PPI advice

[SWMS]

So, when I cut - for example - 3mm MDF without PPI I can do this at 15 mm/s and 50% power with a 60 watt laser. Switch on PPI at 350 ppi with 99% power and 15 mm/s and it won't cut through it. I have to drop the speed to about 5 mm/s.


Any ideas what could be causing this? PPI doesn't seem worth it. I'm using the latest versions of the software as far as I know.


LaserCAD 6.88B

131210V678 of the firmware

Regards


Ryan