Drone BOM and Routing: 50 Quadcopters Planned, 199 Motors in Stock

The plan says 50 quadcopters by Friday. Each one needs four motors, so that's 200 motors, and the warehouse shows 199. Close enough? No. One drone can't fly on three motors, so the plan is already 49 at best. And, as we'll see, the motor isn't even the real problem.

A drone BOM (bill of materials) is the complete list of parts, sub-assemblies, and even firmware versions needed to build one drone, with the quantity of each. A drone routing is the sequence of assembly and test operations, the bench or station where each one happens, and how long it takes. The BOM tells you whether you can build; the routing tells you when and where.

What a drone bill of materials looks like

Take an inspection quadcopter, model Q7, sold in two versions: with a day camera or with a thermal camera. Its manufacturing BOM has three levels:

• Level 0: Quadcopter Q7, 1 pc
• Level 1: Airframe assembly, 1 pc
• carbon arm × 4, center plate × 2, landing gear × 1, M3 screws × 32
• Level 1: Propulsion set, 4 pcs
• brushless motor × 1, ESC (electronic speed controller) × 1
• Level 1: Flight controller, firmware v2.3, 1 pc
• GNSS module × 1, radio link module × 1
• Propellers × 8 (4 on the drone, 4 spares in the case)
• Battery pack 6S × 2
• Payload: day camera or thermal camera, 1 pc
• Transport case × 1

Two lines deserve a closer look.

Firmware is a BOM item. A flight controller flashed with v2.3 is not the same part as one flashed with v2.2. It behaves differently, it may need different calibration, and a customer may be certified on one version only. If the version lives in an engineer's head, you'll ship a mix.

The payload is an option, not a fixed part. One order of 50 can be 30 day and 20 thermal. The BOM has to carry the choice, or MRP will buy 50 of each. Item master data covers how variants like this stay manageable.

Clear to build: the kit calculation

Before a single screw is turned, the planner checks how many complete kits exist. The rule is simple: for each component, divide what's available by what one drone needs (including a scrap allowance), round down, and take the smallest result.

For the order of 50 (30 day, 20 thermal):

• Motors: 199 available ÷ 4 = 49.75 → 49
• Propellers: 8 per drone + 3% breakage in test flights = 8.24. 420 ÷ 8.24 = 50.97 → 50
• Screws M3: 32 + 5% lost on the bench = 33.6. 2,000 ÷ 33.6 = 59.5 → enough for all 50
• Batteries: 120 in stock, but 30 are on quality hold after a cell voltage check. 90 ÷ 2 = 45
• Thermal cameras: 17 in stock for 20 thermal drones → only 17 thermal, so 30 + 17 = 47

The answer is 45, and it's set by batteries, not motors. To ship all 50 you need one motor, ten released or new batteries, and three thermal cameras. That's the dependent demand of the order, calculated from the BOM, and exactly what MRP should flag on Monday, not the bench on Thursday. The bigger idea, clear-to-build and why half-built units are expensive, is in assembly planning.

What a drone assembly routing contains

The routing for Q7, per drone:

1. Op 10 – Kitting, store: 10 min
2. Op 20 – Frame assembly, bench A: 25 min
3. Op 30 – Motor mounting and ESC soldering, bench B: 40 min
4. Op 40 – Electronics and wiring (flight controller, GNSS, radio), bench B: 30 min
5. Op 50 – Firmware flash and configuration, programming station: 15 min
6. Op 60 – IMU and compass calibration, calibration station: 20 min
7. Op 70 – Test flight, test cage: 25 min
8. Op 80 – Payload fit, final inspection, packing, bench C: 20 min

Total: 185 minutes per drone. For 45 drones, 45 × 185 = 8,325 minutes, about 139 hours of work.

The routing also shows where the week gets tight. Ops 30 and 40 both need bench B: 70 minutes per drone, 45 × 70 = 3,150 minutes. Two soldering benches with 450 productive minutes per shift give 900 minutes a day, so bench B needs 3.5 days. The test cage needs 45 × 25 = 1,125 minutes, 2.5 days. Everything else fits easily. The order of operations matters too: you can't calibrate a compass before the wiring is final, because every cable near it shifts the reading.

Myth: "The CAD parts list is the drone BOM"

The CAD model is the engineering BOM. It's grouped by function: propulsion, avionics, structure. It has no firmware version, no spare propellers, no solder or heat-shrink, no transport case, and no calibration.

The manufacturing BOM is grouped by how the drone is built. Think of a LEGO set with numbered bags: bag 1 is everything for the first stage, bag 2 for the next. Kitting per operation means bench B gets exactly the motors, ESCs and wires it needs, and nobody walks to the store halfway through.

Serial numbers and engineering changes

Every Q7 gets a serial number, and the as-built record ties it to the flight controller serial, the firmware version and the motor batch. When a customer reports a problem with drone Q7-0231, you know exactly what's inside it.

Changes happen all the time. Firmware v2.4 fixes a GNSS issue, so engineering issues an ECN: v2.4 from serial Q7-0231 onward. That change belongs in the BOM with an effective point, not in an email. Otherwise the programming station keeps flashing v2.3 because that's what the kit list says.

How this looks in factory.online

In factory.online, the Q7 order shows its multi-level BOM with the airframe and propulsion set as sub-assemblies. MRP explodes 50 drones into 200 motors and 100 batteries and links each shortage, including the 30 batteries on quality hold, back to this order. The eight operations sit on the Gantt, and bench B shows up as the busy resource. As drones pass test flight, output confirmations update what's really done.

If your drone BOM lives in CAD and your routing lives on a whiteboard, book a demo and bring one model.