How fast can I cut 1/4" wood with the 40 watt CO2 laser?

CO2 laser will not cut wood material fast at all. This is just the nature of the laser energy. The wood is a very low absorbent of the laser energy and you will need to run probably around 10 ipm to cut through the wood. CNC is much more efficient for cutting and laser as more efficient at marking or slowly cutting if you need the small kerf. You will also need a relatively high output air source to cut efficiently. The air will blow away the char (carbon) on the wood. The black char will absorb most of the laser energy not allowing the wood to be cut well. We use a compressor for the air source, but you can use a commercial hydroponic air pump instead.