How does Rotary Machining and Vector Wrapping work in VCarve Pro & Aspire for engraving text and designs on cylinders?

Overview

The software's rotary wrapping system lets you design flat 2D vectors and 3D components in the standard flat workspace, then "wrap" the toolpaths around a cylinder when the file is saved. A specially configured wrapped post-processor does the math, converting linear X or Y moves into rotational axis moves. This is how you engrave text on wine glasses, carve designs on table legs, cut flutes in columns, and engrave wedding rings. Rotary jobs, wrapping, and the Wrapped Fluting Layout, Wrapped Spiral Layout and Create Rounding Toolpath gadgets are in both VCarve Pro and Aspire. Two Rail Sweep and Vector Unwrapper (used for shaped columns) are Aspire only.

The Core Concept

Wrapping works by treating your job as an unwrapped cylinder:

• One axis of the job runs along the cylinder (its length)
• The other axis is the angle around the cylinder, so that dimension equals the circumference (π × diameter)

Which axis is which depends on the Orientation you choose in Job Setup (see below). Everything you design in the flat 2D view is wrapped around the cylinder when machined. The key point: design at full physical size as if it were flat. The post-processor converts it. The two edges of the wrapped dimension meet at a seam on the finished piece. Example: a 3.5" diameter cylinder gives a job 3.5 × 3.14159 = 10.996" wide in the wrapped direction.

Setup: Job Setup Form with Rotary Job Type

In 12.5, create a rotary job from the Job Setup form (File > New, then choose the Rotary job type). Fill in:

1. Length and Diameter of your blank (the machinable length and the stock diameter)
2. Z Zero Position: choose Cylinder Axis (center). It is the recommended option for best accuracy
3. XY Datum Position: any corner or the middle of the job (bottom left is the default and most common)
4. Orientation: Along X Axis or Along Y Axis, matching how the rotary axis is mounted on your machine
5. Click OK. The software creates a new job sized to the cylinder

What Orientation means: With Along X Axis, X coordinates represent movement along the cylinder and Y coordinates represent the angle around it, so the job height equals the circumference. With Along Y Axis it is the reverse: Y runs along the cylinder and the job width equals the circumference.

When the job is created, two helper layers are made and switched off by default (press Ctrl+L to show the Layer Control): 2Rail Sweep Rails (two lines for sweeping a profile along a shaped column) and Bounding Box (a rectangle covering the whole job, useful if you will machine the entire surface).

Why Z zero at the cylinder axis (center)?

When rounding a blank, the surface is constantly being removed. If Z is zeroed to the surface, the reference changes as you machine, and you cannot set Z on the surface of a cylinder that does not exist yet. The cylinder center never changes, and some controls work out the correct rotation speed from the distance to the center. The Z origin can be overridden when the toolpath is saved, but center is strongly recommended.

Plan the blank to be longer than the design so the tool stays a safe distance from the chuck and tailstock.

Spiral and Multi-Wrap Designs

For designs that wrap around the cylinder several times (barley twist, rope twist, spiral fluting, vines), use the Wrapped Spiral Layout gadget (Gadgets menu, Wrapping submenu) in a rotary job. It does not create toolpaths itself. It lays out vectors in the 2D view (they extend beyond the job boundary, which is expected) that you machine with the Profile toolpath, using the Machine Vectors On option for spirals and coves.

Visualizing the Wrapped Result

Auto Wrapping mode: Use the Auto Wrapping button to see your flat toolpaths and model displayed wrapped on a cylinder. The software can also draw the toolpath simulation wrapped.

Important caveat: The wrapped simulation is not 100% accurate. Round holes may appear as distorted ovals due to the stretching process, but they cut round on the machine.

Post-Processors for Wrapping

Standard post-processors output flat XYZ moves. For rotary wrapping you need a wrapped post-processor that replaces X or Y moves with angular moves (A or B axis).

• Wrapping post-processors are included with the software. To choose one, open Save Toolpaths and click Manage machine configuration, then press the + button under Associated Post-Processors and pick the wrapped post that matches your machine and orientation
• Right-click a post in that list and choose View to inspect it, which helps if you need to edit one later
• If no included post matches your controller and axis combination, see the Post Processor Editing Guide in the Help menu and search the software maker's user forum for a post for a similar setup

Vector Unwrapper Tool (Aspire only, for Shaped Columns)

For shaped columns (hexagonal, octagonal, other cross sections) on the rotary axis:

1. Draw the cross-section shape as a 2D vector (for example a hexagon). Its radius cannot exceed the radius of the blank
2. Open Vector Unwrapper (only available in rotary projects) and choose the center of rotation (center of contour, center of workspace, or a custom point)
3. Click Apply. The tool converts the cross-section into an unwrapped profile vector with legs on each end, and creates two drive rails on the layer "Unwrapped Vectors Drive Rails"
4. Open Two Rail Sweep, select the two rails and click Use Selection, then select the unwrapped vector and Apply

Key note: The modeling plane must be at the cylinder center (Gap Inside Model reads 0 in Material Setup) or the cross section will come out rounded. Convex shapes and some concave shapes work.

Practical Workflow for Engraving Text on a Cylinder

1. Create a rotary job: enter cylinder diameter and length, Z zero at Cylinder Axis, and the correct Orientation
2. Draw your text in the 2D view at the desired size and position
3. Calculate a V-Carve toolpath on the text
4. Preview and turn on Auto Wrapping to see it on the cylinder
5. Save with the appropriate wrapped post-processor
6. On the machine: Z-zero to the cylinder center (measure from the chuck center)
7. Set X/Y zero at the desired start position
8. Run the file. The rotary axis and linear axes move simultaneously

Common Rotary Project Types

Toolpath Compression Issue for 3D Rotary

Wrapped toolpaths match the flat toolpaths only at the surface of the blank. The closer to the rotation axis (deeper) a toolpath is, the more it is compressed. For 3D toolpaths on rotary projects with significantly different diameters at different points (tapered column, shape changes along the axis), a single toolpath ends up overly compressed in the thinner sections.

Fix: Create boundaries around regions of significantly different diameter and make separate toolpaths for each, using the right settings for each diameter. Components stretched in the wrapped direction also need compensating where the diameter narrows.