In 2009 and 2014, two workers lost part of their right index fingers in a machine.
Volkner declined to comment on the sentencing decision and Avon Industries did not respond to a request for comment.
A week before the accident, a supervisor warned Volkner after seeing saw him climb onto the side of the galvanising bath but the information was not passed on to the company managing director Richard Fisher.
WorkSafe's investigation found Avon Industries had not conducted a risk assessment on either the process or the machine.
A WorkSafe spokesman said Avon Industries did not have in place a safe system of work, or a formal training programme for dealing with machine malfunctions – even though jams were a known issue.
Judge Orchard said there was neither an operating manual for the machine nor safety guards in place to prevent workers falling into the molten zinc.
She said the company could guard against risks through appropriate training, supervision, monitoring and discipline.
"This is particularly so where the potential for death and/or serious injury is great.
"The acknowledged failure in these areas is consequently particularly culpable," Orchard said.