An offshore drawing package should state everything a supplier would otherwise assume: a general tolerance such as ISO 2768-mK, GD&T to ASME Y14.5 on critical features, material by ASTM or UNS grade, finish by standard and thickness, and inspection to ANSI/ASQ Z1.4 at AQL 0 critical, 2.5 major and 4.0 minor. Freeze the revision first, since each change costs a 4–8 week freight cycle.
SSG MFG · design guideDG-12 · 13 rules
13 rules, in the order you meet them on a model. Every value is typical; the principal quoting your part confirms its own limits.
| # | Rule | |
|---|---|---|
| 01 | Freeze the design firstMove offshore only after first article approval of a stable revision | Move offshore only after first article approval of a stable revision |
| 02 | Release one controlled revisionSTEP model and PDF drawing at the same revision, with a note on which governs | STEP model and PDF drawing at the same revision, with a note on which governs |
| 03 | State a general toleranceISO 2768-mK, or a title block such as ±0.005 in (±0.13 mm) on X.XXX | ISO 2768-mK, or a title block such as ±0.005 in (±0.13 mm) on X.XXX |
| 04 | Flag critical dimensionsMark 5–15 critical features with a symbol; GD&T to ASME Y14.5-2018 or ISO 1101; Cpk 1.33 on the most critical | Mark 5–15 critical features with a symbol; GD&T to ASME Y14.5-2018 or ISO 1101; Cpk 1.33 on the most critical |
| 05 | Specify material by ASTM or UNS gradeGrade and temper, accepted equivalents listed, mill certs to EN 10204 3.1 | Grade and temper, accepted equivalents listed, mill certs to EN 10204 3.1 |
| 06 | Specify finish by standard and thicknessZinc per ASTM B633 SC2 (8 µm) Type III; salt-spray hours per ASTM B117; color by RAL or Pantone plus gloss | Zinc per ASTM B633 SC2 (8 µm) Type III; salt-spray hours per ASTM B117; color by RAL or Pantone plus gloss |
| 07 | Write inspection criteria downANSI/ASQ Z1.4 general level II; AQL 0 critical, 2.5 major, 4.0 minor; defect list by class | ANSI/ASQ Z1.4 general level II; AQL 0 critical, 2.5 major, 4.0 minor; defect list by class |
| 08 | Require a first article reportBallooned drawing with every dimension measured on 3–5 samples, or PPAP where required | Ballooned drawing with every dimension measured on 3–5 samples, or PPAP where required |
| 09 | Specify packaging and markingPack quantity, carton weight limit such as 40 lb (18 kg), VCI bags for bare steel, country-of-origin marking | Pack quantity, carton weight limit such as 40 lb (18 kg), VCI bags for bare steel, country-of-origin marking |
| 10 | Compare landed cost on stated IncotermsName the Incoterms 2020 rule and place, such as FOB Ningbo; add freight, duty, tariffs, brokerage, inspection and 20–30% annual carrying cost | Name the Incoterms 2020 rule and place, such as FOB Ningbo; add freight, duty, tariffs, brokerage, inspection and 20–30% annual carrying cost |
| 11 | Protect tooling ownershipOwnership, tool markings and removal rights in the contract; tooling paid in milestones | Ownership, tool markings and removal rights in the contract; tooling paid in milestones |
| 12 | Hold safety stock and plan for holidaysAbout 4–8 weeks beyond transit time; expect 2–4 weeks of reduced output around Lunar New Year | About 4–8 weeks beyond transit time; expect 2–4 weeks of reduced output around Lunar New Year |
| 13 | Dual source critical partsKeep a qualified domestic or second offshore source for A-items | Keep a qualified domestic or second offshore source for A-items |
These build on the short list on the offshore sourcing process page, with the failure each rule prevents and a drawing for each.
Remove callouts from a sample drawing package one at a time and see what an offshore supplier will assume for each one left blank.
DRAWING PACKAGE · 5 OF 7 CALLOUTS
Costs more: 2 decisions handed to the supplier
For each blank, this is what a supplier will typically assume:
Each rule with its typical value, the reason behind it and what happens on the floor when it's ignored. Switch any drawing between Do and Avoid; point at a callout to pick it out.
Rule 01
Move offshore only after first article approval of a stable revision
Rule 02
STEP model and PDF drawing at the same revision, with a note on which governs
Fig. 1A complete drawing package
Do. Every requirement is on the drawing: general tolerance, material by specification, finish by specification, critical dimensions and revision.
Avoid. Whatever the drawing leaves blank, the supplier decides, usually with the cheapest local equivalent.
Rule 03
ISO 2768-mK, or a title block such as ±0.005 in (±0.13 mm) on X.XXX
Standard: ISO 2768-1, ISO 2768-2See Fig. 1, a complete drawing package
Rule 04
Mark 5–15 critical features with a symbol; GD&T to ASME Y14.5-2018 or ISO 1101; Cpk 1.33 on the most critical
Standard: ASME Y14.5-2018, ISO 1101
Rule 05
Grade and temper, accepted equivalents listed, mill certs to EN 10204 3.1
Standard: ASTM, UNS, EN 10204
Rule 06
Zinc per ASTM B633 SC2 (8 µm) Type III; salt-spray hours per ASTM B117; color by RAL or Pantone plus gloss
Standard: ASTM B633, ASTM B117
Rule 07
ANSI/ASQ Z1.4 general level II; AQL 0 critical, 2.5 major, 4.0 minor; defect list by class
Standard: ANSI/ASQ Z1.4
Rule 08
Ballooned drawing with every dimension measured on 3–5 samples, or PPAP where required
Rule 09
Pack quantity, carton weight limit such as 40 lb (18 kg), VCI bags for bare steel, country-of-origin marking
Rule 10
Name the Incoterms 2020 rule and place, such as FOB Ningbo; add freight, duty, tariffs, brokerage, inspection and 20–30% annual carrying cost
Standard: Incoterms 2020
Rule 11
Ownership, tool markings and removal rights in the contract; tooling paid in milestones
Rule 12
About 4–8 weeks beyond transit time; expect 2–4 weeks of reduced output around Lunar New Year
Rule 13
Keep a qualified domestic or second offshore source for A-items
What to call out on an offshore drawing, with a typical callout and a tighter one. Tighter callouts are achievable but raise piece price and inspection cost.
| Feature | Typical | Tight | Cost of tight |
|---|---|---|---|
| General tolerance classMust appear in the title block | ISO 2768-mK | ISO 2768-fH | Moderate |
| Critical dimensions | ±0.005 in (±0.13 mm), flagged | ±0.001 in (±0.025 mm), Cpk ≥ 1.33 | High |
| Hole position | Ø0.010 in (0.25 mm) | Ø0.004 in (0.1 mm) at MMC | Moderate |
| Zinc plating thickness | 5–8 µm (0.0002–0.0003 in) | 12 µm (0.0005 in) min, checked by XRF | Low |
| Powder coat thickness | 2–4 mil (50–100 µm) | 2–3 mil (50–75 µm) | Low |
| Critical defects | AQL 0, zero accepted in sample | 100% inspection of the feature | High |
| Major defectsPer ANSI/ASQ Z1.4 | AQL 2.5, level II | AQL 1.0, level II | Moderate |
| Minor defects | AQL 4.0, level II | AQL 2.5, level II | Low |
Basis: ISO 2768-1, ASME Y14.5, ANSI/ASQ Z1.4. Put a general tolerance note on the drawing and tighten only the features that need it; every tight callout is priced. See the tolerance guide.
The same offshore sourcing rules shift with the alloy or compound.
Call out UNS S30400 to ASTM A240 or A276, not SUS304 alone. Ask for mill certs and a chemistry check, since lower-nickel 201 stainless is a common substitute.
Specify A380 to ASTM B85. ADC12 is the common Asian die-casting alloy and sits closer to A383, so accept it in writing or not at all.
Call out ASTM B86 Alloy 3 (UNS Z33520) and require chemistry on the cert. Lead, cadmium and tin impurities from uncontrolled remelt cause intergranular corrosion.
Specify UNS C36000 to ASTM B16. Local free-cutting brasses have different lead limits, which matters for potable-water and RoHS compliance.
Specify ASTM A108 grade 1018, not Q235 or mild steel. Q235 is a structural grade with looser carbon and sulfur limits that machines and case hardens differently.
Name the resin by brand and grade, or at least its UL 94 rating and color standard. State whether regrind is allowed and cap it, such as 0–25%.
Run these against the model before it goes out for quote. The builder's DFM check catches most of them on an uploaded part.
0 of 12 checked
ISO 2768-mK is a common choice for machined, stamped and fabricated parts, because suppliers worldwide recognize it. The m sets linear limits such as ±0.2 mm from 6 to 30 mm, and K sets general geometric tolerances. Put it in the title block, and tolerance critical features individually rather than tightening the whole class.
AQL 2.5 is the acceptance quality limit in ANSI/ASQ Z1.4 sampling. For a lot of 5,000 parts at general level II, the inspector pulls 200 samples and accepts the lot with up to 10 major defects, rejecting it at 11. Lower AQL numbers accept fewer defects and cost more to inspect.
Send both. Suppliers program and build tooling from a STEP model, but tolerances, material, finish, threads and inspection criteria live on the PDF drawing. Keep them at the same revision and add a note stating which governs if they conflict, usually the drawing for tolerances and the model for untoleranced geometry.
Call out the ASTM product standard and UNS number, such as ASTM A240 UNS S30400 for 304 sheet, rather than SUS304 or 06Cr19Ni10 alone. Require EN 10204 3.1 mill certificates with each lot, and consider a chemistry spot check, since lower-nickel 201 stainless is a common low-cost substitute.
FOB at the origin port is the most common, so the supplier loads the goods and you control ocean freight, insurance and customs. EXW shifts export clearance to you, and DDP puts delivery and duty on the supplier. Name the Incoterms 2020 rule and a specific place, such as FOB Shenzhen, on every purchase order.
A first article report is a ballooned copy of the drawing and a results table with every numbered dimension and note measured on sample parts, often 3–5 pieces from the production tool. It includes material certificates and finish test results. Approve it before releasing production, and keep the approved samples as a reference.
Check your part against these rules.
Drop a STEP file in the builder for an instant DFM check and a budgetary estimate, then send it to principals who run offshore sourcing every day.
