Anyone out there with one of the ebay Chinese 200x300mm 40W laser engravers like this one:
CO2 Laser Cutter ENGRAVER Cutting Machine Support Corel Draw w Air Assist 40W | eBay

Been looking at these for a while and cannot see how the focus length is adjusted. According to some of the auctions they can engrave on up to ~2" thick material. Been looking at all the photos and just don't see how it's adjusted. On the 300x500mm machines there is a nice set of screws that move the bed up and down.

Want to use a honeycomb to support some thin sheeting but not sure if this machine can be adjusted up the 1" the comb will take up.

Thanks,
Wire