Estimated Completion Time Of Mold Design Project With Rework

Mold is an important foundation for modern manufacturing that mold design is the initial stage of it.The mold design process is full of various random uncertainties,there is not only the uncertainty of the task time due to lack of prior knowledge,but also the uncertainty of the network structure caused by the random rework in the new product design R&D project.On the one hand,the designers may find design errors and make rework modifications after they have designed their own.On the other hand,because the customer’s initial product requirements are not clear enough,the mold designer needs to send part of the designed content to the customer for confirmation.When the customer confirms that there is no problem,the product will enter the next design stage,otherwise it will be carried out modify or redesign.It is difficult to estimate the completion time of the design project due to the uncertainty of the rework time and the number of design tasks.In order to solve this problem,this paper will research the method for estimating the completion time of mold design projects under the premise of random task duration and random rework in the mold design process.The details are as follows:(1)Taking the mold design project as the research object,under the premise that the conventional task of the design task and the duration of the rework task are subject to any given probability distribution,a simulation model that integrates the historical project plan is established and used to predict design project completion time.(2)For the problem that completion time of the project is difficult to be estimated due to random rework in the mold design process.The Continuous Time Markov Chain Theory(CTMC)is used to describe the execution state transfer process of the design project and use the phase type distribution(PH)to calculate the probability distribution of the completion time of the project under the assumption that the normal construction period and the rework period of the design task are all subject to the negative exponential distribution.Corresponding computational experiments were designed,and the project completion time obtained from the approximate model was compared with the simulation results.Taking the mold design project and the aero engine maintenance project as examples,the effectiveness of the model and method constructed in this paper is verified.The results show that the proposed method is more efficient than the traditional simulation method.(3)For the problem that project completion time estimated for design task subjected to general distribution.According to the squared coefficient of variation of different task durations,different PH distributions are used to approximate the task duration distribution.Corresponding computational experiments were designed,the project completion time obtained from the approximate model was compared with the simulation results.Hypotheses of the obtained results were performed.The results showed that the approximate model constructed had good reliability.(4)Based on the analysis and study of the estimation of the probability distribution of the completion time of the mold design project,the project tardiness days and weighted tardiness costs are taken as the decision targets,the design project tardiness risk is analyzed,and the calculated project tardiness days probability distribution is calculated.Project delays are forecasted.A large-scale mold enterprise was selected for design projects of different scales,and its tardiness days and weighted tardiness costs were analyzed and calculated.It was found that the probability of task rework had a significant impact on the actual mold project tardiness.This paper conducts a systematic research on the estimation of probability distribution of completion time of mold design projects considering random task rework and random task duration,and applies the relevant models and methods to project tardiness monitoring issues for the mold enterprise provide a decision-making aid in the actual design project management process.