Process Feasibility for Hydroforming

This section covers the following topics:

• Hydroform Feasibility

• Fluid Cell Feasibility

• Deep Draw Feasibility

Hydroform Feasibility

All Hydroform routings require that the part meet all the following conditions:

• Part either has at least one Form whose Sub Type is EMBOSS or CURVED BEND or else has at least one StraightBend.

• Part has at least 3 Xsection GCDs.

• Part can be made from stock of uniform thickness (that is, there are no NotSupported GCDs whose Cause property has value DIFFERENT_THICKNESS).

Fluid Cell Feasibility

Fluid Cell routings are feasible only for parts that have all the following characteristics (other parts use Deep Draw routings, if feasible):

• Sufficiently small overall depth-to-width ratio:

Total Form Depth / Lowest Tier Width > 0.55 (in starting point VPEs)

The total form depth (part height, excluding any long, down-bend flaps) divided by the width of the part’s lowest tier must be less than the cost model variable fluidCellFormingRatioThreshold (0.55 in starting point VPEs). See Lowest Tier and Long Down-bend Flaps for details.

• Sufficiently small depth-to-width ratio for the part’s top tier:

Top-tier Height / Top-tier Width > 0.55 (in starting point VPEs)

The height of the top tier divided by its width must be less than the cost model variable fluidCellFormingRatioThreshold (0.55 in starting point VPEs). The top tier consists of top-most part Xsections of approximately equal width. See Top Tier and Xsection Width for details.

This requirement is ignored if there is no significant EMBOSS form. Small stiffening embosses are not considered significant. An emboss form is generally considered significant if it takes up a sufficient fraction of the main surface. In particular, it is significant if both the following hold:

o The emboss's Min Bend Radius is greater than 0.

o The product of the emboss’s SER Length and SER Width is greater than the product of the main surface’s Convex Hull Area and the cost model variable mainSurfAreaMultiplier—0.75 in starting point VPEs).

Emboss SER Length * Emboss SER Width >

Main Surface Convex Hull Area * mainSurfAreaMultiplier

• No bends with excessive curvature:

Bend SER Width / Bend Length < 0.75 (in starting point VPEs)

For each form whose Sub Type is CURVED_BEND, the bend SER Length divided by the bend Length must be less than the cost model variable excessiveCurvedFormThreshold (0.75 in starting point VPEs).

Note that SER width-to-length ratio reflects, roughly, average degree of curvature. In the current release, aPriori might fail to detect excessive curvature for bends whose degree of curvature varies a great deal (such as fish-hook-shaped bends).

Deep Draw Feasibility

Deep draw routings are feasible only for parts that have at least one of the following characteristics:

• Part has at least one significant Form whose Sub Type is EMBOSS.

Small stiffening embosses are not considered significant. An emboss form is generally considered significant if it takes up a sufficient fraction of the main surface. In particular, it is significant if both the following hold:

o The emboss's Min Bend Radius is greater than 0.

Emboss SER Length * Emboss SER Width >

Main Surface Convex Hull Area * mainSurfAreaMultiplier

• Part has a high-curvature CURVED_BEND form (one that would be excessive for Fluid Cell--see Fluid Cell Feasibility).

That is, there must be a form whose Sub Type is CURVED_BEND, and the bend SER Length divided by the bend Length must be less than the cost model variable excessiveCurvedFormThreshold (0.75 in starting point VPEs).

Bend SER Width / Bend Length < 0.75 (in starting point VPEs)

Note that SER width-to-length ratio reflects, roughly, average degree of curvature. In the current release, aPriori might fail to detect high curvature for bends whose degree of curvature varies a great deal (such as fish-hook-shaped bends).

Top Tier

The top-tier of a part is the maximal set of Xsections such that both the following hold:

• The set includes the top-most Xsection (excluding any Xsection that is less than the blank thickness from the very top of the part).

• All the Xsections in the set have about the same width.

Xsection Width

The width of an Xsection is its smaller dimension orthogonal to the draw direction (calculated from the GCD properties Rectangle Lower Left and Rectangle Upper Right). The height of the top tier is the number of Xsections times the distance between adjacent Xsection pairs (this distance is the same for all adjacent Xsection pairs of a given part).

Long Down-bend Flaps

The depth in the overall depth-to-width ratio excludes Xsections whose width is less than 4 times the blank thickness, as they are likely to be cross-sections of long, down-bend flaps.

Lowest Tier

The width of the part’s lowest tier is the width of the lowest Xsection (excluding any Xsection that is less than the blank thickness from the bottom of the part). The width of an Xsection is its smaller dimension orthogonal to the draw direction (calculated from the GCD properties Rectangle Lower Left and Rectangle Upper Right).