lidl or aldi will do you a stick welder for 30 to 40 quid that will handle up to around 6mm steel or hardox comfortably. Yes it's possible to make a machine without welding but it's such a pain in the arse and are more limited on the shapes and design that it becomes a right pain.

Also I'm assuming your spinner would be covered up before opening up to stop it being rushed. It's a nice idea but if your reveal mechanism gets damaged then your machine is protecting your opponents. Something to consider.

Also 80kg? Throw that weight into the disc and spinner mechanism!