Capability
Sheet metal
Cutting, forming, and finishing, from flat patterns or 3D files.
How this works
Sheet metal parts start as flat stock, are cut to a developed pattern, then bent to shape. Because the material starts flat and stays a constant thickness, the process is fast and cheap for enclosures, brackets, and chassis, and it scales from one part to thousands without tooling.
The constraint that governs everything is that you can only bend, not sculpt. A geometry that would be trivial to machine may be impossible to form, and the fix is usually to split it into two parts and join them.
A formed part is cut flat first. The developed length of the blank is not the sum of the finished legs, because material stretches through each bend. Bend allowance accounts for that, and it is why a part must be modelled as a sheet body rather than a solid.
Processes
| Process | What it does |
|---|---|
| Laser cutting | Cuts the flat pattern with a focused laser. Fast, accurate, and the standard for most materials and thicknesses. |
| Punching | Cuts using a tool and die. Efficient for repeated standard features across high volumes. |
| Waterjet cutting | Cold cutting with abrasive water. No heat-affected zone, and cuts thick or heat-sensitive material. |
| Bending / press brake | Forms the flat pattern to shape between a punch and die. Bend sequence is a real design constraint. |
| Rolling | Forms continuous curves such as cylinders and cones. |
| Welding | TIG, MIG, and spot welding to join formed parts into assemblies. |
| Hardware insertion | Presses PEM-style nuts, studs, and standoffs into the sheet. |
Machine limits
The press brake bed is 3,050 mm, so that is the longest single bend. Longer panels are made in sections and joined, or designed so the long edge is a rolled form rather than a brake bend. The fiber laser cuts to 25 mm in mild steel, 20 mm in stainless, and 16 mm in aluminum; the practical band for enclosure work is 0.5 to 3 mm, where cut quality needs no secondary dressing.
Nesting
Parts are nested into the sheet before cutting, and on a part with a lot of internal cutout the nesting decides the material cost more than the part size does. Two consequences worth designing for: order in round sheet quantities where you can, because a run that lands just over a sheet boundary pays for the whole next sheet, and keep the outline simple enough to tessellate. A part that nests at 80 percent utilization is materially cheaper than one that nests at 55.
Materials
| Material | Chosen for |
|---|---|
| Cold rolled steel | Low cost, strong, forms and welds easily. Requires a finish to prevent corrosion. |
| Galvanised steel | Zinc coated for corrosion resistance without painting. Welding damages the coating locally. |
| Stainless 304 | General corrosion resistance, food and medical equipment. Springs back more than mild steel. |
| Stainless 316 | Chloride and marine environments. |
| Aluminum 5052 | The general-purpose forming alloy. Good corrosion resistance and formability. |
| Aluminum 6061 | Higher strength, but cracks more readily on tight bends. Use generous bend radii. |
| Copper and brass | Electrical conductivity, busbars, decorative parts. |
Design rules for formed parts
- Keep the inside bend radius at least equal to the material thickness. Tighter radii crack the outer surface, especially in 6061 aluminum and harder tempers.
- Keep all bends on a part in the same direction and to the same radius where possible. Each different radius means a different tool and another setup.
- Hold holes and slots at least two and a half times the material thickness away from a bend, or they deform.
- Keep flanges at least four times the material thickness plus the bend radius, or the press brake cannot grip them.
- Add relief cuts where a bend meets an unbent area, otherwise the material tears at the corner.
- Bend allowance changes the flat pattern. Send a 3D model and let the flat pattern be developed, rather than sending your own unless you know the k-factor being used.
- Formed corners are never fully sealed. If the enclosure must be sealed, plan for welding or a gasket.
The outside of a bend is in tension and it is where a bend fails. A radius roughly equal to material thickness is safe in most sheet, and it should be the same value everywhere on the part so one tool forms all the bends. Tighter radii are possible in soft material and in the grain direction, but they need to be agreed rather than assumed.
Tolerances
Sheet metal tolerance is looser than machining tolerance, and formed dimensions are looser than cut ones. Bend angle varies with material springback, which itself varies by alloy, temper, and grain direction.
- Cut features hold tighter tolerance than formed ones, so dimension from cut edges rather than across bends where accuracy matters.
- Tolerance stacks across multiple bends. A dimension crossing three bends accumulates the variation of all three.
- State which dimensions are critical so the bend sequence can be planned to favor them.
- For close-fitting assemblies, allow clearance rather than tightening the tolerance on a formed feature.
Hardware and finishing
Hardware
- Self-clinching nuts, studs, and standoffs pressed into the sheet
- Weld nuts and weld studs where the load requires it
- Riveting and rivet nuts for thin or dissimilar materials
Finishes
| Finish | Applies to | Notes |
|---|---|---|
| Powder coating | Steel, aluminum | Durable colored finish. Thick, so mask threads and mating faces. |
| Wet paint | Steel, aluminum | Wider color and gloss range, thinner build than powder. |
| Anodising | Aluminum | Corrosion resistance and color. Type II decorative, Type III hard wearing. |
| Zinc plating | Steel | Corrosion resistance at low cost, common on brackets and fasteners. |
| Passivation | Stainless | Restores corrosion resistance after cutting and forming. |
| Brushed / grained | Stainless, aluminum | Directional decorative finish. State the grain direction on the drawing. |
| Silkscreen and laser marking | All | Legends, logos, and panel graphics. |
Common questions
Self-clinching hardware is specified by type, not by thread alone. PEM S and SO nuts and standoffs suit steel and stainless; F and FH flush-head studs give a flat reverse face where the panel has to sit against something; CLS and TB types are made for thin or soft sheet where a standard nut would spin. State the type and the sheet side it installs from on the drawing, because installing from the wrong side leaves a witness mark on the show face.
Also available
Other capabilities
Injection molding
Production molding runs from a tool you already own or one we build for you. Quotes cover the part, the tool, and the lead time separately so you can see what you are paying for.
Injection molds and tooling
Tool design, build, and sampling. The tool type follows the part and the volume, so quotes state which configuration is proposed and why.
CNC machining
Milling and turning from metal and plastic stock, for prototypes through to production quantities.
Let’s get started on your part
Send your CAD files and target volumes. We come back with a price, a lead time, and any design notes that would reduce either.