Routing for Stretch Forming
The Stretch Forming cost model supports two process-level routings:
• One that includes transverse stretching
• One that includes longitudinal stretching
The transverse routing includes an operation that stretches the part along the Xsection (see Xsection GCDs) that has the greater curve height (of the two Xsections). The longitudinal routing includes an operation that stretches the part along the Xsection that has the smaller curve height (see Xsection Curve Height for Stretch Forming).
To cost the part, aPriori chooses the lowest-cost, feasible routing for which there is a feasible stretch forming machine (see Process Feasibility for Stretch Forming and Stretch Form Machine Selection).
The routings differ only with regard to which process-level operation the Stretch Form process applies: either Stretch Form—Transverse or Stretch Form—Longitudinal. The routings include the following processes:
• 3-Roll Bending: this process, from the Sheet Metal process group, defines the Coil Uncoil operation on the Component GCD, which accounts for the cost of coiling the blank before heat treatment, as well as the cost of uncoiling it after cold storage.
• One or more stretch form cycles, each of which consists of the following Processes:
o Solution: from the Heat Treatment process group, accounts for the cost of annealing the coiled part in preparation for stretching. The material properties Tensile Yield Strength and Ultimate Tensile Strength are pre-annealed properties, while Annealed Tensile Yield Strength and Annealed Ultimate Tensile Strength are post-annealed properties.
o Cold Storage: accounts for the cost of cooling the coiled stock in order to maintain the post-annealed material properties.
o Stretch Form: this process applies a component-level operation for either transverse or longitudinal stretch forming (Stretch Form--Transverse or Stretch Form—Longitudinal). The component-level operation, in turn, applies a number of operations associated with the stretch forming machine—see below.
The cost model variable defaultNumStretches controls the default number of cycles (1 in starting point VPEs). The setup option Number of Stretch Form Cycles controls the number of cycles on a part by part basis. See Setup Options for Stretch Forming Cycles.
• Shear: from the Sheet Metal process group, this process accounts for the cost of trimming the formed part in order to remove the addenda, which are added to the blank in order to provide material for the machine jaws to grip. See Material Stock Selection for Stretch Forming.
• Bench Operation: this process defines operations for cleaning and inspection of the formed part, and for hand forming of Form GCDs of type CURVED_BEND.
• Router: this process accounts for the cost of performing near-net-shape trimming using a hand router and a template.
• Machining: the part is routed to 5-Axis Mill in the Machining process group, which accounts for the cost of final-shape profile trimming (as well as hole creation, if necessary). Parts can also be manually routed to Chemical Milling. (In the Routing Selection dialog, expand the Machining node, and select Chemical Milling; with this process routing selected, forms of type STAMP are automatically assigned to chemical milling.)
Transverse or Longitudinal Stretch Forming applies the following child operations:
o Inspecting: blank inspection.
o Loading: blank loading onto the stretch forming machine.
o Pre-stretching: optional operation, included only when a tangential stretch forming machine is selected, that is when the machine property Process Type is Tangential.
o Stretch Forming: performed on form of type EMBOSS. If there is more than one EMBOSS form, one is chosen as the primary form and is assigned to the Stretch Forming operation; all other forms of type EMOBOSS are assumed to be created by this operation as well.
o Tool Cleaning: tool cleaning in between stretches.
o Tool Lubricating: tool lubricating in between stretches.
o Unloading: blank unloading from the stretch forming machine.