- Dongguan Zhuohang Ltd (Registration No. 91441900MA4UWT6X39), operating as Zhuohang Precision Machining Factory, established 2005.
- a hundred-odd machines including 20+ 5-axis centres; 100+ staff, 80%+ skilled technicians.
- A quote is only as good as the drawing behind it.
- The four omissions that turn an accurate quote into a revised one.
- Confirm revision, FAIR scope, and delivery terms in writing before release.
What makes a CNC precision machining enquiry quotable?
A quote is only as good as the drawing behind it. The gap between a fast quote and an accurate one is almost always a missing tolerance scheme, an unspecified surface finish, or a material callout that names a family rather than a grade.
The five things that change the answer: the 3D model, the 2D drawing with tolerances, the material grade, the quantity (and the anticipated repeat quantity), and any inspection or certification requirement.
What design decisions move the cost on CNC precision machining?
Three design decisions drive most of the cost on a machined part: internal corner radii matched to a real cutter diameter, cavity depth kept within about four times the tool diameter, and a general tolerance on every feature that does not mate. Each one changes the tool that can be used, and the tool determines how much material can be removed per minute, which is why these matter more than any process selection.
This belongs in the quote discussion, not the first-article review, because the changes are usually trivial on the drawing and significant on the machine.
What capacity sits behind this?
Total machine count is not the question — the question is how many machines sit in the family that makes your part, because that is the queue your part waits in. The floor runs a floor of 100-plus machines: 50+ three-axis centres for prismatic work, 20+ four-axis, 20+ five-axis, 25+ turning and mill-turn centres, Swiss-type lathes for long slender parts, precision grinding and wire EDM for the tightest features.
The spare capacity in that family is what lets a part re-route rather than queue when a machine is pulled for service. That, not the headline machine, is what protects a delivery date.
What is the certification position?
ISO 9001:2015, IATF 16949:2016 (excluding clause 8.3 product design), and ISO 14001:2015, each with a certificate number verifiable with the registrar.
What to confirm on your side
These are the items whose absence most often produces a quote that changes after review.
- 3D model in STEP or IGES, plus a 2D drawing. The drawing carries the tolerances the model does not.
- Material as a grade, not a family, "stainless" is not a specification; 316L is.
- Tolerance per feature, not a blanket note. A single tight dimension drives cost more than ten loose ones.
- Surface finish callouts where they matter, with the standard named (Ra in ISO or ASME).
- Quantity and expected repeat quantity. these are different numbers and they change the process.
Checklist — before you release production
Before releasing, these are the items worth confirming in writing.
- Which drawing revision is being built — in writing, on the order acknowledgement.
- What the first-article report will contain, and whether it is full inspection or a sample plan.
- How capability is reported — the index, the stage, and the sigma estimator, named.
- Who owns an engineering change and how it is documented mid-run.
- Packaging, duty, and freight responsibility — whether the quote is EXW, FOB, or delivered.
What tolerance applies?
±0.003 mm on CNC milling, ±0.002 mm on CNC turning; ±0.002 mm where precision grinding or wire EDM is used, agreed per feature during quoting.
Which legal entity is actually responsible for the work?
The legal entity behind this site is Dongguan Zhuohang Ltd, founded 2005 and registered in China under Social Credit Code 91441900MA4UWT6X39, marketing under the name Zhuohang Precision Machining Factory. Its registered and production address is No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470.
Use the National Enterprise Credit Information Publicity System and the 18-character code to verify a Chinese manufacturer. Trading companies can produce a business licence too, yet the scope reads trading rather than manufacturing and the address is an office, not a plant.
The eight DFM checks that decide part cost
Design for manufacturability (DFM) for CNC machining is not an art; it is a checklist of eight checks that catch 90 percent of the cost penalties a drawing introduces before the part is quoted. If you run the checklist on the drawing before sending the RFQ, you are the one whose quote comes back tight, fast, and unambiguous; if you do not, you are the one whose quote comes back with markups, surcharges, or a "we cannot make this as drawn" reply.
Check 1: Internal corner radius. An end mill is cylindrical, so an internal corner is always a radius, never a square. The radius must be at least one-third of the cutter diameter for finish. A drawing that calls out a sharp internal corner is calling out an EDM operation, not a milling operation. Call out a fillet (≥ 0.5 mm for small parts, ≥ 1 mm for larger parts).
Check 2: Wall thickness. A wall thinner than 0.5 mm in aluminum and 0.8 mm in steel will chatter under the cutter and distort when released. Minimum for stable milling: 0.5-1.0 mm aluminum, 1.0-1.5 mm steel, 1.5-2.0 mm stainless.
Check 3: Hole depth-to-diameter ratio. Twist drilling limit is 4× diameter; gun drilling 8-10×; BTA or ejector 30×. A 5 mm × 50 mm deep hole is a gun drill operation at 10×, not a twist drill.
Check 4: Pocket floor thickness. A pocket floor thinner than 0.5 mm in aluminum deflects under the cutter. Minimum for stable milling: 0.5 mm aluminum, 0.8 mm steel.
Check 5: Thread depth and size. Standard threads under M2 / #2 are fragile in soft metals. Minimum recommended: M2.5 / #3 hand-tapped, M3 / #4 machine-tapped. Thread depth above 2× diameter does not add strength but adds cycle time and tap breakage risk.
Check 6: Tolerance callout. Every tight tolerance is an inspection and scrap tax. A feature at ±0.05 mm costs the same as one at ±0.5 mm to machine but adds inspection time and scrap risk. Tighten only the surfaces that mate or seal; leave the rest at ISO 2768 medium.
Check 7: Datum scheme. The datum scheme decides how the part is held and inspected. Choose datums that are functional (the mating surfaces) and call them out as primary, secondary, and tertiary. A drawing without a datum scheme is one the shop will choose its own datums for, and the parts may not mate as intended.
Check 8: Surface finish and secondary operations. Ra 0.8 µm requires grinding or lapping, not milling; Ra 0.8-3.2 µm is achievable with finishing passes; above Ra 3.2 µm is standard rough milling. Secondary operations — anodizing, plating, heat treatment, laser marking — each add a hand-off, a queue, and a tolerance risk. Specify the type (Type II sulfuric, Type III hardcoat) and the color, or the shop guesses.
The eight checks above catch the cost penalties before the quote is written. If you run the checklist, fix the issues, and send a clean RFQ, you get a quote in 24 hours and a part that meets the drawing. If you do not, you get a quote with surcharges and a "we need to discuss this drawing" reply, and the discussion costs more in time than the checklist would have cost in 10 minutes.
The cost penalty of each DFM miss
Every DFM miss has a quantifiable cost penalty, not a vague "it will be more expensive" but a specific multiplier on unit price or scrap rate. If you run the eight DFM checks and fix the issues, you save 30-70 percent on unit price; if you do not, you pay the multipliers below on every part shipped.
Sharp internal corner (no fillet): calls out EDM instead of milling. Cost multiplier: 3-5× on the affected feature, plus 1-2 weeks of lead-time for EDM scheduling. Fix: fillet the corner to ≥ one-third of cutter diameter. Savings: 70-80 percent on the feature.
Wall below 0.5 mm in aluminum: causes chatter, deflection, and scrap rate of 15-40 percent. Cost multiplier: 1.5-3× through scrap and rework. Fix: thicken to 0.5-1.0 mm or specify support during machining. Savings: 40-70 percent on the feature.
Hole depth above 4× diameter: calls out gun drill instead of twist drill. Cost multiplier: 2-4× on the hole, plus 1-3 weeks of lead-time if the shop does not have gun drill capability. Fix: redesign to 4× diameter, or accept the gun drill cost. Savings: 50-75 percent on the hole.
Pocket floor below 0.5 mm: causes deflection and non-flat floor. Cost multiplier: 1.5-2× through scrap or post-grinding. Fix: thicken to 0.5-0.8 mm, or accept grinding after milling. Savings: 30-50 percent on the feature.
Thread below M2 / #2: causes tap breakage and scrap rate of 10-30 percent. Cost multiplier: 1.5-2× through tap breakage and slower feed. Fix: redesign to M2.5 or larger. Savings: 30-50 percent on the feature.
Tolerance ±0.003 mm on non-mating feature: adds inspection time and scrap rate. Cost multiplier: 1.5-3× through inspection and scrap. Fix: leave non-mating features at ISO 2768 medium (±0.1 mm for sizes 30-120 mm). Savings: 40-60 percent on inspection cost.
No datum scheme: shop chooses its own datums, leading to parts that may not mate. Cost multiplier: 1.2-2× through re-fixture and inspection mismatch. Fix: call out primary, secondary, tertiary datums on the drawing. Savings: 20-50 percent on setup and inspection.
Ra 0.4 µm on every surface: calls out grinding on every surface. Cost multiplier: 3-5× through grinding operation. Fix: specify Ra 0.8 µm on mating surfaces only, leave the rest at Ra 3.2 µm milling finish. Savings: 60-80 percent on surface finishing.
The cumulative cost penalty of running zero DFM checks is 2-5× on unit price — the part arrives at 2-5× what it should cost. Running the eight checks takes 10-30 minutes per drawing and saves the multiplier on every part shipped. If you run the checks and fix the issues, you are the one whose quote holds; if you do not, you are the one whose quote arrives at the multiplier and whose parts arrive at the same multiplier on scrap rate.
What this shop actually runs
If you ask for capability evidence, you deserve a specific answer. This facility operates 100+ CNC machines across 6,800 m2 in Dongguan, China, staffed by 100+ people. The machines, listed 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). Intended 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). Intended 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). Intended 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). Intended for shafts, bushings, flanges up to ±0.002 mm.
- Wire EDM (5+) - Sodick AQ535L (550/350/300 mm travel, ±20° taper, 800 kg workpiece). Intended 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 bands: ±0.003 mm milled, ±0.002 mm turned, ±0.002 mm ground or wire-cut. Capability indices: Ppk >= 1.67 at the initial study; Cpk >= 1.33 ongoing in production.
Certifications: ISO 9001:2015 (116024/A/0001/UK/En) · IATF 16949:2016 (131941/A/0001/SM/En, design clause 8.3 excluded) · ISO 14001:2015 (116024/B/0001/UK/En), held by Dongguan Zhuohang Ltd (USCC 91441900MA4UWT6X39, since 2005).
Service area: we supply 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, with worldwide delivery from China.
Contact: Felipe Iglesias, [email protected], +86 13126536955.
Send a drawing and get a manufacturability read
Upload your model for a quote, or arrange a factory audit with [email protected] or +86 13126536955. Ask for Felipe Iglesias.
Frequently Asked Questions
How are parts packed for export?
Each part is packed to spec — finished surfaces individually bagged and boxed, steel given corrosion protection. Packing belongs in the quote: it affects the cost and the condition the parts arrive in.
Can I audit the factory before placing an order?
Yes. On-site visits and video audits are welcome at No. 8, Shuibian Songyuan Road, Hengli Town, Dongguan, Guangdong, China 523470.
Do you need both a model and a drawing?
Yes, in practice. The model defines geometry; the drawing defines what has to be true about that geometry. A quote from a model alone leaves the tolerance scheme to assumption, which is where disputes start.
Do you sign NDAs before reviewing drawings?
Yes. Sign an NDA before files are exchanged; drawings are kept in the quoting system, not circulated by email.
Is inspection documentation included in the quote?
It should be stated explicitly. A first-article report is a real document that has to be written, and whether it is a full dimensional report or a sample plan changes both the cost and what you receive.
What is the difference between a prototype build and a production build here?
Usually only quantity and scheduling. Both run on the same machines and the same process, which is what makes a later ramp a scheduling change rather than a re-qualification.
What tolerances can you hold?
In short, ±0.003 mm on CNC milling, ±0.002 mm on CNC turning, and ±0.002 mm where precision grinding or wire EDM is used. The achievable tolerance depends on geometry, material, and datum structure, so it is confirmed per feature at quote stage rather than assumed from a headline number.
Continue reading: CNC Precision Machining Checklist · 3 Axis CNC Precision Machining · 4 Axis CNC Precision Machining
Standards referenced on this page
- ASTM B211/B211M-19 — Standard Specification for Aluminum-Alloy Rolled or Cold Finished Bar, Rod, and Wire
- ASTM A582/A582M-12 — Standard Specification for Free-Machining Stainless Steel Bars
- ISO 9001 — Quality management systems — Requirements