A Guide to Gland Selection for Flexible and Robotic Cables

For a flexible or robotic cable, I would first decide where its motion stops before the enclosure. A carrier, robot dress pack or guide controls the moving route. The gland normally belongs at a stationary boundary, with supported cable between the last moving point and its seal. If bending or twisting reaches the gland, request the supplier’s declaration and qualification for that particular moving arrangement.

Key takeaways

• “Flexible,” “continuous-flex,” and “torsion-rated” are different cable duties. Record the actual movement instead of selecting by a broad cable label.
• Treat routing, bend control, axial retention, ingress sealing, shield termination, and enclosure bonding as separate functions.
• Match the cable’s complete outside-diameter range and jacket surface to the gland’s declared cable range; do not size from nominal OD alone.
• A static IP result does not establish protection while the cable is moving. Request the test specimen, motion profile, supports, conditioning, and acceptance criteria.
• Reject a universal flex-cycle promise. Service life belongs to a named cable, gland, support geometry, motion program, environment, and inspection rule.

Build the shortlist from the machine’s cable schedule, the cable maker’s dynamic limits and the machine builder’s risk assessment. I would fix the motion boundary before choosing a spiral or bend-protection tail. Then compare its permitted deflection and torsion with the route it will actually support.

Gland selection for flexible and robotic cables starts at the motion boundary

Motion boundary is the location where intended cable movement stops before the cable enters a stationary enclosure. The boundary may include a carrier end bracket, robot dress-pack anchor, strain-relief clamp, guided service loop, or connector interface. A gland installed downstream of that point can then perform its declared sealing and retention duties without being asked to steer every machine cycle.

Sketch the route from the moving axis to the enclosure. I would mark the last bend, last twisting section, first fixed support and gland centerline. Mark the quiet length too: the section that should stay still before the entry. Include connectors, exposed shields, conduit, hoses and bundle separators that change cable stiffness. A tidy gland detail cannot prevent side load imposed by the upstream route.

IEC 60204-1:2016 applies to electrical equipment of machines and includes documentation, protective-bonding, and EMC requirements within its scope. Use the applicable machine standard and risk assessment to govern the complete electrical installation. Do not present a gland selection as approval of a robot cell or safety function.

Classify what reaches the entry:

I would classify the movement before ordering a “robotic gland.” That label does not tell you whether the entry sees bending, torsion, axial travel, vibration or no intended movement.

How the cable’s motion changes gland selection

Wrist, base, tool and cabinet cables can experience different bending, twisting and exposure. Their routing and connections need to suit those particular movements. A single “robotic cable” description can hide the conditions that make one gland arrangement suitable and another unsuitable.

The following inputs describe the movement the entry needs to accommodate:

Cable suppliers often publish different bend-radius values for fixed and moving use. The igus cable bending-radius data is a manufacturer-specific example that directs users to the applicable radius in the cable’s technical data. It does not set values for another maker’s cable; use the current datasheet and stated motion class for the exact cable.

Calculate the routing envelope from the cable maker’s limit

Use the cable maker’s bend limit to lay out the route. Select the limit for fixed use, occasional movement, continuous flex or torsion and use the verified cable OD. I would check the actual cable centerline through every machine position. Include installation tolerance, how the bundle moves and bracket movement. The gland cannot supply a different cable bend limit.

ToolCable dimensionsCable Bend Radius CalculatorCalculate the preliminary minimum cable bend radius from the verified cable OD and manufacturer-supplied bend factor.Rmin = F × OD; Dbend = 2 × RminCable outside diameterSpecified bend factorStraight allowance after entryOpen calculator ->

The calculator provides a preliminary geometric value. It cannot choose the correct bend factor, account for torsion, predict fatigue life, or approve a cable carrier. If the cable data provides a finished radius directly, use that value. If the cable has different limits by temperature, travel, speed, or installation type, keep those conditions with the calculation.

An undersized bend radius can transfer side load to the seal. I would check both travel endpoints as well as the tightest visible curve. A cable can meet the radius at mid-stroke but become taut at one end, buckle at the other or twist when the robot changes position.

Separate the six functions at the cable entry

Assign each job to the component intended to perform it. This is functional allocation. A robotic entry often needs several parts. I would identify which one guides motion, controls bending, holds axial load, seals the enclosure and provides each electrical connection. Calling them all a “strain-relief gland” can hide the location of a failure.

1. Motion guidance keeps the cable on its permitted path through the moving zone.
2. Bend control prevents a local kink or radius below the cable limit.
3. Axial support and retention prevents cable mass, pull, or acceleration from loading the termination.
4. Ingress sealing closes the cable-to-seal and gland-to-enclosure paths.
5. Shield termination connects the specified screen or braid to the intended conductive interface.
6. Protective bonding maintains the protective-current path required by the installation design.

One part may perform more than one function, but only within its documented scope. IEC 62444:2010 covers construction and performance requirements and tests for complete cable glands. Use the exact gland classification, cable range, assembly, and instructions. A long flexible tail, a metal body, or a compression nut does not by appearance establish the performance of the complete moving route.

Shortlist the entry architecture, then apply rejection rules

I would choose the entry arrangement from the movement at that location. The accessory name matters less than its permitted duty. Use this shortlist to ask suppliers specific questions:

A bend-protection tail may spread a local deflection, but it does not automatically accommodate twisting. A swivel may rotate for installation and then have to remain fixed in service. I would read the drawing and instructions for the permitted actions: tighten, lock, fixed, rotating or continuous. Record the allowed duty explicitly.

Match the cable, seal, and retention ranges independently

Cable range is the complete jacket-diameter interval accepted by the identified gland configuration. Compare it with measured minimum and maximum cable OD, not only a catalog nominal. Include ovality, jacket seams, molded markings, braid exposure, and any tolerance affected by temperature or lot variation.

Use three separate checks:

• Seal fit: the compression element contacts the permitted jacket surface throughout the cable interval.
• Retention fit: the clamping mechanism engages the cable construction without crushing a soft jacket or relying on a moving surface.
• Tail or support fit: any bend-protection feature and external clamp accept the cable OD and stiffness without creating a pressure point.

Use the clamping-range checks to compare the complete cable OD interval with the gland’s complete range. For dynamic cable, I would also check relevant jacket changes from flexing, temperature, liquids and clamp pressure. Near either limit, test a representative assembly on the intended route. Nominal overlap alone cannot establish that fit.

Do not ask the gland to replace cable support. The seal-and-strain-relief guide separates ingress protection, pull resistance, and external support. If a cable carrier or robot dress pack needs its own anchor, specify that anchor as a separate bill-of-material item with a defined position.

Keep shield termination outside the moving bend

Shielded robotic cable adds another vulnerable transition. The outer jacket may be removed, braid opened, foil cut back, or drain conductor routed at the gland. That prepared region no longer has the original cable construction, so repeated bending or torsion there can change contact, damage shielding, or load inner components.

I would place the shield contact in the stationary section. Record preparation length, braid or foil treatment, contact diameter and mechanism, any required coating removal, enclosure bonding surface and tools. Keep signal shielding and protective bonding as separate design decisions. One cannot be inferred from the other.

Evaluate a named termination electrically with EMC transfer-impedance testing. For a robotic route, the test specimen should also preserve the intended mechanical boundary. A good bench result from a straight, untouched cable does not describe a contact that bends at every wrist motion.

The igus discussion of robot-cable construction is a maker-specific example showing that shield and internal construction are designed around torsional movement. It does not show that a generic gland can accept that movement. Obtain compatibility and preparation data for the exact cable and exact termination.

Evaluate jacket, seal, and environment as one interface

Material abbreviations do not settle compatibility. PUR, TPE, PVC, silicone, EPDM, NBR, and FKM are families containing different formulations. Jacket surface finish, additives, plasticizers, cure, hardness, compression, fluid exposure, cleaning, temperature, and time can change friction or deformation at the seal and support.

ASTM D471 provides comparative procedures for evaluating the effect of liquids on rubber and rubber-like compositions. ASTM D573 addresses deterioration of vulcanized rubber in an air oven. These methods can help screen named compounds under stated conditions, but a coupon result is not a completed gland result. The installed interface also includes cable jacket, molded seal geometry, compression, body restraint, and the real exposure sequence.

Request the exact seal compound or governing material specification, cable-jacket designation, declared temperature range, fluid compatibility basis, permitted lubricant, storage limits, and change-notification rule. For hot or cold duty, record the temperatures at the actual cable entry and compare every supplied component on the same basis using the operating-temperature sealing checks.

Record vibration separately from intended cable travel. IEC 60068-2-6:2007 provides sinusoidal-vibration testing at specified severities. IEC 60068-2-14:2023 provides temperature-change tests. Neither defines a universal robot-cable program.

I would specify specimen mounting, severity, duration, operating state, sequence and acceptance for the actual route. When vibration is the main load, use the thread-security and external-support checks for that duty.

Read IP claims as configuration-specific results

An IP code describes a degree of enclosure protection under defined conditions. IEC 60529 classifies degrees of protection provided by enclosures. It does not turn a loose gland, elastomer name, or cable tail into a moving seal declaration.

Ask for the exact configuration behind the IP statement:

• gland part number and revision;
• cable type, jacket, minimum and maximum tested diameter;
• thread or clearance-hole mounting, wall thickness, locknut, face seal, and enclosure material;
• orientation, tightening settings, and installation instructions;
• dust or water method, severity, duration, conditioning, and acceptance;
• whether the cable was stationary or moving during exposure;
• movement before, during, and after the ingress test;
• inspection and retest criteria after the motion sequence.

If the cable stayed still during the IP test, describe the result as static. For protection during movement, I would ask for the dynamic test setup and permitted movement range. Do not extend one tested diameter or straight orientation to every cable and position in the gland range.

Qualify the complete route, not an isolated gland

Dynamic route qualification tests the assembly you intend to use. Include the cable, guide, support, gland, enclosure connection, motion program, exposure and acceptance criteria. I would look beyond a headline such as “passed one million cycles.” The result needs to show which tested specimen and application conditions that count represents.

A useful cycle result must state the test system, travel, speed, acceleration, bend conditions, cable construction, and support geometry. Without those conditions, buyers cannot compare cycle counts across routes or use them to schedule replacement.

Build a qualification matrix around difficult allowed configurations:

Choose a test sequence that reveals interactions. Liquid or temperature conditioning may change jacket friction before motion. Movement may damage prepared shielding before an ingress test. A pull or vibration step may loosen the panel joint. I would keep failed specimens and identify the failed connection rather than assign every outcome to “the gland.”

Prove bend, torsion, side load, and connector motion on the complete route

Commissioning connects the qualified setup and issued route drawing to the real machine. Isolate hazardous energy and follow the robot or machine safety procedure before entering the work area. The OSHA technical manual chapter on robot system safety emphasizes application-specific safety knowledge for operation and maintenance; it does not replace the applicable regulations or the machine builder’s instructions.

Before energizing, confirm cable identity and OD, gland and seal identity, enclosure interface, support positions, cable preparation, permitted lubricant, tightening values, thread engagement, locknut or face seal, and visible jacket condition. Mark the cable and supports with non-damaging reference marks where permitted so unintended slip can be detected.

Run the approved machine program at the prescribed commissioning conditions. Observe the route from safe positions or approved monitoring tools. Check every endpoint and transitional pose for:

• bend radius below the cable limit;
• cable tension, buckling, whipping, rubbing, or bundle crossover;
• rotation migrating into the quiet length or gland;
• side load at the compression seal or shield contact;
• clamp slip, tail collapse, enclosure deflection, or loosening;
• connector or tooling loads transferred into the cable entry.

After the run, inspect the cable jacket, support, gland tail, seal, shield interface, mounting joint, and reference marks. Perform the specified electrical, retention, or ingress verification. Changes to the route or motion program can change those results, so use the tested arrangement when judging a replacement.

Recheck the route when motion, cable, or support changes

I would set inspection intervals from the machine risk assessment, component instructions, actual duty, access, failure consequence and qualification record. There is no monthly interval or fixed replacement cycle suitable for all robotic glands.

Trend observable conditions: movement at the fixed support, cable slip, polish or abrasion, jacket cracking, exposed braid, tail deformation, loose hardware, seal extrusion, corrosion, contamination, panel distortion, and changes in electrical monitoring. Relate findings to operating hours, machine cycles, program changes, collisions, maintenance events, cleaning, and temperature excursions.

Open a change review when any of these changes:

• robot path, speed, acceleration, travel, tool, or payload;
• cable maker, type, OD range, jacket, shield, connector, or bundle arrangement;
• carrier, dress pack, guide, clamp, bracket, quiet length, or gland position;
• gland body, seal, tail, locknut, face seal, thread, coating, or instruction revision;
• enclosure wall, cutout, bonding surface, environment, cleaning method, or acceptance test.

Identify the calculations, drawings, test cases, commissioning checks and spares affected by a change. I would not assume a replacement is equivalent because its nominal OD matches. Flex class, stiffness, torsion limit, jacket and screen construction can change the route’s behavior.

Conclusion

My recommendation is to start with the moving route. Define bending, torsion, stroke, vibration, exposure and electrical functions. Set a fixed support where movement should end and keep a quiet length before the gland. Give sealing, retention, shielding and bonding their own documented connections.

I would shortlist only arrangements whose cable range, mounting, materials and permitted movement fit that route. Then qualify the cable, support, gland, enclosure, motion program and exposure sequence together. A static IP code, long tail or unexplained cycle count cannot replace that record. Reassess the affected functions when the route or parts change, because movement may then reach an interface that was previously stationary.

FAQs about glands for flexible and robotic cables

Can a standard cable gland be used with a continuous-flex cable?

Yes, when the gland is placed downstream of a support that stops intended movement and the cable, gland range, retention, sealing, environment, and mounting all match. The cable may be continuous-flex rated upstream while its gland termination remains stationary. Validate the complete route so bend, torsion, and pull do not reach the seal.

Does a flexible gland tail make an entry suitable for robot motion?

Not by itself. A tail can spread a local bend or protect against limited deflection, but its permitted movement, cable range, bend direction, torsion capability, environmental limits, and test conditions must be stated for the exact assembly. Keep a separate motion guide and support unless the documented design assigns those functions to the tail.

How do I calculate the minimum bend radius near the gland?

Use the cable manufacturer’s limit for the actual installation class and the verified cable OD. The calculator above can convert a manufacturer-supplied bend factor into a preliminary radius, but the final route must also account for tolerance, every machine pose, cable bundling, supports, temperature, travel, and torsion. The gland does not override the cable limit.

Does an IP68 gland stay IP68 while the robotic cable moves?

Only when the exact moving configuration has a supporting test or declaration that covers that duty. Obtain the cable, diameter, mounting, supports, motion program, conditioning, ingress method, and acceptance criteria. A static test should be represented as static and cannot be extrapolated to bending or torsion at the seal.

What information should be sent with an RFQ for a robotic cable entry?

Send the cable identity and full OD range, motion class, route drawing, bend radius, travel, speed, acceleration, torsion, supports, loads, environment, enclosure interface, shield and bonding requirements, acceptance tests, service plan, and expected changes. Ask for complete part numbers, drawings, instructions, configuration-specific test data, exclusions, and change notification.

Sources and technical references

• IEC 62444:2010, Cable glands for electrical installations, accessed 2026-09-12.
• IEC 60529 consolidated version, Degrees of protection provided by enclosures, accessed 2026-09-12.
• IEC 60204-1:2016, Safety of machinery—Electrical equipment of machines, accessed 2026-09-12.
• IEC 60068-2-6:2007, Environmental testing—Sinusoidal vibration, accessed 2026-09-12.
• IEC 60068-2-14:2023, Environmental testing—Change of temperature, accessed 2026-09-12.
• ASTM D471, Standard Test Method for Rubber Property—Effect of Liquids, accessed 2026-09-12.
• ASTM D573, Standard Test Method for Rubber—Deterioration in an Air Oven, accessed 2026-09-12.
• igus, Cable bending radius for dynamic applications, accessed 2026-09-12.
• igus, What to look for when specifying a robot cable, accessed 2026-09-12.
• OSHA Technical Manual, Industrial robot systems and industrial robot system safety, accessed 2026-09-12.

Products

• Cable Glands