Onion Skin Cutting on a CNC Machine

A CNC machine allows you to create projects with exceptional details, providing a means of producing great results with outstanding consistency. For example, you can engrave letters with a CNC that look like they were created by a master wood carver. Or, you will have no problem carving artwork with a CNC, even if you do not have an artistic bone in your body.

What happens, however, when you cut small pieces out from a larger workpiece when running a job on a CNC? If the piece is completely removed from the CNC there is a loss of control. When that happens in the presence of a spinning router bit it can be dangerous, and the workpiece could be damaged. There are ways that you can mechanically secure the work piece, such as double-sided tape, but that can be tedious if there are a lot of small parts involved.

One simple approach that works well in this situation is a technique called “onion skinning”, which involves the following steps:

• Carefully register your router bit at the top of the workpiece prior to running the job.
• Set your CNC cut so that it does not fully penetrate entirely through the work piece. You will leave a layer of wood so thin that you can shine a light through it, hence the name “onion skinning”.
• When the CNC machining process is complete, you will remove the “onion skin” by sanding it off, freeing the small items so that they can be used in your project. This step is best performed on a drum sander, but you could also use a belt sander or orbital sander.

After you have mastered the process of onion skinning, check out our other videos on CNC techniques that you can add to your arsenal.