Three major Phoenix-area libraries with 3D printers say they have policies in place to prevent someone from printing a gun.

The Glendale Public Library says people interested in using its 3D printer must first submit their plans for review.

[RELATED: All your questions about 3D guns answered]

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“If a person wants to use it, they can contact library staff. They have to have their design on a CAD file on a flash drive which gets vetted by library staff to make sure that it's compatible with the machine [and] make sure there's nothing harmful,” said chief librarian Michael Beck.

The library requires users to sign a request form acknowledging that the printer cannot be used for anything “obscene or other otherwise inappropriate for the Library environment” or “unsafe… for example: guns or knives.”

[RELATED: Maricopa Cty. Sheriff Penzone warns 3-D printed guns, aka 'ghost guns,' are public safety danger]

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The machine itself is kept on the Library’s main desk – partly to show off the technology, partly so staff can keep an eye on it, Beck said.

The Mesa Public Library requires users to sign a waiver before using its THINKspot 3D printers, which includes: “As a participant in THINKspot, I will not create any deadly weapons using the Equipment.”

The Phoenix Burton Barr Central Library has several 3D printers but they are only available to kids and teens involved with official classes, not the general public, said spokeswoman Lee Franklin.

[RELATED: Maricopa Co. Sheriff Paul Penzone says, 'Don't flood the country with 3-D printed guns']

A gun rights activist is fighting in court for permission to post online the files needed to print several types of weapons. A judge temporarily blocked the man from posting the files Tuesday night.

Even if the files get out, Glendale says its printer wouldn’t be effective at making a firearm anyway.

“We use a generic PLA plastic. It's a different material type than what would be required to make a 3D-printed gun, so that's an extra safeguard that we have,” Beck said.

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