A Sydneysider facing possible jail time for making replica guns with a 3D printer has claimed he had no idea his hobby could land him in such trouble.

Sicen Sun, 28, was arrested in 2017 after he advertised one of his imitation weapons for sale for AU$1 million on a Facebook buy, swap, and sell group.

He has since pleaded guilty to charges including possessing a digital blueprint for the manufacture of firearms, manufacturing a pistol without a licence permit, and possessing an unauthorised pistol.

"With 20/20 hindsight, I just realise how silly, idiotic, stupid, and naive my actions were," he said during his NSW District Court sentence hearing on Monday.

"I could not even begin to contemplate that a hobby would land me in such strife."

Sun, who dresses up as pop culture characters and was previously described by a lawyer as "something of a fanboy", said he meant for the replica firearms to be used as costume props.

Also see: 3D printing guns at home: Does new technology change America's gun control debate?

A recent Federal Court case in the United States saw a judge rule it illegal to put blueprints for 3D-printed guns on the internet, CNN reported last week.

Cody Wilson, the founder of Defense Distributed -- the company prevented from publishing plans by the court -- told CBS This Morning that while attorneys-general, lawyers, and courts decide the law, it is too late to stop the proliferation of 3D-printable weapons.

"The guns are downloadable, the files are in the public domain, you cannot take them back," he said.

Defense Distributed was sued by 21 states to prevent the plans from appearing online.

Beyond firearm production, 3D printing was used by Newcastle University in the UK to create replacement corneas earlier this year in research that could one day led to corneal transplants.

Read also: Here's how 3D printing makes the robots that make everything else

The process mixes stem cells from a healthy donor cornea with alginate and collagen to create a "bio-ink". This bio-ink is extruded from a low-cost 3D bio printer in concentric circles to form the shape of a human cornea within 10 minutes.

In April, a 1,000 square foot, five-roomed, Y-shaped house was built using 3D-printing over 18 days.

With AAP

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