A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in Engineering. Johannesburg, November 1994. / Inventories are produced, used (e.g. for raw materials, supplies, spare parts, and So forth) or distributed by every organisation. Moreover, inventories represent a major investment from the perspectives of both individual firms and entire national economies. In addition, enormous costs are incurred in the planning, scheduling, control and actual carrying out of replenlshment-Iprocuretnentl related activities. Interest in the subject of inventory management is constantly increasing, yet Silver and Petarsonlll (P(eface) found that "although invi ,~ory management ha.l been studied in considerable depth from a theoretical perspective, yet, those of us who, throuah consulting work, come into. clos>!)contact with mananerlal decision procedures in this arer are repeatedly surprised to find how limited, and ad hoc, many of the existing decision systems actually are. The rate at which theory has been developed has far outstripped the rate at which decision practices of firms have been successft,Jlly upgraded. A major g~o has existed between the theoretical solutions, on the one hand, and the real world problems, on the other". Inventory control is the science-based art of ensuring that lust enough inventory (or stockl is held by an organisation to meet both its internal and external demand commitments economically. There can be disadvantages in holding either too much 01 too little inventory. Therefore, inventory control is primarily concerned with obtaining the correct inventory with compromise between these two extremes. The control and maintenance of inventories is a problem common to all enterprises in any sector of a given economy. The primary aim of this study is to identify What the inventory policy of a company shoull;I be to Secure a reduction in inventory-related costs while maintaining a high level of customer service. Lewis(2) defines two bMlt:~ tvpes of inventory policy. Those in which decisions concerning replenishment are based on the lellel of inventory held, are known as "fixed-order quantity models" or "re-order level policies" and those in which such declslons arc made on a time basis are known as "fixed-time period models" or "re-order cycle policies". According to Nadder(3) (7I 11) the basic distinction between fixed-order quantity models and fixed-tlme period models is that the former are "event-triggered" while the latter are "time-triggered". That is, a fixed-order quantity model initiates an order when the "event" of reaching a specified re-order level occurs. This event may take place at any time, depending on the demand for the items considered. In contrast, the fixed-time period model is limited to placing orders at the end of a predetermined time period; hence, the passage of time alone "triggers" the model. In this thesis, we shall discuss both classical inventory models and heuristic models. We shall also conduct an investigation into the factors affecting high levels of inventory ~ mainly lead times (supplier and internal lea' times) in relation to spare 9arts in the heavv-dutv truck and bus industry. The thesis also suggests guidelines for controlling stock or these types of commodities in a practical environment. This will be done by either researching the existing inventory models or developing new inventory models or a combination of both, the intention being not to look for absolute optimisation, but rather to achieve significant improvements over current operations. / GR 2016

När landsvägar sopas rent från grus samlas inte alltiddetta upp utan sopas istället ned i diket, vid förekomstav vägräcken ackumuleras gruset över tid undervägräcket. Detta leder till att avrinningen av vattenförsvåras vilket kan leda till att vattenmassor samlas påvägbanan, detta leder till en försämrad trafiksäkerhet.Arbetet med att avlägsna detta grus är idagtidskrävande och leder till att framkomligheten påvägen begränsas. På uppdrag av AB Mählers och Sönerskapades ett produktkoncept som skall kunna utföra ettförebyggande underhåll för att undvika det mertidskrävande arbete som utförs idag. Konceptet byggerpå två stycken roterande sopborstar som med enöverbryggande konstruktion placeras på vardera sidaav vägräcket. Konceptet avses att placeras på ettbefintligt sidoplogfäste som finns i AB Mähler &amp; Sönerexisterande produktutbud. För att ta fram detta koncepthar olika metoder nyttjats: intervjuer med identifieradeintressenter har utförts, befintliga lösningar har söktsoch olika koncept har skapats. De genererade konceptenhar betygsatts och eliminerats tills ett koncept kvarstår.Detta koncept har itererats tre gånger för att söka olikalösningar på problemställningen. / When country roads are swept clean from gravel, thegravel is not always collected, but is instead sweptdown into the trench. In the presence of guardrails thegravel accumulates over time under the guardrail. Thismakes the drainage of water more difficult which canlead to water masses accumulating on the roadway,which leads to impaired road safety. The work ofremoving this gravel is today time-consuming and willlimit the accessibility off the road. On behalf of ABMählers and Söner, a product concept was created thatwill be able to carry out preventive maintenance toavoid the more time-consuming work being donetoday. The concept is based on two rotating brusheswhich with a bridging construction are placed on eachside of the guardrail. The concept is intended to beplaced on an mount for a snowplough that currentlyexists in AB Mähler &amp; Söner's product range. Todevelop this concept, different methods have been used:interviews with identified stakeholders have beencarried out, existing solutions have been sought anddifferent concepts have been created. The generatedconcepts have been graded and eliminated until oneconcept remains. This concept has been iterated threetimes to seek different solutions to the problem. / <p>Betyg 2020-07-27</p>