Line between Mech / Elec

Where do you guys draw the line between Mechanical design and Electrical design? I know its always going to be pretty blurry..

For things like Panel size, if its going to be designed into the frame of the machine, or cable tracks / baskets on the machine.

I know there are tons of other examples, but the two that always bother me is:
1) Mech never designs stuff on the machine for wires to go.
2) Mech typically tries to incorporate the panel in the machine frame and its always smaller than I wish.

This always used to be a major issue for me. Since I have been at this company for many years, I have educated the mechanical engineers to work with me early in the project so we can understand the challenges we each face. For the most part, the requirements for the electrical enclosure don't change for me. I don't compromise my design standards. It may require me to design a subplate layout that is wide and short instead of rectangular, or multiple enclosures, but I don't cram components on a subplate without ample wireway space. I also have to work with them to understand the cabling needs of the machine.

nmurray said:

1) Mech never designs stuff on the machine for wires to go.
2) Mech typically tries to incorporate the panel in the machine frame and its always smaller than I wish.

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Reminiscent of Saturday Night Live's tricks tell them at the start the panel will be larger than you want and there will be larger cables, so when they cut it down it will be what you want.

SNL did it with censors all the time to get something to slip past when they censored the really bad stuff out.

This is a huge problem in servo hydraulic control. Servo hydraulic control requires knowledge of hydraulics, mechanics and control. Too many times I have seen machines with abysmal designs that will not work or at least not work the way they want it to.


I have NEVER seen a system designed with a transfer function attached. NEVER! This is a failure of the mechanical and hydraulic engineers. They just kludge something together and then ask can your controller control this to do that with so much precision as if it is the controller and control guys job to cover up for their poor design.


This has been a sore spot for me for many years.


BTW, the combine discipline of mechanics and control is mechatronics.
There should be no line. Know both.

Peter Nachtwey said:

BTW, the combine discipline of mechanics and control is mechatronics.
There should be no line. Know both.

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In our field we HAVE to be able to do both, but the other side never seems to know anything or even care about the controls that have to go on to run their beautiful design.

When I started I worked for a company with the same problem. Even the owner (who was a mechanical guy) would say "We have this much space, so we have a panel this size".

One guy I worked with finally got fed up and asked which part of the machine he wanted to "not work" because he was going to have to leave something out - it won't fit in the panel.

Where I work now is pretty great - because most of my panels are stand-alone on a floor (leg) kit. I don't really care - it is almost always a 60x38 or larger.

We build a few containerized water plants from time to time and I've found it always pays to get in early with the mech and process engineers so I can emphasise that no, I can't install the main switchboard in behind a pump set, or bolt it to the roof, and there are legal requirements around clearances etc.

And if i see their first draft of an equipment list i can generally estimate what size panels we need and where we need them to minimize cable runs etc. When they see that this keeps the cost down they are happy to start the dialog early.

We generally do all the cable tray and support etc in the elec team although i do think it could be easily done by the mech team installing the piping, if we were a more professional organization and designed in 3D CAD. Would certainly be easier!

The other problem is ordering from Mechanical Eng.
They just need a cylinder or valve, you are the one that needs limit switches and a coil at the correct voltage and with the correct connection.

I always let the mechanical guy do their thing first, you can’t even begin to do controls until you what you are controlling
If they need help on placement of sensors or reconditions for sensors I am always there to advise as needed
But they need to tell me what size motor and what speed they need to run it so I can make the best choice. We both need to work together to develop the best solution for the end user

It’s been my experience that chemical and mechanical engineers often tried to crossover to do the electrical design seeming to have the attitude that “anyone can do electrical work.”

And then there are programmers who come out of nowhere and have no idea of how to size wire, fuses, wire duct, junction boxes and a myriad of other electrical design factors. Then when something goes wrong they want to blame the electricians.

GaryS said:

I always let the mechanical guy do their thing first, you can’t even begin to do controls until you what you are controlling

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This isn't so. I can simulate servo hydraulic systems. I can calculate how the system will respond but what is more important is getting a specification and then being able design a cost effective system to meet that specification using the design rules I have developed over 30+ years. The unfortunate part is I am usually asked after the system is built and they just realize they are screwed.


Our controller has simulator built in. The hydraulic systems is defined by an open loop gain, natural frequency, damping factor and stroke. The desired motion can be simulated. The the actual position can't follow the target position then the open loop gain or natural frequency can be increased until it does. The cylinder diameter can be calculated from the required natural frequency and force that must be applied. The damping factor can be changed to simulate different mechanical systems.


The purpose of the simulator is to allow one to test at their desk. It is possible to have the project almost done before the system is built.