In practice, the metric that actually affects production planning is the span between a signed purchase order and the moment a first good part — a part.
When a workshop owner evaluates a CNC (Computer Numerical Control — a system where programmed G-code governs the position and feed of a machine tool's axes) supplier, the published "delivery time" on a quotation is usually the only lead-time figure that gets compared. In practice, the metric that actually affects production planning is the span between a signed purchase order and the moment a first good part — a part meeting dimensional tolerance, surface finish, and repeatability requirements — exits the spindle.
This article breaks that span into measurable phases, provides benchmark ranges based on typical Vertical Machining Center and gantry-type production, and flags where delays commonly originate. The intent is to give procurement managers and workshop owners a framework for interrogating supplier lead-time claims.
For the purposes of this discussion, lead time is segmented into seven phases:
Each phase has a typical duration and a typical variance. Variance is where planning risk lives.
After a purchase order is received, the supplier's engineering team reviews the configuration against the quoted spec. For standard catalog machines — for example, a 3-axis VMC (Vertical Machining Center — a CNC mill with a vertically oriented spindle) with a BT40 spindle taper (BT40 referring to a 40-taper Japanese-standard spindle nose with a 45° contact angle, the most common medium-duty taper in Asia) — this is typically a 3–5 working day review. For configured-to-order machines, such as a 5-axis trunnion table with an HSK-A63 spindle (HSK = hollow-shank taper, a German standard with a short, rigid interface suited to high-speed machining), the review can extend to 10–15 working days as the BOM (Bill of Materials — the structured parts list defining every component in the machine) is locked.
Option selection late in the cycle. Adding a 4th-axis rotary table, a through-spindle-coolant system, or a different CNC controller after the BOM is frozen typically resets Phase 1.
The bed, column, saddle, and headstock of most Chinese-built CNC machine tools are produced from Meehanite-type cast iron (a controlled-solidification grey iron with uniform graphite distribution, used for vibration damping). Castings are either held in inventory — cured, or aged, for a minimum of 6–9 months — or ordered fresh from a foundry partner. Fresh castings require an additional artificial aging cycle (thermal stress relief, typically 550–600 °C held for 8–12 hours) before machining, which adds 2–3 weeks.
Linear guideways (e.g., Hiwin HGH-series — block-and-rail rolling element guides with recirculating balls) and ground ballscrews (precision lead screws with recirculating ball nuts, typically C3 or C5 accuracy class per JIS B1192) are the longest-lead purchased components. Catalogue parts are 2–4 weeks; non-standard lengths (e.g., a 4,500 mm Y-axis ballscrew for a large gantry) can push to 8–10 weeks.
Belt-driven spindles with P4-class bearings (ABEC-7 equivalent, runout within 2–3 µm) are typically in stock. Direct-drive spindles with built-in motors and integrated encoders run 6–10 weeks.
| Phase | Typical Duration (working days) | Variance Range |
|---|---|---|
| 1. Order Confirmation & Engineering Review | 5 | 3–10 |
| 2. Component Procurement & Casting Curing | 30 | 20–60 |
| 3. Machining & Assembly | 25 | 18–40 |
| 4. Geometric Accuracy Calibration | 5 | 3–10 |
| 5. FAT | 3 | 2–5 |
| 6. Packing, Shipping & Customs | 35 | 25–60 |
| 7. Installation, Commissioning & First Good Part | 14 | 7–30 |
| Total (PO to first good part) | ~117 | ~78–215 |
The variance column matters more than the typical column. A supplier quoting "60 days delivery" is technically referring to Phases 1–5, not the full PO-to-first-good-part span.
Major castings are machined on in-house planer-type CNC mills and floor-type boring machines. Way surfaces are hand-scraped (manual removal of 5–20 µm of cast iron with a flat scraper to create oil-retaining pockets) on premium machines, or ground on volume-production machines. Hand-scraping adds 3–5 days per major casting but improves way contact from approximately 60% to 85% or better, with measurable effects on long-term geometric stability.
Sub-assembly of spindle cartridge, gearbox, ATC (Automatic Tool Changer — a cam-driven or servo-driven mechanism that swaps tools from a magazine to the spindle in 1.5–6 s chip-to-chip time) and axis mounting proceed in parallel. Final assembly is where the machine takes shape: spindle installed, axes aligned, way covers fitted, cable harness routed, controller wired.
Typical assembly time for a standard 3-axis VMC is 10–14 working days; for a 5-axis machining center, 18–25.
Each linear axis is mapped with a laser interferometer (a HeNe-laser-based instrument measuring position to ±0.5 ppm over 1 m) to determine pitch error — the lead deviation along the ballscrew — and compensate it in the CNC controller via pitch-error compensation tables. A 3-axis machine typically yields 20–40 mapping points per axis.
A telescoping ballbar (QC20-style) traces a 360° circular path in the XY plane at a fixed feed rate. The trace reveals squareness error, backlash, servo mismatch, and reversal spikes. A typical acceptance ballbar trace shows circularity within 10 µm for a quality VMC; premium machines hold 5 µm.
A typical calibration cycle is 3–5 working days for a 3-axis machine, 6–10 for a 5-axis.
The FAT is run at the supplier's facility before packing. A standard FAT protocol includes:
The sample part is typically a standard aluminum block with pockets, bosses, and a bored hole. This part is the first "good part" produced on the machine, but it is not the first good part in the buyer's facility — an important distinction for production planning.
Machines are sealed in VCI (Volatile Corrosion Inhibitor — a film that releases corrosion-suppressing molecules) film, desiccant-bagged, bolted to export-grade wooden skids (ISPM-15 heat-treated — international phytosanitary standard for wood packaging), and containerized. A standard 40-ft HC (High Cube) container fits one large VMC or two compact ones.
China to US West Coast: 14–18 days ocean transit. China to Hamburg: 30–35 days. Customs clearance: 3–7 days depending on port and HS code (8458.11 — unit for working metal by milling, numerically controlled).
| Lane | Ocean Transit (days) | Port-to-Warehouse (days) |
|---|---|---|
| Shanghai → Los Angeles | 14 | 21–28 |
| Shanghai → Hamburg | 32 | 40–50 |
| Shenzhen → Sydney | 18 | 25–32 |
| Ningbo → Santos (Brazil) | 38 | 50–65 |
Before the machine arrives, the foundation must be poured (typically 200–300 mm reinforced concrete with rebar mat, isolated from the surrounding slab), power drops terminated (3-phase, voltage per machine spec ±5%), compressed air supplied (clean, dry, 0.6 MPa, 4–6 m³/min), and coolant system installed.
Rigging, leveling (using precision machinist's levels, 0.02 mm/m sensitivity), and anchor bolting takes 1–2 days for a VMC, 3–5 for a gantry.
Re-calibration of geometric accuracy after shipping (laser interferometer, ballbar), controller parameter tuning, tool length probe and workpiece probe setup. Typical 3–5 days.
The supplier's service engineer runs the buyer's actual production part program. Achieving a first good part — meaning a part that meets print tolerance — typically requires 2–5 iterations of feed, speed, and offset adjustment. Total time: 2–5 days after commissioning.
The benchmarks above describe standard configured-to-order VMCs and 5-axis machining centers from established Chinese suppliers. They do not apply in several real situations:
A short checklist for procurement managers and workshop owners evaluating a CNC supplier's lead-time claims:
The single most useful question to ask a supplier is rarely asked: "What is the variance, not the typical, for each phase?" Suppliers who answer with ranges rather than single numbers tend to have better process control and more honest scheduling — and that, more than the headline delivery figure, is what determines when the first good part actually leaves the spindle.
Request the configuration list & delivery plan (RFQ) — contact the Gree CNC team.