Cycle-Time Reduction in Machining by Recursive Constraint Bounding

1997 ◽  
Vol 119 (2) ◽  
pp. 201-207 ◽  
Author(s):  
R. Ivester ◽  
K. Danai ◽  
S. Malkin
Keyword(s):  
Cycle Time ◽  
Process Models ◽  
Process Time ◽  
Time Variability ◽  
Optimal Conditions ◽  
Modeling Uncertainty ◽  
Confidence Levels ◽  
Part Quality ◽  
Control Optimization ◽  
Process Feedback

Modeling uncertainty in machining, caused by modeling inaccuracy, noise and process time-variability due to tool wear, hinders application of traditional optimization to minimize cost or production time. Process time-variability can be overcome by adaptive control optimization (ACO) to improve machine settings in reference to process feedback so as to satisfy constraints associated with part quality and machine capability. However, ACO systems rely on process models to define the optimal conditions, so they are still affected by modeling inaccuracy and noise. This paper presents the method of Recursive Constraint Bounding (RCB2) which is designed to cope with modeling uncertainty as well as process time-variability. RCB2 uses a model, similar to other ACO methods. However, it considers confidence levels and noise buffers to account for degrees of inaccuracy and randomness associated with each modeled constraint. RCB2 assesses optimality by measuring the slack in individual constraints after each part is completed (cycle), and then redefines the constraints to yield more aggressive machine settings for the next cycle. The application of RCB2 is demonstrated here in reducing cycle-time for internal cylindrical plunge grinding.

Integration of On-Machine Measurements in the Force Modeling for Machining of Advanced Nickel-Based Superalloys

2012 ◽  
Author(s):  
Andrew Henderson ◽  
Cristina Bunget ◽  
Thomas Kurfess
Keyword(s):  
Cutting Forces ◽  
Gas Turbines ◽  
High Strength ◽  
Extreme Environment ◽  
Subsurface Damage ◽  
Process Models ◽  
Force Model ◽  
Jet Engines ◽  
Part Quality ◽  
Force Modeling

Nickel-based superalloys are specially designed for applications where high strength, creep resistance, and oxidation resistance are critical at high temperatures. Many of their applications are the hot gas sections of turbo-machinery (e.g. jet engines and gas turbines). With greater demands on the performance and efficiency of these types of machines, the firing temperatures are reaching higher levels and nickel-based superalloys are being utilized more because of their excellent mechanical qualities at extreme temperatures. However, the properties that make them attractive for these applications present difficult challenges for the manufacture, particularly machining, of the components that are made from these materials. Considering the extreme environment that these components operate in, part quality, in particular surface quality, is paramount. The damage and stresses introduced to the surfaces of these components during manufacture needs to be well understood and controlled in order to ensure that premature component and machine failures do not occur. With improved process models and on-machine measurement capabilities, the in-process cutting forces and temperatures can be better understood and therefore subsurface damage can be better controlled. Since cutting forces and temperatures are direct contributors to subsurface damage, better control of these aspects would then lead to better control of subsurface damage. This paper discusses the use of on-machine touch probes to measure wear on milling tools and using those measurements to update a mechanistic force model for more accurate prediction of the cutting forces incurred during the milling of nickel-based superalloys.

Process Window Derivation With an Application to Optical Media Manufacturing

2000 ◽  
Vol 123 (2) ◽  
pp. 303-311 ◽  
Author(s):  
David Kazmer ◽  
Liang Zhu ◽  
David Hatch
Keyword(s):  
Quality Attributes ◽  
Process Models ◽  
Process Window ◽  
Feasible Region ◽  
Part Quality ◽  
Performance Space ◽  
Pareto Optimal Set ◽  
Optical Media ◽  
Quality Specifications ◽  
Optimal Set

This paper derives the process window from quantitative process models. Multi-dimensional clipping algorithms are developed that operate on half-spaces defined from the quality specifications. The resulting polytope is difficult to directly interpret. To support interactive tuning and optimization of manufacturing processes, three types of graphical matrices are presented to the decision maker: (1) the function matrix describes the relations between the process parameters and the manufactured part quality attributes; (2) the process space illustrates the feasible processing space constrained by the product quality specifications; (3) the performance space provides the feasible region of the part quality attributes and the Pareto Optimal set corresponding to the processing space. Optimization of optical media manufacturing is presented to demonstrate the use of the process window to locate a feasible solution and proceed to a desired trade-off of multiple quality attributes.

Effect of Thermal Assistance on the Joining of Al6063 During Flow Drill Screwdriving

2015 ◽  
Author(s):  
Jamie D. Skovron ◽  
Durul Ulutan ◽  
Laine Mears ◽  
Duane Detwiler ◽  
Daniel Paolini ◽  
...  
Keyword(s):  
Fuel Economy ◽  
Cycle Time ◽  
Cost Reduction ◽  
Lower Cost ◽  
Process Time ◽  
Mechanical Process ◽  
Significant Challenge ◽  
Material Temperature ◽  
Process Benefits ◽  
Installation Time

An increase in fuel economy standards has affected automakers’ decision toward designing lightweight vehicles and therefore transitioning from steel-based bodies to ones predominantly composed of aluminum. An introduction to lightweight materials couples that of lightweight joining with a thermo-mechanical process, Flow Drill Screwdriving (FDS). This process is favored in terms of robustness, short installation time, and only requiring access to one side. The most significant challenge of this process is reducing the material sheet separation to minimize any possibility of corrosion buildup. Warm forming of aluminum has been shown to increase ductility and formability of the material and thus the process benefits from a reduced cycle time that leads to cost reduction. In this study, the effect of an auxiliary heat source on the flow of Al6063 is investigated for the FDS application. In order to accomplish this task, a conduction-heating ring is implemented into the FDS process to raise the material temperature and thus reduce the total cycle time. Different preprocess material temperatures are studied to determine the effect of material temperature on the process time, installation torque, and sheet separation. As a result, with the thermal assistance, a reduction in the process time up to 52%, the maximum installation torque by 20%, and sheet separation by 11% were attained, indicating better quality joints at a lower cost.

Effective Cycle Time: A Real World Balancing Index for Paced Assembly Lines

2010 ◽  
Vol 14 (5) ◽  
pp. 431-441
Author(s):  
Konstantinos N. Genikomsakis ◽  
◽  
Vassilios D. Tourassis
Keyword(s):  
Performance Measures ◽  
Cycle Time ◽  
Assembly Line ◽  
Assembly Line Balancing ◽  
Line Balancing ◽  
Research Trend ◽  
Time Variability ◽  
Assembly Lines ◽  
Simulation Experiments

Assembly Line Balancing (ALB) aims at optimally assigning the work elements required to assemble a product to an ordered sequence of workstations, while satisfying precedence constraints. Notwithstanding the advances and developments in ALB over the years, recent and thorough surveys on this field reveal that only a small percentage of companies employ ALB procedures to configure their assembly lines. This paradox may be attributed, to some extent, to the fact that ALB is addressed mostly under ideal conditions. Despite the time variability inherent in manufacturing tasks, there is a strong research trend towards designing and implementing algorithms that consider ALB on a deterministic basis and focus on the optimality of the proposed task assignments according to existing ALB performance measures. In this paper, the need to assess the performance of the proposed solutions of various algorithms in the literature is corroborated through simulation experiments on a benchmark ALB problem under more realistic conditions. A novel ALB index, namely the Effective Cycle Time, ECT, is proposed to assess the quality of alternative assembly line configurations in paced assembly lines operating under task times variations.

Dynamic Optimization of the Grinding Process in Batch Production

2008 ◽  
Author(s):  
Cheol W. Lee
Keyword(s):  
Dynamic Programming ◽  
Dynamic Optimization ◽  
Dynamic Scheduling ◽  
Evolution Strategy ◽  
Batch Size ◽  
Grinding Wheel ◽  
Grinding Process ◽  
Batch Production ◽  
Part Quality ◽  
Process Feedback

This paper presents a novel dynamic optimization framework for the grinding process in batch production. The grinding process exhibits time-varying characteristics due to the progressive wear of the grinding wheel. Nevertheless, many existing frameworks for the grinding process can optimize only one cycle at a time, thereby generating suboptimal solutions. Moreover, a dynamic scheduling of dressing operations in response to process feedback would require significant human intervention with existing methods. We propose a unique dynamic programming - evolution strategy (DP-ES) framework to optimize a series of grinding cycles depending on the wheel condition and batch size. In the proposed framework, a dynamic programming module dynamically determines the frequency and parameter of wheel dressing while the evolution strategy (ES) locates the optimal operating parameters of each cycle subject to the constraints on the operating ranges and part quality. A case study based on experimental data is conducted to demonstrate the advantages of the proposed method over conventional approaches.

A modeling study on the effect of operating parameters on RHCM process using split flow channels design

2019 ◽  
Vol 20 (5) ◽  
pp. 503
Author(s):  
Fatma Kria ◽  
Moez Hammami ◽  
Mounir Baccar
Keyword(s):  
Flow Velocity ◽  
Cycle Time ◽  
Numerical Study ◽  
Cooling Water ◽  
Process Efficiency ◽  
Maximum Temperature ◽  
Coolant Temperature ◽  
Maximum Temperature Difference ◽  
Part Quality ◽  
Split Flow

In this work, a three-dimensional numerical study of thermal behavior of RHCM mold for automotive parts production was undertaken. Particularly, simulation of several heating/cooling cycles was conducted to determine, at the regular cyclic regime, thermal behaviors at cavity/core plates and polymer as well as thermal and hydrodynamic behaviors at cooling water. It was demonstrated that heating/cooling channels with split flow design are suitable for RHCM regulation. Besides, to further promote part quality, process productivity, and profitability, the effect of cooling parameters, such as the coolant temperature and flow velocity in channels, on the RHCM process efficiency was analyzed. To highlight the influence of these parameters on the productivity and profitability of the process, the cycle time and the consumed energy were used. Temperature gap at the cavity plate surfaces after the heating phase as well as the maximum temperature difference (MTD) in the polymer part after the cooling phase were used as criteria to evaluate the automotive part quality. The results show that the coolant temperature increase in the range between 30 and 60 °C reduces the energy consumption and improves the finished product quality with almost the same cycle time obtained by low coolant temperature. As regards to coolant flow velocity effect, an optimum value of about 1 m.s−1 improves part quality and provides a compromise between the cycle time and process profitability.

Effect of Electrical Augmentation on the Joining of Al6063-T5 Using Flow Drill Screws

2016 ◽  
Author(s):  
Jamie D. Skovron ◽  
Brandt J. Ruszkiewicz ◽  
Laine Mears ◽  
Tim Abke
Keyword(s):  
Cross Sections ◽  
Fuel Economy ◽  
Cycle Time ◽  
Thermal Softening ◽  
Process Time ◽  
Joining Technology ◽  
Vehicle Mass ◽  
Material Bodies ◽  
Clamping Pressure ◽  
Penetration Time

Increasing fuel economy standards have motivated automakers to reduce vehicle mass with multi-material bodies-in-white. One joining technology particularly suited for onesided multi-material joining is Flow Drill Screwdriving (FDS), a process by which a fastener friction drills, penetrates the joint, thread-forms, and then torques to apply clamping pressure to the joint. The frictional nature of FDS induces thermal softening of the material but requires time for the heat to build. Prior work with thermal assistance has shown that increasing pre-process temperature leads directly to reducing penetration time, but may add to overall cycle time. A more efficient augmentation approach through Electrical Augmentation (EA) is investigated to reduce cycle time. An experimental investigation of the EA-FDS process is presented, with the joint metrics quantified through installation torque, process time, and breakloose torque. EA-FDS is shown to reduce cycle time, and have the ability to join thicker cross-sections.

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