User Inputs for Compression Molding

The Compression Molding process provides the following setup options (it also uses several setup options that are used by all Plastic Molding processes and documented elsewhere: see Cavity Finish, Cavity Texture, Margin Rate (%), SG&A Rate, Import Duty Rate, Freight Rate, Number of Tools, Number of Operators (Piece Part Cost Driver), Select EDM Electrode Material, Stress Relief Mold, and Heat Treating of Mold):

• Cavity Plate Height

• Cavity Texture

• Compression Molding Pressure

• Core Plate Height

• Include Manual Flash Trimming When No Internal Cutouts Exist

• Inserted Component Cost

• Internal Cutouts Are Capped

• Material Charge Mass

• Material Colorant

• Mold Base Size – Length

• Mold Base Size – Width

• Mold Closure Type

• Nominal Wall Thickness

• Number of Inserted Components

• Number of Material Charge Pieces

• Number of Small Rib Inserts

• Number of Medium Rib Inserts

• Number of Large Rib Inserts

• Part Ejection Method

• Plating of the Mold

• Select Mold Material – Clamp Plates

• Select Mold Material – Ejector Box

• Select Mold Material – Main Plates

• Select Mold Material – Rib Inserts

The Parting Line Trim Length setup option is also used by the Compression Molding process:

• Parting Line Trim Length (operation-level PSO)

Cavity Plate Height

This setup option affects machine selection and tooling costs.

This specifies the thickness of the cavity plate prior to machining. By default, aPriori calculates this as follows:

• If the molded part type is a cup shape:

  • Part Box Height * the aPlateCupCavityRatio cost model variable (the fractional percentage of the part cavity height that is within the cavity plate for a cup-shaped part; this is 1 (100%) in starting point Digital Factories but may range between 0 to 1).

  • Plus, the greater of either:

    • The cmAPlateMinThickness cost model variable (the minimum distance from the shallowest point of the cavity to the back of the cavity plate; 85.725 mm in starting point Digital Factories).

      Or:

    • The product of the cmHeaterLineDiameterAllowanceFactor cost model variable (factor applied to the heater line diameter to determine the thickness allowance for the cavity (A Plate) and core (B Plate); 4 in starting point Digital Factories) and the cmHeaterLineDiameter cost model variable (the diameter of the tool heater line; 12.7 mm in starting point Digital Factories).

• Otherwise:

  • Part Box Height * the aPlateFlatCavityRatio cost model variable (the fractional percentage of the cavity height that is within the cavity plate for a flat part; this is 0.5 (50%) in starting point Digital Factories but may range between 0 to 1).

  • Plus, the greater of either:

    • The cmAPlateMinThickness cost model variable (as described above).

      Or:

    • The product of the cmHeaterLineDiameterAllowanceFactor and cmHeaterLineDiameter cost model variables (as described above).

With this setup option, users can override the default on a per-part basis. The minimum value depends on the shape of the part:

• If cup shaped, the minimum value is the greater of either:

  • Part Box Height * aPlateCupCavityRatio (cost model variable, as described above).

    Or the greater of:

    • cmAPlateMinThickness (cost model variable, as described above).

      Or:

    • The product of the cmHeaterLineDiameterAllowanceFactor and cmHeaterLineDiameter cost model variables (as described above).

• Otherwise, the minimum value is the greater of either:

  • Part Box Height * aPlateFlatCavityRatio (cost model variable, as described above).

    Or the greater of:

    • cmAPlateMinThickness (cost model variable, as described above).

      Or:

    • The product of the cmHeaterLineDiameterAllowanceFactor and cmHeaterLineDiameter cost model variables (as described above).

Cavity Texture

For details, see Cavity Texture in the User Inputs Affecting Tooling Costs section.

Compression Molding Pressure

This setup option affects machine selection.

This specifies the press force of the molding tool for the material. By default, aPriori calculates this as the mean average of the material’s Compression Molding Pressure Max and Compression Molding Pressure Min values, in N/mm². The Min and Max are defined in the Material Selection table.

With this setup option, users can override aPriori’s calculated figure by selecting one of the following options:

• Calculated Value: aPriori’s calculated value, as described above.

• Material Recommended Min: The material’s Compression Molding Pressure Min in N/mm², as defined in the Material Selection table.

• Material Recommended Max: The material’s Compression Molding Pressure Max in N/mm², as defined in the Material Selection table.

• User Override: Users can enter their own value. Note that no checks are conducted for viability.

The Compression Molding Pressure is also used in the machine selection criteria for Compression Molding. In addition to checks for platen size and mold height, aPriori uses the Compression Molding Pressure figure as part of the calculation for checking that the required pressing force is less than or equal to the machine’s Press Force (the maximum rated clamping force of the machine in kN; this is defined in the Digital Factory under Plastic Molding > Machines > Compression Molding > [Name of machine] > Press Force. This ensures that the molding pressure is sufficient to distribute the material throughout the mold tool as it is pressing.

For more information, see Compression Molding Machine Selection.

Core Plate Height

This setup option affects machine selection and tooling costs.

This specifies the thickness of the core plate prior to machining. By default, aPriori calculates this as follows:

• If the molded part type is a cup shape:

  • The sum of Part Box Height and the greater of either:

    • The cmBPlateMinThickness cost model variable (the minimum distance from the deepest point of the cavity to the back of the core plate; 85.725 mm in starting point Digital Factories).

      Or:

    • The product of the cmHeaterLineDiameterAllowanceFactor cost model variable (factor applied to the heater line diameter to determine the thickness allowance for the cavity (A Plate) and core (B Plate); 4 in starting point Digital Factories) and the cmHeaterLineDiameter cost model variable (the diameter of the tool heater line; 12.7 mm in starting point Digital Factories).

  • Minus the Nominal Wall Thickness (extracted from the part geometry; see Nominal Wall Thickness setup option).

• Otherwise:

  • Part Box Height * (1 - aPlateFlatCavityRatio) (as described for the Cavity Plate Height setup option).

  • Plus, the greater of either:

    • The cmBPlateMinThickness cost model variable (as described above).

      Or:

    • cmHeaterLineDiameterAllowanceFactor * cmHeaterLineDiameter (cost model variables, as described above).

With this setup option, users can override the default on a per-part basis. The minimum value depends on the shape of the part:

• If cup shaped, the minimum value is the greater of either:

  • (Part Box Height - Nominal Wall Thickness).

    Or:

  • The greater of:

    • cmBPlateMinThickness (cost model variable, as described above).

      Or:

    • cmHeaterLineDiameterAllowanceFactor * cmHeaterLineDiameter (cost model variables, as described above).

• Otherwise, the minimum value is the greater of either:

  • (Part Box Height * (1 - aPlateFlatCavityRatio cost model variable; 0.5 (50%) in starting point Digital Factories).

  • Or:

  • The greater of:

    • cmBPlateMinThickness (cost model variable, as described above).

      Or:

    • cmHeaterLineDiameterAllowanceFactor * cmHeaterLineDiameter (cost model variables, as described above).

Include Manual Flash Trimming When No Internal Cutouts Exist

This setup option affects cycle time.

This specifies whether to automatically include manual flash trimming when no internal cutouts are detected in the part, and therefore omit post-molding trimming (by 5-Axis Router or Waterjet). Instead, any flash is trimmed by the operator while the next part is in the press. The time taken for the manual flash trimming operation is part of the calculation used for Compression Molding Cycle Time Calculation.

By default, aPriori uses the value of the cmAutoIncludeManualFlashTrimming cost model variable for this option; the default in starting point Digital Factories is true.

With this setup option, users can override the default on a per-part basis.

Inserted Component Cost

This setup option affects Additional Direct Costs.

This specifies the cost per individual inserted component loaded into the tool (assumed to be all the same price). By default, aPriori uses the value of the cmInsertedComponentCost cost model variable for this option (0.25 US Dollars in starting point Digital Factories).

With this setup option, users can override the default on a per-part basis. See also Number of Inserted Components.

Internal Cutouts Are Capped

This setup option impacts material utilization.

This specifies whether internal cutouts are ‘capped’ with material during the molding process. By default, aPriori uses the value of the cmInternalCutoutsCappedDefault cost model variable for this option; the default in starting point Digital Factories is true.

There are two options:

• True: Internal cutout areas are ‘capped’ with material during the molding process; post-processing, this material must be removed and scrapped (the cured material cannot be recycled). This results in lower material utilization for parts with cutouts. Note also that parts with cutouts are likely to have a higher Number of Material Charge Pieces.

• False: The mold is designed to shut off material distribution to internal cutout areas. This can result in a much higher material utilization and reduced Material Cost.

Material Charge Mass

This setup option affects cycle time and material utilization.

This specifies the mass of material charge loaded into the tool. This figure has a significant impact on material utilization and therefore material cost. By default, aPriori estimates this using the formula:

Estimated Charge Volume * Material Density

Estimated Charge Volume is the sum of Part Volume, Cutout Volume, and Flash Volume:

• Part Volume: As extracted from CAD file.

• Cutout Volume: This depends on the Internal Cutouts Are Capped and Mold Closure Type setup options, as described in the table below and the detailed calculations that follow:

  Internal Cutouts Are Capped	Mold Closure Type	Cutout Volume
  False	Positive	0
  	Semi-Positive	(Difference in areas calculation + Void Cutouts Flash Area) * Flash Ridge Thickness Semi Positive Type
  	Flash	(Difference in areas calculation + Void Cutouts Flash Area) * Flash Ridge Thickness Flash Type + (Difference in areas calculation using 2 * Flash Ridge Allowance + Void Cutouts Flash Area) * Flash Cavity Thickness
  True	Positive	((Parting Line Solid Shadow Area - Parting Line Projected Area) + Void Cutouts Capped Area) * Capped Cutout Thickness
  	Semi-Positive
  	Flash

  • If Internal Cutouts Are Capped = false and Mold Closure Type = Positive, aPriori uses a value of 0.

  • If Internal Cutouts Are Capped = true, aPriori calculates this as ((Parting Line Solid Shadow Area - Parting Line Projected Area) + Void Cutouts Capped Area) * Capped Cutout Thickness:

    • Parting Line Solid Shadow Area: This is the area of the shadow that would be cast by a light projected from the draw direction. This is the obtained from GCD extraction and visible in the Geometric Cost Drivers panel.

    • Parting Line Projected Area: This is the obtained from GCD extraction and visible in the Geometric Cost Drivers panel.

    • Void Cutouts Capped Area: This is the sum of all viable cutout capped areas.

    • Capped Cutout Thickness: This is specified by the Nominal Wall Thickness setup option.

  • If Mold Closure Type = Semi-Positive, aPriori calculates this as (Difference in areas calculation + Void Cutouts Flash Area) * Flash Ridge Thickness Semi Positive Type:

    • Difference in areas calculation: This is the difference in the ridge areas of flash when the initial circumference of the area (specified by Estimated Internal 3D Perimeter) is shrunk by the Flash Ridge Allowance. The calculation is: (Estimated Internal 3D Perimeter * Flash Ridge Allowance) + (PI * Flash Ridge Allowance²):

    • Estimated Internal 3D Perimeter: See Estimated Internal 3D Perimeter Calculation.

    • Flash Ridge Allowance: This is specified by the cmFlashRidgeAllowance cost model variable (5 mm in starting point Digital Factories).

    • Void Cutouts Flash Area: This is the sum of all viable cutout flash areas.

    • Flash Ridge Thickness Semi Positive Type: This is specified by the cmFlashRidgeThicknessSemiPositiveType cost model variable (0.06 mm in starting point Digital Factories).

  • If Mold Closure Type = Flash, aPriori calculates this as (Difference in areas calculation + Void Cutouts Flash Area) * Flash Ridge Thickness Flash Type + (Difference in areas calculation using 2 * Flash Ridge Allowance + Void Cutouts Flash Area) * Flash Cavity Thickness:

    • Difference in areas calculation: As described above.

    • Void Cutouts Flash Area: As described above.

    • Flash Ridge Thickness Flash Type: This is specified by the cmFlashRidgeThicknessFlashType cost model variable (0.08 mm in starting point Digital Factories).

    • Flash Ridge Allowance: As described above.

    • Flash Cavity Thickness: This is specified by the cmFlashCavityThickness cost model variable (0.01 mm in starting point Digital Factories).

  • In all other cases, aPriori uses a value of 0.

• Flash Volume: This depends on the Mold Closure Type setup option, as described in the table below and the detailed calculations that follow:

  Mold Closure Type	Flash Volume
  Flash	Flash Ridge Area * Flash Ridge Thickness Flash Type + Flash Cavity Area * Flash Cavity Thickness
  Semi-Positive	Flash Ridge Area * Flash Ridge Thickness Semi Positive Type
  Positive	0

  • If Mold Closure Type = Flash, aPriori calculates this as: Flash Ridge Area * Flash Ridge Thickness Flash Type + Flash Cavity Area * Flash Cavity Thickness:

    • Flash Ridge Area: This is the difference in the ridge areas of flash when the initial circumference of the area (specified by Estimated External 3D Perimeter) is expanded by the Flash Ridge Allowance. The calculation is: (Estimated External 3D Perimeter * Flash Ridge Allowance) + (PI * Flash Ridge Allowance²):

      • Estimated External 3D Perimeter: See Estimated External 3D Perimeter Calculation.

      • Flash Ridge Allowance: As described above.

    • Flash Ridge Thickness Flash Type: As described above.

    • Flash Cavity Area: This is the difference in the cavity areas of flash when the initial circumference of the area (specified by Estimated External 3D Perimeter) is expanded by 2 * the Flash Ridge Allowance. The calculation is as described above.

    • Flash Cavity Thickness: As described above.

  • If Mold Closure Type = Semi-Positive, aPriori calculates this as: Flash Ridge Area * Flash Ridge Thickness Semi Positive Type:

    • Flash Ridge Area: As described above.

    • Flash Ridge Thickness Semi Positive Type: As described above.

  • Otherwise, aPriori uses a value of 0.

Material Density is defined in the Material Selection table.

With this setup option, users can override aPriori’s calculated estimate. Typically, machine operators will know what value should be used. The minimum value is Part Volume * Material Density.

Material Colorant

This setup option impacts the total material cost per volume; the cost of some pigments can be significant. See Compression Molding Materials for more information.

This specifies the colorant added during material production (if any). By default, aPriori uses the Colorant Type set as the default in the cmColorantMaterials lookup table; in starting point Digital Factories this is None.

With this setup option, users can override the default on a per-part basis by selecting an alternative from the drop-down list. Note that this will impact the total material cost per volume. The cost of some pigments can be significant. See Compression Molding Materials for more information.

Mold Base Size – Length

This setup option affects machine selection, cycle time, and tooling costs.

This specifies the largest dimension of the mold base in mm, measured perpendicular to the draw direction. By default, aPriori calculates this as the sum of the Part Length and the allowance specified by the cmMoldBaseLengthAllowance cost model variable (150 mm in starting point Digital Factories).

With this setup option, users can override the default on a per-part basis. The minimum value allowed is the length of the part.

Mold Base Size – Width

This setup option affects machine selection, cycle time, and tooling costs.

This specifies the smallest dimension of the mold base in mm, measured perpendicular to the draw direction. By default, aPriori calculates this as the sum of the Part Width and the allowance specified by the cmMoldBaseWidthAllowance cost model variable (150 mm in starting point Digital Factories).

With this setup option, users can override the default on a per-part basis. The minimum value allowed is the width of the part.

Mold Closure Type

This setup option affects machine selection, cycle time, and tooling costs.

This specifies the type of mold used, determining if flash is produced after pressing. By default, aPriori uses the value of the cmMoldClosureType cost model variable; this is Semi-Positive in starting point Digital Factories.

With this setup option, users can override the default on a per-part basis by selecting an alternative from the drop-down list. The options are:

• Flash Type: Produces a flash ridge and flash cavity with a dedicated area for flash around the perimeter of the part. This mold type may affect material utilization, but the impact is generally small, especially where large parts are concerned. This mold type is the lowest-cost option.

• Semi-Positive: Produces a small flash ridge but this is normally very thin and easily removed. This is the most common mold closure type for compression molding.

• Positive: Produces no flash. This is the most expensive option. Tighter tolerances are required for the mold and for the weight of the charge during charge preparation.

The mold closure type impacts the following areas:

• The amount of scrap material produced (utilization process).

• The post-pressing operations required to remove the flash.

Other setup options that impact these areas are Internal Cutouts Are Capped and Number of Material Charge Pieces.

Nominal Wall Thickness

This setup option affects cycle time.

This specifies the nominal wall thickness of the part. aPriori extracts this from the part geometry (see Nominal Wall Thickness).

With this setup option, users can override aPriori’s calculated figure on a per-part basis. The minimal value is 0.1 mm.

Number of Inserted Components

This setup option affects cycle time and Additional Direct Costs.

This specifies the number of inserts (if any) that are manually loaded into the mold tool, for example, threaded metal bushings. The molding process integrates these components into the part. See Plastic Molding Inserts.

Users can also specify the Inserted Component Cost.

Number of Material Charge Pieces

This setup option affects cycle time.

This specifies the number of individual material charge pieces per cavity. More charge pieces are needed, for example, for very large parts, with a lot of draw, or with multiple internal cutouts. Increasing the number of charge pieces has some impact on charge preparation time and on the time required to load the charges into the mold tool. By default, aPriori calculates this using the formula: 1 + Cup Shape Charge Adder + Cutout Charge Adder:

• Cup Shape Charge Adder: This is 2 if the part is cup-shaped, or 0 if otherwise.

• Cutout Charge Adder: This is the parting line’s number of shadow openings (if the setup option Internal Cutouts Are Capped is false, and the parting line’s projected shadow ratio (Parting Line projected Area / Parting Line Solid Shadow Area) is less than 0.7). Otherwise, aPriori uses a value of 0.

With this setup option, users can override aPriori’s calculated estimate.

Number of Small Rib Inserts

This setup option affects tooling costs.

This specifies the number of small rib inserts per cavity (see Plastic Molding Inserts). By default, aPriori counts the number of small inserts used in the CAD file. Ribs must be higher than the value specified by the cost model variable machinedRibThreshold to require inserts. This is 20 mm in starting point Digital Factories.

With this setup option, users can override the default on a per-part basis, up to a maximum of 64.

Number of Medium Rib Inserts

This setup option affects tooling costs.

This specifies the number of medium rib inserts per cavity (see Plastic Molding Inserts). By default, aPriori counts the number of medium inserts used in the CAD file. With this setup option, users can override the default on a per-part basis, up to a maximum of 64.

Number of Large Rib Inserts

This setup option affects tooling costs.

This specifies the number of large rib inserts per cavity (see Plastic Molding Inserts). By default, aPriori counts the number of large inserts used in the CAD file. With this setup option, users can override the default on a per-part basis, up to a maximum of 64.

Part Ejection Method

This setup option affects machine selection and tooling cost.

This specifies the method used to release the part from the mold tool following compression molding. By default, aPriori uses the cmEjectionMethod cost model variable; the default in starting point Digital Factories is Air Poppets. The options are either Air Poppets or Hydraulic Ejector Pins.

With this setup option, users can override the default on a per-part basis. Note that using Hydraulic Ejector Pins increases investment cost (because of the additional hardware required by ejector boxes) and may require use of a larger machine to accommodate the increased mold base shut height.

Plating of the Mold

This setup option affects tooling costs.

This specifies the type of plating used on the mold core and cavity. By default, aPriori uses the cmMoldPlating cost model variable; the default in starting point Digital Factories is None.

With this setup option, users can override the default on a per-part basis by selecting an alternative from the drop-down list. The list is populated from the tblToolCoating lookup table.

Select Mold Material – Clamp Plates

This setup option affects tooling costs.

This specifies the mold material for the top and bottom clamp plates. By default, aPriori uses the Digital Factory default tool shop material (under Plastic Molding > Processes > Compression Molding > Tool Shops > Default > Default Tool Material Name). The default in starting point Digital Factories is AISI 4140.

With this setup option, users can override the default on a per-part basis by selecting an alternative material from the drop-down list.

Select Mold Material – Ejector Box

This setup option affects tooling costs.

This specifies the mold material for the ejector box if hydraulic part ejection is enabled (see the Part Ejection Method setup option). By default, aPriori uses the Digital Factory default tool shop material (under Plastic Molding > Processes > Compression Molding > Tool Shops > Default > Default Tool Material Name). The default in starting point Digital Factories is AISI 4140.

With this setup option, users can override the default on a per-part basis by selecting an alternative material from the drop-down list.

Select Mold Material – Main Plates

This setup option affects tooling costs.

This specifies the mold material for the core and cavity plates, and any additional third plate. By default, aPriori uses the Digital Factory default tool shop material (under Plastic Molding > Processes > Compression Molding > Tool Shops > Default > Default Tool Material Name). The default in starting point Digital Factories is AISI 4140.

With this setup option, users can override the default on a per-part basis by selecting an alternative material from the drop-down list.

Select Mold Material – Rib Inserts

This setup option affects tooling costs.

This specifies the mold material for rib inserts. By default, aPriori uses the Digital Factory default tool shop material (under Plastic Molding > Processes > Compression Molding > Tool Shops > Default > Default Tool Material Name). The default in starting point Digital Factories is AISI 4140.

With this setup option, users can override the default on a per-part basis by selecting an alternative material from the drop-down list.

Parting Line Trim Length (operation-level PSO)

This operation-level setup option specifies the length of parting line requiring an offline trimming operation, either by 5-Axis Router or Waterjet Cut. By default, aPriori calculates this as follows.

• If a positive mold is not being used, this is the sum of Estimated Internal 3D Perimeter and Estimated External 3D Perimeter:

  • Estimated Internal 3D Perimeter: aPriori calculates the square root of (non-accounted for internal cutouts)² + (2 * Parting Line Height)²):

    • Non-accounted for internal cutouts are calculated using the greater of either, 1) the parting line’s Projected Opening Perimeter (extracted from geometry, see GCD Extraction for Plastic Molding) minus the total perimeter of simple holes in the draw direction, or 2) 0.

    • Parting Line Height: This is the PartingLine GCD’s Height property, visible in the Geometric Cost Drivers panel. The measurement is taken in the draw direction between the lowest and highest part on the parting line.

  • Estimated External 3D Perimeter: See Estimated External 3D Perimeter Calculation.

• Otherwise, if a positive mold is being used and the Internal Cutouts Are Capped setup option is true, aPriori uses Estimated Internal 3D Perimeter for the length (as described above).

With this setup option, users can override the default on a per-part basis.

You can find the Parting Line Trim Length setup option in the following locations:

• In the Manufacturing Process panel, right-click the PartingLine GCD (under the selected trimming operation – Routing, Waterjet Cutting, or Manual Flash Trimming), and select Process Setup Options. Alternatively, right-click the PartingLine GCD, select Edit Operation, right-click the selected trimming operation, and select Process Setup Options.

• In the Geometric Cost Drivers panel, right-click the PartingLine GCD, select Edit Operation, right-click the selected trimming operation (Routing, Waterjet Cutting, or Manual Flash Trimming), and select Process Setup Options.

• In the Cost Guide:

  1. Select the Process and Machine Options tab.

  2. If offline flash trimming is included in the routing, right-click the PartingLine GCD (under either Routing or Waterjet Cutting) and click the Set Process Options or Machine... button.

  3. If manual flash trimming is included in the routing, right-click the PartingLine GCD (under Manual Flash Trimming) and click the Set Process Options or Machine... button.