Reasonable Timing - Electrical Design (CAD)

Timeismoney08

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Jul 2012
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Hello everyone,


For a project with 30 inputs, 30 outputs, including 2 servo motors and 4 AC induction motors on VFDs, a interlocking fence circuit, HMI, Safety Relay, and PLC...Just the design in CAD.... What is a reasonable amount of time for most engineers to design this type of system?

I would like to know for reference. I appreciate any realistic feedback on what you think it should take. This is just for selecting the components, design in CAD, and Ordering the components (assuming you know the vendor).


Thank you!
 
It isn't exactly what you want to hear, but this varies from engineer to engineer. My experience when it comes to work is that it takes what it takes to get the job done. You can run into issues when it comes to selecting components, dealing with vendors, availability, etc. That doesn't include CAD stuff either.

Selecting the components is one of the most crucial steps to a job and should not be rushed
 
Well like most other things in life my friend it depends.

It depends on if CAD is the full-time job of the person doing this or if its a plant engineer like I used to be that does the design, CAD, Build, Parts Ordering, Project Management, Installation, Testing, Financing, etc.

If it's a full-time CAD person they will be much faster than a person who only makes 3-4 full drawings sets a year and just small revisions and changes the rest of the time.

It also depends on what kind of drawings you are doing and to what level of detail. Is it just schematic drawings or do you have pictorial drawings also?

Pictorials take a lot more time but are very helpful for installation and maintenance as they would normally show connections point to point where as a schematic will only show how it connects electrically and determining on how it connects physical vs electrically can be very challenging depending on the complexity of the circuit making these types of drawings much more time consuming to create but on a complex circuit are almost a must-have for the panel build shop and for installation.

Also, you may have interior and exterior panel layouts and wire and conduit schedules.

There may also be some mechanical drawings that have to be included showing how and where electrical field components connect like a PSI transducer on a hydraulic system control block.

Are you using common components or is all the latest and greatest? Latest and greatest may not have any CAD block for that component from the manufacturer and does your CAD person have any drawing templates or blocks from previous projects that can be reused or is the needs of this drawing set different than anything else the CAD person has done before?

I can go on and on. As one of the previous posts said it takes what it takes and it depends on what you want or what you are asking for.

I did not mean to make a rant but just wanted to illustrate the point that when doing creative work like this and that's what system design is a lot of creative work it's hard to have hard time constraints without having very hard and defined parameters of what's being asked for and without having prior experience with these parameters to be able to truly determine how long it takes.
 
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as already stated, it all depends on the engineer doing the job.
a beginner who has to create everything from scratch would take weeks.
someone doing this for years and already has a library built would take less than a week.

when i did this full time, all I needed to know was the name of the plc, model #, and what the voltage inputs / outputs were and the devices. 1 day, 2 max.
the servo would take longer as I would have to do that from scratch.
it took several years to create the library and the boss was not patient. he finally realized the benefits as the cad time started to go down. I even programmed autocad lisp menus to help with the design and that reduced time further.

the programmer would review the prints and make changes if required.

james
 
In general, I figure 8 hours plus 2-3 hours per sheet. I still may have to estimate how many sheets to some degree, but for smallish systems this is pretty easy to compute.

The 8 hours is to collect dwg files (or make my own) for the components and other documents from suppliers.
 
the hardest thing I found was developing the symbols and size.
we ended up designing for a 34x22 (D) size page with 1" square symbols.
they will then print on an 11x17 at half scale and a 8 1/2 x 11 at 1/4 scale but very hard to read.


we now have electrical, pneumatic, hydraulic, mechanical components in our library. I would guess 500. with the pull down menus in autocad, drawings go pretty fast.

regards,
james
 
It's hard to say when your doing quotes.
With print sets that could take a far turn before you even get /review the project.
It's always different, obviously but
In general I usually put in my quotes for a 15-20 sheet set. (Electrical) Pretty standard 3 sheets of high voltage, 3 sheets of low voltage, 3 sheets of safety, 6 sheets of I/O, 2 sheets of panel layout, 2 sheets of BOM.
16 hours design. 32 hours electrical. 16 hours pneumatic. 16 hours purchasing, THEN if you need a user manual (pictoral) which mostly we do that's about 24 hours. (Photos, screenshots, explanations, alarm descriptions, startup procedures, ect.. takes longer than you may think. And this is with me already having a general manual layout that I have already created.
 
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It's hard to say when your doing quotes.
With print sets that could take a far turn before you even get /review the project.
It's always different, obviously but
In general I usually put in my quotes for a 15-20 sheet set. (Electrical) Pretty standard 3 sheets of high voltage, 3 sheets of low voltage, 3 sheets of safety, 6 sheets of I/O, 2 sheets of panel layout, 2 sheets of BOM.
16 hours design. 32 hours electrical. 16 hours pneumatic. 16 hours purchasing, THEN if you need a user manual (pictoral) which mostly we do that's about 24 hours. (Photos, screenshots, explanations, alarm descriptions, startup procedures, ect.. takes longer than you may think. And this is with me already having a general manual layout that I have already created.

Thanks you for that, I thought I was alone out there.
 
I hate to agree with everyone here and be vague, but familiarity is the key, in my opinion.

If it is something using components I am familiar with, and I have done similar projects in the past, I would say less than a week, easily. Possibly within a day or two.

If it is something similar to what I have designed before, but with a completely different brand (say - Allen Bradley to Siemens), I'd add an extra week - just in case.

If it is something from scratch that I've never designed before and I'm using brands I'm not familiar with, it could take several weeks.
 

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