Carvera Air Spoilboard for SMW Fixture Plate

How to Machine a Spoilboard for Your Carvera Air CNC equipped with Saunders Machine Works Fixture Plate (or stock fixture plate)

If you're looking to get the most out of your Carvera Air CNC, one of the first upgrades you’ll want to make is a custom-machined spoilboard. A spoilboard protects your machine’s bed, improves workpiece hold-down, and provides a flat reference surface for precise machining. In this Instructable, I’ll walk you step-by-step through the process of setting up, and machining your own spoilboard specifically for the Carvera Air.

This guide is great for beginners and seasoned CNC users alike. Whether you’re trying to improve accuracy or just want a reliable base for your projects, a properly machined spoilboard is a must-have addition to your setup.

Let’s get started and level up your CNC game!

1. 1/4" MDF Stock
2. 2" Painters Tape & Superglue
3. Single Flute 1/8" Endmill (25 mm flute)
4. Optional
5. Deburring Tool
6. Sanding Blocks
7. Saw

Begin by placing your SMW Fixture Plate directly on top of the MDF stock. Carefully trace around the edges to define the profile of your spoilboard.

Using a saw (a jigsaw or bandsaw works well), cut along the traced outline. This doesn’t need to be perfect, just close to the final dimensions.

Sand down the cut edges for a smoother finish. If you'd like to add a touch of craftsmanship, consider beveling the edges for a cleaner, more polished look.

Thoroughly dust off the MDF. This step is crucial, any debris left behind can weaken the bond of the painter’s tape during the machining process.

Before machining begins, it's important to protect your SMW Fixture Plate from potential damage. During the cutting process, the end mill may extend slightly beyond the edge of the MDF stock. To avoid accidentally cutting into your precision fixture plate, install the original stock fixture plate that came with your Carvera Air.

Note: If you’ve already upgraded to the SMW Fixture Plate, take a moment to swap it out for the stock plate before proceeding. This precaution will help preserve the accuracy and longevity of your upgraded fixture plate.

Apply the painter’s tape to both the MDF stock and the stock fixture plate, aligning the strips to match each other as closely as possible. Consistent coverage ensures a strong bond when the two surfaces are joined.

Fold over a small tab of excess tape on each strip, creating easy-to-grab pull tabs. These tabs will make it significantly easier to remove the spoilboard once machining is complete.

Tip: Press the tape down firmly to ensure full adhesion, especially around the edges. Avoid overlaps or air bubbles, as these can weaken the hold during machining.

With the painter’s tape in place on both surfaces, apply super glue directly onto the taped area of the fixture plate. Use a zigzag pattern when applying the glue—this helps distribute it evenly and ensures a consistent bond.

Important: Use glue sparingly. Excess glue can squeeze out beyond the taped area and bond directly to the MDF or fixture plate, making removal difficult and potentially damaging your spoilboard or plate.

To ensure a strong, even bond and to eliminate any trapped air, place a weighted object, such as your SMW Fixture Plate on top of the assembly.

Begin by adjusting the attached CAD model to reflect the actual thickness of your MDF stock. This ensures accurate toolpaths and prevents cutting too deep or too shallow during machining.

For the hole pattern, I used the Bore operation in Fusion 360, but you’re free to use the CAM software and strategy that best suits your workflow. The key is to ensure the toolpath clears the entire hole area; set the final depth to 0.1 mm beyond the bottom of the hole to guarantee all material is cleanly removed.

You can refer to the operation settings shown in the images above for guidance. The order of the bore operations isn’t critical, so feel free to organize them in a way that makes sense for your workflow or tool changes.

Tip: Double-check your stock setup and origin point in your CAM to match how the MDF is mounted on the machine.

A special thanks to Saunders Machine Works for making the CAD model of the Carvera fixture plate publicly available. Having access to this model was incredibly helpful in accurately developing and aligning the attached spoilboard design.

Once your CAM file is post-processed, import it into the Carvera Controller App. I'm using the community firmware and controller, and I want to give a big thanks to the amazing community members who continuously improve this powerful toolset.

If your stock box point is correctly defined in CAM, you’ll need to set your work origin to (-15, -15) from Anchor 1 within the controller app. This offset ensures proper alignment with the fixture layout.

Important:

Disable "Scan Margin" before starting the job. If you leave it enabled, the gantry may extend beyond safe limits and collide with the machine frame.

Probing: Use a stock Carvera probe at the center of your stock, coordinates (153, 111), to set the probing location.

Auto-Leveling: If your stock surface is flat, auto-leveling is not necessary. However, if there’s any unevenness, you can perform a 3x3 probing matrix, offset 20mm inward from the outer boundary for clearance.

With everything set up, it's time to start machining your spoilboard.

Double-check all your settings, say a quick prayer (optional but recommended!), and turn on your dust collection system to keep MDF dust under control and maintain visibility.

If this is your first time machining a spoilboard, it’s a good idea to stay close with your hand on the emergency stop (E-Stop) just in case something goes off course. Mistakes can happen, and being ready gives you peace of mind.

Once machining is complete and the spindle has come to a full stop, it's time to remove the spoilboard. Using a flat prying tool or plastic scraper, gently lift the board from the fixture plate, working your way evenly around all sides.

Take your time, lifting gradually and evenly helps avoid cracking the MDF or damaging the fixture plate.

Tip: Those folded-over painter’s tape tabs you left earlier will come in handy here, they make it much easier to get under the spoilboard without prying too aggressively.

Inspect the machined spoilboard for any small burrs or wisps of MDF, particularly around the hole edges. If needed, deburr these areas using a utility knife, deburring tool, or fine sandpaper.

For a smooth, flat finish, I recommend lightly sanding both the top and bottom surfaces using a 220-grit sanding block. This helps remove any residual fuzz and ensures a clean, even contact surface for mounting.

To secure the spoilboard to your fixture plate, use low-profile M6 bolts around the edges. This ensures the top surface remains unobstructed during machining operations. Tighten the bolts evenly to maintain flatness and prevent distortion of the MDF.

Note: The stock Carvera flat stock clamps are compatible with M6 bolts and work perfectly with the SMW Fixture Plate.