Six months later he was diagnosed with depression - and worse - and it was put down to the accident.
"I was feeling pretty sorry for myself but, with lots of support from my wife and family, my boss and ACC, I picked myself up," he says.
That got him thinking.
Even after the accident other guys in the factory were not always using safety gear properly, so Muller decided to do something about it.
His plan was to make sure power tools wouldn't work unless a safety helmet was being worn properly.
He built a Bluetooth system into a helmet - networked to the power supply.
There are two connectors - one to ensure the helmet is in contact with skin and a second to make sure the visor is down. Only then will the power supply switch on.
Mr Muller says having made it work in a safety helmet, he can see potential for other applications - such as in motorcycle helmets and lifejackets.
He brought his demonstration device to the Fieldays Innovation Centre to gauge reactions and to look for people with the business and sales knowledge to promote the product. "The response was amazing."
So Muller he quit his day job to concentrate on Safety Buddy.
It came second in People's Choice.
He is now building a prototype.
-Safety Buddy: rotobuddy@live.com.