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David O. Kazmer
Injection Mold Design Engineering
| Nomenclature |
Mold engineering requires analysis, and so an extensive nomenclature has been developed. L, W, and H refer to the length, width, and height dimensions as shown in Figure 1.
Figure 1 Length, width, and height nomenclature
Variable names have been selected and consistently used as expected (e. g., T for temperature, C for cost, P for pressure, etc.). R refers to rate-related constants (with time dependence) and κ refers to monetary constants (with cost dependence). To provide clarity, variable subscripts are unabbreviated throughout most of the book. The nomenclature for many of the variables and their units are as follows.
Table 1 Nomenclature
| Variable | Meaning |
| α | Thermal diffusivity [m2/s] |
| β | Compressibility [1/MPa] |
| δ | Deflection [m] |
| δbending | Deflection due to bending [m] |
| δcompression | Deflection due to compression [m] |
| δtotal | Deflection due to bending and compression [m] |
| Strain [m/m] |
| Plastic's strain to failure [%] |
| Shear rate [1/s] |
| Maximum allowable shear rate for a plastic melt being molded [1/s] |
| η | Viscosity [Pa s] |
| κ | Thermal conductivity [W/m°C] |
| κinsert | Cost per unit volume of core and cavity insert materials [$/m3] |
| κmold | Cost of mold metal per kilogram [$/kg] |
| κplastic | Cost of plastic per kilogram [$/kg] |
| λ | Tolerance limit [m] |
| μ | Apparent viscosity for Newtonian model [Pa] |
| μstatic | Coefficient of static friction [‒] |
| ρ | Density [kg/m3] |
| ρinsert | Density of core and cavity insert materials [kg/m3] |
| ρplastic | Density of plastic [kg/m3] |
| φ | Draft angle [°] |
| θ | Draft angle [°] |
| σbuckling | Stress level at which column buckles [MPa] |
| σcyclic | Imposed cyclic stress [MPa] |
| σendurance | Maximum allowable stress given cyclic loading [MPa] |
| σhoop | Hoop stress [MPa] |
| σlimit | Maximum allowable stress given cyclic loading or yielding [MPa] |
| σyield | Maximum allowable stress given yield failure [MPa] |
| T | Shear stress [Pa] |
| V | Specific volume [‒] |
| Ωejectors | Total perimeter of all ejectors [m] |
| Acavity_Projected | Projected area of the mold cavity [m2] |
| Acompression | Area exposed to compressive stress [m2] |
| Aeff | Effective area under stress [m2] |
| Aejectors | Total area of all ejectors [m2] |
| Apart | Total surface area of the molded part |
| Ashear | Area exposed to shear stress [m2] |
| C | Tolerance coefficient for a standard fit [m2/3] |
| Cauxiliaries | Total cost of all auxiliaries [$] |
| Cinserts | Total cost of all cavities [$] |
| Cinsert_finishing | Cost of finishing one set of core and cavity inserts [$] |
| Cinsert_machining | Cost of machining one set of core and cavity inserts [$] |
| Cinsert_materials | Cost of materials for one set of core and cavity inserts [$] |
| Cmold | Total cost of purchasing mold [$] |
| Cmold/part | Cost of purchasing mold amortized across total production quantity [$] |
| Cmold_base | Total cost of mold base and modifications [$] |
| Cmold_customization | Total cost of all customizations of mold base [$] |
| Cmold_steel | Initial purchase cost of mold base or steel [$] |
| Cpart | Total cost per molded part [$] |
| Cplastic/part | Cost of material used in molding one part [$] |
| Cprocess/part | Cost of machinery and labor used to mold one part [$] |
| CPplastic | Plastic's specific heat [J/kg °C] |
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