32 research outputs found
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Bevel Cutting Methods and Cutting Trajectory Control for Steel Laminations Used in Tooling
Bevel cutting of steel laminations used in profiled-edge laminated tooling allows for a more accurate
representation of the intended die surface, since stair-stepping at the edges is eliminated. Based on experiments
involving maximum cutting speed, bevel angle and kerf quality, the three recommended methods for bevel cutting
steel are (best to worst) pulsed Nd:YAG laser with hard-optic delivery, abrasive water jet, and machining with the
flute edge of an endmill. For each method, bevel angles of up to 80 degrees are possible. Further experimentation
was used to determine the optimal process parameters for kerf quality, with constant cutting speed being one ofthe
main requirements. Finally, a new techIlique to assure constant velocity along the entire lamination cutting trajectory
is developed.Mechanical Engineerin
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Freeform Powder Molding for Rapid Tooling
Tooling development can be quite time consuming and costly. Several iterations may be
required, and later product or process modifications may necessitate tooling redesign. Rapid
prototyping techniques capable of meeting the structural requirements of short-run and end-use
tooling will have a significant impact on the product development cycle. This paper presents a
technique for producing tooling using the Freeform Powder Molding process. Resulting tooling
can be made from a wide variety of readily available metal powders, and mechanical properties can
be tailored for customized tool design and fabrication. The example presented in this paper focuses
on the rapid production of tooling for sheet metal formingMechanical Engineerin
Biomarkers of Nutrition for Development (BOND)—Iron Review
This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health. The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation
‘Stealth’ nanoparticles evade neural immune cells but also evade major brain cell populations: Implications for PEG-based neurotherapeutics
A Preliminary Study of Sealing and Heat Transfer Performance of Conformal Channels and Cooling Fins in Laminated Tooling
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Bonding Methods for Laminated Tooling
Laminated tooling consists of an array of stacked laminations that are mechanically
clamped or bonded together, depending on the requirements of the manufacturing process.
Various manufacturing processes that can benefit from tooling constructed oflaminations include
sheet metal forming, thermoforming, composites molding, metal extrusion, injection molding,
resin transfer molding, and compression molding. When bonding of the laminations is required
(e.g., incorporation of conformal cooling passages for injection molding temperature control)
then laminations can be joined together by diffusion bonding, brazing and using adhesives.
However, for a tooling engineer to effectively design a laminated tool, the physical and
mechanical properties of these joints must be known. Consequently, a set of experiments is
outlined for determining the tensile, shear, and peel strengths, tensile and shear elastic moduli,
thermal contact resistance, and specific permeability (for gasses or liquids) ofthe aforementioned
bonded joints for both steel and aluminum laminations. Some preliminary results with aluminum
and future work are presented.Mechanical Engineerin
Simplifying the Development and Usage of Fixtures for Sheet Metal and Composite Aircraft Parts
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Recent Developments in Profiled-Edge Lamination Dies for Sheet Metal Forming
The Profiled-Edge Lamination (PEL) method was developed by the Walczyk and Hardt as an improvement oer the current method of stacking and bonding contured laminations in
terms of the lead-time and cost of toolIng development for sheet metal forming dies. It is also a
viable alternative to conventional CNC-machining of such dies. In pursuit of successful
commercial realization of the PEL method in industry, this paper discusses several important issues
including:
• the origin of this method and advantages over other tooling techniques
• the general procedure for creating PEL machining instructions
• determining the geometric error introduced by the straight bevel approximation
• the propensity for PEL die delamination from high forming loads
• methods for cutting bevels into die laminations and
• the machinery needed for PEL die fabrication.
Future research and developmental work on the PEL die method will also be outlined.Mechanical Engineerin