600mm wide?!? :shock: You'd be unlikely to find a thicknesser with that kind of capacity for as much as the ones you mentioned originally! :shock:
You might be better off going for a drum or wide belt sander. They give good results without tearout. Trouble is, you have to remove a very small amount of material with each pass (unlike a thicknesser).
Using a portable belt sander isn't as tricky as some might think (I do it a lot now :wink
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- think of how you would flatten a large panel with a hand plane... Cross-hatching and working across the diagonals to remove the high spots. Then, carefully going with the grain to remove the cross-grain scratches. Don't let it linger in one place and try to keep it moving. 4in sanders are better for this than 3in.
For some models, you can also buy frames that limit the projection of abrasive below (ie. you only remove x-amount of material from the entire surface). I've not used one though and they don't seem to be available for my Makita 9404. I find they're much better at this than random orbit sanders, which can create dips and low points.
Another possible issue with using a thicknesser to clean up a panel of edge-jointed boards is that, if the grain isn't running in the same direction on all the boards, the cutter block will rip some of it to shreds, where you're cutting against the grain direction.