The item you need can be found in the Workshop Menu under 'Power > Manufacturing > Machinery > Builder'
The Builder requires 2 Circuitry, 3 Gear, 4 Rubber and 10 Steel and is what will be producing your items.
Once built it requires 8 Power to operate. This can be achieved with 3 Small Generators (remember to attach all the wires to the builder).
Once powered simply stand on the side of the Builder and press
to transfer items. Transfer as many junk items as you can and the Builder will automatically produce new items.
I built 3 Builders to run simultaneously and the achievement took about 10 minutes to unlock. You can build as many Builders as you like to unlock this achievement quicker, but if you are running low on resources 1 Builder should take approximately 30-40 minutes.
As always you can make a save before attempting this achievement to reload from, minimising wasted resources. You can also scrap the items that the Builder makes and put them back in the Builder.