A Dunedin company's been fined $55,000 after a machinery malfunction forced an employee to take seven months off work.

'Keep It Clean ' has been told to pay Stuart Morgan $50,000 reparation after he was hit in the back by a 32 kg machinery lid.

It flung off a machine at the meat rendering plant causing lacerations, fractures and a punctured lung.

WorkSafe New Zealand found an employee had made the replacement lid for the second hand machine and hadn't fitted it properly.

Chief investigator Keith Stewart says it's a warning to employers.

"It's not good enough to just whip up something and hope it will do the job. When machinery can cause injury it has got to be designed and fitted to the manufacturer's specifications."