Choosing a Drag Chain Cable - Which One Fits Your Axis?
A drag chain cable carries power, signals or data across moving axes and must survive millions of flex cycles. This guide shows how to select one by bending radius, torsion and travel speed, and which conductor design fits.
View drag chain cablesWhat sets a drag chain cable apart from rigid cable?
A drag chain cable is built for continuous motion inside an energy chain. Instead of simple layered stranding, the fine wires are bundled in short lay lengths around a tension-proof core so they slide when bent rather than stretch.
The jacket is abrasion resistant, usually PUR (polyurethane) or TPE, so it does not stick in the chain or drag the motion. Fine-wire conductors of class 5 or 6 per IEC 60228 make the core flex fatigue resistant.
- Short lay length (bundle stranding) instead of layered stranding.
- Strain relief through a centre core or aramid braid.
- Abrasion resistant, low-friction PUR or TPE outer jacket.
- An inner jacket (gusset fill) keeps the round cross section stable.
How do I choose by bending radius, torsion and speed?
Three loads drive the choice: the bending radius of the chain, whether the axis twists (robot) and how fast and how often it travels. The key figure is the permissible bending radius, given as a multiple of the outer diameter d.
For purely linear motion a flex-rated cable with the right radius is enough. As soon as the axis is twisted - on a robot arm or a rotary index axis - you need an explicitly torsion-rated cable with a stated twist angle per metre, otherwise the conductors break from the inside.
How do you route drag chain cables correctly?
Even the best cable fails early if it sits under tension in the chain. Lay the cores free of tension and twist, and separate thin from thick cables with dividers so they do not chafe through each other.
- Never tie cables together with zip ties - they must move freely.
- Fit strain relief at one or both ends of the chain.
- Route large and small diameters separated by dividers.
- Keep chamber fill below 80 percent.
- Before the first run, check no core sits below its bending radius.
Frequently asked questions
How do I read the minimum bending radius?
It is given in the datasheet as a multiple of the outer diameter d, for example 7.5 x d. On a 15 mm cable that is about 112 mm radius. Always use the moving value, not the fixed one.
When do I need a torsion-rated cable?
Whenever the axis twists, so on robot arms, turntables or swivel axes. A plain flex cable breaks from the inside there. Torsion cables are specified with a twist angle such as ±180°/m.
PUR or PVC jacket?
PUR is abrasion resistant, oil and cold resistant and the first choice for fast, long travel runs. PVC is cheaper but less flex durable and turns brittle in the cold - only for slow, short moves.
Can I bundle several cables together?
No. Inside the chain the cores must move freely relative to each other. Zip ties create tension points where the cable breaks. Use dividers instead of bundling.
Looking for the right drag chain cable?
We supply flex- and torsion-rated cables with PUR or TPE jackets for every axis - matched to bending radius and travel speed.
Million-cycle tested
Cables with a documented cycle count in the energy chain.
Oil and abrasion resistant
PUR jacket for harsh industrial environments.
Correctly sized
Bending radius and torsion matched to the axis.
Expert advice
We help with selection and chain fill.