Compression Molding Machine Selection

aPriori selects the feasible Compression Molding machine with the lowest overhead (specified by the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate). A machine is considered feasible if it passes the following checks:

Platen Length Check

aPriori checks that the Total Mold Base Length is less than or equal to the Platen Length machine property. Total Mold Base Length is calculated as the sum of Mold Base Length (specified by the Mold Base Size – Length setup option) and Plate Overhang Allowance (specified by the cmPlateOverhangAllowance cost model variable; 75 mm in starting point Digital Factories).

Platen Width Check

aPriori checks that the Total Mold Base Width is less than or equal to the Platen Width machine property. Total Mold Base Width is calculated as the sum of Mold Base Width (specified by the Mold Base Size – Width setup option) and Plate Overhang Allowance (as described above for Platen Length Check).

Press Force Check

aPriori checks that the Required Press Force is less than or equal to the Press Force machine property. Required Press Force is calculated as: ((Projected Area * (Material Molding Pressure + (Excess Depth Factor * Excess Depth))) * Press Safety Factor:

  • Projected Area: This is the Projected Area property of the Parting Line GCD.

  • Material Molding Pressure: As specified by the material’s Compression Molding Pressure in MPa, as defined in the Material Selection table.

  • Excess Depth Factor: This varies between 1.44 - 5.17 MPa for thicknesses between 25.4 - 38.1 mm.

  • Excess Depth: This is calculated as the part’s Max Thickness geometric property - Excess Thickness Threshold (specified by the compressionMoldingExcessThicknessThreshold cost model variable; 25.4 mm in starting point Digital Factories).

  • Press Safety Factor: As specified by the cmPressForceSafetyFactor cost model variable (1.25 in starting point Digital Factories).

Mold Height Check

aPriori checks that the combined Shut Height and Travel Distance is less than or equal to the Daylight machine property. Combined Shut Height and Travel Distance is calculated as (Mold Base Shut Height + Required Travel Distance):

  • Mold Base Shut Height: This is calculated as: (Cavity Plate Thickness + CM Core Plate Min Allowance + Top Clamp Plate Thickness + Bottom Clamp Plate Thickness + Ejector Box Height):

    • Cavity Plate Thickness: This is specified by the Cavity Plate Height setup option.

    • CM Core Plate Min Allowance: This is calculated as: Core Plate Height (setup option) - maximum reach of the tool (calculated from the parting line) + Cup Cavity Height In B Plate (see below) if the part is cup-shaped and the maximum reach of the tool is greater than Cup Cavity Height In B Plate.

      • Cup Cavity Height In B Plate is calculated as: (1- aPlateCupCavityRatio (cost model variable; see Cavity Plate Height) * Part Box Height).

      • Otherwise, this is specified by the Core Plate Height setup option.

    • Top Clamp Plate Thickness: This is specified by the cmTopClampPlateThickness cost model variable (75 mm in starting point Digital Factories).

    • Bottom Clamp Plate Thickness: This is specified by the cmBottomClampThickness cost model variable (75 mm in starting point Digital Factories).

    • Ejector Box Height: If the Part Ejection Method setup option is set to ‘Hydraulic Ejector Pins’, aPriori uses the value of the cmEjectorBoxRailsHeight cost model variable (152.4 mm in starting point Digital Factories). Otherwise, aPriori uses a value of 0.

  • Required Travel Distance: This depends on the shape of the part:

    • If cup shaped: Part Height * Travel Distance Multiplier Cup (as specified by the cmTravelDistanceMultiplierCup cost model variable: 2.5 in starting point Digital Factories).

    • Otherwise: Part Height * Travel Distance Multiplier Flat (as specified by the cmTravelDistanceMultiplierFlat cost model variable: 4 in starting point Digital Factories).

aPriori prioritizes preferred machines, provided the cost model variable usePreferredMachines is set to true, before selecting the machine with the lowest overhead (specified by the sum of the machine properties Direct Overhead Rate and Indirect Overhead Rate). A machine is considered preferred if it has the Is Preferred property set to true. Otherwise, aPriori selects from all machines.

You can find Compression Molding machines in the Digital Factory under Plastic Molding > Machines > Compression Molding.