- SPC Cpk 1.851 (one characteristic on one part, not a blanket capability claim) on a recorded length characteristic (76.1–76.5 mm) — key characteristics Ppk ≥ 1.67 initial, general ≥ 1.33.
- Hexagon GLOBAL S CMMs plus laser microscope, roughness/profile, gear, hardness, coating, salt spray, and tensile equipment.
- XRF material checks against the mill certificate on every incoming lot.
- Three certificates: ISO 9001, IATF 16949, ISO 14001 — with scope stated honestly.
Why is documented quality the strongest supply-chain risk control?
Quality risk is supply-chain risk. A part that measures wrong is not just a defect — it is a line stop, a recall, a missed ship date, or a customer lost. The cheapest way to buy down that risk is to verify a supplier's capability before the order, using evidence you can audit rather than promises you cannot.
That is the difference between a quality claim and a quality system. A claim says "we make good parts." A system shows you an SPC chart with a real Cpk, a CMM report from a real job, a verifiable certificate number, and a material certificate backed by XRF. This page is the system, laid out so you can check it the way an auditor would.
The cost of weak quality is not just the defective part. It is the line stop when the part does not fit, the expedite fee when a replacement has to fly in, and the customer conversation when a shipped batch comes back. Each of those costs more than the inspection that would have caught the problem early. Buyers who understand that arithmetic stop asking "how cheap can you make it" and start asking "what evidence do you have that it is right", because the second question is the one that actually protects their schedule and their margin.
What process capability does the shop demonstrate?
Process capability is the honest number behind "we hold tolerance." It measures not whether one part passed, but whether the process is centered and stable enough that whole batches will pass. The recorded evidence here is specific.
| Metric | Recorded value | Target |
|---|---|---|
| SPC Cpk (length, 76.1–76.5 mm) | 1.851 (one characteristic on one part, not a blanket capability claim) | ≥ 1.67 (key characteristics) |
| General characteristics | Held in process | ≥ 1.33 |
| Sample method | 25 subgroups × 4 samples | Control-chart monitoring |
A Cpk of 1.851 (one characteristic on one part, not a blanket capability claim) means the process mean sits comfortably inside the tolerance band with margin on both sides — the process is capable, not just scraping by on a lucky sample. If a print calls out a dimension the process cannot reliably hold, it is flagged in the design-for-manufacturing review before cutting begins.
For you who has not lived in a metrology lab, Cpk is the number that says whether a process stays inside its tolerance band with margin. A Cpk of 1.0 means the process edge just touches the limit — any drift and parts fail. A Cpk of 1.33 means roughly a four-sigma spread, the common minimum for general characteristics. A Cpk of 1.67 means roughly a five-sigma spread, the automotive expectation for key characteristics. The recorded 1.67 sits above that, so the process is centered with room to drift before a part leaves tolerance.
How are incoming materials verified?
Material substitution is one of the quietest failure modes in machining: a cheaper alloy that looks identical but fails in service. The defense is to check every lot at the door, not to trust the paperwork blindly.
- XRF (iCHEQ) spectrometer reads the elemental composition of each incoming lot and compares it against the mill certificate.
- Mill certificate is retained with each batch so the alloy is traceable to its heat.
- Hardness testing (HVS-1000A micro-Vickers) adds a mechanical check where the print requires it.
Mixed or substituted lots are caught at the door. The alloy on the drawing is the alloy in the part, and there is a paper trail to prove it.
How are parts inspected before shipment?
Inspection is your evidence of what actually shipped. The bench here is the same class of equipment a buyer would use to audit the shop, and the results are documented, not just stamped pass/fail.
- Hexagon GLOBAL S CMMs for dimensional verification, plus a gear measuring center and vision measuring machines.
- KEYENCE VK-X3000 laser microscope and SURFCOM 1800D for surface finish and profile.
- HVS-1000A micro-Vickers hardness tester, Fischer coating thickness gauge, and salt spray and tensile testers for material and coating properties.
Each of these instruments produces a documented result rather than a pass/fail stamp, so you can see what was measured, not just that something was checked.
Which certifications back the quality system?
Certifications tell you a third party has already surveilled the system. Three are held, with scope stated honestly rather than inflated.
| Standard | Certificate number | Scope |
|---|---|---|
| ISO 9001:2015 | 116024/A/0001/UK/En | Machining of metal parts |
| IATF 16949:2016 | 131941/A/0001/SM/En | Manufacture of CNC metal machining parts (excludes product design, Clause 8.3) |
| ISO 14001:2015 | 116024/B/0001/UK/En | Environmental management related to machining of metal parts |
Honest scope note: IATF 16949 excludes product design under Clause 8.3. This is a build-to-print manufacturer. If a program needs design ownership, it is scoped up front rather than over-promised.
What APQP/PPAP evidence exists?
Automotive-grade quality is best demonstrated by having delivered automotive-grade documentation. A completed customer program produced the full APQP/PPAP pack:
- Process flow chart — from incoming inspection through machining, post-processing, and shipping.
- Control plan — critical characteristics, tolerances, speeds and feeds, and sampling frequency.
- SPC control charts — the Ppk ≥ 1.67 at the initial study on key characteristics record cited above.
- PFMEA — failure modes with severity, occurrence, detection, and RPN, plus corrective actions.
This is the documentation discipline a buyer would audit, running on every job rather than only automotive ones.
PPAP runs in levels, and the level tells you how much evidence you demand before production ships. A lower level is a warrant plus a few records; a full level-3 submission packs dimensional reports, material certificates, capability studies, and the control plan together for review. The point for a machining buyer is not to memorize the levels but to know that a shop which has produced a full PPAP pack has already been forced, by a customer with leverage, to document its process end to end, and that discipline carries over to every job it runs afterward.
How is traceability maintained end to end?
When a non-conformance appears, the cost of finding it depends on whether the supplier can trace it. The MES/ERP system records the full chain on every lot: raw material source and usage, process parameters, machine data, production batch, machining time, operator, and inspection results.
The practical outcome: if a problem ever surfaces, the shop can tell you exactly which lot, which machine, and which operator, and isolate the impact instead of guessing. That is the difference between a supplier who manages risk and one who hopes for the best.
Traceability pays for itself the first time a field failure appears. If a batch of shafts fails in service, a supplier with lot traceability can say which heat of material, which machine, and which operator produced them, and you can quarantine the affected lot instead of recalling the whole run. A supplier without it has to assume the worst and recall everything. For automotive and regulated buyers, that difference is measured in real cost, not in paperwork.
What quality evidence should you request from any supplier?
Whether you buy here or elsewhere, request the same evidence. A supplier who cannot produce it on demand is asking you to take quality on faith.
- A CMM report or SPC chart from a real job, not a capability statement.
- A verifiable certificate number — real ISO/IATF certificates have numbers you can check with the registrar.
- A material certificate backed by XRF, not just a vendor's word on the alloy.
- Disclosure of outsourced steps — who owns finishing and heat treatment.
How does inspection run at each stage of a job?
Inspection is not a single event at the end of a job; it is a chain that catches problems at the cheapest point. Three stages run on most work.
| Stage | What is checked | Why it matters |
|---|---|---|
| Incoming | Material composition by XRF against the mill certificate | Catches a substituted alloy before it becomes scrap |
| In-process | SPC sampling on key characteristics while the run proceeds | Catches drift before a full batch is out of tolerance |
| Final / first article | Full CMM verification of critical dimensions before shipment | Confirms what actually shipped, with a report to prove it |
The order matters. A defect caught at incoming costs a material return; the same defect caught at final inspection costs a scrapped batch and a missed ship date. A supplier who inspects only at the end is selling the most expensive way to find a problem, which is why the incoming and in-process checks are the ones you should ask about first.
What this shop actually runs
Capability evidence should come as specifics, not slogans. Behind this guide is a 6,800 m2 plant in Dongguan, China running 100+ CNC machines with 100+ staff. The machine list by category:
- 5-axis machining centres (10+) - Mazak VARIAXIS I-600 (510/910/510 mm travel, 12,000 rpm, 22 kW, 71.6 N·m, 30-tool BT40) and Mazak INTEGREX I-250H S (B-axis 0.0001°, 24 kW, 124 N·m, 38-tool HSK-A63). Best for compound-angle parts, single-setup multi-face prismatic work, and aerospace fittings where datum transfer loss is unacceptable.
- 3-axis / 4-axis machining centres (50+) - Brother SPEEDIO S500Z2N / S700Z2N (10,000 rpm, 14/21-tool ATC, 0.7 s tool-to-tool, Z-axis 2.2 G) and Mazak VCE-430A L / VCE-570C L (10,000 rpm, 118 N·m, 24-tool ATC). Best for prismatic parts, plates, brackets, housings.
- Swiss-type turning centres (10+) - Citizen Cincom A20-3F7 (Φ20 mm, 10,000 rpm), TSUGAMI B0206-III / B0205-III (Φ20 mm, 0.1 µm), STAR SR-32JII / SR-32J Type N (Φ32 mm, 8,000 rpm). Best for long, slender rotational parts at ±0.002 mm.
- CNC turning centres (20+) - HEADMAN T70M/1250 (720 mm swing, 117 mm bore, 3,000 rpm, BMT75 12-station turret). Best for shafts, bushings, flanges up to ±0.002 mm.
- Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Best for hardened tool steel, internal splines, sharp internal corners that milling cannot reach.
- Inspection: Hexagon CMM + 20+ gauges - Hexagon CMM for coordinate measurement, plus vision system, profilometer, hardness tester, coating thickness gauge, XRF for material verification. The 10:1 rule (gauge 10x more accurate than the band) is applied to every feature.
- Machine highlights - VARIAXIS I-600: one-setup multi-face 5-axis + MAZA-CHECK auto-calibration; INTEGREX I-250H S: DONE-IN-ONE mill-turn, B-axis 0.0001° + Ai thermal shield; SPEEDIO S500Z2N / S700Z2N: Z-axis 2.2 G + 0.7 s ATC; Swiss-type: guide-bush switchable + 0.1 µm resolution.
Tolerance: ±0.003 mm CNC milling / ±0.002 mm CNC turning / ±0.002 mm grinding and wire EDM. Capability: Ppk >= 1.67 initial on key characteristics, Cpk >= 1.33 ongoing.
Certificates: ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En, with design clause 8.3 excluded, stated openly) and ISO 14001:2015 (116024/B/0001/UK/En), issued to Dongguan Zhuohang Ltd, registration 91441900MA4UWT6X39, founded 2005.
Where we ship: Austria, Belgium, the Czech Republic, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, the Netherlands, Spain, Sweden and the United Kingdom in Europe; Brazil, Canada, Mexico and the United States in the Americas; China, Israel, Japan, Singapore and Sri Lanka in Asia; Australia and New Zealand in Oceania; and South Africa in Africa — plus other countries and regions worldwide, shipped from our base in Dongguan, China.
Contact: Felipe Iglesias, [email protected], +86 13126536955.
Request the quality evidence before you commit
Email [email protected] or call +86 13126536955 to request SPC, CMM, and certificate evidence for your part.
Frequently Asked Questions
Why is documented quality the strongest supply-chain risk control?
In short, A documented quality system turns quality from a promise into evidence you can audit before a failure reaches your line. SPC charts, CMM reports, and material certificates let you verify capability in advance, which is the cheapest way to buy down the risk of late, scrap, or out-of-spec parts.
What process capability does the shop demonstrate?
In short, On a representative length characteristic of 76.1–76.5 mm, the recorded SPC shows Cpk = 1.851 (one characteristic on one part, not a blanket capability claim) against a target of Ppk ≥ 1.67 at the initial study on key characteristics and ≥ 1.33 on general characteristics. This means the process is centered and capable, not just within limits on a one-off sample.
How are incoming materials verified?
Every incoming lot is checked by XRF (iCHEQ) spectrometer against its mill certificate before it reaches a machine. This catches mixed or substituted alloy at the door, so the material on the drawing is the material in the part.
How are parts inspected before shipment?
In short, Critical dimensions are verified on Hexagon GLOBAL S CMMs, supported by a KEYENCE VK-X3000 laser microscope, SURFCOM 1800D roughness and profile measurement, a gear measuring center, vision measuring machines, and hardness, coating thickness, salt spray, and tensile testers.
Which certifications back the quality system?
ISO 9001:2015 (116024/A/0001/UK/En), IATF 16949:2016 (131941/A/0001/SM/En), and ISO 14001:2015 (116024/B/0001/UK/En). The IATF 16949 scope excludes product design under Clause 8.3, so this is a build-to-print manufacturer.
What APQP/PPAP evidence exists?
In short, A completed customer program delivered the full APQP/PPAP quality pack — process flow chart, control plan, SPC control charts, and PFMEA. This is the same automotive-grade documentation a buyer would audit, applied to every job rather than only automotive ones.
How is traceability maintained end to end?
In short, The MES/ERP system records raw material source and usage, process parameters, machine data, production batch, machining time, operator, and inspection results on every lot. A non-conformance can be traced to the exact lot, machine, and operator, and the impact isolated.
What quality evidence should you request from any supplier?
In short, Ask for a CMM report or SPC chart from a real job, a verifiable certificate number, a material certificate with XRF verification, and disclosure of outsourced steps. A supplier who cannot produce these on demand is asking you to take quality on faith.
What do SPC and Cpk actually measure?
In short, SPC (statistical process control) samples parts during a run to watch the process, and Cpk is the number that says how much margin the process has inside its tolerance band. A Cpk of 1.0 means the edge touches the limit, 1.33 is roughly four sigma, and 1.67 is roughly five sigma — the automotive expectation for key characteristics.
What are first article and in-process inspection?
In short, First article inspection verifies the first part of a run against every dimension on the drawing before the run proceeds. In-process inspection samples parts at intervals during the run to catch drift before a whole batch goes out of tolerance.
4 Axis CNC Milling Quality — Related Pages
Continue reading: 3 Axis CNC Milling · 5 Axis CNC Milling
Standards referenced on this page
- IATF 16949:2016 — Automotive quality management system standard
- ASTM A582/A582M-12 — Standard Specification for Free-Machining Stainless Steel Bars
- ISO 14001 — Environmental management systems — Requirements with guidance for use