For PLA printing, the bed can be from 40°C to 60°C. The lower end isn't too hot, but what can happen is as the bed cools the cat will find it pleasing. Of course, you could build a sheet cover from aluminum foil. Cats hate that stuff. I know what you mean about doing it yourself, but it also has to take into account the level of frustration you are willing to tolerate. It can get pretty high with 3D printing, but if you put a 0.2 mm nozzle in your printer, you'll learn quite a bit.