Instructions for Using Fully Enclosed Engineering Plastic Energy Chains

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  How fully enclosed engineering plastic energy chains are built
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  Bend radius, travel length and fill weight for enclosed chains
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  Installing cables inside a closed carrier
• 4
  Where fully enclosed plastic energy chains fail first
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  Step-by-step setup for a closed chain axis
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  Enclosed chain compared with open chain and steel carrier

A closed energy chain is a string of molded links pinned end to end. Each link carries a hinged cover that snaps shut after the cable is laid in the channel. When the chain bends, the covers on the outside of the arc separate slightly; on the inside they close against each other. That movement is what stops chips, mist and fine dust from reaching the cable jacket.

The links are usually glass-filled PA or POM, sometimes PEEK for high-temperature axes. Glass-filled PA gives the stiffness a long unsupported span needs. POM slides better against itself, so it runs quieter at high speed but creeps under sustained load. The pin and the bore are the wear pair, and their clearance sets how much the chain droops on a horizontal run.

Inside the channel there are dividers. You set the number of chambers to match cable count, and the divider height to match cable diameter. A cable that can move 2–3 mm sideways in its chamber will rub against the wall for the whole life of the machine. That rub, not the hinge, is what usually ends the chain's service life.

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  Link pitchShorter pitch follows a tight radius; longer pitch carries more weight per link.
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  Cover typeSnap-on covers open for cable replacement without breaking the chain.
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  DividersSet chamber count and height to the actual cable bundle, not to the nominal size.

Radius is the first number to fix. The rule of thumb is 7.5 × the cable outer diameter for a flexible control cable, and 10 × for a stiff power or fiber cable. If the chain bends tighter than that, the conductors inside the cable work-harden and crack before the jacket shows any damage. Measure the stiffest cable in the bundle and size the whole chain to it.

Travel length then sets the chain length. For a gliding arrangement on a long axis, chain length is roughly half the travel plus the bend arc plus a safety margin at each end. For a short unsupported run, the chain must be stiff enough that it does not sag into itself on the return. A sagging chain slaps the lower run and the covers crack at the hinge line.

Fill weight is the number people skip. Every chain has a maximum unsupported load per meter. Add the cable weight, the divider weight and any hose filled with coolant. A chain loaded past about 80% of its rated fill will droop, wear the pins fast and start to twist on the return stroke. Leave headroom for the next cable you add.

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  Minimum radius7.5 × cable OD for flexible cable, 10 × for stiff cable.
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  Fill limitKeep total fill under roughly 80% of the rated load.
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  Chain lengthAbout half of travel plus bend arc plus end margin on gliding runs.

Lay the heaviest and stiffest cable in the outer chamber. That cable has the largest bend radius, so it should sit where the arc is widest. Fill the inner chambers with the flexible signal and sensor cables. Never stack two cables on top of each other in one chamber; the upper one will press the lower one into the divider and wear the jacket.

Leave a small amount of slack, about 1% of the chain length, so the cable is not under tension when the chain is straight. Too much slack is worse than none: the cable loops, rubs the cover and eventually wears through. Anchor both ends of the cable at the fixed point and at the moving carriage, not just at one end.

Separate power and signal cables into different chambers. A servo cable carrying a fast-switching current will induce noise into an unshielded encoder cable that shares a chamber. If the layout forces them into the same chamber, keep at least 20 mm of separation and ground the shield at the drive end only.

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  One cable per chamberNo stacking. Stacked cables wear on each other.
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  SlackAbout 1% of chain length, anchored at both ends.
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  Power vs signalDifferent chambers, 20 mm apart, shield grounded at one end.

The hinge pin is the classic wear point, but it is rarely the first to go. In most field failures the cover latch breaks before the pin wears out. The latch takes the load every time the chain passes through the bend arc on a high-cycle axis. Once a latch fails, the cover lifts, chips enter, and the cable jacket is cut within days.

Cable fatigue is the next one. A cable that is too stiff for the radius breaks its conductors in the middle of the arc, and the jacket still looks intact. You only find out when the axis loses an encoder signal at a certain position. If a machine faults at the same coordinate every time, suspect the cable before the drive.

Chemical attack is common on wet machining centers. Coolant mist, tramp oil and fine swarf collect on the covers. Most glass-filled PA grades handle mineral coolant well. Strong alkaline cleaners and some synthetic coolants will soften the surface and let swarf embed. Wipe the chain at each service interval rather than washing it with a solvent.

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  Latch breakageCover lifts, chips enter, cable jacket is cut soon after.
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  Conductor fatigueFault at a repeatable position points to the cable, not the drive.
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  Chemical softeningWipe with a cloth. Avoid solvent washes on glass-filled PA.