I second what Robert mentioned&#; running your router power line in the chain will induce a lot of noise on your endstop wires. Shielding and filtering can help prevent problems if you go this route. What I did was make some custom clips that hold my router power line about 2&#; away from the chain&#; the clips attach to the chain links. I also have input filtering with Schmitt triggers to stop false endstop triggers.
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Also, I think an xt60 is designed in a way that may well turn out safe with 120vac, but they are not rated/tested for it. So be careful using them like that. As an alternative, there are a lot of other 120v rated connectors you could use instead. Here is one example:
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Also, instead of buying some strand for this, if it is long enough you can just reuse the existing power cord that you cut off. If it is a good brand router, chances are it has really good cable already.
A: The majority of dress pack failures, about 85%, are cable and hose failures. This ranges from broken strands causing intermittency issues with a fieldbus or control cable to catastrophic failure of the cable at high stress points along the length of the cable. As for drag chain cables, the most common failure is &#;bird caging.&#; We will go into further detail related to these modes of failure later in this Q&A.
Q: What is the number one design flaw you see in the field with drag chain applications?
A: Many engineers are somewhat designed into a corner. The drag chain is not a high priority component in the design process. But at some point, the cables and hoses need to get from the panel to the X axis over to the Y axis and then on to the Z axis, in the case of a gantry robot. What design engineers are left with may be a physical envelope that does not allow for the proper geometries needed to manage the fill package correctly. Machine repairs and upgrades can be a source of this issue as well. There have been instances where an electrical contractor has fished a PVC-jacketed Ethernet cable through the drag chain on top of a TPE-jacketed servo cable, while completely ignoring the safety factor needed for free movement because &#;there was room.&#; Whether the fill package was originally designed with too much content or it happens over numerous machine repairs or upgrades, a drag chain stuffed full to the brim will have a decreased lifespan and much more downtime.
Q: What other systemic design flaws do you encounter in the field?
A: There are several but I&#;ll only go over a few I see the most in my travels. Uneven weight distribution is the most often design flaw next to an overfill situation. Over time this may lead to the drag chain leaning to one side. This will cause undue stress on the individual links of the drag chain, thus reducing the lifespan of the drag chain itself, especially in a long travel, gliding application. Next on my list is the lack of internal separation. This can cause a myriad of issues. The rule of thumb for separation is to create a cavity with 10% safety factor for cables and 20% safety factor for hoses. This means if a cable has an O.D. of 20 mm, the inside dimensions of the cavity it travels in should be 22 mm x 22 mm. Adding internal dividers and separators does increase the initial cost of a drag chain, but over the lifespan it will reduce total cost of ownership and downtime. Another systemic design flaw that causes a good share of downtime and failure is the physical placement of each component. Going back to the example in the previous question, PVC and TPE jackets have different levels of abrasion resistance (a.k.a. friction coefficients). Placing dissimilar jacket types next to each other without the proper separation as mentioned before, can cause the cables to possibly bind and wear prematurely. Finally, the last design flaw is one that is a pet peeve of mine. It&#;s typically found in older drag chains in an MRO situation&#; zip ties&#; everywhere. The only &#;strain relief&#; needed is at each end of the drag chain.
Q: What are some of the best key practices when designing and building a plug-and-play drag chain solution?
A: I would recommend this above all else; determine what your fill package will consist of first. Even if you are not sure about some of the other parameters the fill package will drive the mechanical envelope the drag chain must operate in. Matching all components properly to the application is another key. An example would be using cables that are rated for an acceleration of 5 m/s² when the real-world acceleration is 20 m/s². Will the cable work? Possibly, but for how long? Confirm the bend radius of the drag chain will accommodate each cable/hose bend radius. Cables that are constantly stressed longitudinally beyond their specified bend radius will fail prematurely. The last one I will mention relates to the use of support and guidance systems, sometimes referred to as guide troughs. These are sort of like a seat belt for your drag chain. They keep the drag chain properly aligned (no snaking), ensuring there is proper support and a uniform, obstruction free path in which to operate.
Q: What are some of the best indicators that an end user can look for to determine if their drag chain is beginning to fail?
A: A clear indicator that you may have an issue is when frame stays are missing or appear to be partially unsnapped from its link. This indicator is tricky because it could be a symptom of a deeper, unseen systemic issue. Maybe you have a drag chain that looks &#;twitchy&#; as it moves from the retracted to the extended position. I see this issue quite often. The possible causes could be one or more links are beginning to fail or there is debris in the drag chain and/or guidance system. Look for cables that begin to crossover their neighbors or show signs of cork screwing. This is one sign that should be looked at sooner than later, similar to the low tire indicator on your car. These issues should be evaluated by an experienced field support representative to determine your best course of action for repair, redesign, or replacement.