Feasibility and Routing
When you choose the Bar&Tube Fab 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 Routing
Process routings for Bar&Tube Fab are divided into the following categories and subcategories:
• Bent Part routings:
o CTL/[Punch]/[Bend]: Performs cutting with a saw or shear, followed by optional punching, bending, trimming, and/or forming.
o Tube Laser/[Punch]/[Bend]: Performs cutting and hole making with a tube laser, followed by optional punching, bending, trimming, and/or forming.
• Unbent Part routings:
o CTL/[Punch]: Performs cutting with a saw or shear, followed by optional punching, trimming, and/or forming.
o Tube Laser/[Punch]: Performs cutting and hole making with a tube laser, followed by optional punching, trimming, and/or forming.
o Roll Bending: Performs cutting followed by rolling, followed by laser seam welding.
Following are the available routings for each subcategory (optional processes are in brackets):
• CTL/[Punch]/[Bend]: [Cut To Length] > [Punching] > [Bending] > [Punching] > [Trimming] > Forming
• Tube Laser/[Punch]/[Bend]: [Tube Laser] > [Punching] > [Bending] > [Punching] > [Trimming] > Forming
• CTL/[Punch]: [Cut To Length] > [Punching] > [Trimming] > Forming
• Tube Laser/[Punch]: [Tube Laser] > [Punching] > [Trimming] > Forming
• Roll Bending: Sheet Blank Cut > Rolling > Laser Seam Welding > [Punching] > [Tube Laser] > Forming
Note: Roll Bending is never auto-evaluated; you must manually select it.
Note that even though Forming is non-optional, all of its subprocesses are optional.
Every routing has a special initial process or group of processes:
• Sheet Stock for Roll Bending routings: serves as the locus of material cost and utilization calculations (see Material Cost and Utilization).
• Material Stock Extrusion for extrusions routings: consists of Billet Preheat, Die Preheat, and Extrusion. The Extrusion process serves, among other things, as the locus of material cost and utilization calculations (see Extrusion).
• Material Stock for all other routings: serves as the locus of material cost and utilization calculations (see Material Cost and Utilization).
Note that end forming is not supported for extrusions.
Cut to Length is one of the following alternative processes:
• Band Saw
• Circular Saw
• Reciprocating Saw
• Plasma CNC
• Plasma Torch
• OxyFuel Torch
• Shear
Circular Saw, Reciprocating Saw, Plasma Torch, OxyFuel Torch, and Shear are never auto-evaluated.
Bending is one of the following alternative processes:
• Rotary Draw Bending
• Compression Bending
• Bar Bend Brake
Trimming is one of the following alternative processes:
• Band Saw
• Circular Saw
• Reciprocating Saw
• Shear
Circular Saw, Reciprocating Saw, and Shear are never auto-evaluated.
Sheet Blank Cut is one of the following alternative processes:
• Sheet Laser Cut
• Sheet Plasma Cut
• Sheet OxyFuel Cut
Rolling is one of the following alternative processes:
• 2 Roll Bending
• 3 Roll Bending
• 4 Roll Bending
Forming is the following sequence of processes (each element of which is optional):
• Reduction
• Expansion
• Flaring
• Flanging
• Flattening
• Bar Forming
• Slotting
• Notching
• Knurling
Tube Laser and Punching have no subprocesses.
You can manually assign Forming processes to each end of a part. However, some stock shapes do not support all processes (see Process-level Feasibility).
Certain parts require you to manually specify additional processes for Punching or Trimming. For example, parts with bend features close to an end may require extra trim material for the bend machine to grip--the extra material is trimmed after the bending process. Similarly, some parts require a punching process after a bending process. You can add these additional processes by using the Routing Selection dialog.
For routings with two occurrences of Punching, you must manually specify which holes are handled by the second punching process by moving them from the first punching process to the second one. Follow these steps to move a hole:
1 In the Manufacturing Process panel, expand the current punching process and operations to view the list of holes associated with it.
2 Left click the desired hole and drag it to the second punching process. The hole appears under the new process.
If you have licensed the Machining process group, your routing can include any of the following secondary processes:
• 3-Axis Milling
• Cylindrical Grinding
• Gun Drill
• 2-axis Wire EDM operations
• Single Index Milling and Rotor Grinding operations (if helical groove geometry is present)
If you have licensed the optional Turning module, your routing can include the turning processes using the following lathe types:
• 2-axis
• 3-axis
• 4-axis
• 6-axis
Your routing can also include the following subsequent optional processes, if you have licensed these modules:
• Heat Treatment
• Surface Treatment
• Part Assembly
• Other Secondary Processes (packaging)
Process-level Feasibility
The following table lists the feasible stock forms for each process:
The following processes have additional feasibility requirements:
• Bar Bend Brake
o Each bend is circular (the curve of the bend is a portion of a circle), that is, no bend has the value false for the GCD property Is Circular.
• Compression Bending
o Each bend is either planar (lies in a single plane) or circular (the curve of the bend is a portion of a circle), that is, no bend has the value false for both Is Planar or Is Circular.
• Tube Laser
o Holes are not flanged, countersunk, or threaded.
• Sheet Laser Cut, Sheet Oxy Fuel Cut, Sheet Plasma Cut
o Part has no flanged holes, countersunk holes, threaded holes, or forms.
• Rolling
o Diameter to Thickness ratio exceeds the minimum ratio.
o Part does not have expansions, reductions, or bends.
o Part bend is a full 360°.
For the following processes, if tolerance or roughness are not within Process Tolerance Capability, aPriori adds a machining process to the routing:
• Tube Laser
• Punching
• Laser Cut, Oxy Fuel Cut, Plasma Cut
Note that in some cases this can result in inflated costs, because when machining is required to obtain the required tolerance, the actual manufacturing process will use machining to create the hole, rather than using one of the above processes followed by machining.
See also Extrusion Routing Feasibility.
Extrusion Routing Feasibility
The Extrusion process is feasible only if all the following hold:
• Material type: Current material’s Material Type is Aluminum.
• Critical tongue ratio: If the part has at least one semi-hollow CrossSectionHollow (see Extrusion GCDs), the part’s Critical Tongue Ratio must be no greater than the value of the cost model variable defaultMaximumTongueRatio (14 in starting point VPEs).
• Material exit speed limits: Values for the material properties Minimum Extrusion Exit Speed and Maximum Extrusion Exit Speed must be present for the current material in the material table.
The Billet Preheat and Die Preheat processes are feasible only if values are present in the material table for the properties Specific Heat RT and Solidus Temp.
Material 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 (Steel, HR, AISI 1010 for all starting point VPEs).
In CAD-independent mode, aPriori selects the VPE default material (Steel, HR, AISI 1010 for all starting point VPEs).
In both direct integration and CAD-independent mode, you can 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).
You can select from a list of common stock sizes or from virtual stock. Actual stock can be automatically or manually selected. Actual stock uses the stock's unit cost. Virtual stock uses the material composition's unit cost and assumes a virtual sheet length of 20 ft.
For extrusions, the material must be aluminum—see Extrusion Routing Feasibility.
You can override the unit cost if desired. aPriori chooses to use actual or virtual stock based on the cross section recognition and size. You can override the part cross section. In addition, you can specify the use of a custom cut for which you can choose to use a Size to Fit Trim or a Custom Size Length, both specified in millimeters.
Machine Selection
If aPriori is configured to automatically select a machine, it generally selects the machine with the lowest overhead rate that satisfies all the feasibility rules. (Note that aPriori never auto-selects Roll Bending in the Bar & Tube process group. You must manually select it.)
For end cutting operations, the machine selection affects the cut speed and axial feed speed used to create the ends. The cut speed can vary across processes and machines. In general, a more powerful machine has a faster cut speed. Cut speed also varies based on material composition and thickness.
For forming operations, the machine selection affects the bend/form time, bend traversal time, and stock rotation time. Similarly, for hole-making operations, the machine selection affects the cutting time and hole traversal time.
For Extrusion, aPriori selects the feasible machine that results in the lowest cost per mass (see Machine Selection for Extrusion).
Following are the machine feasibility requirements:
• Band Saw, Circular Saw, Reciprocating Saw
o Stock fits within the machine’s Max Stock Height and Max Stock Width.
o End cuts are planar.
o Ends max cut angle does not exceed the machine’s Max Cut Angle.
• Tube Laser
o Stock diameter does not exceed the machine’s Max Stock Diameter.
o Stock length does not exceed the machine’s Max Stock Length.
o Stock thickness does not exceed the machine’s Max Stock Thickness.
• Punching
o Stock fits within the machine’s Max Stock Diameter, Length, and Thickness.
o Required punch force (based on max hole perimeter, wall thickness, material Shear Strength, and machine Punch Tip Factor) does not exceed the machine’s Punch Force.
o Stock form is compatible according to the machine property Stock Compatibility.
o Hole diameter to wall thickness ratio exceeds the machine’s Min Hole Dia-to-Thickness Ratio
o Hole diameter does not exceed the machine’s Max Hole Diameter.
• Bar Bend Brake
o Material thickness does not exceed the machine’s Max Thickness.
o Part’s largest bend radius to thickness ratio does not exceed the machine’s Max Radius-to-Thickness Ratio.
o Part’s smallest bend radius to thickness ratio exceeds the machine’s Min Radius-to-Thickness Ratio.
• Compression Bending
o Tube diameter falls within the machine’s Max Tube Diameter and Min Tube Diameter.
o Part’s center-line radius falls within the machine’s Max Part Center-Line-Radius and Min Part CenterLine-Radius.
o Distance between bends exceeds the machine’s Min Distance Between Bends.
o Bend angle does not exceed the machine’s Max Bend Angle.
• Rotary Draw Bending
o Tube diameter falls within the machine’s Max Tube Diameter and Min Tube Diameter.
o Part’s center-line radius falls within the machine’s Max Part Center-Line-Radius and Min Part CenterLine-Radius.
o Distance between bends exceeds the machine’s Min Distance Between Bends.
o Bend angle does not exceed the machine’s Max Bend Angle.
• Bar Forming, Expansion, Flanging, Flaring, Flattening, Knurling, Notching, Reduction, Slotting
o Stock diameter falls within the machine’s Max Stock Diameter and Min Stock Diameter.
• Laser Cut, Oxy Fuel Cut, Plasma Cut
o Blank fits on the machine according to the machine’s Bed Length and Bed Width.
o Material thickness does not exceed the machine’s Max Thickness.
• Shear
o Material thickness does not exceed the machine’s Max Thickness.
o Part height does not exceed the machine’s maximum height for the current stock shape.
o Part outside diameter does not exceed the machine’s Max Diameter.
o Part cut width does not exceed the machine’s maximum width for the current stock shape.
• 2 Roll Bending
o Part inside diameter is greater than machine minimum diameter (1.15X top roll diameter)
o Part length is less than machine roll working Length
o Part thickness is less than machine maximum thickness (factor of material yield strength and maximum machine working length /part length)
• 3- and 4-Roll Bending
o Part inside diameter is greater than machine single pass diameter ( ~ 1.3 to 3X top roll diameter)
o Part length is less than machine roll working length
o Part thickness is less than machine maximum thickness (factor of material yield strength and maximum machine working length /part length))
o Part weight is less than machine maximum part weight
• Extrusion
o A single part can fit within the usable area of the die face.
o Some acceptable ram speed (based on part complexity, number of die cavities, and quench type) must result in an exit speed that is within range for the current material.
o Maximum acceptable ram speed (see above) must exceed the global lower bound on ram speed specified by the cost model variable minimumAcceptableRamSpeed.
o Machine’s maximum billet volume can accommodate at least one part.
o If the user has used a setup option to specify Billet Length, then it must fall between the machine’s maximum and minimum billet length.
o Part length must be less than the machine’s runout length.
See Machine Selection for Extrusion for more information.
Note: For Roll Bending, machine maximum thickness is typically the maximum pre-bend thickness. Machine capacities are usually rated for steel A36 with a tensile yield strength of 36000 psi. This is the reference material strength. To find the maximum thickness for other materials we use the following equation:
The pre-bend thickness given in machine specs are usually given for the maximum plate width. If the part length is less than the maximum plate length, the pre-bend thickness usually increases. So a ratio of machine maximum working length/part length is applied in the maximum thickness calculation.
Machine Selection for Extrusion
For Extrusion, aPriori selects the feasible machine that results in the lowest cost per mass extruded. Cost per mass extruded is calculated as follows:
Cost per Mass = Machine Direct Overhead Rate / Machine Mass Rate
Cost per mass depends on the following:
• Machine direct overhead rate: specified by the machine property Direct Overhead Rate.
• Machine mass rate: see formula.
Machine Mass Rate =
Total Extrudate Cross Section Area * Exit Speed * Material Density
Machine mass rate depends on the following:
• Total extrudate cross-sectional area: this is the product of the Number of Die Cavities and the value of the geometric property Area for the CrossSection GCD.
• Exit speed: see Maximum Acceptable Ram Speed.
• Material Density: specified by the material property Density. This value is converted from kg/m3 to kg/mm3 for use in this formula.
An Extrusion machine is feasible only if all the following hold:
• A single part can fit within the usable area of the die face. This means the radius of the part cross section is less than the radius of the die face minus a clearance allowance. These radii and clearance values are determined as follows:
o Radius of the cross section is the radius of the cross section’s smallest enclosing circle, given by half the geometric property Outside Diameter for the CrossSection GCD.
o Radius of the die face is given by half the product of the machine property Billet Diameter. And the tool shop variable Die Diameter Adjustment Factor.
o Clearance allowance is looked up in the lookup table tablStandardSizes. It is given by the value in the Size column for the row that has dieClearanceForNesting in the Variable column and the current system units (US or metric) in the Unit column.
• Some acceptable ram speed must result in an exit speed that is within range. What counts as an in-range exit speed is specified by the following:
o Material property Minimum Extrusion Exit Speed
o Material property Maximum Extrusion Exit Speed
What counts as an acceptable ram speed depends on the following:
Acceptable ram speed is bounded above by the machine property Max Ram Speed.
• The maximum acceptable ram speed must exceed the global lower bound on ram speed, specified by the cost model variable minimumAcceptableRamSpeed (1mm/sec in starting point VPEs).
• Machine’s maximum billet volume can accommodate at least one part (see Billet Size and Parts per Billet).
• Part Length is less than the Machine property Max Runout Length.
• If the user has used a setup option to specify Billet Length, then it must fall between the machine’s maximum and minimum billet length, specified by the machine properties Max Billet Length and Min Billet Length.
Operation-level Feasibility and Routing
Below are the bar and tube operations that have associated feasibility rules, grouped by GCD type. Each operation is accompanied by necessary conditions for the operation’s selection. aPriori checks the operations in the order specified by the operation templates, and selects the first operation for which the current GCD satisfies all the necessary conditions.
Bend
• Compression Bending
o Distance between this bend and all other bends is greater than or equal to the machine property Minimum Distance Between Bends.
o Bend angle is less than or equal to the machine property Maximum Bend Angle.
• Rotary Draw Bending
o Distance between this bend and all other bends is greater than or equal to the machine property Minimum Distance Between Bends.
o Bend angle is less than or equal to the machine property Maximum Bend Angle.
Complex Hole
• ComplexHoleLaserCutting
o Tube thickness is nonzero.
o Tolerance is nonzero.
o GCD is not flanged.
o Tolerance is greater than or equal to the minimum allowable tolerance given the GCD’s MEC (maximum enclosed circle) diameter and the current machine. This minimum tolerance is the product of the following values: (1) value for the GCD’s MEC diameter in the lookup table toleranceCapability, (2) the machine property toleranceFactor, and, if the GCD’s length is greater than the plant variable thinToThickCutThreshold, (3) the plant variable thickCutToleranceFactor.
• ComplexHolePunching
o MEC (maximum enclosed circle) diameter is nonzero. (The MEC diameter is the diameter of the largest circle that fits in the complex hole.)
o Length (depth) is nonzero.
o Tolerance is nonzero.
o MEC diameter-to-thickness ratio is greater than or equal to the machine property minHoleDTratio.
o MEC diameter is less than or equal to the machine property maxHoleDia.
o Tolerance is greater than or equal to the minimum allowable tolerance given the GCD’s MEC diameter and the current machine. This minimum tolerance is the product of the following values: (1) value for the GCD’s MEC diameter in the lookup table toleranceCapability and (2) the machine property toleranceFactor.
Curved Surface
• AsSupplied
o Part length equals stock length.
o GCD is planar.
• Bar & Tube Fab
o Roughness is greater than or equal to site default roughness (roughnessDefault).
o Tolerance is greater than or equal to site default tolerance (toleranceDefault).
• CurvedSurfaceAsSuppliedSurface
o GCD is a stock surface or part of a complex hole or a non-ring surface in tube stock
• EndSawingSurface
o GCD is accessible to a saw.
Curved Wall
• AsSupplied
o Part length equals stock length.
o GCD is planar.
• Bar & Tube Fab
o Roughness is greater than or equal to site default roughness (roughnessDefault).
o Tolerance is greater than or equal to site default tolerance (toleranceDefault).
• CurvedWallAsSuppliedSurface
o GCD is a stock surface or part of a complex hole or a non-ring surface in tube stock
o GCD is not threaded.
• EndSawingSurface
o GCD is accessible to a saw.
End
• AsSupplied
o Part length equals stock length.
o GCD is planar.
• Shearing
o GCD has at least one planar child GCD.
Form
• Expansion
o GCD is an expansion.
o GCD is adjacent to an end.
• FormAsSupplied
o GCD is a supported type of form.
o GCD is either adjacent to an edge or neither reduction nor expansion.
• Reduction
o GCD is a reduction.
o GCD is adjacent to an end.
Multistep Hole
• MultiStepHoleLaserCutting
o Inner-hole diameter is nonzero.
o Inner-hole length (depth) is nonzero.
o Inner-hole tolerance is nonzero.
o Inner hole is not flanged.
o Inner hole is not threaded.
o Inner hole is not countersunk.
o Inner hole is not blind.
o Roughness is greater than or equal to site default tolerance (roughnessDefault).
o Tolerance is greater than or equal to the minimum allowable tolerance given the inner-hole diameter and the current machine. This minimum tolerance is the product of the following values: (1) value for the inner-hole diameter in the lookup table toleranceCapability, (2) the machine property toleranceFactor, and, if the GCD’s length is greater than the plant variable thinToThickCutThreshold, (3) the plant variable thickCutToleranceFactor..
• MultiStepHolePunching
o Inner-hole diameter is nonzero.
o Inner-hole length (depth) is nonzero.
o Inner-hole tolerance is nonzero.
o Inner-hole diameter-to-thickness ratio is greater than or equal to the machine property minHoleDTratio.
o Inner-hole diameter is less than or equal to the machine property maxHoleDia.
o Inner hole is not threaded.
o Inner hole is not countersunk.
o Inner hole is not blind.
o Roughness is greater than or equal to site default tolerance (roughnessDefault).
o Tolerance is greater than or equal to the minimum allowable tolerance given the inner-hole diameter and the current machine. This minimum tolerance is the product of the following values: (1) value for the inner-hole diameter in the lookup table toleranceCapability and (2) the machine property toleranceFactor.
Planar Face
• AsSupplied
o Part length equals stock length.
o GCD is planar.
• Bar & Tube Fab
o Roughness is greater than or equal to site default roughness (roughnessDefault).
o Tolerance is greater than or equal to site default tolerance (toleranceDefault).
• EndSawingSurface (cutting and trimming)
o GCD is accessible to a saw.
• PlanarFaceAsSuppliedSurface
o GCD is a stock surface or part of a complex hole or a non-ring surface in tube stock
Ring
• RingAsSupplied
o This operation is never feasible (unless infeasibility is manually overridden).
Simple Hole
• LaserOnly
o Diameter is nonzero.
o Length (depth) is nonzero.
o Tolerance is nonzero.
o GCD is not flanged.
o GCD is not threaded.
o GCD is not countersunk.
o GCD is not blind.
o Roughness is greater than or equal to site default tolerance (roughnessDefault).
o Tolerance is greater than or equal to the minimum allowable tolerance given the GCD’s dimensions and the current machine. This minimum tolerance is the product of the following values: (1) value for the GCD’s diameter in the lookup table toleranceCapability, (2) the machine property toleranceFactor , and, if the GCD’s length is greater than the plant variable thinToThickCutThreshold, (3) the plant variable thickCutToleranceFactor.
• PunchOnly
o Diameter is nonzero.
o Length (depth) is nonzero.
o Tolerance is nonzero.
o Diameter-to-thickness ratio is greater than or equal the machine property minHoleDTratio.
o Diameter is less than or equal to the machine property maxHoleDia.
o GCD is not threaded.
o GCD is not countersunk.
o GCD is not blind.
o Roughness is greater than or equal to site default tolerance (roughnessDefault).
o Tolerance is greater than or equal to the minimum allowable tolerance given the GCD’s diameter and the current machine. This minimum tolerance is the product of the following values: (1) value for the GCD’s diameter in the lookup table toleranceCapability and (2) the property toleranceFactor.
• SimpleHoleAsSupplied
o GCD is the interior of a tube (the part is made from tube stock, the GCD’s center is on a turning axis, and the GCD’s diameter equals the part’s cross-section diameter).
• SimpleHoleLaserCutting
o Diameter is nonzero.
o Length (depth) is nonzero.
o Tolerance is nonzero.
o GCD is not threaded.
o GCD is not countersunk.
o GCD is not blind.
• SimpleHolePunching
o Diameter is nonzero.
o Length (depth) is nonzero.
o Tolerance is nonzero.
o Diameter-to-thickness ratio is greater than or equal the machine property minHoleDTratio.
o Diameter is less than or equal to the machine property maxHoleDia.
o GCD is not threaded.
o GCD is not countersunk.
o GCD is not blind.