I don't like roughly sanding panels with power tools that throw too much dust out of the filter bag and as time went by I got the idea that sanding each board before assembling the panel might be satisfying. The following technique is not workable in all cases but enables for accurate butt joints which are required to machine raised panels as instance.

Unfortunately that method does not work on every combination machine and is related to several modifications and shop-made jigs and fixtures. Only a variable frequency drive enables for dynamic adjustment of the tool speed so that the sanding paper does not burn the workpiece and you may see the tooling below.

The method is nearly the same than in the sanding square document but the below spindle moulder arrangement use the fence plate locked on the sliding table to push the workpiece through the sanding disk and the front guard design helps for most of the dust to be channelled toward the back outlet. Board are previously and typically squared on the table saw before that thicknesser calibrates and smooths the widest faces.

The sanding disk on the table saw edges the workpieces with fine grit so that improving as much as it can the butt joint. Here too the nozzle design of the over blade guard channels nearly all dust toward the vacuum hose.

Outcomes are most of time close to perfect but thoroughly assembling the boards demands much care than the classic method. Finally a wood scraper removes the glue excess without need of flattening with a power belt sander.