Simulation Study Of The Short Barrel Of The Gun Manufacture

This paper deals with the use of computer simulation aiming at more efficient production of the manufacturing system. In our case, the possibilities of use are demonstrated on a particular example from industrial practice. The purpose was to build up a model of the existing short barrel of the gun manufacturing line, and, especially, to propose a solution for increase of productivity, and to find bottlenecks of the system. The Witness simulation environment was used for modelling and subsequent simulation. On the basis of predefined requirements of the user, several simulation experiments were suggested. The results of these experiments have revealed non-economy and a very small passage ability of the existing system. INTRODUCTION The computer simulation of discrete events is becoming a necessary supporting instrument in making the operation of production systems more effective. Among other things, this is due to its capability of simulating and following up both stochastic and dynamic properties of individual processes, and thus predicting their behaviour. In the present so-called turbulent environment, any effective operation of the production systems cannot be achieved any more only by local optimization of individual parameters or subsystems. These are so interacting that it is not possible to solve them separately, and the whole system has to be considered globally, and the optimum of the system as a whole must be searched for. High dynamics, complexity and, as such, also insecurity at the solution of company tasks require more and more the use of such methods and such supporting means that allow a complex access to the design of production systems, as well as fast tests of a variety of different variants of the solution, and thus minimization of a risk of erroneous decisions. Therefore, a significant help is a complex dynamic analysis of the production systems by means of computer simulation. So, at the present time, the computer simulation is a necessary part of every large production process. With its help you can perform the simulation of real environment. If the process has been modelled correctly, the production simulation can be made for a few days or weeks in advance. This instrument gives the companies the possibility of operational planning at minimizing energies, inventories and labour. This paper deals with the simulation study of a particular manufacturing line, in our case this is the short barrel of the gun manufacturing line in a company producing the guns. The production process is described in detail in Section 2. This study includes an analysis of the current status of the plant, data collection, construction and verification of the model, and, in particular, a proposal and implementation of simulation experiments. The aim was to propose a solution for increase of productivity and to find bottlenecks of the manufacturing system. The simulation experiments were proposed on the basis of the predefined requirements of the user. The task was to determine an appropriate number of machines in individual workplaces, or, rather, to establish a correspondent number of shifts of the operation of these workplaces. The Witness simulation environment was used for the construction of the model and subsequent simulation. Basic information on this environment is to be found in Section 3. In this Section, the process of model creation in the Witness environment is outlined. Description of the proposed simulation experiments and evaluation of achieved results is presented in Section 4. DESCRIPTION OF THE SHORT BARREL OF THE GUN MANUFACTURE The machines used in the manufacture serve for machining the products in various production phases. These are, in particular, lathes, grinding and drilling machines. All these machines are machining only one product at a given moment. Thus, only one part enters the machine and a specific operation is carried out on it, and also only one part leaves the machine. Individual machines are arranged into groups. Each group forms a workplace to perform a certain operation. Every machine (except for one machine) is operated by one operator. For this reason, labour does not have to be considered in the model. Table 1 shows quantities of Proceedings 23rd European Conference on Modelling and Simulation ©ECMS Javier Otamendi, Andrzej Bargiela, José Luis Montes, Luis Miguel Doncel Pedrera (Editors) ISBN: 978-0-9553018-8-9 / ISBN: 978-0-9553018-9-6 (CD) machines in individual workplaces which are used in the system for machining the products, together with the number of shifts during which the workplace is in operation. Table 1: Number of machines in individual workplaces and number of shifts Workplace No. Description of workplace Number of machines Number of shifts 1 Drilling of the short barrel of the gun 3 2 2 Drilling –countersinking 1 2 3 Turning-Lathe – Fischer 3 2 4 Turning-Lathe SV 18 7 2 5 Turning-Lathe Liberty 6 2 6 Honing 5 2 7 Forging 2 3 8 Grinding 6 2 9 Turning-Lathe – chambers 3 2 10 Polishing chambers 2 2 11 Manual treatment 9 1 Each workplace performs a certain operation. The product comes through some workplaces repeatedly, therefore one workplace carries out a few different operations. The manufacturing process is described step by step below, in Table. 3. Here is given the number of the workplace where a particular operation is made, and the time of individual operations. This data was provided by the operator of the plant from its planning system where the data for all machines are stored. The data collection was carried out in that workplace for a long time, hence we can consider this data to be very correct. So any further measurement directly in operation would be just waste of time. Products’ handling in the production is made with the help of vehicles. Material handling is not controlled in real manufacture; this is done in case of emptying individual buffers. Time of material handling from one machine to another is minimal, as the distance is very short. Therefore we can say that the time of material handling is negligible. The manufacturing plant works in three-shift operation. Most workplaces are in two-shift operation, though (see Table 1). Overview of individual working shifts of the manufacturing system is shown in Tab. 2. Table 2: Working shifts of the department of short barrel of the gun Shift Shift start Break Shift end Morning shift 5:45 10:30-11:00 14:15 Afternoon shift 14:00 17:30-18:00 22:00 Night shift 22:00 2:00-2:30 6:00 In operation, maintenance of the machine is done on a regular basis. Thanks to this maintenance, faults occur on individual machines only exceptionally. Time of maintenance together with elimination of faults will take 3 % of machine time. Table 3: Manufacturing procedure of the short barrel of the gun Operation No. Description of operation Workplace No. Process Time [s] 1. Hole drilling for preparation of a bore 1 17,4 2. Countersink of ends at the bored hole 2 7,8 3. Turning of the recess on one side of the cut for clamping onto the copying machine 3 14,4 4. Turning of surface either for cone or cylinder shape according to the type of the forging, or final shape of the short barrel of the gun, respectively 4 13,8 5. Execution of ends is done for clamping for the forging and honing operations that follow 5 10,2 6. Honing. This is final treatment of the hole before the very forging. Honing is done to achieve necessary hole size and roughness 6 40,2 7. Forging is carrying out the final sizes of the bore and surface of the forged piece as per the calibre required and type of the short barrel of the gun 7 49,2 8. Cutting-off and planing the face of the short barrel of the gun to the length required acc. to the type – the so-called first face 4 10,2 9. Turning operation of turning of the faces and recess 3 22,8 10. Again, cutting off, countersinking, milling of the shape in the area of the cartridge chamber, turning of the diameter of the short barrel of the gun plus addition under the grinder 4 155,4 11. Grinding of the diameter of the short barrel of the gun to the final size, shape and machining 8 94,8 12. Turning with connection to the subtoothing and the very turning of the toothing 5 84 13. Turning of the cartridge chamber and turning of the muzzle, where its final length is determined acc. to individual types 9 91,2 14. Polishing the chute and polishing the cartridge chamber 10 28,2 15. Checking and preparatory activities for the next work with the product, such as size check, cleaning the conservation coat, degreasing, etc. 11 1,8 The simplified scheme of the operation of the production plant is presented in Figure 1.