TechTalk Design Advice: The-less-is-more-approach-to-robotic-cable-management


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Managing cables and hoses may seem simple, but in reality it is an important part to of any well-functioning robot.

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TechTalk Design Advice: The-less-is-more-approach-to-robotic-cable-management

  1. 1. TECHTALK DESIGNADVICE SERIES YOUR CONTACTTHE LESS IS MORE APPROACH TOROBOTIC CABLE MANAGEMENT Cable management has come into the limelight more and more because machine reliability has Don Nester increased dramatically in recent Product manager, Chainflex® years, even though robots have continuous-flex cables grown more complex. However, the methods used to attach and guide cables have not quite followed suit. Since the >> Subscribe to e-newsletter 1960s, cable management on >> Contacts in your location robots hasn’t changed significantly (on-site within 24-48 hours)and, in fact, is often overlooked altogether. Managing cables and hoses >> Request catalogs / freemay seem simple, but in reality it is an important part to of any well- samplesfunctioning robot. >> myigusMost experts agree one of the top blunders designers make isunderestimating cable-management issues. For instance, during a >> myCatalogconference hosted by the Robotic Industries Association (RIA), a groupof leading system integrators cited cable issues as the number onereason for downtime in robotics cells. Headaches range from tangledand corkscrewed cables to complete breaks that cause downtime, lost igus Inc.revenue, and damaged reputations. PO Box 14349 East Providence, RI 02914New Thinking P. 1-800-527-2747Currently used systems try to keep the cables static, while everything F. (401) 438-7270operating around them is dynamic. In essence, using one, long sales@igus.comrestrictive cable package prevents movement in sync with the robot.Restrictions stress cables, which accelerates failure. Often, techniciansseverely bind cables with excessive dress packs (protective coverings
  2. 2. on cables and hose), cable ties, and even duct tape. The goalmight be to minimize tangling and interference with themachine, but instead these techniques actually causescorkscrewing and failure.Instead, engineers need to consider a six-axis robot as threeseparate segments: the sixth to third axis; the third to secondaxis; and the second to first axis. This breakdown is imperativeto longer-lasting cables. Each cable segment should feature aminimal dress pack, strain relief with service loops, and ajunction box that contains and protects the electricalconnectors joining the cables. For the best results, follow thefollowing recommendations.From the sixth to third axis: 1. Use strain-relief cables (we’ll talk more about ‘long-life’ cables in an upcoming section) on the moving end (sixth axis) with a one- to two-foot service loop. 2. Protect cables and hoses with a modular, multi-axis cable carrier. 3. Segment cables at the third axis and install a junction box for quick diagnostics and cable replacement.From the third to second axis: 1. Use strain-relief cables on the third axis with a one to two-foot service loop. 2. Use a modular, multi-axis cable carrier. 3. Segment cables and install a junction box at the second axis.Finally, from second to first axis: 1. Strain-relief cables on the second axis with a one to two foot service loop. 2. Install a multi-axis, reverse-bend cable carrier to protect and guide cables and hoses rotating around the robot. 3. Segment cables and install a junction box at the first axis.Segmenting the dress pack into three shorter sections prevents it from wrapping, catching, or snaggingon machines, and minimizes stress on cables and hoses. This approach applies to any six-axis robot,regardless of manufacturer or application. While other fixes, such as duct tape and ties wraps, mightwork temporarily and cost less, in the long run properly designed dress packs reduce unnecessarydowntime and maintenance costs. igus Inc. | 1-800-521-2747 | |
  3. 3. Additional TipsAnother step that should extend cable life is to allow sufficient clearance inside the carrier for electricalcables, pneumatic hoses and tubing for other media. This compensates for relative forces betweencables and hoses. Carrier suppliers typically provide this data.For instance, general rules of thumb for igus®, Triflex® R carrier are: 1. Total cable and hose diameters must not exceed 60 percent of the carrier diameter. 2. Leave at least a 10 percent clearance between any two cables and hoses. 3. Cables and hoses need to move freely inside the carrier.Safety is also a major concern within robotics cells. With the less-is-more approach, designers can letcables and hoses move freely, but not to the point where they could potentially injure workers.As six-axis robots evolve, cable-management systems need to develop along with them. Designersshould consider the less-is-more approach for every robotic applications, as it eliminates cabledamage, expensive maintenance and downtime. Of course, a number of other elements, including therobot’s function, space constraints and budget also play a role. But for any combination, there is asuitable less-is-more approach that keeps vital cables away from harm’s way while enabling them tomimic the fluid movements of a six-axis robot.Continuous-flex Cables In addition to the appropriate dress pack, it is imperative that six-axis robots use dynamic cables specifically designed for continuous flexing. Two important features to take into account are a cable ’ s torsion-resistance and shielding. Shielded cables face a greater risk offailure, as constant movements can easily compromise the cable jacket. Use unshielded, high-flexcables whenever possible to avoid problems.For example, igus® offers its own range of robotic cables called CF Robot. These including hybrid, bus,measuring system, fiber optic, motor, servo and more. All of these cables are specifically designed forand tested in applications involving high levels of torsion and ideal for use in Triflex® R cable carriers.In contrast to conventional braided copper shields, which are counter-wound, a torsion-resistant, tin-plated copper shield sheath is used with CF Robot. The forces affected on the cable by any torsionalmovement are largely absorbed by sliding and buffer elements between the sheath, shield andinsulation. This prevents early failure of the shield. The outer sheath material is a high-grade TPEmixture with particularly good wear properties. igus Inc. | 1-800-521-2747 | |
  4. 4. ConclusionIf you’re working on a multi-axis robot application, consider taking a less-is-more approach to cablemanagement. It will extend the life of your cables and hoses and improve overall performance. If youhave any questions or want to discuss a specific application, please call 1-800-521-2747 to speak withan igus® sales engineer.Useful Links and ToolsLearn more about Triflex® R cable carriers.Learn more about igus® line of high-flex cables specifically for robotic applications.Click here to read an archived edition of TechTalk about how to specify robot cables. igus Inc. | 1-800-521-2747 | |