The handbook
A working reference for machine frame buyers
Every check that gets run on a drawing here, written down. 45 chapters, roughly 28,600 words, organised the way the decisions actually arrive — what to build it from, how to draw it, how it gets made and verified, and how it reaches your floor.
Free and open. No registration, no gated PDF, no form in front of it. Written by Ryan, independent sourcing agent in Ho Chi Minh City, Vietnam.
01
Design and materials
What should this frame be made of, and what shape should it be?
What the structure is made of and where the material goes. Cast iron against welded steel, grade selection, the geometry that buys stiffness, and the dynamics that decide whether a stiff frame is also a quiet one.
- Cast iron or welded steel for a machine baseDamping, rigidity, cost and lead time compared for cast iron and welded steel machine bases — and the volume point where the answer flips.
- Choosing a steel grade for a machine frameQ235, Q345, S355, A36, A572 and A516 compared for welded machine frames — equivalence, weldability, and why the grade on your drawing affects lead time.
- Rib and box-section design for stiff machine framesWhere to put material in a welded machine frame so it buys stiffness instead of weight — box sections, rib spacing, shear webs and the mistakes that add mass for nothing.
- Natural frequency, chatter and why a stiff frame can still ringWhy static stiffness does not guarantee a quiet machine — modes, damping, stability lobes, and what a frame designer can actually change.
- Bolted or welded: how to split a large machine frameWhen a bolted machine frame beats a one-piece weldment — shipping limits, damping, serviceability, and how to design a joint that does not lose stiffness.
- Mineral casting versus welded steel for a machine baseEpoxy granite and polymer concrete machine bases compared with welded steel on damping, stiffness, tooling cost, lead time and repairability.
- Aluminium extrusion frames versus welded steel framesT-slot aluminium extrusion frames compared with welded steel for machine builders: stiffness, damping, joint behaviour, thermal growth, cost and where each one fits.
- Gantry frames for large-format CNC routersHow welded gantry and bed frames for large-format CNC routers are designed: beam depth, racking, rail flatness, stress relief and what to specify for fabrication.
- Frames for fibre laser cutting machines: heat, speed and stiffnessWhat a fibre laser cutting machine frame must do: carry heavy sheet, hold rail flatness, resist heat and vibration. A guide to bed, gantry and drawing requirements.
- Normalised plate and why it machines more predictablyWhat normalising does to structural plate, how it differs from as-rolled and TMCP delivery, and when it is worth paying for on a welded machine frame.
- Packaging machine frames: stainless, washdown and hygieneHygienic design rules for stainless packaging machine frames: grades 304 and 316, sloped surfaces, continuous welds, sealed sections, pickling and passivation.
- S355J2 or S355JR: the impact grade question on machine framesWhat the J2 and JR suffixes mean in EN 10025-2, when impact toughness matters on a welded machine frame and how to write the grade on a drawing.
- Frames for semiconductor and inspection equipmentWelded frame requirements for semiconductor, metrology and inspection tools: vibration isolation, cleanroom finish, stainless welding, stiffness targets and drawing notes.
- Square tube or I-beam for a light machine frameCompare square and rectangular hollow section with I-beam and H-beam for light machine frames: torsional stiffness, weld access, tolerances and cost per kilogram.
02
Drawings and specification
How do I write this drawing so the quotes come back tight?
The callouts that decide whether five shops quote the same job. Datums, weld symbols, tolerance strategy and which welding standard to invoke — with the notes to copy onto a drawing.
- Weld symbols on machine frame drawings, and what they cost you when they are wrongHow to read and write weld symbols on fabrication drawings — arrow side, fillet size, intermittent pitch — and the ambiguities that make quotes diverge.
- GD&T and datum strategy on welded structuresWhy as-welded surfaces make bad datums, how to set a datum frame on a fabricated machine base, and which geometric controls actually earn their cost.
- Which welding standard to put on a machine frame drawingAWS D1.1, ISO 3834 and EN 1090 do different jobs. What each one certifies, which market demands which, and how to specify without over-buying.
- Tolerance stack-up on fabricated machine structuresHow tolerances accumulate through a welded and machined frame, why worst-case analysis over-builds, and where to spend the tolerance budget on a machine base.
- A drawing checklist for welded machine basesThe callouts that decide whether quotes for a welded machine base come back tight or scattered — datums, weld symbols, machining allowance, inspection and the notes shops need.
- How to write a machine frame RFQ that gets a real quoteEvery field a machine frame RFQ needs, why each one changes the number, and a template you can copy before sending a drawing to a fabrication shop.
- Mill certificates for frame steel: 2.2, 3.1 or 3.2What EN 10204 types 2.1, 2.2, 3.1 and 3.2 actually prove, how to check a mill certificate against the plate and what to ask for on a welded machine frame order.
- Fillet or full-penetration welds on a machine frameFillet, partial and full penetration welds compared for welded machine frames: where each belongs, what it costs in weld metal and how to call it on the drawing.
- Plate thickness tolerances and why your frame drawing needs themRolled steel plate is rarely exactly the thickness you ordered. See how EN 10029 classes work, how errors stack up on a frame and what to write on the drawing.
- Test rig and dynamometer frames: what the drawing must sayWhat a test rig or dynamometer frame drawing must state: loads, torque reaction, natural frequency, alignment tolerances, containment and inspection records.
03
Fabrication and quality
How does this get built, and how do I know it was built right?
What happens on the shop floor and how it is verified. Weld sequence and distortion, stress relief, large-envelope machining, NDT scope and the inspection record that makes any of it checkable.
- Controlling distortion on large weldmentsWeld sequence, fixturing, restraint and joint design — the levers that decide whether a four-metre machine frame comes off the table straight.
- NDT on machine frame welds: what to specify, and what not toUltrasonic, magnetic particle, dye penetrant and radiography compared for machine frame welds — which method suits which joint, and why blanket NDT wastes money.
- What actually machines a four-metre weldmentFloor-type boring mills, gantry mills and planer mills compared for finish-machining large machine frames — envelope, accuracy, setup time and what limits each.
- First article inspection on a large weldmentWhat an FAI report on a machine frame must contain, how to measure a four-metre part you cannot put on a surface table, and the hold points worth booking.
- Stress relieving welded machine bases: thermal, vibratory, or neitherThermal versus vibratory stress relief on welded machine frames — what each method actually does, when natural aging is defensible, and how to write the requirement into a drawing.
- Checking flatness and squareness on a large frame before shipmentHow flatness and squareness are checked on large welded frames: straightedge, precision level, laser tracker, support points, temperature and the record you should ask for.
- Robotic or manual welding for small-batch machine framesWhen a robot or cobot beats a manual welder on a machine frame and when it does not: batch size, fit-up, joint access and what to ask a partner shop at quote stage.
- Plasma, laser or oxy-fuel cutting for thick frame plateHow plasma, fibre laser and oxy-fuel cutting differ on 20 to 100 mm frame plate: kerf, edge angle, heat-affected zone and what each means for weld fit-up and machining.
- Weld preheat and interpass temperature on thick frame sectionsWhy thick machine frame plate needs preheat, how carbon equivalent and thickness set the temperature, and what to ask a partner shop about interpass control.
- Welding fixtures for repeat machine frame productionWhen a welding fixture pays for itself on a machine frame, what types exist, how accurate they must be and who should own the tooling at a partner shop.
- Welding consumables for machine frames: wire, flux and strength matchHow to choose filler wire, flux and electrodes for S355 machine frames: strength matching, MAG, flux-cored and submerged arc, hydrogen control and what to ask shops.
- Dimensional reports on weldments: CMM, laser tracker or tapeWhat each measuring method can prove on a welded machine frame, what uncertainty to expect, and how to specify a dimensional report that you can actually use.
04
Sourcing and logistics
Who builds this, what does it cost, and how does it get to me?
Everything between the drawing and the loading dock. Where the cost actually sits, why material sets the schedule, how to audit a shop, what coating survives a sea transit, and scaling from one frame to fifty.
- Plate availability is what sets your lead timeWhy a machine frame schedule is usually decided by steel plate availability rather than shop capacity, and the drawing decisions that avoid an eight-week mill order.
- Surface treatment for machine frames that cross an oceanBlast grade, primer, topcoat, dry film thickness and masking — how to specify paint on a machine frame so it survives thirty days of sea freight.
- What actually drives the cost of machine frame fabricationPlate is rarely the expensive part of a welded machine base. A breakdown of where the money actually goes in machine frame fabrication, and which drawing decisions move the quote.
- Shipping a ten-tonne machine frameContainer limits, out-of-gauge freight, crating and lashing, Incoterms and the paperwork that decides whether a heavy machine frame arrives straight and on time.
- How to audit a heavy fabrication shopThe questions that separate a shop that can build your machine frame from one that will subcontract it — equipment, procedures, QC evidence and the walk-around.
- Vietnam, China or India for heavy fabricationAn honest comparison of Vietnam, China and India for machine frames and large weldments — capacity, price, lead time, certification depth and where each one is genuinely weaker.
- From one frame to fifty: what changesHow cost, tooling, tolerance and supplier relationship change between a prototype machine frame and a production run — and what to decide before unit one.
- Sourcing agent or direct factory for machine frames? How to decideWhat a sourcing agent, a trading company and a direct factory relationship each cost in money, control and time for a machine frame order — and which fits your stage.
- Conveyor and automation line frames at volumeHow to buy conveyor and automation line frames in tens to hundreds: design for repeatability, fixture and cut strategy, tolerances, coating and quality sampling.
Alongside the handbook
Calculators for the arithmetic
The numbers behind several of these chapters are worked by hand often enough to be worth automating: fillet weld sizing and deposited metal, plate weight, stress-relief soak time, grade equivalence and whether a frame fits a container.
Reading order is not prescribed. If you are about to release a drawing, start withthe drawing checklist. If you are choosing a supplier, start withthe audit questions. If a quote surprised you, start withthe cost drivers.
For Vietnamese fabricators
Become a sourcing partner
The heavy-fabrication network is open to new shops. If you build large weldments, machine frames or precision-machined bases and you have export experience, send a capability profile. We reply within 24 business hours.
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