Custom Tube Bending Services

Introduction

Tube bending is a core metal‑forming process that enables rigid tubes to be formed into complex shapes without joints. BACH INDUSTRY AG is a specialist in this field, offering tube bending services for business‑to‑business customers. We serve engineers, purchasing managers and operations leaders in sectors ranging from aerospace to heat‑exchanger manufacturing. Our products and services are available for sale across Switzerland, Germany, Austria, Liechtenstein, Belgium and Africa, ensuring competitive price and dependable support wherever your facility is located.

What is Tube Bending?

Rigid metal tubes are usually made from mild steel, stainless steel, aluminium or copper; they can be round, square, rectangular or even oval. Compared with flexible hose or welded fabrications, bent tube offers a more robust and longer‑lasting solution, often at lower total cost, while also reducing weight and leak paths. There are three fundamental bending methods:

• Compression bending holds one end of the tube and pushes it around a form. It is suitable for simple shapes and small diameters.

• Draw (rotary draw) bending pulls the tube around a die; CNC machines clamp the tube to the die and rotate it while a pressure die presses it into the former. If the tube wall is thin or the radius is tight, a mandrel is inserted inside the tube to support the wall and avoid collapse.

• Roll (push) bending feeds the tube through three rollers to create large‑radius curves. This method is used when draw bending is impractical because of the tooling size or when very gentle curves are required.

A fourth technique, freeform bending, uses a single die to bend thin‑walled tubing without clamping; it is ideal for multiple‑radius bends or angles over 180°, especially in furniture and medical equipment.

Materials, Shapes and Bend Radii

Bend radius is measured to the tube’s centreline. A widely used rule of thumb for draw bending is to choose a radius of 2 × D (twice the outside diameter); for example, a 20 mm OD tube would ideally have a 40 mm radius. Smaller radii down to ½ × D are possible but usually require mandrel support and specialised tooling. For roll bending, the minimum radius is about 7 × D. These guidelines help balance tooling cost against design flexibility; larger or unusual radii may require custom dies and therefore additional expense.

Material choice also affects bend quality. Stainless steel, aluminium and copper have different levels of ductility and may require changes in radius or tooling. High‑strength steels can be bent with minimal deformation when a properly sized mandrel supports the tube. Square or rectangular tubes require specialised mandrels and dies, and engineers should remember that bending thin‑wall tubing or very small diameters may demand additional support from wiper dies and mandrels.

CNC and Mandrel Bending: Precision and Simulation

Modern CNC tube bending services rely on numerical control to achieve repeatable angles, rotations and lengths. Operators enter or upload length, rotation and angle (LRA) data from the print and then run a bending simulation to check that the tube clears the machine and tooling; if a collision is detected, the program can be adjusted. Simulation software reduces setup time and scrap and is particularly useful for multi‑radius or 3D bends.

A mandrel tube bending machine inserts a metal rod slightly smaller than the tube’s inside diameter to shore up the inside wall. As the tube is drawn over the die, the mandrel holds the outside radius back in its original shape, allowing it to stretch and preventing collapse. The clearance between mandrel and tube varies by application: aerospace or high‑precision bends may use a clearance of 0.003–0.005 in; automotive and high‑volume work typically uses 0.010–0.015 in; heavy‑wall tubing may require up to 0.080 in. When extremely tight radii or thin walls are involved, a wiper die is used alongside the mandrel to wipe wrinkles from the inside radius and minimise out‑of‑round deformation.

Design Data and Tolerances

Accurate bending depends on understanding tolerances and compensating for material behaviour. According to updated manufacturing standards, bend angle tolerance is ±1°, rotation tolerance is ±2° and segment length tolerance is ±0.030 in. Center‑line radius (CLR) will be matched to the closest common tooling and may vary by ±0.25 in. Ovality—flattening of the cross‑section—should not exceed 10 % (5–8 % typical) of the nominal diameter. Wall thickness deviation is normal because the outside of the bend stretches and the inside compresses.

To maintain these tolerances, mandrels and wiper dies are sized based on wall thickness and bend radius; improper sizing can lead to wrinkles or flattening. Wiper die tips are typically offset 0.060–0.300 in from the tangent point to eliminate wrinkles; increasing pressure on the die can also help. For square versus round tubes, larger radii and thicker walls may be required to avoid cracking; stainless steel tends to spring back more than aluminium or copper, so allowances must be made in the bending program.

Dimensional Inspection and Digital Measurement

Quality control uses either length, rotation and angle (LRA) data or XYZ coordinates to define each bend. First‑article inspection is standard and may be repeated depending on part complexity. Simple parts can be checked with manual gauges, but complex shapes benefit from digital measurement: high‑definition cameras scan the bent tube, create a 3‑D model, and compare the actual geometry with specification. The system provides real‑time feedback to the CNC machine, enabling operators to adjust the program immediately and reduce throughput time. BACH INDUSTRY AG integrates this inspection technology into its tube bending design software, ensuring tight tolerances and quick turnaround.

Common Defects and How to Prevent Them

Two fundamental issues occur during rotary draw bending: the outside wall collapses and thins, and the inside wall compresses and wrinkles. A basic setup includes a bend die, clamp die and pressure die; however, thin‑wall or tight‑radius projects also require a mandrel and wiper die. Wrinkles occur when the mandrel no longer provides enough counter‑force on the inside radius; a properly positioned wiper die supports the tube and wipes out wrinkles. Choosing the right mandrel style and wiper die and adjusting pressure settings are critical for high‑quality bends. Additionally, ensuring appropriate material ductility and selecting a suitable radius can mitigate defects; for example, using a larger radius or thicker wall reduces the risk of ovality and cracking.

Industry Applications

Bent tubes are ubiquitous in modern manufacturing and appear in numerous sectors:

• Aerospace & aviation – precision‑bent components add structural integrity; accuracy is critical.

• Agriculture – bent tubing forms parts for farm equipment such as combines, tractors and attachments.

• Automotive – exhaust systems and structural or safety components use bent tubing.

• Construction – cranes, building frames, stairways and handrails rely on bent tubing.

• Furniture & recreation – handles, frames and even amusement‑park rides incorporate bent tubes.

• HVAC – heating, ventilation and air‑conditioning systems use bent pipes.

• Musical instruments and consumer products – trombones and tubas are formed from bent tube.

• Oil & gas and shipbuilding – continuous bent tubing reduces leaks by eliminating welded elbows and carries fuel, water and hydraulic fluids in ships.

BACH INDUSTRY AG offers industry‑specific tube bending services for aerospace, automotive and heat‑exchanger/HVAC customers, including custom materials (stainless steel, aluminium, copper, titanium), shapes (round, square, rectangular, coil) and sizes (micro tube to large diameter). We can also combine tube bending with fabrication and welding to deliver complete assemblies.

Tooling, Dies and Accessories

Quality bends require the right tools. The bend die defines the centreline radius and matches the tube’s outside diameter; pressure dies stabilize the tube while it wraps around the bend die; clamp dies hold the tube in place. Mandrels prevent collapse and minimize ovality. When thin walls or tight radii are involved, wiper dies wipe wrinkles from the inside radius. BACH supplies a full range of tube bending dies—including square dies for non‑round sections—along with mandrel tube bending machines, fixtures, jigs and other accessories. Our tooling inventory allows us to accommodate a wide variety of radii, reducing tooling lead time and cost. For unique projects, we design custom tooling to ensure tight tolerances and smooth surface finish.

Software, Design and Simulation

Effective tube design often begins with CAD. Our tube bending design software includes 3‑D modelling and bending simulation to check for collisions and ensure manufacturability. Designers can work with XYZ coordinate measurement data or LRA data; our software translates CAD models into bend instructions and exports cnc tube bending quotations. Integrated tube bending simulation software predicts springback, calculates bend allowances and suggests optimum radii. Combined with digital measurement systems that provide real‑time feedback during production, this software helps engineers refine designs and shorten development cycles.

Requesting a Quote and Next Steps

If you need custom tube bending services, mandrel tube bending services, or cnc tube bending services, BACH INDUSTRY AG can help. Our team will review your drawings, material and tolerance requirements and provide a prompt cnc tube bending quote. We also offer tube bending & fabrication, tube bending & welding and tube bending & laser cutting options to deliver finished components.

We have a competitive service prices in Switzerland, Germany, Austria, Liechtenstein, Belgium and Africa. Contact us today to discuss your project, arrange a facility visit or request an RFQ for tube bending.