Feasibility and Routing
When you choose the Plastic Molding process group, aPriori selects process-level routings, operation-level routings, as well as machines and materials. These procedures are described in the following sections:
Process-level Feasibility and Routing
When you select the Plastic Molding process group, and use auto selection mode, aPriori always selects Injection Molding (as it is the only process in this group that aPriori auto evaluates). To manually specify a process routing, select Edit > Routing Selection in the Manufacturing Process pane (see also Selecting a primary process group in Manufacturing Process Information).
You can also manually select one or both of the following optional, secondary processes:
• Surface Treatment, which includes the following processes:
o Shot Blast
o Degrease
o Painting Processes
o Electroplating
o Labeling
• Other Secondary Processes (Packaging, including the following processes):
o Carton Forming
o Pack and Load
o Carton Sealing
A plastic molding process is feasible only if all the following hold:
• Compatible material
• For SFM, compatibility of selected foaming agent (see PSO) with selected material
• Min wall thickness
• Max wall thickness
aPriori uses only one process level routing rule for IM and RIM, which checks the compatibility of the process with the material under consideration (and for SFM, . For SFM, aPriori checks for insufficient wall thickness, as well as material compatibility with both the process and the foaming agent under consideration.
Operation-level Feasibility and Routing
Below are the plastic molding operations that have associated feasibility rules, grouped by GCD type. Each operation is accompanied by necessary conditions on the GCD for the operation’s feasibility. aPriori checks the operations in the order specified by the operation templates.
Combo Void
• ComboVoidNoCore
o Accessible from the top or bottom, or small enough to deflect
• ComboVoidLifter
o Undercut or obscured
o Not accessible from the void direction
o Too large to deflect
• ComboVoidSideCore
o Undercut or obscured
o Accessible from the void direction
o Too large to deflect
Multistep Hole
• MstepNoCore
o Accessible from the top or bottom
o Not threaded
• MstepLifter
o Undercut or obscured
o Not accessible from the hole direction
• MstepSideCore
o Obscured
o Not threaded
• MstepUnscrewMandrel
o Threaded
SimpleHole
• HoleNoCore
o Accessible from the top or bottom, or small enough to deflect
o Not threaded
• HoleLifter
o Undercut or obscured
o Not accessible from the hole direction
o Too large to deflect
• MstepSideCore
o Obscured
o Too large to deflect
o Not threaded
• HoleUnscrewMandrel
o Threaded
Void
• VoidNoCore: This operation is feasible for a given void (that is, the void may not require a core) if both the following are true of that simple hole:
o Accessible from the top or bottom, or small enough to deflect
• VoidLifter: This operation is feasible for a particular void (that is, the void requires a lifter) if all the following are true of that void:
o Undercut or obscured
o Not accessible from the void direction
o Too large to deflect
• VoidSideCore : This operation is feasible for a particular void (that is, the void requires a slide) if all the following are true of that simple hole:
o Undercut or obscured
o Accessible from the void direction
o Too large to deflect
Material Feasibility and Selection
In direct integration mode with Pro/ENGINEER, if the composition selection mode is MCAD, aPriori selects the MCAD composition from the part, if available. Otherwise aPriori selects the VPE default material (ABS for all baseline VPEs).
In CAD-independent mode, aPriori selects the VPE default material (ABS for all baseline VPEs).
In both direct integration and CAD-independent mode, you can either use aPriori’s selection or else manually select a material composition and override the material unit cost. To manually specify a material, select Edit > Material Selection in the Manufacturing Process pane (see also Selecting material in Manufacturing Process Information).
Note that the process level routing rule fails with one of the following errors if you select a thermoset for IM or SFM:
• Failed because you cannot Injection Mold this type of material
• Failed because you cannot Structural Foam Mold this type of material
Similarly, if you select a thermoplastic material for RIM, the process level routing rule fails with the following error:
• Failed because you cannot Reaction Injection Mold this type of material
Two boolean-valued properties in the Material Selection table indicate which materials are feasible for which processes:
• Can_IM_SFM
• Can_RIM
Additional SFM Feasibility Checks
aPriori performs the following additional feasibility checks for structural foam molding:
• Thickness: The plant variable minSFMWallThickness specifies minimum wall thickness for SFM. If the current part’s average thickness lies below the minimum, the following error results:
• The average wall thickness for this part ( <average-thickness> mm ) is less than the plant limit for Structural Foam Molding ( <min-SFM-thickness> mm )
• Valid Foaming Agent: The table below shows two columns of the Foaming Agents lookup table, which stores information on foaming agents and compatible materials. Each foaming agent is only compatible with certain materials. If the agent name is not applicable for the selected material, the process fails with the following error:
• <agent-name> is not a valid foaming agent for the selected material
• Valid Foam Material: If a material is selected that does not exist in Foaming Agents lookup table (because it has no compatible foaming agents) the process fails with the following error:
• .<material-type-name> material type does not have a compatible foaming agent
Agent Name | Material Type |
Azodicarbonamide | ABS |
Azodicarbonamide | PET |
P-toluenesulfonylsemicarbazide | Polypropylene |
Sodium bicarbonate/citric acid ester | Polystyrene |
Azodicarbonamide | Polystyrene |
Sodium bicarbonate/citric acid ester | ABS |
5-phenyltetrazole | Polycarbonate |
Sodium bicarbonate/citric acid ester | Nylon |
5-phenyltetrazole | PET |
P-toluenesulfonylsemicarbazide | ABS |
P-toluenesulfonylsemicarbazide | Nylon |
Sodium bicarbonate/citric acid ester | PET |
5-phenyltetrazole | Nylon |
P-toluenesulfonylsemicarbazide | Polystyrene |
Azodicarbonamide | Polypropylene |
Sodium bicarbonate/citric acid ester | Polypropylene |
Machine Feasibility and Selection
If aPriori is configured to automatically select a machine, it selects the machine with the lowest clamp force that satisfies all the feasibility rules.
The feasibility rules require all the following:
• The mold required for the part can fit on the machine.
• The clamp force required for the part can be achieved by the machine.
• The shot size required for the part can be provided by the machine.
• The machine can open wide enough for the part to be removed.
More specifically, a machine is feasible only if all the following are true:
• Machine clamp force is greater than or equal to the required force (see Required Clamp Force).
• Required shot size (see Required Shot Size) is a sufficiently small fraction (0.75 in starting point VPEs) of the machine property Shot Size. VPE administrators can customize the fraction with the cost model variable recommendedShotSizeLimitUpper.
• Required shot size (see Required Shot Size) is a sufficiently large fraction of the machine property Shot Size. VPE administrators can customize the fraction with the cost model variable recommendedShotSizeLimitLower (0 in starting point VPEs).
• Horizontal machine tie bar distance is greater than or equal the horizontal dimension of the mold base.
• Vertical machine platen length is greater than or equal to the vertical dimension of the mold base. (For Injection Molding and Structural Foam Molding, if the machine property for platen length is not populated with a value, the machine property for vertical tie bar distance is used.)
• Machine maximum mold height is greater than or equal to the mold base height.
• Travel distance for mold open or close (see Travel Distance in Times for Plastic Molding) does not exceed the machine's Opening Stroke.
aPriori calculates the mold dimensions, clamp force, and shot size required for a given part based on a number of factors, including the number of cavities in the mold. The number of cavities defaults to one, but can be specified in Process Setup Options or calculated by aPriori. Calculation of required shot size, required clamp force, and number of cavities is described in more detail in Required Shot Size, Required Clamp Force, and Number and Layout of Mold Cavities.
aPriori selects only from preferred machines, if there is a feasible preferred machine and the cost model variable usePreferredMachines is set to true (the default in starting point VPEs). If there is no feasible preferred machine, or if the cost model variable usePreferredMachines is set to false, aPriori selects from all machines. A machine is preferred if the machine property isPreferred (typically displayed as Is Preferred) is true.
To manually select a machine for a given process, select Edit > Routing Selection in the Manufacturing Process pane, right-click on the process in the Routing Selection window, and select Machine Selection from the context menu (see also Selecting a machine for an operation in Manufacturing Process Information).