Reference
Glossary: machine frame and trade terms
Sourcing a weldment from another country means reading two vocabularies at once — the shop floor and the shipping desk. This covers both, in one list of 38 terms.
Compiled by Ryan. Terms link to a longer post where one exists.
Design & GD&T
The vocabulary a drawing is written in.
- Datum
- The reference surface or feature a dimension is measured from. A drawing whose datums shift between views gets quoted with a guess in it.
- GD&T
- Geometric dimensioning and tolerancing. Controls form, orientation and position of a feature rather than a single linear size.
- Flatness
- How closely a surface matches a true plane, independent of its size. Called out on mounting faces and slide surfaces, not the whole base.
- True position
- A GD&T control on where a feature sits relative to its datums. Usually cheaper to hold than four separate linear dimensions to the same hole.
- Weldment
- A structure built by welding plate, bar and profile together, then usually machined on selected faces. What most machine bases are.
- Rib / stiffener
- An internal plate added to a weldment to raise stiffness or shift its natural frequency without adding much mass. Rib design for stiffness →
- Natural frequency
- The frequency a structure vibrates at when disturbed. A frame whose natural frequency sits near the machine’s operating frequency resonates and loses accuracy. Natural frequency in machine structures →
Fabrication & welding
What happens on the shop floor.
- WPS
- Welding Procedure Specification. The document stating exactly how a joint is welded — process, consumable, current, travel speed, preheat.
- PQR
- Procedure Qualification Record. Test results proving a WPS actually produces a sound weld before it is used on real work.
- WPQ
- Welder Performance Qualification. Evidence a specific welder can run a specific WPS to an acceptable standard.
- Fit-up
- The joint alignment and gap before welding starts. Most weld defects trace back to a fit-up problem, not the weld itself.
- Distortion
- The shape change a weldment picks up from uneven heating and cooling during welding. Managed by weld sequence, not fixed after the fact. Distortion control on large weldments →
- Stress relief
- A process — thermal (furnace) or vibratory — that removes residual stress locked into a weldment so it does not move later when machined. Stress relieving welded bases →
- Splice
- A joint added to reach a plate length longer than standard mill stock. Its position on the drawing decides whether it is invisible or a liability.
- Machining allowance
- Extra material — typically 3–6 mm per face — left on a weldment so distortion can be machined away without leaving the wall too thin.
- Weld symbol
- The AWS/ISO shorthand on a drawing specifying joint type, size and process, so a shop does not have to guess at intent. Weld symbols on machine frame drawings →
Quality & inspection
Proving the frame is right before it ships.
- NDT
- Non-destructive testing. An umbrella term for UT, MT, PT and RT — methods that check a weld without cutting it open. NDT for machine frame welds →
- UT — ultrasonic testing
- Sound-wave inspection for internal, volumetric flaws in thick-section welds.
- MT — magnetic particle testing
- Surface and near-surface flaw detection on ferromagnetic steel only.
- PT — dye penetrant testing
- Surface-breaking flaw detection that works on non-magnetic materials too.
- RT — radiographic testing
- X-ray inspection for internal flaws that leaves a permanent film record, at higher cost and time than UT.
- First article inspection (FAI)
- Every characteristic on the drawing measured and recorded on the first piece, before the rest of the order runs. FAI on large weldments →
- Dimensional report
- Named characteristics measured against the drawing and reported with actual values, not just pass or fail.
- Mill certificate
- The material producer’s document giving chemistry and mechanical properties for a specific heat of steel. Traceability depends on the heat number surviving the whole job.
- Certificate of conformity
- A supplier statement that the goods meet the purchase order. A declaration, not a measurement — ask for the dimensional report behind it.
- Hold point
- A defined stage — fit-up, post-weld, pre-paint — where inspection happens before work continues, rather than one check at the end.
Trade & logistics
The vocabulary of getting it from the shop floor to yours.
- EXW
- Ex Works. You collect from the shop and handle everything after — export clearance, freight, import duty — yourself.
- FOB
- Free On Board. The shop delivers to a named Vietnamese port and clears export; risk passes once the goods are on board the vessel.
- DAP
- Delivered At Place. The shop’s forwarder delivers to your address; you pay import duty and taxes. Delivered does not mean cleared. Incoterms for heavy weldments →
- Incoterms
- Standard three-letter rules allocating cost, risk and transport responsibility between buyer and seller. They do not transfer legal title.
- Heavy-lift / breakbulk
- Freight handled outside a standard container — on a flat rack or as loose cargo — because the frame exceeds container dimensions or weight.
- Crating
- Export packaging built to survive ocean transit and handling: bracing, VCI wrap on machined faces, moisture barrier, fumigated timber.
- Bill of lading
- The carrier’s document for a sea shipment — the contract of carriage and, in negotiable form, title to the goods in transit.
- Certificate of origin
- A document stating where the frame was made. Preferential forms can lower the import duty rate; non-preferential forms simply state origin.
- HS code
- The commodity code that decides the import duty rate. Agree it before shipping — a mismatch between export and import filings triggers customs questions.
- Landed cost
- Unit price plus freight, insurance, duty and inland handling — the number that actually compares two quotes on different Incoterms.
- Lead time
- Elapsed time from a defined start point — usually a confirmed purchase order — to parts ready to ship. Confirm the start point in writing.
- MOQ
- Minimum order quantity. Heavy fabrication has no real technical minimum — a single frame is a normal order — so a stated MOQ is a commercial minimum, not a machine limit.
Need the numbers behind these terms?
The tolerance, welding-standard and material tables that put these definitions to work are on the standards reference. Or send a drawing straight through.
For Vietnamese fabricators
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