Last updated on August 27th, 2026 at 10:00 am
Custom tubular frames are welded structures made from round, square, or rectangular tubing and are commonly used to support equipment, panels, enclosures, carts, machinery, and other assemblies. Good frame design needs to account for tube size, wall thickness, joint geometry, welding distortion, tolerances, finishing, and how the individual tubes will locate during assembly.
Approved Sheet Metal (ASM) specializes in producing high-quality custom tubular frames for applications including medical equipment, industrial machinery, test equipment, racks, carts, and supporting structures for enclosures.
Our range of fabrication techniques, including tube laser cutting, welding, forming, hardware installation, and assembly, allows us to manufacture prototype and low-volume tubular frames with complex geometry and tight assembly requirements.
Common Types of Tubular Frames
ASM fabricates tubular frames for a wide range of custom equipment and assemblies. Common examples include:
- Medical Equipment Frames: Welded structures used for carts, equipment bases, trays, racks, and other medical equipment assemblies.
- Machine and Equipment Frames: Structures designed to support machinery, controls, panels, and equipment components.
- Enclosure Support Frames: Tubular structures that support enclosures, panels, doors, and other sheet metal components.
- Chassis and Equipment Structures: Welded frames used to locate and support mechanical and electrical components, including custom chassis assemblies.
- Rack Frames: Frames used to support electronics, instrumentation, networking hardware, and custom rack assemblies.
- Cart and Mobile Equipment Frames: Structures designed to support panels, shelves, casters, handles, and equipment that needs to be moved or serviced.
- Test Equipment Frames: Custom structures used to locate equipment, instruments, fixtures, and supporting components.
- Welded Tubular Assemblies: Multi-part frames that combine tube, sheet metal, hardware, brackets, and other fabricated components.
Materials and Tube Sizes for Custom Frames
Tubular frames can be fabricated from a variety of materials, including stainless steel, carbon steel, and aluminum.
| Material | Why Engineers Choose It | Fabrication Considerations |
|---|---|---|
| Stainless Steel | Corrosion resistance, durability, and clean appearance | Higher material cost and additional welding or cosmetic finishing may be required |
| Carbon Steel | Strength and cost effectiveness | Typically requires paint, powder coating, plating, or another finish when corrosion protection is needed |
| Aluminum | Low weight and natural corrosion resistance | Welding and heat distortion behave differently than steel and need to be considered during frame design |
Tube size availability matters just as much as material selection. A common square, rectangular, or round tube size may be readily available, while an uncommon wall thickness, metric profile, or specialty extrusion may require a special order.
Using readily available materials and tube sizes can reduce sourcing time and material cost.
ASM also fabricates frames using proprietary or extruded components such as Unistrut. If your design uses a manufacturer-specific tube, extrusion, rail, or profile, provide the manufacturer and exact part number with your RFQ so we can source the correct component.
Why Tube Laser Cutting Changes Tubular Frame Design
Traditional frame fabrication often relies on saw-cut tube ends followed by manual measuring, coping, drilling, and locating during welding. Tube laser cutting allows many of those features to be created directly in the tube before assembly.
Depending on the tube geometry, the laser can create:
- Miters and angled end cuts
- Copes and notches
- Holes on multiple tube faces
- Slots
- Tabs
- Assembly keys and locating features
- Cutouts for mating tubes or sheet metal components
- Part-marking or assembly references
This capability can reduce secondary operations and make complicated welded frames easier to assemble consistently.
Design Tubular Frames to Self-Locate Before Welding
One of the biggest opportunities when designing for tube laser cutting is to build assembly location directly into the tube geometry.
Tabs, slots, notches, and mating profiles can help individual frame members mechanically locate against one another before welding.
Self-locating tube joints can provide several manufacturing advantages:
- Faster fit-up
- Less manual measuring during assembly
- Improved squareness
- Reduced fixturing requirements
- More repeatable joint position
- Easier tack welding
- Less movement while the frame is being welded
For prototype and low-volume frames, these features can be especially valuable because they reduce the amount of custom fixturing needed to hold one specific assembly.
Raw Tubing Is Not a Perfect Machined Block
Engineers should remember that tubing itself has manufacturing tolerances before ASM ever cuts or welds it.
Raw tubing can vary in:
- Outside dimensions
- Wall thickness
- Straightness
- Twist
- Corner radii on square and rectangular tubing
A tube laser can accurately locate features relative to the material presented to the machine, but the dimensional variation of the raw tube still influences the final frame.
For that reason, applying machining-level tolerances to every dimension across a large welded tubular frame can create unnecessary manufacturing complexity and cost.
How Welding Affects Tubular Frame Tolerances
Welding introduces localized heating and cooling that can move the frame as the welds shrink.
Welding can affect:
- Overall frame squareness
- Diagonal measurements
- Flatness
- Parallelism
- Mounting-hole locations
- Alignment between separate frame members
ASM controls these effects using proper fit-up, tack sequencing, welding sequence, fixturing, inspection, and self-locating joint geometry where appropriate.
The drawing should clearly identify the dimensions that are truly critical after welding. Tightening every overall dimension on a welded frame can add significant fixture, inspection, straightening, and secondary-processing requirements without improving the function of the assembly.
When Secondary Machining May Be Appropriate
If a finished frame requires exceptionally tight mounting surfaces, bearing locations, precision hole relationships, or other features that cannot reasonably be held through cutting and welding alone, a secondary machining operation may be required after welding.
Identifying those critical features early allows the manufacturing process to be planned around the actual functional requirements of the frame.
Establish Clear Functional Datums
Tubular frames often contain mounting holes and features across several different tube faces. The drawing should make it clear which surface, hole pattern, or frame plane controls the functional relationship between those features.
Rather than independently applying tight dimensions to every tube face, establish datums around the surfaces and features that control assembly fit.
This helps the fabricator understand what needs to be held tightly and what dimensions can follow normal tube and welding tolerances.
Advanced Fabrication Capabilities and Finishing Services
ASM performs core frame-fabrication operations such as tube laser cutting, forming, welding, hardware installation, and assembly in-house.
Keeping these fabrication processes coordinated under one roof can improve communication between cutting, welding, sheet metal fabrication, and final assembly while helping control lead time and manufacturing cost.
Cosmetic Welding and Grinding
Cosmetic requirements should be identified before the frame is quoted.
A hidden structural weld generally does not need the same level of finishing as a customer-facing biomedical or equipment frame. Depending on the application, welds may be left as-welded, cleaned, blended, ground, or polished.
Engineers should clearly identify visible surfaces and required weld appearance because extensive grinding or polishing can add significant labor.
For more information, review our welding guidance.
Finishing Large Tubular Frames
Frames may also require finishing such as powder coating, painting, plating, passivation, or another treatment depending on material and application.
A frame may be straightforward to fabricate but too large for a standard powder coating oven, plating tank, or finishing line.
ASM coordinates outside finishing services when required, and oversized frames may need specialized vendors. These requirements should be identified early to avoid unexpected cost or finish lead time.
Large Tubular Frames Require More Than Welding Capacity
Large frames introduce additional manufacturing considerations including fixturing, movement through the shop, inspection, transportation, and finishing.
For example, ASM recently fabricated a biomedical frame approximately 10 feet long, 8 feet tall, and 6 feet wide. A frame of that size requires planning not only for cutting and welding but also for how the structure will be supported during assembly, moved through production, transported, and accommodated by finishing equipment.
This kind of planning is why maximum frame size is not determined by one machine dimension alone. The entire manufacturing and logistics process needs to be considered.
What Should You Include in a Tubular Frame RFQ?
Providing complete design information allows ASM to evaluate tube availability, cutting, welding, tolerance, assembly, and finishing requirements before production begins.
For an efficient RFQ and DFM review, provide:
- 3D CAD model of the complete frame
- 2D drawing identifying critical dimensions and tolerances
- Tube profile and size, including square, rectangular, or round tubing
- Wall thickness
- Material specification
- Critical overall dimensions
- Critical squareness, flatness, or parallelism requirements
- Mounting-hole locations and functional datums
- Weld locations and weld symbols
- Cosmetic weld expectations
- Finish requirements
- Hardware or inserted components
- Manufacturer and part numbers for proprietary extrusions or purchased components
- Any sheet metal panels or assemblies that will attach to the frame
The 3D model helps us understand how the frame fits together, while the drawing identifies which relationships are most critical to the final assembly.
Why Engineers Choose ASM for Custom Tubular Frames
At ASM, decades of custom fabrication experience allow us to support tubular frames ranging from small prototype assemblies to very large welded structures.
Our combination of tube laser cutting, sheet metal fabrication, welding, hardware insertion, assembly, and DFM review allows us to evaluate more than just whether each individual tube can be cut. We look at how the complete frame will locate, weld, remain within tolerance, finish, and integrate with the rest of the product.
By working closely with customers during design review, we can identify opportunities to simplify joints, use readily available tubing, reduce fixture complexity, control welding distortion, and avoid unnecessary finishing or tolerance requirements.
Get Started with ASM Today
If you’re an engineer looking for a reliable partner to manufacture your custom tubular frame, Approved Sheet Metal is ready to review your design.
Contact us today to request a quote. Whether you need a prototype frame or low-volume welded assemblies, send us your 3D model and drawing and we’ll review the project for manufacturability.
