The cumulative curve is an analytic technique that is used for the improvement of production processes and planning in manufacturing. We have already proposed that the cumulative curve can be expressed as GM (1,1) and GM (1,2) models. This paper discusses the problem of classification for cumulative curve and the characteristic of coefficients in GM (1,1) and GM (1,2) models. The coefficients of the cumulative curve for the nine shapes are computed from the Grey Theory. The variations of curve are given as the differences of slope and curvature of the cumulative curve. This paper shows that all kinds of cumulative curves are classified into five basic curves. The classification of cumulative curves can be computed from the coefficients of the GW (1,1) and GM(1,2) models. The classification of curves is used with the Mahalanobis distance in discriminant analysis. The proposed method has also been tested by using numerical examples. This paper shows that all kinds of cumulative curves can be given as the coefficients of GM (1,1) and GM (1,2) models.
The standards of a working area are usually proposed to be determined by standard size of body and the range of movement. This study examined the proper operation area in view of vision and movement load while working through measuring the visual characteristics and muscle load in movement while working. The experiment was conducted through the assembly of model products and the retrieval and placement of parts with changed arrangements of parts within various working areas. As the result, the following was revealed : 1) Accordingly, as the working area is extended, the view stopping time decreases significantly, and the horizontal arrangement of parts is more efficient than vertical arrangement in terms of visual recognition. 2) It was identified that the muscle load caused by retrieval and placement varies according to the angle and the distance. 3) It was proven that the working area is divided by the muscle load and proper part arrangement area for particular conditions.
A new multiple linear regression model has been proposed based on the synchronization of the raw discrete data and the estimated set of dead-times. In this method, intermittent discrete variables would be adopted, if necessary, in addition to the ordinary synchronous discrete variables with the dependent variable. The observational interval consistency of these intermittent data is obtained by natural spline interpolation and resampling. The optimal dead-times are included in the model with respect to explanatory variables. This estimation of dead-time set is performed by the coefficient of determination and t-test. The proposed model has been applied to estimate a price formation function for industrial natural rubber. The goodness of fit of this estimated model has been improved as much as 66 percent, which is four times better than that of the ordinary model. This improved model is fairly compatible with persuasive explanation in economics.
Evolving from cost, quality and delivery time, flexibility is becoming a key dimension of a firm's competitive priorities. The need to explicitly consider flexibility makes it necessary to develop measurements for various types of manufacturing flexibility and analyze their strategic and/or economic value in improving the performance of manufacturing systems. This paper provides investigative insights into the impact of machine flexibility, routing flexibility and volume flexibility on manufacturing performance in a production system which consists of part fabrication process and an assembly line. A variety of experiments are conducted on the simulation model under the condition that urgent orders and machine breakdown cannot be regarded as being negligible, when the three types of flexibilities are introduced alone or simultaneously. The experimental results provide management with a guideline for priority or determining the scope or scale of such activities as standardization in design, process/operations improvement, and investment in equipment, toos, fixtures, etc.
The ability of production equipment should be decided according to demand. It is supposed that production equipment has the upper limit of production quantity in a period and an adjustable range of production quantity without extra cost. The former is called "productive capacity" of production equipment, and the latter is called "flexibility of quantity" of production equipment. Generally, the higher the productive capacity and flexibility of quantity are, the more costly the maintenance and management of production equipment is. Then, for economically deciding the ability of production equipment depending on fluctuation in demand, one should consider both productive capacity and flexibility of quantity. In this paper, we present a distribution-free approach for deciding the ability of production equipment based on the min-max criterion using only expectation and variance for demand fluctuations
This paper deals with the problem of sequencing methods for autonomous complete assembly lines. At first, we propose to set up a multi-channel buffers in each buffer storage, and we formulate the sequencing problem of determining the sequences for the lines. Then, we develop approximate sequencing methods to determine the cooperative and non-cooperative sequences for the lines. Finally, we numerically analyze the effects of the cooperative and non-cooperative sequences for self-completion assembly lines.
In soldering, the position of parts assembled perpendicularly to each other has to be estimated accurately to achieve high quality attachment. Image processing can be applied to inspect soldering positions in two dimensions, but it is hardly ever used to inspect positions of assembled parts in three dimensions. We have developed a method to recognize a three-dimensional object using the information of three-dimensional computer aided design (3D-CAD). Therefore, we propose an inspection method for soldering robots, which enables the measurement of an opening angle formed by two base metals which intersect in a straight line and the discrepancy of their position by comparing the standard figure made by 3 D-CAD with the input image. First, an assembly drawing written by three-dimensional CAD is projected onto a virtual plane in order to obtain a projection drawing which can be used as the two-dimensional standard assembly figure. After an image of actual boards is input and processed, the straight-line intersection of the two boards is detected and set as a reference line. Second, the standard figure is rotated, zoomed and moved in a virtual plane in order to set the two reference lines of the standard figure and input image superimposed precisely on each other. Finally, the standard figure and input image are compared to detect errors of the opening angle and the position of the actual base metals assembled. An experimental application proved that the proposed method is able to inspect three-dimensional objects soldered less in than one second.