How to create an item sorter in Mindustry

Question

Keywords: Erekir, Duct-Router (keywords used because I can't create new tags yet)

Mindustry can be a frustrating game due to its seriously high learning curve and remarkably deep problem-solving context. One of my earliest difficulties was figuring out how to use the Duct Router to sort items. The ability to sort items can minimize resources and complexity needed to bring a lot of resources into your industrial area.

The problem that frustrated me is that the Duct Router is a positive flow device. When not allocated for a single resource, it will allow items that come in "the back" to move out forward or to either side. When set to pass a single resource, only that resource will move forward back-to-front. All other items will discharge to the sides.

But there's a catch.

If you're passing one resource to an industry, say Beryllium to a Breach Turret, and that turret fills up, backing up the ducts all the way to the Duct Router, a piece of Beryllium stays in the router blocking everything else from discharging to the sides.

Therefore, how can one use the Duct Router to sort items?

Answer 1

The basic configuration needed to create a sorter is the combination of a Duct Router and Underflow Duct.

An unallocated Duct Router is shown on the right. The flow arrow (back-to-front) is pointing left. Next to it is an unplaced Underflow Duct pointing in the same direction. The Underflow Duct will push items to the sides and only allow flow to the front when the sides are blocked.

This configuration is necessary to guarantee you can clean out the resource that would otherwise be stuck inside the Duct Router. Below is a four-item sorter.

Click the above image for a larger view. The four Duct Routers are now colored...

• Green for Beryllium
• Pink for Thorium
• Charcoal or Battleship Gray for Tungsten
• Light blue for Graphite

In this configuration, all four resources are flowing into the sorter from the right. The sorter is pushing the sorted items up from each paired Underflow Duct. In the example, I'm recombining the items into a single path that leads to a base just to keep everything moving. In an actual game, those resource paths would be routed to various industries for processing.

This configuration was also used for convenience. An Overflow Duct could have been used to push the outbound resources to the left... but the detritus of the sorter must go somewhere or the sorter will plug up, so a tighter configuration is difficult to achieve.

In this configuration, the unwanted items are routed down from each Duct Router into the next router. Since all items are being sorted, the last router on the bottom has no side discharge path from the router itself. I've used configurations like this to also move items that won't be sorted (like Surge Alloy) that I want to simply shuttle to the base. In that case, the side discharge of the last router must be routed to the global discharge path.

The global discharge path

However you do it, you need to allow things that don't want to be sorted cleanly to escape. In most instances, this is the outlet of the Underflow Ducts. Once the outlet path is full (e.g., the Beryllium path for Breach Turrets), the excess Beryllium must go somewhere. In this example, the forward path of each Underflow Duct is passed to the right and combined into a single path that leads to the base.

At all costs, everything through the sorter must be kept moving. It's a significant (read: base-destroying) event to let the sorter become clogged.