A robot cell can lose availability because of a low-cost pneumatic line that kinks at full reach, rubs through inside a dress pack, or works loose after repeated movement. Selecting the best tubing for robotic arms is therefore not simply a matter of matching tube outside diameter to a push-in fitting. The tubing must tolerate the arm’s motion profile, the compressed-air duty, the surrounding environment and the available routing space over a high number of cycles.

For machine builders and maintenance teams, the correct choice usually comes down to polyurethane, nylon or PTFE tubing. Each material has a defined place in robotic automation. The right option depends on where the tube sits, how it moves and what media or cleaning regime it encounters.

What robotic arm tubing must withstand

Pneumatic tubing on a fixed machine frame sees a very different duty from tubing routed through a robot wrist or external energy package. At the moving end of the system, the tube may bend, twist, accelerate and contact guides or neighbouring lines repeatedly. A material that performs well on a static manifold can be unsuitable on the final axis.

Assess the installation against four practical factors:

  • Dynamic bend radius: The tube needs sufficient flexibility to follow the intended route without flattening, kinking or placing excessive load on fittings.
  • Pressure and flow demand: Smaller tubing can reduce weight and improve routing, but may restrict airflow to grippers, cylinders or vacuum generators.
  • Abrasion and external contact: Cable carriers, clamps, robot dress packs and sharp edges can wear the tube wall over time.
  • Environmental exposure: Heat, cold, oils, washdown chemicals and hygiene requirements can rule out otherwise suitable materials.

Tube routing has as much influence as material selection. Avoid forcing tubing into the shortest possible path if that path creates a tight bend at an elbow fitting or exposes it to repetitive rubbing. Provide controlled slack where the arm changes position, support longer runs and keep the tube clear of pinch points throughout the robot’s working envelope.

Polyurethane: often the best tubing for robotic arms

Polyurethane, commonly referred to as PU, is frequently the first choice for dynamic pneumatic connections on robotic arms. Its key advantage is flexibility. PU tubing can generally accommodate tighter routing than nylon while retaining good resistance to repeated flexing. That makes it well suited to pick-and-place systems, end-of-arm tooling, compact grippers and installations where several air lines must pass through a confined dress pack.

The trade-off is that PU is not automatically the best material for every pressure, temperature or chemical exposure. Higher-pressure circuits, sustained high temperatures and aggressive cleaning media may call for another material. Engineers should also check the manufacturer’s pressure rating at the actual operating temperature rather than treating a nominal room-temperature rating as a universal limit.

For many standard automation duties, PU offers the best balance of flexibility, manageable bend radius and installation convenience. It is particularly useful where tube movement is continuous and the arm’s cable management has limited space.

Use PU tubing when flexibility drives the design

Choose polyurethane where the pneumatic line must travel with the robot and bend regularly through a controlled path. It is a practical option for low-to-medium pressure control air, gripper actuation and vacuum-related pneumatic services, subject to the tube’s stated specification.

Select the outside diameter around the flow requirement and fitting compatibility, not solely the space available. Common sizes from 4 mm to 12 mm OD allow designers to match compact end-effectors with larger supply lines. A smaller tube is easier to route, but excessive pressure drop can slow actuator response and reduce cycle performance.

Nylon tubing for higher pressure and firmer routing

Nylon, or polyamide, is a stronger and more rigid alternative. It is typically selected where pressure capability, mechanical strength and a more stable tube path matter more than minimum bend radius. On a robotic installation, nylon is often better suited to static or lightly moving sections, such as the supply route from the air preparation unit to the robot base, or protected runs with generous bends.

Its relative stiffness is both an advantage and a limitation. Nylon can hold its shape well and resist damage in demanding industrial surroundings, yet it can transmit more force to a push-in fitting when an arm moves. If it is bent below its allowable radius, it can kink or create a persistent set that compromises the route.

Nylon is a sound choice for applications with higher working pressures or where a PU tube would be too soft for the routing arrangement. It should not be selected merely because the tube appears tougher. On an active wrist axis, dynamic flexibility normally has greater value than rigidity.

PTFE tubing for temperature, chemicals and cleanliness

PTFE tube is the specialist option when the process environment is more demanding than ordinary compressed-air duty. It offers excellent chemical resistance, a wide temperature capability and a clean, low-friction surface. These properties make it relevant to pharmaceutical, food-related and laboratory equipment, as well as systems exposed to chemicals or elevated temperatures.

For robotic arms, PTFE is most appropriate when the environment dictates the material. A dispensing robot handling process fluids, or an automated cell with strict cleaning requirements, may justify PTFE even where the routing is more difficult. The material is less flexible than PU, so it needs a larger bend radius and careful support. It is not usually the most economical or convenient answer for a conventional robot gripper air supply.

Where hygienic operation is required, tubing selection must be assessed together with fittings, cleaning methods and the complete wetted or exposed system design. A suitable tube alone does not make an installation hygienic.

Match tube and fitting as one connection system

Robotic movement can expose a poor tube-to-fitting combination quickly. The tube outside diameter must match the fitting exactly, and the tube end must be cut square and free from damage before insertion. An angled or crushed cut can prevent the collet from gripping consistently and may create a slow leak that is difficult to find during commissioning.

Push-in fittings are efficient for robotic pneumatic circuits because they support fast assembly and replacement. However, fitting material and location still matter. Plastic push-in fittings are often suitable for standard automation air lines where weight and compact dimensions are priorities. Stainless steel push-in fittings are more appropriate where corrosion resistance, washdown exposure or a more demanding process environment is involved.

Avoid placing a fitting at the point of greatest flex. If the final connection must sit close to an end-effector, use routing that allows the tube to approach without being repeatedly pulled sideways. A fitting is designed to retain correctly sized tubing, not to act as a pivot for the moving arm.

Design for replacement before failure occurs

Tubing is a service item in dynamic automation. During planned maintenance, inspect high-movement sections for surface abrasion, whitening, flattening, cuts, stiffness changes and witness marks at clamps or guides. Check for leakage with the arm positioned at both extremes of travel, not only in its home position.

If failures recur in the same location, replacing the tube with the same material may only repeat the problem. Review bend radius, guide alignment, clamp pressure and the relative movement between tubing and cable management. A change from nylon to PU may solve a flexing issue, while a move to nylon or PTFE may be necessary where pressure, temperature or chemical exposure is the actual cause.

For trade buyers, holding compatible tubing and push-in fittings in the required sizes reduces downtime when a line needs replacing. Nexo Air supplies pneumatic tubing and fittings for industrial applications, with material selection based on operating conditions rather than a one-material approach.

The most effective specification is the one that treats tubing as part of the robot’s motion system. Start with the route and movement, confirm pressure and environment, then select the material and outside diameter that can maintain that performance over the required service life.