How do I create a double-sided 3D machining project: setup, flip registration, and matching top/bottom components?

Overview

Double-sided machining lets you design and machine both the top and bottom faces of a material blank in one project file. It is useful for thick 3D carvings (figures, fish, dimensional signs) with detail on both sides, or parts that need machining on the front and back. The critical skill is registration: making sure that after flipping the material, the bottom-side toolpaths line up exactly with what was machined on the top.

Setting Up a Double-Sided Job

1. Create a new job (File > New)
2. Set Job Type to Double Sided
3. Set the job size to your material blank size, including the thickness, using the real measured thickness
4. Z Zero Position: choose whether the tool tip is set off the surface of the material or off the bed (table) of the machine. The Zero off same side option makes Z Zero reference the same physical location whether or not the material is flipped, which gives a consistent tool zero.
5. XY Datum Position: set at any corner or the middle of the job. It is the location on your design that matches the machine at X0, Y0. It must match your flip jig setup. Use Offset sets a datum other than X0, Y0.
6. Flip Direction Between Sides: choose horizontal or vertical flipping. The software uses this to manage the alignment of the geometry for each side.
7. Click OK

Switching sides:

• Press 1 to switch to the Top side
• Press 2 to switch to the Bottom side
• Or use the Top and Bottom controls in the View toolbar

The Component Tree: Top and Bottom

In a double-sided job you create components independently for each side, or use the right-click option to copy or move a component to the opposite side. Components on the Top side are only part of the model while the Top side is active, and the same for the Bottom.

Designing the top side:

• Press 1 to make the Top side active
• Create, import and position all the 3D components for the top face, and the 2D vectors for top-side toolpaths
• Calculate the top-side toolpaths

Designing the bottom side:

• Press 2 to make the Bottom side active
• Create the 3D components for the bottom face
• Use Multi Sided View (the = key, or the View menu) to see the top and bottom components in the 3D view together

Registration: The Most Critical Step

Registration is how you make sure the bottom cut lines up with the top after flipping. These are common methods.

Method 1: Edge Registration (Simplest)

Cut the blank to exact dimensions and use the physical edges of the material as the reference:

1. Set the XY Datum to a corner (for example lower left)
2. Machine the top side
3. Flip the material in the direction you chose under Flip Direction Between Sides
4. The datum corner of the flipped piece is now in the same machine position as before
5. Re-check X0 and Y0 at that corner

Flip direction matters. The way you physically flip the material must match the Flip Direction setting in the job.

Method 2: Dowel Pin Registration (Most Accurate)

1. Machine two dowel holes (for example 3/8 inch diameter) in your spoilboard at known X, Y positions, usually near two corners of the job
2. Drill matching holes in the blank so they line up with those pins on both faces
3. Machine the top side normally
4. Flip the blank and fit the holes over the pins
5. The material is registered to within the accuracy of your hole drilling

Why it is a good method: physical pins remove accumulated positioning error and re-zeroing guesswork.

Method 3: Registration Lines

Machine shallow scribed lines at two edges as reference marks. After flipping, line them up with a fence or reference edge.

Multi-Sided View

Multi Sided View shows components on both the Top and Bottom sides in the 3D view. In the Toolpath Preview form of a project with toolpaths for both sides, it also shows the simulation for both sides. If it is not selected you can use the Preview all Sides option in the Toolpath Preview form instead.

Use it to:

• Check that features from the top and the bottom line up where you intend
• Check that the carving depth from the two sides does not leave a thin wall in the middle
• Confirm the two sides meet cleanly at the intended depth in the material

Matching Top and Bottom Components

For thick 3D carvings the top and bottom must match at the center plane:

1. Design the top component to a suitable depth (for example 0.8 inch into a 1.5 inch blank)
2. Switch to the Bottom side (press 2)
3. Create the bottom component so it joins the top at the intended depth in the material
4. Use the Zero off same side option for a consistent depth reference

Thickness check: in the 3D preview with Multi Sided View, look for areas where the two sides come close together, because thin walls can crack during carving.

Saving Toolpaths for Double-Sided Jobs

1. Make the Top side active (press 1) and save the toolpaths for the top side
2. Tick Add side to toolpath name on the Save Toolpaths form. When you create aligned toolpaths for a two-sided part, it adds the side name to the toolpath name as it is saved, to keep your toolpaths organized.
3. Make the Bottom side active (press 2) and save the toolpaths for the bottom side
4. Run the top-side toolpaths first, flip the material, then run the bottom-side toolpaths