“Real-Time Spatial Particulate Mass Deposition Tester”

Inventors: V.M. Puri, et al.

PSU Invention Disclosure No. 97-1707

Issued U.S. Patent No. 6,089,100

A wide variety of products such as medicinal tablets, tool inserts, electronic components, automobile parts, and food pellets are produced by subjecting a fixed mass or volume of dry cohesive particulate material, poured into a die, to high pressures. This manufacturing technique is referred to as compaction or pelletization. The quality of the product made by pelletization is recognized to be dependent upon many factors such as intrinsic material properties, particulate material properties, nature of applied load, and die geometry. Many pelletization defects such as lamination, capping, and stress cracking etc. are caused by anisotropic compaction of the particulate material. Anisotropic compaction also contributes to non-uniform pre-compaction fill density of the particulate material in the die.

The subject invention represents a relatively low cost, compact, robust and portable test equipment designed to solve the problem of determination of pre-compaction fill density distribution in dies. This invention is based on the principle that an anisotropic fill density distribution would result in an uneven particulate vertical pressure distribution on the inside face of the bottom surface of the die.

A prototype has been designed and tested. As shown in the attachment, five different powders have been used as the test materials. Four powders, one each from four different categories, 1) Food – Wheat Flour, 2) Ceramic – Alumina, 3) Powdered metal – Silicon nitride, and 4) Pharmaceutical – Micro-crystalline cellulose, 5) and glass beads (around 100 micron particle size). The glass beads serve as the control powder, since they are near spherical in shape, have a narrow particle size distribution, and are free of additives such as lubricants and binders. Data interpretation of the attachment leads to the inference that die shape, size and rate of fill may be significant factors affecting die fill density distribution. This is indicated by the different ratios of the cumulative mass accumulation values for; a) different aspect ratios at the same filling rate, b) both load cell locations, and c) both die cross sections.

As demonstrated, this device has potential wide applications in and benefits to industries that deal with particulate materials handling, storage, and processing such as pharmaceuticals, chemicals, pigments, minerals, foods, ceramics and powder metals.