Additive vs CNC Machining Cost Comparison and Break-Even Calculator
AM wins on parts that are expensive to machine and loses on parts that are cheap to machine. This calculator makes the trade-off explicit: it compares one-time costs, batch setups and per-part cost for each route and finds the quantity where the cheaper process flips.
Your numbers
Quantity for the comparison. The chart sweeps this from 1 to 400.
Machine time, powder and post-processing per part. Use the AM build cost estimator.
DfAM, support strategy, build prep and first-article qualification.
Total machine minutes per part across all operations.
Burdened rate for the machine class used (3-axis, 5-axis, mill-turn).
Bar, plate or forging cost. Include the scrap you machine away.
CAM programming, fixtures, gauges and first-article.
Your results
Cost comparison only. Material properties, surface finish, tolerances, lead time and qualification requirements often decide the choice before cost does.
Cost per part vs quantity: AM against CNC
Sweeps Order quantity from 1 to 400, holding your other inputs fixed.
Make-or-print analysis from your own data
Optional: a review of how to run this comparison across your parts list using ERP routings and costs.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the AM variable cost per part, from the build cost estimator or a quote, along with setup per build, parts per build and one-time engineering. For CNC, enter total cycle time across operations, machine rate, stock, tooling consumed, setup per lot and one-time programming and fixtures. The quantity field sets the comparison point and the chart sweeps quantity from 1 to 400. Break-even quantity is where total costs are equal.
- Use realistic stock cost including the material you machine away.
- Include fixtures and CAM programming as one-time CNC cost.
- Include DfAM and qualification as one-time AM cost.
Formulas
AM total = one-time cost + quantity x AM cost per part + builds x setup per build, where builds = ceiling(quantity / parts per build). CNC total = one-time cost + quantity x (cycle hours x rate + stock + tooling) + lots x setup per lot. Cost per part is total divided by quantity. Break-even quantity = difference in one-time cost / difference in run cost per part, where run cost includes batch setups spread over a full batch. The result is meaningful only when one process has higher one-time cost and lower run cost.
Reading the result
Using the defaults, AM is cheaper below roughly 120 parts, because CNC carries higher fixture and programming cost, and CNC is cheaper above that because its run cost per part is lower. If the break-even reads zero, one process dominates across all quantities. The stair steps in the chart come from rounding up to whole builds and lots. A better AM case usually comes from part consolidation, lighter weight or lead time, none of which appear in this cost-only view.
Common mistakes
Comparing an AM as-built part to a fully machined finished part is the classic error: AM parts still need heat treat, support removal, interface machining and inspection, which belong in the AM variable cost. Another is ignoring scrap and rework on either side. Also, annual volume matters: a one-time AM qualification spread over years of demand changes the answer. Finally, include the cost of the stock you cut away, which is often the main CNC cost driver for exotic alloys.
Frequently Asked Questions
At what quantity is 3D printing cheaper than machining?
There is no universal number. Complex parts with long machining cycles and expensive stock can favor AM into the hundreds or thousands of parts, while simple prismatic parts favor CNC at very low quantities. Use your own costs to find the crossover.
Should I include lead time in the comparison?
Lead time and inventory are valid benefits, but they are not in this model. If AM avoids tooling lead time or buffer stock, estimate the carrying cost saved and subtract it from the AM cost as a separate line.
How do I handle part consolidation?
If one AM part replaces an assembly, compare AM against the full assembly cost: all machined parts, fasteners, assembly labor and inspection. Enter the combined CNC and assembly cost per part in the CNC fields.
Why does the chart have steps?
Batch costs are charged per whole build or lot, so the cost per part jumps when quantity crosses a batch boundary. The steps are real and represent partial batches that still carry a full setup charge.
If you want make-or-print decisions made from your own routing, cost rollup and quote history, we can build that analysis against your ERP data.
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