Cable drag chain selection is driven by five numeric gates, not by brand: inner cross-section, bend radius, travel length, travel speed, and ambient temperature, with frame material chosen last to fit the duty [S5]. A drag chain (also called an energy chain or cable carrier) is the articulated guide that keeps power, signal, and pneumatic lines alive on a moving axis, and getting its size wrong kills cables faster than any other single mistake on a CNC, robot, or gantry build [S9].
Reference ranges published for industrial drag chain frames sit at 15-100 mm inner height, 10-500 mm inner width, 18-500 mm bend radius, 0.5-10 m/s travel speed, -40 to 85 °C operating temperature, 5-50 kg/m load capacity, and 0.5-15 kg/m weight per meter, with IP40-IP65 sealing and UL 94 V0-V2 flammability on premium bodies [S5]. The job below is to map those numbers to your axis, not to memorise them.
Five Numeric Gates That Decide the Model
Inner cross-section is the first gate: the chain's inner height must clear the tallest cable or hose in the bundle with at least 10% free space, and the inner width must fit the bundle diameter plus 10-15% fill margin, since overstuffing is the single most common cause of jacket abrasion inside a drag chain cable carrier [S5]. Stock plastic-chain inner widths run from 10 mm up to 300 mm on adjustable frames, with custom widths available beyond that on steel and aluminium bodies [S4].
Bend radius is the second gate and is fixed by cable physics: the chain's bend radius should be roughly 10x the outer diameter of the thickest cable in the bundle, and small-radius chains are paired with short travel, while large-radius chains are mandatory on long-travel steel frames [S3]. Published TLG steel-chain radii span 50-600 mm across the five frame sizes TLG10 through TLG50, with corresponding chain heights of 50-150 mm and a maximum travel of 32 m on the largest frame [S3].
Travel length, speed, and acceleration form the third, fourth, and fifth gates. Travel length sets whether a self-supporting plastic chain is even possible: unsupported plastic runs typically top out around 6-8 m before sag becomes a problem, while steel TLG frames carry up to 32 m without intermediate support [S3]. Travel speed on standard engineering-plastic bodies sits in the 0.5-10 m/s band typical of CNC axes and small gantries, and acceleration above 10 m/s² pushes the design toward reinforced or steel-link chains [S5].
Frame Material: Plastic, Steel, or Stainless/Aluminium
Engineering plastic (PA66 nylon, POM, PP) is the default for indoor CNC, 3D-printer, and small-robot axes, with operating temperature -40 to 85 °C and the widest published IP and UL 94 options [S4][S5]. Nylon/polyamide and reinforced-PP bodies cover roughly 80% of factory-automation cells because they are quiet, light (often 0.5-3 kg/m), and inexpensive to replace [S4]. They are not, however, the right pick for outdoor, washdown, or long-travel heavy-load duty, where UV, hot coolant, and unsupported sag each push the design off plastic.
Steel drag chains (the TLG family being a typical example) are specified when unsupported travel exceeds roughly 6-8 m, when the bundle weight per metre is high, or when the cell contains hot chips or weld spatter that would destroy a plastic frame [S3]. TLG pitch ranges from 50 mm on the TLG10 up to 175 mm on the TLG50, and the supporting plate can be cut to customer width up to 1200 mm on the aluminium-alloy "Sliver Star" enclosed version [S3]. Stainless steel and aluminium-alloy bodies are the third tier, used for washdown food plants, outdoor crane power feeds, and corrosive chemical cells where PA66 would swell or stress-crack [S8].
For a direct material comparison on a buyer-relevant axis: engineering plastic (PA66) runs roughly -40 to 85 °C, 0.5-10 m/s, IP40-IP65, 5-50 kg/m load, and the lowest cost per metre; steel (TLG-class) handles the same -40 to 85 °C envelope, longer travel up to 32 m, higher mass per metre, and roughly 3-5x the cost of plastic; stainless/aluminium sits at the high end for corrosion resistance and supports up to 5 million reciprocating motions under standard load, well above the typical plastic life of 1-3 million cycles [S5][S8]. Always confirm the IP and UL 94 rating per IEC 60529 and UL 94 on the specific model datasheet, since ratings vary by frame size even within one product line [S5].
Open, Bridge, or Closed Type: Picking the Geometry
Openable (or "open-type") chains are the workhorse: cross-bars swing open so cables can be laid in or swapped without threading the entire bundle through the end, and they dominate CNC and general-automation cells [S4][S6]. Bridge-type chains carry cables on top of a series of bridges and are used where chips and coolant would otherwise pool inside a closed channel, common in machine-tool chip pans [S4]. Fully enclosed chains (the TLG "Sliver Star" aluminium board is a typical example) protect against hot chips, weld spatter, and heavy oil exposure, and are the right pick for harsh cells where open chains would collect debris [S3].
Stock inner sizes for entry-level plastic chains cluster around 18 mm inner height with 18-50 mm inner width, and stock carrier lengths are sold in 1 m increments from 1 m up to 10 m, with per-metre price stepping at 1/2/3/4/5/6/7 m on common e-commerce lines [S6]. That 18x-series is fine for a 6 mm sensor cable bundle or a small stepper-motor pigtail, but it is the wrong starting point for a servo-power + encoder + brake triplet, which typically needs a 35-50 mm inner height and a 75-100 mm bend radius [S3][S6].
Cable and Hose Pairing Rules
Drag chain-compatible cables are not the same as standard PVC flexible cable: they use stranded conductors, low-friction jacket compounds, and short lay-length shielding so the bundle survives millions of bend cycles without failing [S1]. Pairing stiff, low-flex cables with a tight-radius chain is the most common field failure mode, since the cable, not the chain, dictates the minimum bend radius [S3]. When in doubt, size the chain to the thickest, stiffest member of the bundle and route the rest around it [S5].
Fill ratio inside the chain should be kept at roughly 50-60% of the inner cross-section to allow the bundle to reposition as the chain bends; above 70% fill, jackets scuff and energy-chain life drops sharply [S5]. For background on the difference between an energy chain and a conveyor chain, the function is similar (articulated links guiding something) but the duty is not: an energy chain is built for low speed, high cycle count, and tight bend radius, while a conveyor chain is built for high load, low cycle count, and large pitch [S3][S9].
Who Should NOT Pick the Cheapest Plastic Chain
Long-travel unsupported runs over roughly 6-8 m, outdoor installations with direct UV, washdown food cells, and any axis with ambient temperature above 85 °C or below -40 °C should skip the entry-level PA66 chain and step up to steel, aluminium, or stainless [S3][S5][S8]. High-speed axes above 10 m/s, or axes with high acceleration (above roughly 10 m/s²), also need reinforced or steel-link chains because plastic links can crack at the pivot pin under repeated shock load [S5]. Cells with continuous chip or weld-spatter exposure need an enclosed "Sliver Star" or equivalent aluminium cover, since open plastic chains collect debris and jam within months in those conditions [S3].
If the application is a stationary cable run with no motion, a drag chain is the wrong product entirely: use a roller chain energy guide, a cable tray, or a flexible cable carrier specifically rated for static duty, since adding a moving-part chain to a fixed run adds cost, weight, and a wear item for no benefit [S9]. For process plants that do need guided cable on long, slow-travel valves or dampers, pairing the chain with a properly specified cable gland at each transition is critical: a cable gland sizing guide walks through the IP and thread logic that keeps the transition sealed [S5].
Sourcing Signals and Standards to Verify
Confirm the IP rating per IEC 60529 and the flammability rating per UL 94 on the specific model datasheet, not on the catalogue cover, since both vary by frame size and by whether the chain is sold open or with a closed aluminium board [S5]. For the underlying cable, look for chain-rated jacket compounds and a published minimum bend radius that the chain's geometry can honour; drag-chain-rated cable typically lists 5-10x OD as the static minimum and roughly 10-15x OD as the dynamic, drag-chain minimum [S1]. For long-travel steel chains, verify the unsupported length rating at your actual fill weight, not at the catalogue's empty-chain weight, since adding 20-30 kg/m of cable and hose can cut the allowable unsupported travel by half [S3][S5].
Trackable next signals for a buyer shortlist: (1) request the model's published max unsupported travel at your actual fill weight, not the empty-chain figure; (2) confirm IEC 60529 IP code and UL 94 class on the specific frame size, not the product family; (3) for harsh cells, request the enclosed-cover option (TLG "Sliver Star" or equivalent) and the stainless/aluminium material variant up front, since retrofitting an enclosed cover is rarely as clean as ordering it initially [S3][S5][S8].