This is another short guide on how to make the printer in Astroneer auto print. I also get asked this question about once a week.
To enable auto printing, first make sure the printer is powered and that it has the resources needed to print the selected item.
After this, interact with the printer and depress the circular auto function button as shown below.
After this, depress the green printer button and you should be good to go. The printer should auto print the selected item as long as it has power and resources.
To turn the auto function off, simply press the auto function button again and now it will only print every time you press the green print button.
Refer to the embedded video at the top of this article if you need more help!