set by the mining industries have created the need for reconfigurable or adaptable mining machineries that are able to carter for different production variations as shown in Fig. 1.

Fig. 1.
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Variation in processing small and large capacity.

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According to Wills and Napier-Munn [15], the size of the screen length should be double or three times the screen width. In situations where the space is limited an RVS will be an alternative solution. Barabady et al. [16], stated that a major part of the mining systems operating costs is due to unplanned system stoppages. Samanta et al. [17] further justified that the reduction in the downtime cost due to unnecessary machine breakdown plays a very important role in the profitability of the company. Hence, a RVS can be deployed to address some of these challenges.

This paper presents the current state of the newly designed beneficiation machine amidst its counterparts according to the University Research Innovation Ratings. The aim of this paper is to investigate the need for reconfigurable systems in meeting fluctuating production demands in small to medium mining industries. The paper first provides an overview of RMS and its application in the industry, then establishes production targets with relation to the challenges and trends. In addition, the paper discusses the theoretical aspects of the RVS, then the discussion continues on how each feature can solve industry problems. The paper then concludes with a technical comparative analysis and market analysis of the RVS compared to the conventional methods.

2 Methodology

Ideally in order to design a machine or technology that can meet production targets numerous number of factors have to be considered, such as its maintainability, reliability, ease of operation and last but not least safety. Figure 2 presents the features of the developed RVS.

Fig. 2.
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Features of the developed RVS.

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There are currently different technologies that exist that can also address the issue of production targets; mobile screen is currently an obvious alternative that companies consider. The market analysis of this newly designed machine was done by the Tshwane University of Technology (TUT) Research Innovation Committee.

This committee is made up of 10 experts in different disciplines such as law, engineering, management and technology innovation. This committee thoroughly investigates and assess through reconnaissance survey carried out with different experts involved in the production of products similar to the innovative product. The essence is to bench mark for the strength, weakness, opportunities and threats among its counter parts. The information obtained by this committee gives a clear indication to the potential funders of the innovative product of the product feasibility or viability when produced in the market. Proposing the design to be applied to mineral processing industry, a comparative market assessment with the existing method of mineral beneficiation was conducted by the described and aforementioned TUT Research Innovation Committee. The rating was done on a scale of 1–6, 6 being the highest rating. The rating was based on capacity, energy efficiency, reliability, versatility, cost and equipment maintenance as key performance indices. Figure 3 depicts a market analysis carried out by the TUT University Research Innovation Committee. The committee thoroughly investigated and reported that as at this present time, the capacity rating of RVS among its counterparts is 5, which makes it have high competitive strength with Pilot Crushtec and KPI-JCI Mobile Screens of the same rating. The reliability rating among its counterparts is 4, which makes it have high competitive strength with Linear Motion Screens and Exciter Driven Vibrating Screen of the same rating. The versatility rating among its counterparts is 5, which makes it have high competitive strength with Pilot Crushtec and KPI-JCI Mobile Screens of the same rating while the operating cost and equipment maintenance cost rating is 4, indicating that RVS is maintained and operated at low cost compared with its other counterparts.

Fig. 3.
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Market assessment.

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3 Results and Discussion

From the comparison of the efficiency and productivity of RVS and conventional vibrating screens it can be affirmed as seen in Table 1, that RVS can achieve variations in mineral volume productivity due to its variable screen structure.

Table 1. RVS model configurations aimed at meeting production targets in mining industries.
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The screen surface of 2000 mm by 1600 mm, 2000 mm by 2000 mm and 2000 mm by 2500 mm can produce 60 tons, 80 tons and 100 tons of mineral concentrates per hour respectively, this is achieved through screen extensions modules in its width of 400 mm, 400 mm and 500 mm sequentially. This increases the mineral concentrates productivity in the mineral processing industry for 2nd, 3rd and 4th configurations of RVS achievable by 2 times, 2,7 times and 3.3 times that of the conventional vibrating screens, which is the first configuration of RVS. In view of this variation in configurations, which results in increase in mineral volume productivity, most of down time lost due to mining machine failure and unforeseen contingencies will be recovered when RVS is being utilized in mining industries. Also, the ability to meet variations in terms of decrease or increase in mineral concentrates demands at any time (t) is being achieved at very low production cost. Furthermore, the results from the market assessment indicated that the reconfigurable vibrating screen has an equal advantage over the existing conventional vibrating screens. (Note that the capacity of different modules attached to the standard RVS as different scenarios against the conventional vibrating screen may be compared).

4 Conclusion

The aim of this paper was to investigate the need for reconfigurable systems in meeting fluctuating production demands in small to medium mining industries. This was achieved through a market assessment of the proposed RVS and other existing screening technologies performed by experts. After comparing the market analysis of the existing conventional vibrating screens with the newly developed vibrating screen, the RVS proved that it is capable of adjusting its structure according to industrial requirements, thus, achieving a higher processing capacity as compared to existing conventional vibrating screens. In this regard, the RVS is considered to be a cost-effective approach and it is concluded that it is the technology to meet production targets. The issue of meeting production targets in mining industries can be addressed through the deployment of a reconfigurable beneficiation technology. Future works can test the RVS in other mineral processing industries for more performance evaluation.