The K40 laser cutter is quite a bargain (I paid £350 for mine), but you get what you paid for.
Should you upgrade a budget laser cutter?
Simple Stuff Matters Everything as simple as possible, but not simpler
K40 BOARD UPGRADE: Not only an ideal replacement motherboard for any OMTech K40 laser engraver, our 24V K40+ control board is packed with cutting-edge
OMTech K40+ Laser Engraver Motherboard Upgrade, Replacement Control Board for CNC CO2 Laser Cutter Engraver Machines with Rotary Axis Autofocus
Buyers guide to the Chinese K40 laser cutter
K40 Laser Cutter Xtreeem: Changing the Controller for Better Performance : r/ChineseLaserCutters
K40 Upgrades: A Helpful Summary Of The Xtreeem Fixings
Make That Laser Cutter Blaze: Upgrade a K40 - Make
Tales Of A Cheap Chinese Laser Cutter
K40 Laser Cutter Rebuild (12x24in) – Paladin Fox
DGT-3000 Raspberry Pi Connector
Story of the cheap Chinese K40 laser cutter engraver
Free STL file Chinese CO2 Laser Cutter & Engraver Mirror Alignment Tools 🪞・Design to download and 3D print・Cults