Magdalena Diering

Statistical Approach to Making Decisions in Manufacturing Process of Floorboard

The study was conducted at a Polish company operating in the wood industry under the R&D project “Increasing the effectiveness of use of wood in manufacturing processes”, aimed at reducing raw material waste in the surface layer manufacturing process. Results of our studies on the improvement of the wet cutting technology are presented in this paper. Minimization of variability is the first step to reduce material consumption in the process of cutting wood into lamellas. Appropriate values of factors which significantly affect lamella thickness after the cutting operation can be determined through real-life experiments. The methodology is to improve and/or reduce operational allowances and to redesign the tolerance and machine parameters/setting.

Measurement System Analysis Combined with Shewhart’s Approach

The paper presents new procedure of methodology for statistical assessment of measurement systems variation (methodology known in the literature as Measurement Systems Analysis, MSA). This procedure allows for calculation and monitoring in real time (that is on-line) of measurement system (MS) characteristics which determine its usability for manufacturing process control. The presented solution pointed out the gap in process control, which consists in lack of methods for monitoring measurement processes in the on-line way. Their key point consists of taking samples that are also needed for the process control chart for the needs of the MSA method. This means that the samples are taken directly from the production line and during the production process. The method is combined with the standard procedure of statistical process control (SPC) with the use of process control charts. It is based on two control charts. The first one is called AD-chart (Average Difference chart) and it allows to estimate the variation between the operators and stability of the monitored measurement system. The second control chart illustrates the %R&R index (Repeatability and Reproducibility) and allows to monitor the MS capability.The paper also presents authors’ proposal of guidelines about the reference value for the %R&R index calculation and assessment. Recommendations and guidelines for choosing the reference value are based on two criteria: information about sample and manufacturing process variation and the purpose of using MS (product or process control).

Soft Modelling-Based Methodology of Raw Material Waste Estimation

The paper looks at soft modelling-based estimation of raw material waste for various variants of a technological process under development. A methodology of assessment of new technology variants, in terms of minimization of the input material waste, is presented. Results of an analysis of variants of a new technology of manufacturing of the middle layer of a flooring board, carried out according to the developed methodology, are shown. The assessment is performed in an original software tool for waste simulation. It is shown that the developed methodology supports the estimation of material waste and assists in the selection of the optimal variant of the process, taking into consideration the constraints of the organization.

A Study of Raters Agreement in Quality Inspection with the Participation of Hearing Disabled Employees

This paper presents results of a study of the level of agreement of assessments and decisions made by quality controllers in a sensory inspection. The study subjects included persons with hearing disability. The study was conducted in an automotive manufacturing company. The employees with hearing loss perform product quality inspection which includes, among other things, visual inspection of the goods. The measurement system analysis (MSA) procedure for attributes, with the use of Gwet’s AC1 coefficient, was applied to estimate the level of agreement of decisions made by the raters. The study results show that the quality of work performed by employees with hearing disability is at least as good as that of able-bodied employees. Based on the knowledge possessed by the authors, this approach to the problem is characterized by novelty.

Organization of Visual Inspection and Its Impact on the Effectiveness of Inspection

The research presented in this paper was aimed to analyse and evaluate the impact of organizational factors on the effectiveness of visual inspection in the manufacturing of electronic systems for the automotive industry. The study was carried out according to the authors’ own methodology consisting of three stages: detailed description of the process, developing a study plan and analysis of the results. The experiment was conducted and influence of three factors: type of inspection, shift and type of defect, was taken into consideration and evaluated. Recommendations were made to improve the quality of such inspections that will lead to the improvement in the final quality of the product.

Methodology Supporting the Planning of Machining Allowances in the Wood Industry

The paper presents a methodology of determination of technological allowances in the manufacturing process of semi-products of deciduous timber (oak). Soft modelling has been proposed for the determination of allowances for the variability of consecutive technological processes caused by the material, machine, operator, measurement system and random factors. The proposed methodology has been applied in the technological process of manufacturing the surface layer of a floor board (lamella). The method of identification of a soft model for the process of cutting timber into lamellas has been presented. Twenty soft models have been identified and recommendations have been made, based on experiments, for reducing the variability and centering the process. The proposed process modelling method facilitates economic estimation of allowances, controlling the manufacturing process and forecasting its future condition. As a result of the research, the manufacturing capacity of lamellas of acceptable quality has been increased by ca. 30%.

Improvement of Acceptance Sampling Inspection for the Operation of Sealing Packages

One of the many purposes for which data are gathered from manufacturing processes is assessment of these processes against predefined criteria. Assessment results are often used for monitoring and supervising the process based on a developed statistical model. This paper looks at the issue of selection of sample size for sampling inspection in the process of packaging medical products. Packaging is an important stage of manufacturing medical products, since the package ensures safety and sterility of the product. In the process of packaging medical products, the operation of sealing the package is of key importance in terms of following medical procedures. Tensile strength of the seal is the critical feature. This paper presents a case study in which an efficient statistical sampling plan was executed for the process of sealing medical packages which led to the saving of time as well as cost.

IMPROVEMENT OF SURFACE LAYER GRINDING PROCESS WITH THE USE OF DESIGN OF EXPERIMENTS METHODOLOGY

The authors introduce the problem of excessive waste of raw material in the wood industry on the basis of the floorboard manufacturing process. The study was aimed to optimize the process of lamella grinding – the final stage in the manufacturing of the oak surface layer. The paper describes implementation of the design of experiments (DoE) methodology to improve the production process of the floorboard surface layer (lamella). The authors made certain assumptions and designed an experiment to obtain high quality lamellas and minimize the waste of raw material. A three -factor full factorial experiment was conducted. The paper presents the conducted study and the authors’ recommendations concerning the determination of optimal machining parameters (on the basis of the results of Experiment 1), parallel arrangement of lamellas (on the basis of Experiment 2), and minimum machining allowance (Experiment 3).