Stop Paying the Cable Companies!

April 09, 2016, by Reid Hunt

Machine builders focus on functionality and reliability when first designing a new machine.  Ideas are put on paper and components are strung together in block diagrams with thin lines to show the association of all the pieces.  It is the most creative time in the cycle.  Things can be moved and shifted with ease because everything is on a whiteboard.  Even if you are far enough in the cycle to work in a CAD model, changes require no physical effort and the task of putting it together is still just an idea. 

Slowly, cable connections start to creep into the picture.  Most builders are starting with the previous generation or variation of the machine in mind, so nobody forgets that they need to hook all this stuff up with cabling, but far too many builders don't look at cable management as an opportunity for competitive advantage.  This could be any type of a connection signal or power.  In both cases, cables have tremendous hidden costs.  They are more expensive than most people imagine.  You pay by the meter and it always takes more length than seems necessary.  They are intensive to install because they must be chased through the machine in a way that leaves them protected.  Inside the panel, it is similarly challenging because of the proliferation of din rail terminal block connections.  Every end of every connection should be stripped, tagged, and crimped with a ferrule.  Other than software programming, it seems to be the most time consuming part of the design and build process.  

There is help now.  Manufacturers have finally realized that simplicity and ease-of-use are important to machine builders because of this cabling and wiring struggle.  Tons of systems are now on the market which integrate machine functions and connectivity.  Early products on the market were simple and effective, but not up to performance standards of industrial builders.  Integrated motor/drive products were around 500 watts and had limited performance.  In the last few years more and bigger options have shown up on the market.  Another new option of late uses separate drives and motors, but places the drives very close to the motor axis due to its environmental sealing.  This solution provides max power and preserves motor flexibility.  This is a decentralized drive system.   

The benefit of applying any of these new solutions is very clear to an engineer that has dealt with a large multi-axis machine.  As an example, for an eight axis machine with 3 meters between each motor (imagine a long machine process that convey down a line) a traditional "drive in the cabinet" machine requires 372 meters of cabling.  The decentralized solution runs feedback, power, and bus on one cable.  Since the drives are now out on the machine chassis, only one homerun is required.  The drives are daisy chained to avoid a bundle of cables going back to the panel.  This results in a simple architecture and a more reliable machine because of the connection reduction.

 Decentralized Drive Approach

Inside the panel is substantially different as well.  A much smaller cabinet is used and the amount of terminal blocks is reduced dramatically.  About 15 terminal blocks per drive is a rule of thumb. 

If you are a machine designer that has been constrained in the past due to cable runs, now is the time to look at these new approaches.  Not only do they avoid the cost and trouble of cable and wiring, they open up possibilities to make much smaller machines as well.  Don't discount the benefits; although cabling is the last consideration on paper, it affects nearly every design consideration in the physical machine.  Stop paying the price of cable!

 

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