Cycle Time & Cost per Part Calculator — Machining Economics
Industrial-grade machining cost calculator: physics-based cutting time, itemized non-cutting time, setup amortization over batch, machine hour rate, labor, material, overhead and margin build-up to selling price, batch-size sensitivity and full audit trail.
Decision:Run the stated engineering model, review its assumptions and warnings, then make the release decision against the governing standard and verified source data.
SectorCalc SC-023 turns process parameters into a defensible unit price. Cutting time comes from physics — length, feed and RPM — not from guesswork; non-cutting time is itemized (rapids, tool changes, load/unload); setup is amortized over the batch; and the cost build-up stacks machine hour rate, attended labor, material, overhead and margin into a selling price. Batch-size sensitivity shows exactly how much a small order really costs. Results are reference-grade estimates — final quotations must reflect your actual cost accounting and commercial policy.
Cutting time from first principles
Tcut [min] = passes · L [mm] / (f [mm/rev] · n [rpm])
This is the only part of the cycle that adds value, and the only part the feeds-and-speeds engine (SC-020) can shorten. Doubling feed halves cutting time — until surface finish or tool life objects. The extra cutting time field folds in drilling, tapping (SC-022) and milling operations estimated elsewhere.
On small parts, load/unload and tool changes routinely exceed cutting time. A 4-second turret index on a 30-second cycle is 13 % of capacity; an operator walking to a pallet rack is pure loss. Itemizing these times is the first step of any SMED or automation business case.
A 45-minute setup adds 27 seconds per part at batch 100 but 4.5 minutes at batch 10 — often doubling the small-batch price. The sensitivity chart quantifies this so you can defend minimum-order quantities or justify changeover reduction investment with numbers.
Machine hour rate (from SC-038) carries depreciation, interest, space, energy and maintenance. Labor is charged only for the attended share via the manning factor — 0.5 for one operator running two machines. Overhead is applied to conversion cost plus material as a single allocation.
Margin is applied on the price basis (12 % margin ⇒ price = cost/0.88), the convention that survives discount negotiations intact. Markup-on-cost and margin-on-price diverge fast above 20 % — the report states which basis is used so sales and costing read the same number.
Frequently asked questions
Why does my quote lose money on small batches?
Setup amortization. Check the batch-size chart: below the knee of the curve, setup dominates. Either enforce a minimum order quantity, charge setup as a separate line, or invest in changeover reduction.
Should material carry overhead and margin?
Practices differ. This engine applies overhead to material + conversion (full absorption) but margin to the total, which is the conservative common practice. If your policy excludes material from overhead, reduce the overhead input accordingly.
Where does the machine hour rate come from?
From SC-038 (Machine Hour Rate Calculator): purchase price depreciation, imputed interest, floor space, energy and maintenance per planned operating hour. Never use the purchase price divided by warranty years — that understates the true rate by 30–50 %.
How do I cost a lights-out shift?
Set manning to 0.25 (attended only during tending windows) and increase load/unload to reflect robot cycles. The machine rate usually stays constant; the labor line collapses — that difference is the automation business case.
