New metallurgy & mold software highlight tooling conference.

A new bi-metal bonding process for mold components, powder-metallurgy mold steels, and novel mold-filling analysis capabilities using the power of graphics supercomputing, were among the developments presented at last month's SPE Moldmaking and Mold Design RETEC in Rosemont, Ill.

BI-METAL BONDING PROCESS

A new bi-metal process that combines steels and nonferrous materials for better mold performance has been introduced by Cavaform Inc., St. Petersburg, Fla. The bi-metal process, called Cavaclad, follows an initial cold-forming process, known as Cavaforming, for the manufacture of deep mold cavities. Under Cavaforming, a mandrel with the mold cavity configuration is first produced in hardened high-speed tool steel. A tool steel blank is then cold formed around the mandrel, reproducing in size and finish the mandrel form. Cavities reportedly are alike within a few tenths of a mil, and surface finish is consistent down to 4-6 micro-in. repeatability.

During the Cavaclad process, the Cavaform cavity is lathe-turned and hardened at an optimum size to include shut-off areas, gates, vents, etc. The hardened Cavaform cavity is then clad with an outer shell, or jacket, using the same cold swaging process.

The jacket can be another tool steel compatible in its heat-treatment cycle with the original material, or a material of greater thermal conductivity and higher corrosion resistance can be used to improve the cavities' cooling capability. Some beryllium-copper alloys, as well as Ampcoloy 940 and 945 alloys from Ampco Metal, Inc., Milwaukee, are recommended by Cavaform for this purpose.

The cladding process can be reversed to manufacture core pins with highly conductive noncorrosive material cold-swaged as an internal heat sink. Applications include closures, parisons, heavy-wall medical and cosmetic parts, and writing instruments. (CIRCLE 8)

Wear-resistant tool steels produced by powder metallurgy are available from Bohler Brothers of America, Inc., Wood Dale, Ill. Bohler's M390 Isomatrix PM grade consists of large percentages of chromium and vanadium carbides in a matrix containing at least 12% chromium, providing high corrosion resistance, wear resistance and excellent polishability, the company says. Suitable mold applications include inserts for compact disks, electronic microchip encapsulation, and tools for chemically aggressive plastics or ones containing highly abrasive fillers. (CIRCLE 9)

DYNAMIC FLOW ANALYSIS

A proprietary mold analysis that uses the benefits of supercomputing graphics is being offered as a consulting service by Eastman Chemical Co.'s Performance Plastics Div. in Kingsport, Tenn. The so-called Kodak Glyph Visualization System is said to overcome limitations of conventional mold-analysis packages that use static displays in a two-dimensional format, which may make interpretation difficult.

Sun UNIX-based SPARC stations are used to create the finite-element models. These workstations are networked to a Sun server workstation, which is used to control the glyph analysis display. The heart of the system is an AT&T Pixel Machine, which has the supercomputing power to dynamically display flow front, temperature, pressure, flow direction, and velocity, in high resolution at the same time. Models are created using the I-DEAS software of Structural Dynamics Research Corp. (SDRC), Milford, Ohio. The actual flow simulation is performed using a modified version of the Cornell Injection Molding Program (CIMP).

Glyphs are little on-screen icons in the shape of triangular towers that are superimposed on the part geometry to symbolically convey abstract information. A glyph consists of layers of triangular slabs, each of which represents a section of plastic wall thickness, so that the entire glyph conveys the complete part thickness at that location. The direction in which the triangles point indicates the flow direction. The length of each layer is proportional to the flow velocity in the layer. Colors of the layers represent melt temperatures across the thickness of the advancing flow front.

One advantage of this approach is that the results of the analysis are displayed at many different layers within the flowing melt, rather than using bulk averages. Shear effects may be dynamically displayed by only displaying glyph layers above a certain temperature.

The software can produce an x-y plot of gate pressure, clamp force, and flow rate vs. time, as well as numerical temperature and velocity values at different layers of a mesh element at particular instants of time. Eastman can also present the results of the analysis in video format to ease interpretation of the data. (CIRCLE 10)