MOTION SYSTEMS HANDBOOK
Flexible and controlled
cabling and connections
Electrical cabling is often overlooked in motion control system design. If you use something other than industrial cabling — which is designed 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.
One-cable technology, like igus’ encoder cable integrated into servo cable, combined with readychain energy chains from igus met the highspeed demands of wood processing machinenery.
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.
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,
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/s2) and a maximum speed of 11 mph (300 m/min). 44
DESIGN WORLD — MOTION
Cables & Connectivity — Motion Control HB 08-19 Vs5.indd 44
8 • 2019
motioncontroltips.com | designworldonline.com
8/21/19 11:20 AM
