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CNC tube bending

by Jan 31, 2022Pipe & Tube Bending

Estimated Reading Time: 5 minutes

CNC tube bending is an efficient alternative to manual tube bending, welding or additional fittings in many situations. CNC tube bending is an effective solution for building a variety of complex assemblies. A CNC bender is a proven machine for exceptional performance, versatility and reliability of bent tubes.

What is CNC tube bending?

A computer numeric controlled (CNC) bending machine produces bent metal tubes to move liquids or gasses through a manufacturing process that do not break or wrinkle. It’s the most-precise bending process for metal tubing. While each CNC tube bending machine is different, here’s an example of the CNC tube bending process on an electric/hydraulic CNC tube bending machine (a common choice for CNC bending):

  • The metal tube is sized and it receives a clean, dry cut (no oils).
  • The cut piece of tube is inserted into the bender’s mandrel and is clamped down.
  • The CNC tube bender operator loads the program that includes the part number that informs the bending machine of the proper bend.
  • The CNC operator presses a foot pedal to begin the process (which is part of the safety features of a bender).
  • The tube bends in less than one minute using the sheer force of the bender.

A hybrid electric/hydraulic bender combines electric drive bending with hydraulic bending actuation. This type of CNC bender is environmentally friendly and consumes a small amount of power and produces low noise and heat. The clamp and pressure die of the CNC bender are hydraulic driven while the mandrel is hydraulic with early withdrawal.

Benefits of CNC tube bending

  • Using a CNC bending machine, welds, joints and expensive fixtures are eliminated from a complex assembly system.
  • CNC bending is a cleaner option compared to other bending/welding processes.
  • Projects are generally less expensive as fewer fittings equals a lower overall cost. If you can eliminate five fittings from each of your 10 systems, you can effectively eliminate the cost of 50 fittings.
  • Eliminating welds and joints within a system also eliminates the risk of leaks that may occur in welded or jointed complex assembly systems.
  • The semiconductor industry benefits from building systems without the wall thinning that can occur in welded systems. With CNC tube bending, the integrity of the materials is maintained.
  • CNC tube bending also produces a much smoother finish than other processes. Depending on how the system is being implemented, an engineer may prefer a system that looks better cosmetically.
  • Fewer bends in a system minimize flow restrictions for chemicals and liquids that may otherwise get trapped in joints or sharp corners.
  • Precision tube pipe systems are produced faster and more precisely on CNC  bending machines, allowing time savings of up to 95 percent.

CNC tube bending is recommended for these production systems

Control systems

In chemical engineering production, it’s essential to have a seamless flow of gasses or liquids. There are zero kinks in CNC bent tubing systems to trap or slow materials flowing through the system.

Delivery systems

CNC machine bent tubing creates liquid-tight and airtight seals for consistent movement of matter through the entirety of your system.

Purification systems

Purifying processes often include the use of caustic chemicals, which can cause filler material on welded tubes to break down over time. Bent tubing has no filler material, but consists only of the base metal, leaving precise pathways for materials to flow.

Storage systems

Manufacturers in chemical production may use tube systems to deliver potentially hazardous materials into temporary or long-term storage. The interior of tubes used to transport that material must remain clean. Bent tubing has no sharp curves inside to trap materials, so the interior remains uncontaminated after materials flow through.

Testing systems

Materials flowing through testing systems must retain their original properties. With bent tubing, there is a much lower risk of contamination as opposed to using a welded tube system or a system with multiple joints. The more components added to a system increases the opportunity for contamination.

Frequently asked questions about CNC tube bending

If the outside diameter of the tube I plan to use is not a standard size, what is a solution for the design?

Tube bending experts can look at your design requirements to see if there’s a solution to bend a standard size tube into a shape or angles that will fit into your space requirements, with minimal fittings to ensure consistent performance without degradation.

If the radii requested is not standard, what is a solution for the design?

Bending experts will look at your design plan to see if the radius of the tube bends can be adjusted and still achieve your goals. One possibility is utilizing both tube bends and high-purity orbital welding to achieve your goal. Back-to-back bends are sometimes requested, as designers look to fit tubing into a small space. Back-to-back bends typically require custom tooling, which adds cost to a project. If the size of the project justifies the cost of the tooling, that may be your best solution.

Is a CNC bender an option for bending tempered or heat-treated tubing?

Some tempered or heat-treated tubes are more likely to rupture, crack or damage internally when bent by a machine. 

Basic components of a CNC bender 

Mandrel 

The mandrel inserts into the tube for support during bending to avoid wrinkling, distortion, collapse, flattening, rippling or breakage during the process. Using a mandrel provides better control over the tube’s ovality or roundness. Mandrel tube bending elicits highly accurate, repeatable results for jobs with tight or large radius bends. The firmness of a mandrel is very important, and should correlate to the firmness of the tube. For extremely durable tubing, a soft mandrel is used, and a hard mandrel is used on softer tubing. This prevents the mandrel from sticking to the inside of the tube, which can damage the tube.

Bend Die 

The radius of the bend die takes into account the durability of the tube to adjust for radial growth. Bending a harder material requires a bend die with a smaller radius.

Clamping Die 

The ideal length of a clamping die is three times the diameter of the tube. Clamping short puts too much pressure on a short section of the tube, resulting in a damaged component.

Wiper Die 

The wiper die supports the tube on the inside of the bend to prevent wrinkles. The wiper die should be positioned at a slight angle with its contact point extremely sharp at all times. Lubrication at the point of contact is important to avoid premature wear.

Lubrication

Proper lubrication is critical for top-quality bends. Lubrication lowers friction during bending for clean, smooth results. Non-petroleum-based synthetic lubricants in a paste or gel are advised. Durable metals often require more lubrication to prevent friction.

One more thing to note about CNC tube bending: not only does utilizing a CNC bender guarantee a high quality product, it also allows the service provider to achieve the same high-quality result over and over again. Bend radii can be set to fit necessary specifications, and the machine will accurately bend each and every time a tube is run through it.

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