We’ve seen and experienced varied results when using or not using masking on various materials.
A current thread about leather getting “blown out” on the back side has me thinking - this is a common problem when cutting, milling, or drilling wood; and in many instances, a sacrificial backing board is used to prevent the underside from chipping along the edge.
I wonder if we could use various backing materials to help in situations like this? Perhaps chipboard behind leather, for example. We don’t need to worry about cutting thru the backing, just ensure that it “masks” the target material to prevent damage underneath…
A sound solution, just be sure to include the additional thickness in the material settings. In the early days of the pre-release flashback on the material was an issue, but (when I remembered to) I put down a piece of cardstock for protection.
I think @takitus was masking most of crumbtray to successfully eliminate flashback.
This is similar to what I was thinking about after making these bookmarks.
This material is from 6" x 4" blanks from cardsofwood.com
and have a center layer of plastic. The end result is 1.25" x 5.5". They are great for strength, but I’m not sure if it’s the plastic that is burning the back, the tightness of the pattern or the flash-out on the back. I was thinking about the sacrificial material as my next test.
Top image is walnut with no masking. The second one down is cherry with my own masking on it, and the third one is my own masking on the backside of the cherry. In some cases, the plastic is melted clear through, but in most cases the wood is burnt deep enough that sanding will just remove the wood. Typing that out now, that might not be the worst result. Wood on top, plastic on back.
Looking at the shapes of the burn marks, it seems that the speed is way too low, allowing the material to burn thru. Have you tried faster cuts with multiple runs?