Flexible and controlled cabling and connections

Dynamic requirements — acceleration, speed, etc. – have increased and created more mechanical stress and electromagnetic interference (EMI) on cable designs. Helukabel’s HELUKAT PROFINET Type R Torsion industrial Ethernet cable is rated Category 5e and has been tested to withstand more than five million torsion cycles under loads of ±180°/m, and more than five million flexing cycles in a drag chain at acceleration rates of two Gs (20 m/s 2 ) and a maximum speed of 11 mph (300 m/min).

Electrical cabling is often overlooked in motion control systemdesign. If you use something other than industrial cabling — which isdesigned to flex continuously — premature failures can result.

Continuous-flex cables are designed to cope with the tight bending radii and physical stress associated with motion control applications. A regular cable typically manages 50,000 cycles, but a flexible cable can complete between one and three million cycles.

Flexible cables can be divided into two types: those with conductors stranded in layers inside the cable, and those that have bundled or braided conductors.

Cables with stranded layers are easier to produce, and usually less expensive. The cable cores are stranded firmly and left relatively long in several layers around the center and are enclosed in an extruded tube-shaped jacket. However, this design can lead to core rupture.

Bundled designs feature braided conductors that surround a tension-proof center. A pressure filled outer jacket ensures the cores cannot twist, so these cables are often stiffer than standard cables, but last longer in constant flex applications.

Flat cables can incorporate power, signal, and video conductors as well as air or liquid tubing and fiber optics in a single compact cable suitable for continuous flexing.

Flat cables with silicone jacketing resist abrasion and other harsh environmental impacts and will even self-heal minor nicks.

To select the right cables, determine the application type, such as whether it will be stationary or moving, and what type of movement it is—flexing, torsion, or both?

If there is bending or motion involved, the bend radius must be specified. The bend radius depends on the wire gauge and kind of conductors used. With continuous flexing, conductors containing multiple strands of fine-gauge wire generally last the longest.

One-cable technology, like igus' encoder cable integrated into servo cable, combined with ready chain energy chains from igus met the high-speed demands of wood processing machinery.

MAKING THE CONNECTION

Most cable assemblies use some type of interconnect device to transmit the signals from the cable to the motor or drive. Commonly used connectors include M12 and M8 connectors, which are circular connectors with a 12- or 8-mm locking thread used for sensors, actuators, Fieldbus and industrial Ethernet, primarily in factory automation applications. Often with ratings of IP65, IP68 and IP69K, they are ideal for washdown and corrosive environments.

High-speed, miniature connectors are growing in use in industrial automation, where signal density, electrical performance, and mechanical dependability in smaller package sizes are critical for efficient, compact and accurate machines. Modular connectors, micro connectors, heavy-duty connectors with locking systems, and more are used to provide constant, reliable connectivity for high-vibration environments.

Where rotating motion is present, slip rings should be used. These electromechanical connectors transmit electrical signals, power and data from a stationary structure to a rotating machine.

Cable glands are critical when terminating cables in hazardous or harsh environments, where ingress protection, sealing and grounding is necessary to safely pass a cable, wire or tube through an enclosure. They provide strain relief and contain electrical sparks or flames that may occur in hazardous environments. Lapp’s Hygienic and INOX series cable gland series feature stainless steel construction and smooth, edge-free surfaces that prevent fluids from accumulating which can otherwise cause microorganisms to gather.

ELIMINATE CABLE ENTANGLEMENT

Cable management is also critical. A simple, low-cost form of cable management uses twist-tie type bundlers that tie together groups of wires and cables. However, bundling them together may pose weight problems that cause sagging and put undue strain on the cables.

For stationary applications, cable trays safely and cleanly route cables. They are made of an U-shaped open channel into which cables can safely lay. They can be open or closed for protection against contaminants. When selecting a cable tray, consider what type of cable is to be routed, including its diameter and weight, the span between supports, the distance of the cable run, and environmental conditions.

Cable carriers can house a large volume of cables and wires and support their weight all without sagging or putting stress on the cabling. They can be made of plastic, steel, or a metal alloy in open or closed designs.

Knowing length of travel, number of cables or hoses, size and weight of the cables, required speed and acceleration and environmental factors such as exposure to any debris, excessive heat or chemicals is critical to selection. A key specification factor is knowing the carrier’s bend radius, factor is knowing the carrier’s bend radius, which is measured from the center of the curve loop to the center of the pivot pin on the side link. A larger bend radius means less stress on the cable and a longer service life.

SEALED AND GROUNDED TERMINATIONS

Cable glands are critical when terminating cables in harsh environments, where ingress protection, sealing and grounding is necessary to safely pass a cable, wire or tube through an enclosure. They provide strain relief and contain electrical sparks or flames that may occur in hazardous environments. Additionally, they act as a seal, preventing outside contaminants from causing damage to the cable and electrical system, such as dust, dirt, and fluids. They also prevent cables from twisting and being pulled out of the machine.