Laser cutting
How does laser cutting of sheet metal work?
A focused laser beam melts or vaporises the material along a programmed contour, while a cutting gas — usually nitrogen or oxygen — blows the melt out of the kerf. Modern fibre lasers cut steel, stainless steel and aluminium in one operation, with no tool change between different contours.
Up to what sheet thickness does laser cutting make sense?
Fibre lasers in the multi-kilowatt range can technically cut mild steel beyond 20 mm; economically, the sweet spot is usually 8–15 mm depending on laser power. Above these thicknesses, or for very simple contours in large quantities, flame or plasma cutting can be cheaper.
Fibre laser or CO2 laser — what is the difference?
Thanks to their shorter wavelength, fibre lasers couple better into metals and cut steel, stainless steel, aluminium and copper faster and more energy-efficiently. CO2 lasers used to be the standard for sheet metal but have largely been replaced by fibre lasers in metalworking.
Why does my laser-cut part have a burr?
Burrs are usually caused by incorrect gas pressure, worn nozzles, the wrong focus position or a feed rate that is too high for the sheet thickness. With correctly set parameters, modern fibre lasers cut practically burr-free.
How accurate is laser cutting?
Typical cutting tolerances are ±0.05 to ±0.1 mm for thin sheet and somewhat wider for thicker material. The actual part accuracy also depends on residual stresses in the raw sheet and on heat input.
Which assist gases are used in laser cutting?
Nitrogen (inert) produces bright, oxide-free edges and is preferred for stainless steel and aluminium. Oxygen (active) speeds up cutting of mild steel through an exothermic reaction but leaves a slightly oxidised edge that usually needs painting.
Why do small parts stay attached in thin sheet (micro-joints)?
These are deliberately placed micro-joints that stop small parts from tilting or shifting in the machine during cutting. They are broken off by hand or mechanically after removal and leave a minimal nub on the edge.
What is the minimum web between parts on a sheet?
As a guideline, allow a minimum web of about one to two times the sheet thickness between two contours so the material does not distort or overheat during cutting. Thin, delicate geometries need larger webs.
Tube bending
How do you bend tubes without wrinkles or ovality?
In mandrel bending, an internal tool supports the tube wall during bending so the cross-section stays round and no wrinkles form. Tight radii require a multi-ball mandrel; without a mandrel, the tube ovalises, especially with small radii and thin walls.
What is the minimum bend radius for tubes?
As a rule of thumb, the minimum centreline radius is about 1 to 1.5 times the tube diameter for standard mandrel bending. Tighter radii are possible with special tooling but increase the risk of wall thinning and wrinkling.
What is the difference between tube bending and tube laser cutting?
Tube bending plastically deforms the tube into a new geometry such as bends or S-shapes. Tube laser cutting cuts contours, holes and notches without changing the basic shape — the two processes are often combined.
Why does my tube crack or kink when bending?
Usually because the bend radius is too small for the wall thickness, mandrel support is missing, or the material is unsuitable or brittle. Thin-walled tubes with a large diameter-to-wall ratio are most likely to kink on the inside of the bend.
How many bends can be made on a tube in one clamping?
Modern multi-axis CNC bending machines perform several bends in different planes and angles one after another without re-clamping the tube.
What is the difference between mandrel bending and mandrel-less bending?
Mandrel bending supports the inside of the tube wall with a core tool and allows tighter radii without wrinkles. Mandrel-less bending is simpler and faster but only works with larger radii and thicker-walled tubes.
How much does a tube typically ovalise during bending?
With suitable mandrel tooling, ovality usually stays below 5–8 % of the original diameter. Without mandrel support or with very tight radii, the deviation can be considerably higher.
Tube laser cutting
When is tube laser cutting better than sawing and drilling?
As soon as a tube needs more than one straight cut — contours, notches for tube-to-tube joints, holes — tube laser cutting becomes more economical because everything is produced in one pass without re-clamping. For simple straight cuts in small quantities, sawing is usually cheaper.
Which tube cross-sections and lengths can be laser cut?
Industrial tube lasers typically process round, square and rectangular profiles up to around 300 × 300 mm cross-section and lengths of several metres, often 7 to 12 m.
What does 'ready to join' mean for tube laser parts?
A ready-to-join part leaves the machine with all contours, holes and notches needed for the next step — usually welding — already cut, with no further machining.
What is a tube-to-tube joint and how is it made?
One tube is fitted precisely into the contour of another and welded, without a separate connector. The tube laser cuts the matching, three-dimensionally curved notch in a single pass.
Can tubes be laser cut after bending?
Yes. Modern 3D tube lasers with rotating optics also follow bent contours and cut ends, holes or notches after the bending operation.
Press braking & sheet forming
What is a press brake and how does it work?
A press brake bends sheet metal by pressing it into a die with a punch; press force in tonnes and tool geometry determine the possible sheet thicknesses and bend radii. CNC press brakes perform several bends on one part automatically in sequence.
What is springback in press braking and how is it handled?
After bending, sheet metal springs back elastically by a small amount, so the angle ends up slightly larger than set during pressing. Shops compensate by overbending, bottoming or coining, and material-specific correction values in the CNC control.
How do you determine the minimum bend radius for sheet metal?
As a rule of thumb, the minimum inside radius is about one to one and a half times the sheet thickness, depending on the material. Softer materials such as aluminium often tolerate tighter radii than high-strength steels.
How close can a bend line be to a hole or cut-out?
As a guideline, keep a distance of at least three to four times the sheet thickness so the hole does not distort during bending.
Why do scratches or marks appear on sheet metal during press braking?
Usually because of dirty or damaged tooling, excessive pressure or missing edge protection on visible, decorative surfaces.
What is the difference between air bending and bottoming?
In air bending, the sheet does not fully contact the die — flexible and tool-saving, but more prone to springback. In bottoming, the punch presses the sheet fully into the die.
Welding
MIG, MAG or TIG — which welding process is right?
MAG with active shielding gas is the standard for steel in series production, MIG with inert gas is used for aluminium and stainless steel, and TIG delivers the highest seam quality and appearance.
What does ISO 3834 mean and who needs this certification?
DIN EN ISO 3834 defines quality requirements for welding companies, graded from elementary to comprehensive, and requires qualified welders, approved welding procedure specifications and a designated welding coordinator.
What is EN 15085 and what is it used for?
EN 15085 is the welding standard for railway vehicles, graded into four certification levels (CL1–CL4) according to safety relevance.
Can aluminium be welded to steel?
Not directly by conventional fusion welding — the materials form brittle intermetallic phases and have very different melting points. Joints are made by mechanical fastening, adhesive bonding or special processes.
How do you avoid distortion when welding?
Limited heat input, a symmetrical welding sequence, rigid fixtures and pre-setting or straightening after welding are the most common measures.
What causes porosity in a weld seam?
Mostly trapped gases from dirty, oily or damp base material, inadequate gas shielding in draughts, or incorrect wire feed and voltage settings.
What is robotic welding and when does it pay off?
A programmed welding robot guides the torch along a fixed path. Robotic welding pays off from medium quantities upwards — for one-offs, manual welding remains more economical.
Does a weld seam need finishing?
Structural seams usually only need spatter removal; visible or corrosion-critical seams are additionally ground or brushed.
CNC machining
What is the difference between 3-axis and 5-axis milling?
3-axis milling moves the tool in X, Y and Z. 5-axis milling additionally tilts and rotates, so undercuts and freeform surfaces can be machined in a single setup.
When to mill and when to turn?
Turning suits rotationally symmetrical parts such as shafts and bushings. Milling is for non-rotational geometries, pockets and hole patterns.
What tolerances are typically achievable in CNC machining?
For general dimensions, ±0.05 to ±0.1 mm is standard; tight fits reach ±0.01 to ±0.02 mm with appropriate machine quality.
What is surface finish (roughness) and how is it achieved?
Roughness (Ra value) describes how smooth a machined surface is. It is controlled via cutting speed, feed, tool geometry and, if needed, a finishing pass.
Why does a turned part with tight tolerances cost much more?
Tighter tolerances require lower cutting speeds, more measurements during production and often several finishing steps.
What is the difference between stock, blank and finished part?
Stock is the raw material, the blank is the roughly pre-machined shape, and the finished part is the dimensionally accurate end product after all machining and surface steps.
Materials & material selection
Steel, stainless steel or aluminium — how do I choose the right material?
Steel is the economical choice for load-bearing structures not exposed to corrosion; stainless steel for corrosion resistance, hygiene or appearance requirements; aluminium for weight savings, but more expensive and harder to weld.
What is the difference between S235 and S355 structural steel?
The number indicates the minimum yield strength in N/mm² — S355 is stronger than S235 and allows thinner walls for the same load.
Why does stainless steel sometimes rust after all?
Mostly due to contamination from iron particles from nearby steel processing, a damaged passive layer, or the wrong stainless grade for the environment.
Which stainless steel is suitable for outdoor use or aggressive environments?
For salty or chloride-laden environments, the molybdenum-alloyed, more corrosion-resistant grade 1.4404/1.4571 (316L/316Ti) is usually preferred over the standard grade 1.4301 (304).
How much lighter is a part if you switch from steel to aluminium?
Aluminium has roughly one third of the density of steel. Wall thicknesses often have to be increased for load-bearing structures, but the weight advantage usually remains significant.
Does every part need a material certificate?
No — standard parts usually do without. For rail, pressure equipment or safety-relevant applications, an inspection certificate 3.1 to EN 10204 is usually required.
Quality, metrology & sourcing
What is a first article inspection report?
A first article inspection report documents that the first part produced in a series meets all drawing characteristics, usually with full measurement of every dimensioned feature.
What does a 3D coordinate measuring machine measure?
A tactile or optical probe measures defined points on the part and compares the coordinates with the nominal values from the CAD model or drawing.
What does a manufacturer need for a reliable quotation?
A drawing or 3D model (STEP, IGES, DXF/DWG or STL), the required material, the quantity and the target date. Without a drawing, a sample or photo is often enough.
What is the difference between prototype, small batch and series production?
A prototype is usually made manually without special tooling. Small batches justify simple fixtures; high-volume series need dedicated tooling and automated loading.
How do I find the right contract manufacturer for sheet metal and tube parts?
What matters is suitable machine capacity, certifications such as ISO 9001, references in your industry and whether engineering and assembly are offered from one source.
What is the difference between first article inspection and ongoing production control?
First article inspection is carried out once at the start of production and checks every dimensioned feature completely. Ongoing production control checks samples during the series.
What does traceability mean in manufacturing?
Traceability means that the material batch and inspections for each part produced can be identified afterwards — usually via lot numbers.
How long does it typically take to manufacture a sheet metal or welded part?
A few days is realistic for a simple cut part; for a complex welded assembly, several weeks — depending on tooling availability and material lead time.