Machine frames by application
A frame for a grinder and a frame for a carton packer are both welded steel, and they are specified completely differently. What each application asks of the frame, how it is usually built and which tolerances matter. Ranges are typical across the partner network, not one shop's equipment list. The shop that quotes your drawing confirms what it holds.
Applications at a glance
The first column of a frame RFQ is the application. It tells the shop which property comes first and which tolerances it can relax. Values are typical, not a specification for your part.
| Application | What drives the design | Typical construction | Typical critical tolerance |
|---|---|---|---|
| Machine tool frames | Static stiffness, damping, thermal stability | Stress relieved steel weldment, cast iron or mineral casting | Guide rail pads flat to about 0.02 mm, ground or scraped when tighter |
| Automation frames | Repeatable mounting points, quick build | Welded tube or plate, aluminium extrusion for light cells | Machined pads about ±0.05 to ±0.1 mm, rest to general tolerance |
| Packaging machinery | Cleanability, corrosion, open access | Stainless 304 or 316L tube and plate, continuous welds | Frame to ISO 13920 class B, machined pads where drives mount |
| Test rigs | Stiffness and mass against the test load | Heavy plate bedplate, T-slot table, isolated seismic mass | T-slot face flat to about 0.05 mm per metre |
| Semiconductor equipment | Vibration, flatness, clean surfaces | Welded steel or stainless, machined plates, extrusions for enclosures | Mounting plates flat to about 0.02 to 0.05 mm |
The cutting, welding, stress relief and machining behind these frames is on the fabrication technology page. Tolerance classes and grade equivalents are on the standards reference.
Machine tool frames
Bases, beds, columns, gantry beams and crossrails for milling machines, lathes, grinders, routers and laser or plasma cutters. The frame carries the guideways, so its job is to hold geometry under cutting load and over temperature, for years.
Welded steel wins on lead time and one-off cost. Cast iron and mineral casting win on damping and on volume. Steel weldments for machine tools are stress relieved before machining, ribbed for stiffness and machined on a gantry or boring mill so all guide rail pads share one datum. Background on the machine class is on Wikipedia.
Put on the drawing or RFQ
- Guide rail type and size, and which pads carry them
- Flatness and parallelism between rail pads
- Whether pads are finished by grinding or scraping
- Stress relief method you accept
Handbook: Cast iron or welded steel for a machine base · Rib and box-section design for stiff machine frames · Gantry frames for large-format CNC routers · Frames for fibre laser cutting machines: heat, speed and stiffness
Automation frames
Robot cell bases, conveyor and transfer frames, gantry robot structures and assembly line stations. Loads are lower than a machine tool, but the frame has to be repeatable: the same mounting points in the same place on every copy, because the line is often built many times.
Light cells often use aluminium extrusion. Welded steel takes over when a robot base sees high dynamic load, when the frame is long or when the line is built in volume and a welding fixture pays for itself. Only the mounting pads are machined; the rest of the frame runs to general welding tolerance.
Put on the drawing or RFQ
- Robot model and base load, or the payload and acceleration
- Which faces are machined and their datum
- Expected build quantity per year
- Paint or powder coat colour and specification
Handbook: Aluminium extrusion frames versus welded steel frames · Conveyor and automation line frames at volume · From one frame to fifty: what changes
Packaging machinery frames
Frames for fillers, cartoners, wrappers and form-fill-seal machines, often in food, beverage or pharmaceutical plants. Washdown and hygiene decide the design more than load: open profiles, sloped top surfaces, no hollow sections open to the product zone, continuous welds instead of stitch welds and no crevices that trap residue.
Stainless 304 is the usual choice, 316L where chlorides or aggressive cleaning agents are used. Hygienic design guidance such as EN 1672-2 and EHEDG documents sets the rules. Welds are typically ground and the frame is pickled and passivated after welding to restore the passive layer.
Put on the drawing or RFQ
- Stainless grade and finish on visible and product-zone surfaces
- Washdown class or cleaning agents used
- Whether hollow sections must be sealed
- Pickling and passivation requirement
Handbook: Packaging machine frames: stainless, washdown and hygiene · Surface treatment for machine frames that cross an ocean
Test rigs
Dynamometer beds, fatigue and durability rigs, T-slot bedplates and engine or gearbox test stands. The frame is part of the measurement: if it deflects or resonates under the test load, the result is wrong. Stiffness, mass and the first natural frequency are set against the load and the excitation range.
Rigs are usually built from heavy plate, stress relieved and machined, with T-slots cut into the top face. Many sit on a seismic mass isolated from the building floor. Large bedplates are often split into sections with machined joint faces so they can be shipped and aligned on site.
Put on the drawing or RFQ
- Test load, frequency range and the deflection you can accept
- T-slot size and pitch, to DIN 650 or ISO 299
- Bedplate flatness and how it will be measured
- Split points and alignment features if it ships in sections
Handbook: Test rig and dynamometer frames: what the drawing must say · Natural frequency, chatter and why a stiff frame can still ring
Semiconductor equipment frames
Frames for wafer handling modules, inspection and metrology tools, and process tool subassemblies. Vibration and flatness drive the design: stages and optics need a stiff, well damped structure with a high first natural frequency, on machined mounting plates that hold their flatness after assembly.
Frames are welded steel or stainless, machined after stress relief, then powder coated, painted or electropolished to suit the cleanroom class. Particle generation, outgassing from coatings and the seismic anchoring the equipment maker specifies all go on the drawing. Background on cleanroom classes is on Wikipedia.
Put on the drawing or RFQ
- Flatness and parallelism of each mounting plate
- Finish and cleanroom compatibility of the coating
- Natural frequency target or vibration criterion
- Cleaning and double bagging before packing
Handbook: Frames for semiconductor and inspection equipment · Natural frequency, chatter and why a stiff frame can still ring
Questions about frame applications
Can one shop build frames for different applications?
Often, but the skills differ. A shop that builds machine tool bases knows stress relief and precision machining. A packaging frame needs stainless welding, grinding and passivation. The shortlist is built around the application on your drawing, not around the shop's general capability.
Welded steel, cast iron or aluminium extrusion?
Welded steel suits one-offs and low volume, heavy loads and large sizes. Cast iron and mineral casting suit volume and high damping. Aluminium extrusion suits light automation cells that change often. The deciding factors are load, damping, quantity and lead time.
Which tolerances should apply to the whole frame?
Only the general ones. Use a general tolerance class such as ISO 13920 class B for the weldment and ISO 2768 for machined features, then put tight tolerances only on the surfaces that carry rails, drives or instruments.
Does the network handle defence or export-controlled equipment?
No. Export-controlled work (ITAR, defence, dual-use) is declined at enquiry stage, whatever the application.
Cite or link this page
Free to quote, reference or link with attribution. The calculation method is stated above so it can be checked rather than taken on trust.
Frame drawing ready for one of these applications?
Send it with the application and the surfaces that matter. It gets matched with shops in the network that already build that kind of frame. Reply within 24 business hours.
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.