Processing sheet forming

In the sheet-forming process, stainless steel, bronze, nickel-base alloys, or titanium powders are mixed with a thermosetting plastic and presintered to polymerize the plastic. Sintering takes place in wide, shallow trays. The specified porosity is achieved by selecting the proper particle size of the powder. Sheet is available in a variety of thicknesses between 16 x 30 mm and as much as 60 x 150 cm. A sheet can be sheared, roUed, and welded into different configurations. 

Sheet forming processes, such as vacuum forming, do have effects on the product. The designer should be aware that these will affect the performance of one s product and one should learn how to modify the design to minimize any deleterious effects. Probably the most serious problem encountered in formed film or sheet products results from the fact that the materials are made from film or sheet at temperatures well below the melt softening point of the plastic, usually near the heat distortion temperature for the material. Forming under these condition when the draw down ratio is exceeded for a specific plastic can result in over stretched orientation of the material, the production of frozen-in stresses, poor product reproducibil-... 

Keywords Operability, Sheet Forming Process, Non-square Systems, Model Predictive Control. 

The final chapter (Chapter 10) focuses on web and sheet forming processes. It demonstrates how the statistical techniques can be applied to evaluate process and control performance for quality assurance and to acquire fundamental insight towards the operation of such processes. 

A unique characteristic of the process data for sheet forming processes is the presence of two independent variables, space n and time k. In most cases the target of the process is to maintain the uniformity of Y for all n and k. For some applications a predefined constant CD profile ay... 

Gram polynomials are orthogonal and defined uniquely for discrete data at equidistant positions much like the spatial data collected in sheet forming processes. For N data positions, discrete-point scalar components of the mth-order polynomial vector pm = [Pm,i---Pm,n---Pm,jv] are defined as... 

Performance objective for sheet forming processes is to maintain uniformity or flatness in (Y - The target matrix represents y T for... 

Sheet forming processes have univariate MD and multivariate CD controllers. Process dynamics for both are dominated by gain and time delay. Most of the appreciable dynamics arise from the design of signal filters and... 

A Rigopoulos, Y Arkun, and F Kayihan. Identihcation of full prohle disturbance models for sheet forming processes. AIChE J., 43(3) 727-739, 1997. 

FIGURE 2.65 Flow diagram of radiation cross-linked polyolefin foam sheet forming process. 

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