The accident happened in June 2017 when an employee was trying to fix an intermittent fault on one of its printing presses and his hand became trapped between the rollers resulting in his hand being crushed and degloved.
At the time the business was trading independently as Afon Tinplate, before it was acquired by Tinmasters parent firm CMDH in August 2018.
The Health and Safety Executive launched an investigation into safety standards at the company, following the accident and found that the front guard's electronic interlock device was not working properly.
Furthermore, there was no risk assessment for fault finding on the printing press and no safe system of work, including providing suitable training for employees.
As a result of the investigation, Tinmasters Swansea was fined £29,000 and ordered to pay costs of £1713.40 by Swansea Magistrates Court after entering a guilty plea.
According to the company website the business, which specialises in coating and printing tinplate, was founded in 1923 and currently employs eight people.
Speaking after the hearing, HSE inspector Lee Jones said: “This injury was easily preventable, and the risk of injury should have been identified.
"Employers should make sure they properly assess and apply effective control measures to minimise the risk from dangerous parts of machinery, especially during maintenance and fault-finding activities.”