Compression Molding Times

This section describes the following Compression Molding times:

• Compression Molding Cycle Time Calculation

  • Tool Clean Time Calculation

  • Release Agent Application Time Calculation

  • Insert Loading Time Calculation

  • Charge Load Time Calculation

  • Rapid Close Time Calculation

  • Compress Time Calculation

  • Cure Time Calculation

  • Mold Open Time Calculation

• Compression Molding Labor Time Calculation

Compression Molding Cycle Time Calculation

Cycle Time = Process Time * Cycle Time Adjustment Factor

• Process Time: This includes operation times when the press is both open and closed. Typically, when the press is closed, operators can prepare the next charge and manually trim the previous part. Process Time is calculated as the greater of either (Charging Time + Manual Trim Time) or Press Time:

  • Charging Time: This is the time required to prepare the material charge and is factored by mold closure complexity. It is calculated as: Charge Prep Time * Mold Closure Complexity (see below for calculation).

  • Manual Trim Time: This is the time for manually trimming the parting line flash from the part following removal from the mold tool. If no manual trimming is involved (for example, the part is being sent to a separate trimming station (5-Axis router or Waterjet Cut), this will be 0.

  • Press Time: This is the total time for all press operations (see below for calculation).

• Cycle Time Adjustment Factor: This is specified by the cost model variable cycleTimeAdjustmentFactor. This factor is 1 in starting point Digital Factories. Digital Factory Administrators can modify the factor to adjust cycle times across processes within the current Digital Factory.

Charging Time = Charge Prep Time * Mold Closure Complexity

• Charge Prep Time: This is the time required to prepare the material charge for molding, including cutting and weighing. It is calculated as the sum of (Material Cutting + Remove Backing Film + Charge Weighing):

  • Material Cutting: This is the total time required to cut all individual pieces of SMC or BMC material when preparing the material charge. It is the product of Charge Cutting Time (as specified by the cmChargeCuttingTime cost model variable; 5 seconds in starting point Digital Factories) and Number of Charge Pieces (as specified by the Number of Material Charge Pieces setup option).

  • Remove Backing Film: This is the total time required to remove backing film from all individual pieces of SMC material when preparing the material charge. It is the product of SMC Remove Backing Film Time (as specified by the cmRemoveBackingFilmTime cost model variable; 10 seconds in starting point Digital Factories) and Number of Charge Pieces (as described above). Note that the Remove Backing Film value will be 0 for BMC materials as they do not have a backing film.

  • Charge Weighing: This is the total time required to weigh all individual pieces of SMC or BMC material when preparing the material charge. It is the product of Charge Weighing Time (as specified by the cmChargeWeighingTime cost model variable; 5 seconds in starting point Digital Factories) and Number of Charge Pieces (as described above).

• Mold Closure Complexity: This is the complexity factor applied to mold base considerations based on the Mold Closure Type being used:

  • For Flash closure types, the complexity factor is specified by the cmFlashClosureFactor cost model variable (1 in starting point Digital Factories).

  • For Semi-Positive closure types, the complexity factor is specified by the cmSemiPositiveClosureFactor cost model variable (1.15 in starting point Digital Factories).

  • For Positive closure types, the complexity factor is specified by the cmPositiveClosureFactor cost model variable (1.3 in starting point Digital Factories).

Press Time = Tool Clean Time + Release Agent Application Time + Insert Loading Time + Charge Load Time + Rapid Close Time + Compress Time + Cure Time + Mold Open Time + Unload Time

• Tool Clean Time: This is the total time to clean the mold tooling using compressed air (see Tool Clean Time Calculation).

• Release Agent Application Time: This is the time required to apply release agent to mold base (see Release Agent Application Time Calculation).

• Insert Loading Time: This is the total time to load inserted components into mold tool (see Insert Loading Time Calculation).

• Charge Load Time: This is the time required to load the uncured material charge into the mold tool (see Charge Load Time Calculation).

• Rapid Close Time: This is the time required to close the mold tool before compression of the material charge (see Rapid Close Time Calculation).

• Compress Time: This is the time required to fully close the mold tool in the final portion of travel stroke (see Compress Time Calculation).

• Cure Time: This is the time for one complete curing process of the applicable machine to make a single part (see Cure Time Calculation).

• Mold Open Time: This is the time required to open the mold allowing the cured part to be removed (see Mold Open Time Calculation).

• Unload Time: This is the time required to remove cured part from the tool. aPriori performs a lookup in the partHandlingTimes table and returns the Part Handling Time for the part based on its box dimensions (Box Length greater than or equal to Part Length, and Box Width greater than or equal to Part Width, ordering first by Box Length).

Tool Clean Time Calculation

Tool Clean Time = Mold Base Area / Air Hose Cleaning Rate Area + Estimated External 3D Perimeter / Air Hose Cleaning Rate Linear

• Mold Base Area: This is the projected area of the mold base. It is the product of Mold Base Length and Mold Base Width (specified by the Mold Base Size – Length and Mold Base Size – Width setup options respectively).

• Air Hose Cleaning Rate Area: This is the rate at which excess cured material can be removed from the face of the mold tool using an air tool. This is specified by the cmAirHoseCleaningRateArea cost model variable (1,000,000 mm²/second in starting point Digital Factories).

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

• Air Hose Cleaning Rate Linear: This is the rate at which excess cured material can be removed from the parting line of the mold tool using an air tool. This is specified by the cmAirHoseCleaningRateLinear cost model variable (100 mm/second in starting point Digital Factories).

Release Agent Application Time Calculation

Release Agent Application Time = max((Mold Base Area * 2) / Release Agent Application Rate, Minimum Release Application Time)

aPriori calculates this as whichever is the greatest of either: (Mold Base Area * 2) / Release Agent Application Rate, or Minimum Release Application Time:

• Mold Base Area: This is the projected area of the mold base. It is the product of Mold Base Length and Mold Base Width (specified by the Mold Base Size – Length and Mold Base Size – Width setup options respectively).

• Release Agent Application Rate: This is the rate at which spray release agent is applied to the mold base. This is specified by the cmReleaseAgentApplicationRate cost model variable (800,000 mm²/second seconds in starting point Digital Factories).

• Minimum Release Application Time: This is specified by the cmMinReleaseAgentApplicationTime cost model variable (5 seconds in starting point Digital Factories).

Insert Loading Time Calculation

Insert Loading Time = Number Of Inserted Parts * Load Time Per Insert

• Number of Inserted Parts: This is specified by the Number of Inserted Components setup option.

• Load Time Per Insert: This is the time required to manually load an insert into the compression molding tool, as specified by the cmInsertManualLoadingTime cost model variable (8 seconds in starting point Digital Factories).

Charge Load Time Calculation

Charge Load Time = (handlingTableLookup.handlingTime * Number Of Charge Pieces) / Number Of Operators

aPriori performs a lookup in the materialHandling table and returns the Handling Time for the material that corresponds to (Rough Mass / Number of Material Charge Pieces setup option) being less than or equal to the material Weight in the table.

• Rough Mass: This is the mass of the workpiece prior to production, calculated as (Finish Mass / Utilization):

  • Finish Mass: This is the mass of a single part after processing is complete. It is the product of: Part Volume (obtained from GCD extraction) and Material Density (specified in the Material Selection table).

  • Utilization: This the ratio of the mass of a single part after all operations are done to the mass of the workpiece prior to production. It is calculated as: Part Volume (obtained from GCD extraction) / Charge Volume (Material Charge Mass setup option / Material Density).

• Number Of Charge Pieces: This is specified by the Number of Material Charge Pieces setup option.

• Number Of Operators: This is the number of operators tending to the machine. A value less than 1 indicates that an operator tends multiple machines. This is specified by the Number of Operators machine property.

Rapid Close Time Calculation

Rapid Close Time = Required Travel Distance / Machine Rapid Travel Rate

• Required Travel Distance: This is the total length required to open or close the mold tool.

  • If the part is cup-shaped, this is the product of Part Height and the cmTravelDistanceMultiplierCup cost model variable (2.5 in starting point Digital Factories).

  • Otherwise, this is the product of Part Height and the travelDistanceMultiplierFlat cost model variable (4 in starting point Digital Factories).

• Machine Rapid Travel Rate: This is the rate at which the compression molding machine travels to close the tool before compression, as specified by the Rapid Travel Rate machine property.

Compress Time Calculation

Compress Time = (4 * Nominal Wall Thickness) / Machine Compression Travel Rate

• Nominal Wall Thickness: This is extracted from the part geometry; see Nominal Wall Thickness setup option.

• Machine Compression Travel Rate: This is specified by the Compression Travel Rate machine property.

Cure Time Calculation

Cure Time = Material Cure Time * Part Max Thickness

• Material Cure Time: This is the time to cure the material, expressed as a time per thickness of material. The maximum thickness of the part determines the thickness to be cured. This is specified as the Cure Time value in the Material Selection table.

• Part Max Thickness: This is the Max Thickness of the part, as extracted from geometry.

Mold Open Time Calculation

Mold Open Time = Rapid Close Time + Compress Time

• Rapid Close Time: See Rapid Close Time Calculation.

• Compress Time: See Compress Time Calculation.

Compression Molding Labor Time Calculation

Labor Time = Cycle Time * Number of Operators * Labor Time Standard

• Cycle Time: See Compression Molding Cycle Time Calculation.

• Number of Operators: This is the number of operators tending to the machine. A value less than 1 indicates that an operator tends multiple machines. By default, this value is specified by the Number of Operators machine property, in the Digital Factory under Plastic Molding > Machines > Compression Molding.

• Labor Time Standard: By default, this value is specified by the Labor Time Standard machine property, in the Digital Factory under Plastic Molding > Machines > Compression Molding.