How do I use tabs in VCarve Pro & Aspire's Profile toolpath to hold parts in place when cutting them out?

Overview

Tabs (also called bridges) are small sections of uncut material left attached to a part during a through-cut profile pass. They prevent the part from shifting, lifting, or flying out of the material when it becomes fully separated. Without tabs, a free-floating part can grab the spinning bit and be launched, which is a serious safety hazard.

Setting Up Tabs in the Profile Toolpath

1. Set up your 2D Profile Toolpath as normal (Outside/Inside/On, tool, depth)
2. In the toolpath form, check ✔ Add tabs to toolpath
3. Set Tab Length, how long each tab bridge is along the cut path (typical starting point: 0.4 to 0.6")
4. Set Tab Thickness, how tall the tab is from the bottom of the cut upward (typical starting point: 1/4 to 1/3 of material thickness)
5. Click Edit Tabs to open the tab placement dialog. Click Add Tabs to place them automatically (Constant number or Constant distance between tabs), or place them yourself
6. To place tabs interactively, click the vector path where you want each tab. Click an existing tab to delete it, or drag a tab to move it
7. Close the dialog when done, then Calculate

2D Tabs vs 3D Tabs

2D Tabs (flat top):

The cutter lifts vertically to the tab thickness, runs flat across the tab, then plunges back down. Creates a flat-topped bridge. The abrupt stop-and-plunge can leave a small mark at the tab edges.

3D Tabs (triangular, ramp top), recommended:

Check ✔ Create 3D Tabs in the toolpath form. The cutter ramps smoothly up to tab height and back down, creating a triangular profile. The machine often runs quicker and smoother because it does not have to stop to move in Z at each tab, and the tab is easier to remove with a chisel or flush-trim router bit.

For most jobs, use 3D tabs whenever possible. The ramp motion is smoother on the machine and the triangular shape is easier to sand or trim flush.

Tab Sizing Guide

These are starting points to test on scrap, not software rules.

General rule used across these entries: tab thickness is about 1/4 to 1/3 of material thickness. Tab length is about 1/2 to 3/4 of material thickness.

Tab Placement Strategy

• Place at least 2 tabs per part, on opposite sides
• For irregular or fragile shapes: place a tab at every fragile extension or thin protrusion
• For large parts: 3 to 4 tabs evenly distributed
• Place tabs on less visible edges where cleanup will be easier
• Avoid placing tabs at sharp corners (the Avoid corners and curved regions option helps with automatic placement)
• For letters or text: each disconnected island needs its own tabs

Why Tabs Don't Show in Preview (Common Troubleshooting)

Tab thickness too large: Tab thickness is measured from the bottom of the cut depth upward. If the tab thickness is as large as the cut depth, the tab fills the whole cut and there is nothing left to cut at the tab position. Keep tab thickness at about 1/4 to 1/3 of the cut depth.

Tab length too long: If a tab length is set to 5" on a 2" part, there is no room for the tab to fit. Reduce tab length significantly for small parts (try 0.1 to 0.2" for intricate letter cutouts).

Start depth issue: If a start depth is set, the cut depth is measured from it. Tabs that fall below the material bottom will not machine.

Tabs for 3D Models (Important Difference)

For parts being cut out with 3D roughing + finishing toolpaths, the 2D profile tabs have no effect on the 3D toolpaths. 3D toolpaths do not know about 2D tabs.

Solution, the onion skin method:

1. Set the 3D rough and finish toolpaths to stop just above the material bottom (leave 0.03 to 0.05" of material)
2. Run the 3D toolpaths
3. Create a 2D Profile toolpath to cut through the remaining skin, adding tabs in the Profile form
4. The profile then becomes the only through-cut pass, and it fully respects your 2D tabs

This is a reliable method for tabbing 3D carved cutout parts.

Removing Tabs After Cutting

• Flush trim router bit in a trim router: fastest and cleanest
• Oscillating multi-tool / reciprocating saw: cuts through the tab quickly
• Hand chisel or knife: works well for thin 3D tabs
• Sand the remaining nub flush with 80 to 120 grit on a random orbit sander

Common Mistakes

• Tab thickness set as tall as the whole cut: the part is held on by a solid block, not a tab. Keep it to about 1/4 to 1/3 of the cut depth
• Tab length too long for small letters: reduce to 0.1 to 0.15" for intricate work
• Only placing one tab on a part: always use at least two on opposite sides
• Expecting 2D tabs to work with 3D toolpaths: they do not; use the onion skin method