Feature Belts, pulleys & chains


nergy Chain applications are commonly horizontal, but they also offer some very useful solutions for guiding and protecting cables in vertical motions.


Taking a vertical approach E


There are a number of installation orientations that can be considered when working with an Energy Chain cable carrier system. Justin Leonard of igus UK examines the options available to OEMs for vertical installations


The two most common configu- rations are hanging or standing. The third, which is less conven- tional, involves a ‘zig-zig’ arrange- ment. As all are very different, it is important to consider the design attributes of each.


Vertical standing Vertical standing configurations are often used in machine tool and pick- and-place applications and, generally, will be shorter travel lengths. The most important factors to consider in a vertical standing application are how the cables are laid in the cable carrier and how they are secured at the end points. When installing the cables, it is crucial that they can bend freely and are strained relieved at both ends. In addition, mounting brackets must be attached so that the cable carrier does not bow outwards. Locking mounting brackets are available for almost every style and size of Energy Chain from igus. In vertical standing applications in particular, locking ‘KMA’ style mounting brackets are highly recommended because they can


Vertical standing configurations are often used in machine tool and pick-and-place applications


be attached flush to the machine. If lateral acceleration occurs, the Energy Chain should also be supported along the outer radius; and for taller standing applications, it is generally recommended that a minimum of the first three links on the outer radius are supported. For extreme heights and weights, it is advisable for the entire distance of the Energy Chain to be supported.


Vertical hanging Vertical hanging energy chains are often used with storage and retrieval systems as they can easily achieve the longer travel lengths required due to gravity. In this type of application, an Energy Chain can be used to house the different types of moving cables and hoses used on the system, while at the same time preventing them from becoming caught on shelf parts or protruding pallets.


As with vertical standing, the two most important factors in a vertical hanging application are how the cables are laid in the cable carrier and how they are secured at the end points.


Right:


The zig-zag configuration


When hanging the cables, it is crucial that they bear their own weight so that the Energy Chain does not


When old sprockets have to go... David Turner, of Renold Chain, gives advice on when worn transmission chain sprockets need to be replaced


Looking at the faces of the sprocket's teeth will give an indication of the amount of wear that has occurred – this will be seen as a polished worn strip, about the pitch circle diameter, on each of the teeth. If the depth of the wear, X, has reached a value equal to 10% of the dimension Y, then the sprocket has reached the end of its life and needs to be replaced. A good quality sprocket should last through the life of several chains. When changing sprockets it's a good time to check the alignment of both the sprockets and the shafts to which they are fitted. Misaligned sprockets is another factor in premature chain wear. Accurate alignment of shafts and sprocket tooth faces provides a uniform distribution of load across the entire chain width and contributes substantially to achieving maximum drive life. Use a straight edge across the machined faces of the sprockets in several different positions, if possible, as a check against wobble. Should end-wise float of shafts be present, make due allowance so that sprocket align- ment is correct at the mid position of float. When alignment is correct within closest practical limits, drive the keys home and take a final check on sprocket alignment. If you're fitting new chain at the same time don't forget to correctly lubricate it. The lubrication that's on the chain when it comes out of the box is only sufficient to prevent corrosion and aid initial bedding in. Renold Chain UK T: 01283 512940


S www.renold.com Design Solutions MECHANICAL COMPONENTS SUPPLEMENT – MARCH 2011


prockets that have worn beyond a certain point will cause rapid chain wear and should be replaced as soon as possible. But how much wear is too much, and what sort of visual checks should be carried out to determine this?


have to do so. It is also important to secure the cables at both end points and use interior separators to keep the cables from tangling.


A traditional igus Energy Chain with camber is suitable for a hanging applica- tion if enough space is available. However, most storage and retrieval systems have to operate in narrow aisles and so an Energy Chain without camber (pretension) will deliver the best perfor- mance because it will operate within a smaller space. If the space restrictions are rigid, this ‘no-camber’ or ‘NC’ version should always be used. If the application involves vertical motion without lateral acceleration, the Energy Chain can be installed with- out lateral support. If there is lateral acceleration, the Energy Chain should be guided laterally.


Partial guidance is also an option, however, at minimum it has to cover the area where the Energy Chain might sway. As lateral acceleration can occur in two directions, lateral guidance must be installed accordingly. Also, keep in mind that additional guidance along the side of the Energy Chain helps increase its stability.


In these situations, the use of locking mounting brackets will help increase the performance of the Energy Chain system. In restricted spaces, other custom- designed solutions are available from igus. Secure strain relief and clear separation of the cables are absolutely essential, although it is important to remember that cables must be able to move freely and bear their own weight.


Zig-zag solutions For applications with strict space constraints, a less conventional configuration known as ‘zig-zag’ can be used. This is very common for lifts and stages within theatres and other event venues, where a variety of cables need to be housed and protected.


igus energy chains can simply be reversed at any point to allow the system to fold over in a controlled way, forming a ‘zig-zag’ style application which is compact when stowed. It is important once again to ensure good cable separation and strain relieving in this orientation because of the various moving joints. It is also recommended that the system has a basket built to control and contain the Energy Chain while it is stowed. A standard metal basket solution can be provided by igus for any ‘zig -zag’ Energy Chain system, which also makes installation of the system very simple.


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igus T: 01604 677240 www.igus.co.uk


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