Chemical Milling Formulas
This section covers formulas associated with the following processes and their operations:
Bench Operation Formulas
The Bench Operation process models a number of different operations that are performed at a bench work area (see Machine Selection for Bench Operation). The process has one child operation for each such operation: Cleaning, Final Inspection, Identing, Line Sealing, and Spark Testing.
Process-level formulas are listed below, followed by operation-level formulas.
Cycle Time = Process Time * Adjustment Factor
Cycle time is the product of the following:
• Process time (see formula below)
• Adjustment factor (specified by the cost model variable cycleTimeAdjustmentFactor). This factor is 1 in aPriori starting point VPEs. VPE administrators can modify cycleTimeAdjustmentFactor in order to adjust cycle times across processes within the current VPE.
Process Time = Operations Time + Handling Time
Process time depends on the following:
• Operations time: this is the sum of the cycle times of the child operations. See formulas below.
• Handling time (see formula)
Handling Time = Load Time + Unload Time
Handling time is the sum of the following:
• Load time (see formula)
• Unload time (see formula)
Load Time = Number of Handling Operators * Handling Time per Operator
Load Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Unload Time = Number of Handling Operators * Handling Time per Operator
Unload Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Expendable Tooling Cost Per Part
This is the sum of the consumable materials costs for the child operations. See the formulas below.
Cleaning Operation Cycle Time = Part Surface Area / Cleaning Rate
Cycle time for the Cleaning operation depends on the following:
• Part surface area (specified by a geometry property)
• Cleaning rate: this is looked up by the flattened part’s projected area in the lookup table tblChemicalMilling.
•
Cleaning Operation Consumable Materials Cost = Cleaning Wipes Quantity * Cleaning Wipes Cost Each
• The cost model for the Cleaning operation assumes the use of Diestone SR (PF-SR) Wipes. Consumable materials cost is the product of the following:
• Cleaning wipes quantity: the cost model assumes the use of at least one wipe, and one wipe per square meter of the blank’s surface area.
• Cleaning wipes cost each: this is specified by the tool shop variable consumableMaterial_Diestone_SR_Wipes.
Final Inspecting Operation Cycle Time
Cycle time for the Final Inspecting operation is the time for the final, visual inspection of the part. By default, it is specified by the cost model variable defaultFinalInspectionTime (5 minutes in starting point VPEs). Users can override the default on a part-by-part basis with the setup option Final Inspection Time—see Bench Operation Options.
Identing Operation Cycle Time
Cycle time for the Identing operation is the time to vibro etch an identifier onto the part. By default, it is specified by the cost model variable defaultIdentingTime (45 seconds in starting point VPEs). Users can override the default on a part-by-part basis with the setup option Identing Time—see Bench Operation Options.
Spark Testing Operation Cycle Time
Cycle time for the Spark Testing operation is specified, by default, by the cost model variable defaultSparkTestTime (2 minutes in starting point VPEs). Users can override the default on a part-by-part basis with the setup option Spark Test Time—see Bench Operation Options.
Blank Line Sealing Operations
Cycle Time = Part Surface Area / Line Sealing Roller Rate
Cycle time for the Line Sealing operation performed on the Blank GCD depends on the following:
• Part surface area (specified by a geometry property)
• Line sealing roller rate: by default, this is specified by the cost model variable lineSealingRollerRate (92903 mm2/sec in starting point VPEs).
Consumable Materials Cost = Line Sealer Quantity * Line Sealer Cost Per Liter
• Consumable materials cost for the Line Sealing operation performed on the Blank GCD is the product of the following:
• Line sealer quantity: the cost model assumes two coats of line sealant, where each coat uses 0.91 liters per square meter of part surface area.
• Line sealer cost per liter: this is specified by the toolshop variable consumableMaterial_LineSealer_JW533Red.
Curved Surface, Curved Wall, Form, and Planar Face Line Sealing Operations
Cycle Time = GCD Perimeter / Line Sealing Brush Rate
Cycle time for the Line Sealing operation performed on surfaces of individual pockets (Form GCDs) depends on the following:
• GCD perimeter (specified by a geometry property)
• Line sealing brush rate: by default, this is specified by the cost model variable lineSealingBrushRate (20 mm/sec in starting point VPEs).
Consumable Materials Cost = Line Sealer Quantity * Line Sealer Cost Per Liter
• Consumable materials cost for the Line Sealing operation performed on surfaces of individual pockets (Form GCDs) is the product of the following:
• Line sealer quantity: the cost model assumes two coats of line sealer, where each coat uses 0.91 liters per square meter of surface area sealed. The surface area sealed is the GCD perimeter times an assumed brush width of 1 inch.
• Line sealer cost per liter: this is specified by the toolshop variable consumableMaterial_LineSealer_JW533Red.
Mask Spray Formulas
See Mask Spray Formulas in the Surface Treatment chapter of this Guide.
Mask Cure Formulas
Cycle Time = Process Time * Adjustment Factor
Cycle time is the product of the following:
• Process time (see formula below)
• Adjustment factor (specified by the cost model variable cycleTimeAdjustmentFactor). This factor is 1 in aPriori starting point VPEs. VPE administrators can modify cycleTimeAdjustmentFactor in order to adjust cycle times across processes within the current VPE.
Process Time = Operations Time + Handling Time
Process time depends on the following:
• Operations time: operation cycle time (cure time) is looked up in the lookup table tblMaskingMaterials.
By default, masking material is specified by the table’s first entry. Users can override the default on a part-by-part basis with the setup option Select maskant material used.—see Mask Cure Options.
• Handling time (see formula)
Handling Time = Load Time + Unload Time
Handling time is the sum of the following:
• Load time (see formula)
• Unload time (see formula)
Load Time = Number of Handling Operators * Handling Time per Operator
Load Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Unload Time = Number of Handling Operators * Handling Time per Operator
Unload Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Scribe Formulas
Cycle Time = Process Time * Adjustment Factor
Cycle time is the product of the following:
• Process time (see formula below)
• Adjustment factor (specified by the cost model variable cycleTimeAdjustmentFactor). This factor is 1 in aPriori starting point VPEs. VPE administrators can modify cycleTimeAdjustmentFactor in order to adjust cycle times across processes within the current VPE.
Process Time = Pocket Scribing Time + Rapid Traverse Time + Handling Time
Process time is the sum of the following:
• Pocket scribing time: this is the sum of the operation-level scribing times (cycle times) for each scribed GCD (see Operation Cycle Time formula).
• Rapid traverse time (see formula)
• Handling time (see formula)
Operation Cycle Time = Pocket Perimeter / Scribing Rate
This is the scribing time for a single pocket, that is, for a single GCD on which the Scribing operation is performed. Scribing time depends on the following:
• Pocket perimeter: this is the perimeter of the GCD on which the operation is being performed.
• Scribing rate (specified by the machine property Feed Rate)
Rapid Traverse Time = Rapid Traverse Distance / Rapid Traverse Rate
Rapid traverse time is estimated based on the following:
• Rapid traverse distance: this is estimated as the fraction of the part’s box width specified by the cost model variable rapidTraverseDistanceFactor (0.5 in starting point VPEs).
• Rapid traverse rate (specified by the machine property Rapid Traverse Rate)
Handling Time = Load Time + Unload Time
Handling time is the sum of the following:
• Load time (see formula)
• Unload time (see formula)
Load Time = Number of Handling Operators * Handling Time per Operator
Load Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Unload Time = Number of Handling Operators * Handling Time per Operator
Unload Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume (blank area times blank thickness).
Programming Cost = Programming Rate * Programming Time
By default, this is the product of the machine properties Programming Rate and Programming Time. Users can override the default on a part-part basis with the setup option Programming Cost--see Scribe Option.
Etch Cell Formulas
Note that all of the process time contributes to labor time for the Etch Cell process, since it is the responsibility of the operators to monitor the time spent in the etch tank (which is critical to within seconds) as well as to monitor the tank temperatures and the movement of parts between tanks.
Cycle Time = Process Time * Adjustment Factor
Cycle time is the product of the following:
• Process time (see formula below)
• Adjustment factor (specified by the cost model variable cycleTimeAdjustmentFactor). This factor is 1 in aPriori starting point VPEs. VPE administrators can modify cycleTimeAdjustmentFactor in order to adjust cycle times across processes within the current VPE.
Process Time = Total Etch Cycle Time + Handling Time
Process time depends on the following:
• Total etch cycle time: this is the sum of the cycle times for the Etch Cell Cycle child operations (see formula below), together with desmut time (specified by the cost model variable defaultChemMillDesmutTime—10 minutes in starting point VPEs) and desmut rinse times (specified by the cost model variable defaultChemMillDesmutRinseTime—10 minutes in starting point VPEs).
• Handling time (see formula)
Cycle Time for Etch Cell Cycle = Depth Inspecting Time + Drying Time +
Pocket Etching Time + Pocket Peeling Time + Rinsing Time
There is one execution of the Etch Cell Cycle operation for each unique depth of the etched pockets. All pockets that have the same depth are etched in the same Etch Cell Cycle execution. Pockets with the greatest depth are etched first, while the other pockets remain covered with maskant. They are etched to a depth that is the difference between their final depth and the final depth of the next deepest pockets. Then the maskant is peeled from the next deepest pockets, and they are etched to the difference between their final depth and the final depth of the next, shallower group of pockets, and so on.
Cycle time for each Etch Cell Cycle execution depends on the following:
• Depth inspecting time (see formula)
• Drying time: specified by the cost model variable defaultChemMillDryingTime (25 minutes in starting point VPEs)
• Pocket etching time (see formula)
• Pocket peeling time: this is the sum of the cycle times for the Pocket Peeling child operations (see Pocket Peeling Cycle Time formula)
• Rinsing time: this cost model assumes the part is rinsed twice, so this is the time specified by the cost model variable defaultChemMillRinsingTime (25 minutes in starting point VPEs) times two.
Depth Inspection Time = Default Depth Inspecting Time * Number of Pockets to Inspect
Depth inspection time is product of the following:
• Default depth inspection time: this is the time to inspect the depth of one pocket, specified by the cost model variable dimInspectTimePerFeature (40 seconds in starting point VPEs).
• Number of pockets to inspect: this is the product of the number of pockets etched in the current cycle and the cost model variable defaultInspectionSampleRatio (0.25 in starting point VPEs), rounded up to a whole number of pockets.
Pocket Etching Time = Current Etch Step Depth/ Defined Etching Rate
Etching time for all the pockets etched in the current cycle depends only on the following:
• Current etch step depth: this is the difference between the final depth of the pockets currently being etched and the final depth of the pockets to be etched in the next etch cycle (that is, the depth of the next-shallower group of pockets).
• Defined etching rate: by default, this is specified by the cost model variable defaultChemicalEtchingRate (0.0381mm/minute in starting point VPEs). Users can override the default on a part-by-part or etch-cycle-by-etch-cycle basis with the setup option Chemical Etch Rate—see Etch Cell Options.
Pocket Peeling Cycle Time = Pocket Area / Peeling Rate
This is the per-pocket peeling time. It depends on the following:
• Pocket area (specified by the GCD property Area)
• Peeling rate: looked up by the flattened part’s projected area in the lookup table tblChemicalMilling.
•
Handling Time = Load Time + Unload Time
Handling time is the sum of the following:
• Load time (see formula)
• Unload time (see formula)
Load Time = Number of Handling Operators * Handling Time per Operator
Load Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times blank volume.
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times blank volume.
Unload Time = Number of Handling Operators * Handling Time per Operator
Unload Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).
DeMask Formulas
Cycle Time = Process Time * Adjustment Factor
Cycle time is the product of the following:
• Process time (see formula below)
• Adjustment factor (specified by the cost model variable cycleTimeAdjustmentFactor). This factor is 1 in aPriori starting point VPEs. VPE administrators can modify cycleTimeAdjustmentFactor in order to adjust cycle times across processes within the current VPE.
Process Time = Operations Time + Handling Time
Process time depends on the following:
• Operations time: this is the sum of the cycle times for each child operation. See the formulas for Peeling Residual Maskant Cycle Time and Dressing Edges Cycle Time, below.
• Handling time (see formula)
Peeling Residual Maskant Cycle Time = Residual Area / Peeling Rate
Cycle time for peeling the residual maskant off the part depends on the following:
• Residual area: this is the portion of the part not subject to any etching in any step of the process. That is, it is the surface area of the blank minus the surface area of the etched portions.
• Peeling rate: looked up by the part’s projected area in the lookup table tblChemicalMilling.
•
Dressing Edges Cycle Time = Edge Length / Dressing Rate
This is the cycle time for dressing the edges of an etched GCD. It depends on the following:
• Edge length: this is the GCD perimeter, that is, the perimeter of the etched pocket.
• Dressing rate: specified by the cost model variable defaultEdgeDressingRate (10 mm/sec in starting point VPEs).
Handling Time = Load Time + Unload Time
Handling time is the sum of the following:
• Load time (see formula)
• Unload time (see formula)
Load Time = Number of Handling Operators * Handling Time per Operator
Load Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).
Unload Time = Number of Handling Operators * Handling Time per Operator
Unload Time is the product of the following:
• Number of handling operators: this is looked up by weight in the lookup table tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).
• Handling time per operator: this is interpolated from values looked up by part weight in tblHandlingTimes. Part weight is material density times part volume, where part volume excludes the total volume removed by etching. The volume removed by etching for a given etched GCD (surface or form) is the GCD’s surface area times the etching depth (as defined by the part geometry).