Custom CNC flattening & surfacing
Cupped tabletop
Cupping often occurs in wood & epoxy projects while curing epoxy resin as the resin shrinks while hardening and “pulls” the wood, thus causing deformations
The bigger they are, the worst the deformations can be
As you’ve probably guessed, the larger the project, the deformations are easier to spot. In this case, the table was approx. 1×2,4 meters and the highest cupping point was about 17mm
Fixing the problem
Luckily, we managed to flatten the tabletop so the end result required only minor fixes and a decent sanding. In this case, at least some of the cupping could have been avoided if the boards were properly flattened before pouring the epoxy.
Board flattening
Sometimes wide boards that weren’t stored properly can also cup. In this case, a client started making a shelf out of a wide glued board and left it in the basement for almost a year. The only way to get it flat was using a CNC with a specialized bit as it was too wide for any type of planer.
Flattening a “cookie”
A client brought us a wood cookie, also known as a tree trunk slice or tree round, is a cross-sectional slice cut horizontally from the trunk or a large branch of a tree. It shows the growth rings of the tree, which can be used to estimate the tree’s age and environmental conditions during its life.
Why are wood cookies so hard to flatten?
Wood cookies are hard to flatten because the grain runs in a circular pattern from the center outward, unlike straight-grained boards. This radial grain orientation causes uneven movement as the wood dries, leading to warping, cupping, or cracking. The irregular grain makes planing or sanding challenging, as the tool cuts across changing grain directions, increasing the risk of tear-out and an uneven surface. In other words, jointers and thicknessers/planers can damage the surface so a router bit is your best bet.