Dradjad Irianto

AN INTEGRATED MODEL FOR PROCESS SELECTION AND QUALITY IMPROVEMENT IN MULTI-STAGE PROCESSES

All production processes produce variance around the desired target value of quality characteristic. This variance affects the product quality level. Accordingly variance reduction needs to be done as the main goal of quality improvement programs. However effort to improve quality of each product unit must take into account to improvement costs. This paper proposes an optimization model for quality improvement in multi-stage processes using a non linear programming model by selecting alternatives process and determining unit of production of each stage to maximize profit as the difference between total income and total relevant cost. Total cost includes manufacturing cost, quality loss cost, rework and scrap cost, and quality improvement implementation cost. This optimization model is implemented in make-to-order manufacturer that produces crimper (a parts of joining plastic packages in packaging machine) which consist of five main stage manufacturing processes. Sensitivity analysis shows that the optimal solution is not sensitive if little changes occur in the constraints scenario. Thus, adding the value constraint on the quality specification, stage capacity, and quality improvement budget will not improve the objective function.

Inspection and correction policies in setting economic product tolerance

Abstract Traditionally, inspection for quality of a product is performed only at the final stage of the production process. This means that any non-conformance has been manufactured at the time they are inspected. Recently, incorporating the complete inspection into the production process becomes available due to manufacturing automation and smaller production lot size. These also permit, for certain products, necessary correction or rework in order to meet product specifications or requirements. For being competitive, additional expenses come from inspection as well as correction should be minimized. In this paper, we consider an approach called product loss function, together with costs of inspection and correction, to develop an expected cost model. Optimization is done based on trading off the components of the model to select the most profitable tolerance. This optimization procedure not only leads to an optimum product tolerance, but also reflects the balance between manufacturer expenses to improve the quality of product and the loss suffered by a customer. Similarly, a different policy is applied and seeks the effect on tolerance. The effect of imperfect measurement on product tolerance will also be presented.

PRIORITIZING KEY CHARACTERISTICS

Key characteristics (KCs) priority has to be determined by manufacturing company to help them in determine which KC has the most influence to the manufacturing cost and quality loss. This paper proposes a simple method to prioritize key characteristics using pareto diagram based on the result of an optimization model. The model is developed to find optimal tolerance and process characteristics of KCs. The objective function of the optimization model is to minimize the manufacturing cost and quality loss. Vice jaw is used as an example to illustrate the implementation of the model.

Optimization Models for Deriving Optimum Target of Key Characteristics

The aim of this research is to develop optimization models in deriving optimum target of key characteristic (KC). There are two kinds of product KCs introduced in this paper, namely performance and dimension product KC. The performance product KC target values must be determined by balancing customer and designer utilities subject to design cost and time provided by a company. The KCs of a product can be visualized using a KC flow-down which shows the hierarchical structure of the product. The flow-down may consist of many levels from product KC to process KC. Using axiomatic design as a methodology to map the flow-down, we conclude that product KC, assembly-components KC, and process KC are in functional domain, physical domain, and process domain respectively. In this paper, the objective function of the model for deriving optimum product KC target is to minimize utility gap between customer and designer subject to design cost and time. The assembly-component KCs have to be derived considering the product KC targets. In the absence of product KC target, the objective function of the model is to maximize the desired effect or minimizing the undesired effect. In the existence of product KC target, the objective function of the model is to attain the target considering technical constraints of the product. We use a shaft design problem as a numerical example to show the implementation of the models.

Collaborative Manufacturing for Small-Medium Enterprises

Manufacturing systems involve decisions concerning production processes, capacity, planning, and control. In a MTO manufacturing systems, strategic decisions concerning fulfilment of customer requirement, manufacturing cost, and due date of delivery are the most important. In order to accelerate the decision making process, research on decision making structure when receiving order and sequencing activities under limited capacity is required. An effective decision making process is typically required by small-medium components and tools maker as supporting industries to large industries. On one side, metal small-medium enterprises are expected to produce parts, components or tools (i.e. jigs, fixture, mold, and dies) with high precision, low cost, and exact delivery time. On the other side, a metal small- medium enterprise may have weak bargaining position due to aspects such as low production capacity, limited budget for material procurement, and limited high precision machine and equipment. Instead of receiving order exclusively, a small-medium enterprise can collaborate with other small-medium enterprise in order to fulfill requirements high quality, low manufacturing cost, and just in time delivery. Small-medium enterprises can share their best capabilities to form effective supporting industries. Independent body such as community service at university can take a role as a collaboration manager. The Laboratory of Production Systems at Bandung Institute of Technology has implemented shared manufacturing systems for small-medium enterprise collaboration.

Servicing strategy and preventive maintenance for products sold with one-dimensional warranties

A manufacturer sells its product with a longer warranty period in order to increase the product competitiveness. Offering a product with a longer warranty period increases the warranty cost to the manufacturer. For a repairable product, an appropriate servicing strategy can reduce the warranty cost significantly. Many servicing strategies involving replacement or imperfect repair have been studied in the literature. In this paper, we study a servicing strategy which considers preventive maintenance and imperfect repair to reduce the warranty cost.

Bearing Procurement Analysis Method by Total Cost of Ownership Analysis and Reliability Prediction

In making bearing procurement analysis, price and its reliability must be considered as decision criteria, since price determines the direct cost as acquisition cost and reliability of bearing determine the indirect cost such as maintenance cost. Despite the indirect cost is hard to identify and measured, it has high contribution to overall cost that will be incurred. So, the indirect cost of reliability must be considered when making bearing procurement analysis. This paper tries to explain bearing evaluation method with the total cost of ownership analysis to consider price and maintenance cost as decision criteria. Furthermore, since there is a lack of failure data when bearing evaluation phase is conducted, reliability prediction method is used to predict bearing reliability from its dynamic load rating parameter. With this method, bearing with a higher price but has higher reliability is preferable for long-term planning. But for short-term planning the cheaper one but has lower reliability is preferable. This contextuality can give rise to conflict between stakeholders. Thus, the planning horizon needs to be agreed by all stakeholder before making a procurement decision.

Interaction capability, process quality, and outsourcing success: A vendor perspective in offshore IT outsourcing

Nowadays the competition in IT offshoring is fierce along with the rapid growth of IT offshoring. Some of Indonesian IT vendors succeed in acquiring IT projects from clients abroad, but some of them are not successful in delivering the project. Some previous studies have included interaction capability as the determinant of IT outsourcing success, but the concept of interaction is considered as one dimension. This study will explore dimensions of interaction capability including its determinants. Based on the result of semi-structured interview with the representative of Indonesias leading offshore IT outsourcing company, the interaction between the company and client is very important for the success of software development. Our results show that communication and coordination are the main dimensions of interaction capability. The supporting determinants of interaction capability include human resources management and technology. The inhibiting determinants of interaction capability include cultural distance and temporal distance.

Comparison of quality engineering practices in Malaysian and Indonesian automotive related companies

The main motivating factor driving this research is to find differences between the automotive related companies in Malaysia and Indonesia with regard to quality engineering (QE) implementation. A comparative study between Malaysia and Indonesia provides the opportunity to gain perspective and thorough understanding of the similarities and differences on the critical factors for successful QE practices in the context of both these countries. Face to face interviews are used to compare the QE practices in two automotive companies in Malaysia and Indonesia, respectively. The findings of study showed that both countries have clear quality objectives to achieving zero defects in processes and products and total customer satisfaction. Top and middle management in both countries were found to be directly involved in quality improvement on the shop floor to provide On-The-Job training and actively encourage team members to perform quality problem solving through the formation of quality control circles (QCC) particularly in Indonesia automotive industry. In Malaysia automotive industry, the implementation was not fully effective, but they have started to cultivate those values in the daily execution. Based on the case study results and analysis, the researcher has provided suggestions for both countries as an improvement plan for successful QE implementation. These recommendations will allow management to implement appropriate strategies for better QE implementation which hopefully can improve companys performance and ultimately the making the automotive industry in both countries to reach world class quality. It is strongly believed that the findings of this study can help Malaysia and Indonesia automotive industries in their efforts to become more effective and competitive.

Improving Quality of Seal Leak Test Product using Six Sigma

Seal leak test part is a polyurethane material-based product. Based on past data, defect level of this product was 8%, higher than the target of 5%. Quality improvement effort was done using six sigma method that included phases of define, measure, analyse, improve, and control. In the design phase, a Delphi method was used to identify factors that were critical to quality. In the measure phase, stability and process capability was measured. Fault tree analysis (FTA) and failure mode and effect analysis (FMEA) were used in the next phase to analize the root cause and to determine the priority issues. Improve phase was done by compiling, selecting, and designing alternative repair. Some improvement efforts were identified, i.e. (i) making a checklist for maintenance schedules, (ii) making written reminder form, (iii) modifying the SOP more detail, and (iv) performing a major service to the vacuum machine. To ensure the continuity of improvement efforts, some control activities were executed, i.e. (i) controlling, monitoring, documenting, and setting target frequently, (ii) implementing reward and punishment system, (iii) adding cleaning tool, and (iv) building six sigma organizational structure.