Processing Unit to Rocket Part Chain

Lore & Background

In the early days of the alien planet, the Survivor's first glimpse of the Processing Unit recipe felt less like a crafting instruction and more like a dare. The item demanded a Processor, which demanded Boards and Circuits, which demanded Wire, which demanded a furnace that had not yet been built. The factory grew not by plan but by necessity, each new machine a response to the previous one's hunger. Belts multiplied. The landscape, once open and quiet, became a lattice of humming machines and the soft clatter of pistons. The Plastic Bar, meanwhile, came from a different world entirely—the thick, sluggish flow of petroleum drawn up by a pumpjack, married to coal in a chemical plant that hissed and ticked. The juxtaposition was strange: the cold, precise geometry of circuit boards on one side of the final assembling machine, and the warm, organic stench of refined oil on the other. Yet the Rocket Part demanded both, as if the alien technology the Survivor was reconstructing had been designed by hands that understood both the mineral and the molecular. Players who have balanced this chain describe a particular feeling when the ratios finally lock: the belts no longer stutter, the intermediate buffers stop oscillating, and the assembling machines run in a steady, almost musical rhythm. It is the moment the factory stops being a collection of recipes and becomes a single, breathing organism.

In Their Own Story

The night the last copper vein ran dry, Mara stood in the control room watching the Electronic Circuit belt slow to a crawl. Outside, the assembling machines ticked over in idle, their pistons half-raised, waiting. The Processing Unit buffer held eleven units. The Rocket Part recipe wanted one. She had exactly enough for the final part, if the Plastic Bar pipeline held. She walked the factory floor in the blue glow of the overhead lights, tracing the belt lines with her finger. Copper wire. Electronic circuit. Processor. Each station a small altar to patience. The chemical plant at the far end still gurgled, petroleum and coal merging in their slow dance. She could smell it—sweet, acrid, alive. At 03:47, the last Copper Plate dropped into the wire assembler. The belt shuddered, caught, and the chain resumed its long, grinding march toward the final machine. Mara pulled up a stool, wrapped her arms around her chest, and watched the numbers climb. One. Two. Three Processing Units. The buffer ticked upward like a heartbeat. And then, with a soft pneumatic sigh, the assembling machine spat out a single Rocket Part, gleaming faintly in the machine-light, and the factory exhaled around her.

Reader's Guide

Raw inputs: Copper Ore, Iron Ore, Coal, Petroleum (from pumpjack). Stage 1 – Furnace: Copper Ore → Copper Plate; Iron Ore → Iron Plate. Stage 2 – Assembling Machine: Copper Plate → Copper Wire (1:1). Stage 3 – Assembling Machine: 2 Copper Wire + 1 Iron Plate → Electronic Circuit. Stage 4 – Assembling Machine: 1 Copper Plate + 3 Copper Wire → Electronic Board. Stage 5 – Assembling Machine: 2 Electronic Board + 1 Electronic Circuit → Processor. Stage 6 – Assembling Machine: 2 Electronic Circuit + 1 Processor → Processing Unit. Stage 7 – Chemical Plant: 1 Petroleum + 1 Coal → Plastic Bar. Stage 8 – Assembling Machine: 1 Processing Unit + 1 Plastic Bar → Rocket Part. The optimal ore ratio per Processing Unit is 14 Copper Ore to 3 Iron Ore. The Copper Wire stage is the most common bottleneck because it is a 1:1 conversion that still consumes an assembling-machine slot, and it feeds into both the Circuit and Board lines simultaneously. As the factory scales, players typically upgrade to Advanced Assembling Machines at the Circuit and Processor stages, and to Electric Furnaces for the copper smelting, to keep the 14:3 ratio from stalling the downstream lines. The Chemical Plant for Plastic Bar is independent and rarely the limiting factor unless oil logistics are neglected.

Did You Know?

• Copper Wire is a 1-to-1 conversion of Copper Plate, yet it still requires a full assembling-machine recipe slot, making it one of the most 'wasteful' recipes in the game by design.
• The Processing Unit chain is the only production line in Factorio that requires both an Assembling Machine and a Chemical Plant to complete a single end product (the Rocket Part).
• Every single Copper Plate in the PU chain ultimately feeds either a Copper Wire or an Electronic Board, meaning no copper is ever 'wasted' in the ideal ratio—but any misallocation cascades through five downstream stages.
• The Rocket Part is the only item in the game that combines a purely mineral/electronic component (Processing Unit) with a petrochemical one (Plastic Bar), bridging the two major resource families the game presents.