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The Construction step

Define the construction for each catheter section. All sections share this one step; switch between them from the section entries under Construction in the step rail, or from the colored section bar across the top of the page. Either swaps the page to that section's stackup, dimensions, and reinforcement.

The page is a master–detail layout, in three columns:

  • Left: the layer stack. The section's length and color, the Clone... button, and the list of layers from the inside out, each showing its type, material and thickness. Click a layer to open it. The foot of the stack shows the section's resolved OD, ID, and wall, updating as you edit.
  • Center: one layer editor. The layer you picked, and only that layer.
  • Right: the cross-section. A scaled cross-section of the whole section that redraws as you type.

Clone & Match Shortcuts​

Above the layer stack on the left, the Clone... button opens a menu with two shortcuts that let you quickly align a section to another already-defined section, instead of re-entering every layer by hand:

  • Clone From...: Pick another section in the design and copy its entire construction (layer stackup, materials, reinforcement, pull-wire settings, and overrides) into the active section. Useful when you want to carry over a shared liner and braid from another section and then change a single parameter, such as the jacket material.
  • Match Dimension To...: Pick another section in the design and match the active section's outer or inner diameter to that section. A second dialog then asks which layer in the active section to adjust so the new OD or ID is met (typically the jacket). Useful for maintaining a continuous OD across adjacent sections that otherwise have different layer compositions. (Not available in Fixed OD and Fixed ID mode, since all sections already share globally fixed boundaries.)

Both shortcuts only act on the currently active section and copy values once: later edits to the source do not follow. To keep a layer in step with the section before it, use Continues from (below). Clone From copies a layer's values but never its links.

Continues from the Previous Section​

A liner, braid, coil or pull-wire lumen layer often runs unbroken through several sections. On every section after the first, these layer cards have a Continues from box that names the section just before it. Tick it and the layer takes that section's matching layer: its thickness, material, color and name, plus every braid or coil setting, or the pull-wire layer's construction, lumen and lumen liner. Its inputs gray out, and a link symbol shows on the card and beside the layer in the stack. Edits to the source flow down the chain as you make them. Untick the box to edit the layer again; it keeps its current values.

  • Matching: the liner continues the liner and the pull-wire layer continues the pull-wire layer. The first braid continues the first braid, the second the second, and coils likewise. A braid never continues a coil.
  • The pull wires: a braid or coil cannot cross the pull-wire layer. One that sits under the wires in one section and over them in the next gets no box. Sections past the pull-wire anchor have no pull-wire layer, so there is nothing to cross there.
  • The Pullring is a section like any other. Its liner can continue from the section before it, and the next section can continue from the Pullring. The ring tube itself never links.
  • New sections start unlinked.
  • Reordering or deleting sections keeps a link only if the new previous section already has the same layer values, so nothing changes without you seeing it. Otherwise the box unticks, the layer keeps its values, and the status bar says so.

Cross-Section Visualizer​

In the right-hand column, a scaled cross-section view displays a dynamic representation of the active section's layers, materials, and internal lumens. The view updates in real time as you modify layer properties.

Section Settings​

Modify the section length and representation color directly from the top of the left-hand column, without going back to the Design step. On multi-lumen core designs this strip also has a "Use multi-lumen core in this section" checkbox (on by default); uncheck it to build this one section on a plain bore instead, e.g. a soft tip in front of a multi-lumen shaft.

Layer Stackup​

Layers are defined from the inside out: Layer 1 is the innermost layer (liner) and the final layer is the outermost jacket. The list in the left-hand column shows the whole stack in that order; click an entry to open it in the editor beside it.

Stack controls (at the foot of the layer list):

  • Up/Down arrows swap the selected layer with a neighbor.
  • The red "X" deletes the selected layer.
  • The green "+" inserts a new polymer layer just inside the selected layer, or just outside the liner when the liner is selected.

Per-layer properties:

  • Color: Click the color swatch next to the layer name to change its representation in the 3D Viewer and Peel-away Visualizer.

  • Name: An optional label for the layer (e.g., "Outer Jacket," "Braid," "Liner").

  • Adaptive Layer Toggle: Only available when the global design mode is set to "Fixed OD and Fixed ID". Clicking the Adaptive toggle automatically calculates and locks this layer's thickness to satisfy the global inner and outer diameter constraints. Only one layer can be adaptive per section, and it defaults to the outermost polymer layer (Jacket).

    Note: Reinforced layers (Braid/Coil) cannot be adaptive.

  • Material: For polymer layers, select the material from the dropdown. Reinforced layers (Braid/Coil) don't show a material selector; they automatically inherit the polymer from the layer immediately outside (which becomes the matrix material when the catheter is reflowed).

  • Layer type: Choose the structural type of the layer:

    • Polymer: A pure polymer layer. Innermost and outermost layers must be polymer layers.
    • Braid: A woven wire reinforcement pattern.
    • Triaxial Braid: A braid with added straight axial wires running along the catheter axis, for extra axial and bending stiffness. See Triaxial Braid specifics below.
    • Coil: A helical wire reinforcement pattern.

  • Thickness:

    • For Non-Reinforced Layers: Enter the wall thickness manually (unless marked as the Adaptive layer). A layer you have not edited keeps a default wall that follows the catheter diameter (see the Design step); the first edit anywhere on the layer's card makes the layer yours.
    • For Reinforced Layers: This field is read-only. The software automatically calculates the thickness from the wire dimensions: 2× wire thickness for Braids, 2× wire thickness plus one axial-wire thickness for Triaxial Braids, and 1× wire thickness for Coils. A very dense braid adds a small amount for the wires riding over one another; sparse braids do not.

  • Dimensions (ID/OD): Displays the calculated Inner Diameter (ID) and Outer Diameter (OD) based on the cumulative thickness of previous layers.

When the stack does not fit. In the Fixed OD modes the layers have to fit inside the radius. When they do not, the Action Required box on the section page gives the two numbers and the ways out, for example the layers are too thick for the 0.0200 in OD. They add up to 0.0110 in per side; the OD leaves 0.0100 in per side. Make the layers 0.0010 in thinner in total, or increase the Outer diameter. It also says how much of that the pull-wire layer takes, and that a smaller Lumen ID makes it thinner. The section's entry in the step rail gets an amber badge, so the problem is visible from every step. A pull-wire lumen you typed smaller than the wire plus its 0.001 in clearance is reported the same way rather than changed. When no wall is left for even the thinnest layer, the + buttons are disabled and say so.

Pull-Wire Layer Settings​

If pull wires are enabled in the Global Settings, a special "Pullwires" layer is automatically injected into the stackup. This layer manages the position and space required for the pull wires and their optional liners.

The layer card carries the section's pull-wire lumen settings as regular rows of the card itself: the lumen inner dimensions (Lumen ID for a round wire; Lumen thickness and Lumen width for a flat wire) and the Lumen liner selector: None, Polymer (material and wall thickness) or Coil. Each inner dimension is floored at the global wire dimension + 0.001" clearance: it can be set larger per section, never smaller.

A Coil liner is a fully closed, single-filar metal coil wound directly on the lumen. Enter the coil wire shape (round or flat), its size and its material; there is no pitch or filar input because the coil is assumed closed (pitch = the wire's axial dimension). Tick Polymer jacket over coil to add a polymer tube outside the coil, a mini-catheter lumen: the jacket reuses the material and thickness rows. A coil-lined lumen is always round, even around a flat pull wire (its ID is then floored at the ribbon diagonal + clearance). The coil is modeled as a plain closed spring, not as a composite: it bends with the Wahl helical-spring stiffness, resists axial compression as a solid metal tube and stretches as a helical spring, and that stiffness flows into the composite calculator and every module that reads it. The right-column illustration shows the closed coil at the lumen scale while the pull-wire layer is selected. Simulated values, not measurements.

The section's cross-section preview shows the resolved lumens (with their liners when enabled) at this section's dimensions, and, when the wire cross-section is specified on the Pull-wire settings page, the pull wire itself, drawn to scale in dark gray metal inside each lumen.

  • Construction Type:
    • Individual Mandrels: Use this setting if the lumens are constructed by individual mandrels prior to reflow. The layer's thickness is automatically calculated based on the pull-wire lumen and liner dimensions defined in the global settings. The material is inherited from the layer immediately outside of it.
    • Multi-Lumen Extrusion: Use this setting if the lumens are created with a multi-lumen extrusion. The layer is modeled as a continuous multi-lumen polymer extrusion. You can manually enter the layer thickness (minimum thickness is constrained by the lumen dimensions) and select a polymer material from the library.

Ring Layer Settings​

Inside the Pullring section one layer is the ring itself. Its card takes the tube as ordered rather than a wall thickness, and the wall follows from it.

By default the tube sits inside the pull-wire layer of the section before it, at the closest stock size that fits (a Custom tube filling that layer when none does). Under it are that section's own liner and any braid or coil inside the wires. The jacket flows through the ring: it fills any gap between those layers and the tube, and covers the tube out to the same OD.

  • Ring size: Custom takes an ID and OD directly. The rest of the list is hypotube gauges, smallest to largest, with each one's dimensions in inches; picking one fills in the ID and OD.

The card is always the ring: it cannot be changed to another type and cannot be deleted. Other reinforcement layers can sit above or below it. The section carries no pull-wire lumen layer.

The Pullring can also be switched to Manual Stiffness or Rigid Body, like any section. Its layers, the ring included, are then set aside, and it has no pull-wire offset of its own.

In every mode the pull wires end in the Pullring at the same offset they ran at in the section before it.

Reinforcement Settings​

If "Braid", "Triaxial Braid", or "Coil" is selected for a layer, a sub-panel appears to define the wire geometry. A dynamic preview of the pattern (including the calculated braid angle) is displayed.

Common settings:

  • Wire material: Select the wire material from the material library. The list shows metals only by default (e.g., Stainless Steel, Nitinol), since those are the overwhelmingly common choice. To use a non-metal wire (PEEK, aramid, or any custom material whose Material Family is not Metal), choose More materials… at the bottom of the list, which re-opens it showing your entire library. Loading a design whose saved wire is a non-metal expands the list automatically, so your selection is always visible.
  • Wire shape: Choose between Round or Flat/Ribbon wire.
  • Wire Dimensions:
    • Round: Enter the wire diameter.
    • Flat: A dropdown of common ribbon sizes is provided for quick selection, or enter a custom thickness and width.
    • Defaults: a layer switched to Braid or Coil starts with a wire sized from the catheter diameter, stepping down the common sizes as the catheter gets smaller (.003 in x .005 in flat and .003 in round at 10 Fr and above, .0005 in x .0025 in and .0005 in at 020). Choosing the layer type does not count as editing the layer; editing the wire, or anything else on the card, does.

Braid specifics:

  • Picks per inch (PPI): The number of wire crossings per inch of length. A braid you have not edited holds a 45 degree braid angle on its own mean diameter, so its PPI follows the diameter (about 20 PPI on a 10 Fr layer, about 135 on a 020 layer, in steps of 5, never past the jam limit); edit it, or anything else on the card, and it stays where you put it. A PPI or coil pitch you typed is never changed by the app afterwards, whatever you do to the carriers, the wire or the diameter: a weave past its jam limit reads Too dense: the wires will likely jam and a coil pitch tighter than its wire reads The turns overlap in the Status line, and the fix is yours to make.
  • Number of carriers: The number of bobbins used in the braiding machine (e.g., 16, 32, 64).
  • Number of filars: How many wires each carrier loads, running side by side (1–10, default 1). A multi-filar (multi-end) braid lays down a wider band at every carrier position, so its coverage saturates sooner and it jams at a lower PPI than a single-filar braid with the same carrier count. Filars sit beside each other rather than stacking, so they add no wall thickness on their own, though a band too wide for its slot makes the weave bulge outward. Total wires = carriers × filars.
  • Calculated angle: The resulting braid angle relative to the longitudinal axis.

Triaxial Braid specifics:

A triaxial braid keeps the bias-braid controls above and adds straight axial wires running along the catheter axis, which increase axial and bending stiffness. (The Number of Filars setting applies to the bias wires only; axial wires are always single.) It exposes two extra settings:

  • Number of axial wires: How many straight wires to add. The practical capacity is carriers ÷ 2 wires for a Full Load pattern, or carriers ÷ 4 for Half Load and Diamond.
  • Match axial wire to bias wire: Enabled by default, so the axial wires reuse the bias wire's shape, dimensions, and material. Uncheck it to set the axial wire's shape, size, and material independently.

Coil specifics:

  • Pitch: The distance between the center of one wire wrap and the center of the next.
  • Number of carriers: How many independent runs the coil is wound from (1–10, default 1). Several carriers are spaced evenly around the circumference, one even fraction of the pitch apart: a multi-start helix.
  • Number of filars: How many wires each carrier loads, running side by side (1–10, default 1). Carriers spread out along the pitch; filars hug their carrier. Coverage, jamming and wire length depend on the total, carriers × filars.

Manual Override Options​

  • Layer Construction: The default selection. The catheter section is constructed from layers, and bulk section properties are calculated automatically.

  • Manual Stiffness: Allows you to manually enter the bulk section properties:

    • Bending Stiffness (EI)
    • Torsional Stiffness (GJ)
    • Axial Stiffness (EA)

    On steerable designs a Pullwire offset field also appears. A hand-entered section has no layer stack to place the pull-wire lumens, and the offset is the tendon's moment arm, so it changes how the section deflects rather than just how it is drawn.

  • Rigid Body: The section is modeled as a single, non-deformable rigid body.

Multi-lumen cross-sections:

Catheters built on a multi-lumen inner geometry are supported natively: set the Design Mode to Multi-Lumen Core and shape the profile from a parametric template (double-D, satellites, crescents, ...). Asymmetric profiles bend anisotropically in the simulation, and the analysis reports the core-appropriate KPIs. See Multi-Lumen Core.

Alternative methods to determine stiffness values (EI, GJ, and EA):

Accurate stiffness values are essential for a realistic dynamic simulation. If these properties are unknown for your design, here are two common methods to determine them:

1. Calculation from Geometry

Ideal if you have a CAD model of the catheter's cross-section and know the material properties.

  • Bending Stiffness (EI): The material's Young's Modulus (E) multiplied by the cross-section's Area Moment of Inertia (I).
  • Torsional Stiffness (GJ): The material's Shear Modulus (G) multiplied by the cross-section's Polar Moment of Inertia (J).
  • Axial Stiffness (EA): The material's Young's Modulus (E) multiplied by the cross-section's Area (A).

2. Physical Measurement

Directly testing a physical sample is the most accurate method, as it captures the real-world performance of the manufactured component.

  • Bending Stiffness (EI): Typically found using a three-point bend test, where a known force is applied to a sample and the resulting deflection is measured.
  • Torsional Stiffness (GJ): Found by fixing one end of a sample, applying a known angle of twist at the other end, and measuring the torque.
  • Axial Stiffness (EA): Found by pulling a sample of known length in tension and measuring force against elongation.

While high-precision test equipment is ideal, simple benchtop setups can provide reasonable estimates for simulation purposes.