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Best way to work with a linked Cad file in Revit

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Message 1 of 6
biancy
3592 Views, 5 Replies

Best way to work with a linked Cad file in Revit

I know variations of this have been answered before, but I just need to ask for myself so please bear with me ๐Ÿ˜„

I am brand spanking new to Revit and as a training exercise we are going to 'draft' a project in Revit with CAD architecturals. I am fine with linking it in - my Q is this:
What is the best way to go about drafting our mech, elec, plumbing?

 

I've been modelling the walls with the arch tools, and I guess it's reasonably quick (but still taking me a while cos I'm new and worried about inaccuracies), but what about when the arch changes? I have to go back every time and remodel elements? My boss doesn't even like us having to change any arch layers or move text or anything in CAD - the time required to model over and over could be an issue. Unless I guess the overall time vs CAD is significantly reduced.

Also, when I come to issue to the architect, I'm sure my model won't be spot on to their background and they may notice something is up. If you guys follow this method, do you hide/freeze/whatever the model walls etc, so you're just printing the arch CAD background and your services? Or do you print it with your dummy model.

Alternative: Just drafting over the CAD file - no modelling. Is this an option? I read somewhere about someone using 'planes' to host their diffusers etc. Can someone explain this to me in newbie terms? And can you create planes for walls and stuff or do you just snap to the CAD background.

 

Thanks in advance for your help - like I said this is a training exercise and I'm a total newbie ๐Ÿ™‚ Saying 'there's no point using 2D cad in Revit' wouldn't really help me ๐Ÿ˜ž

Thanks again! 

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Message 2 of 6
dennis
in reply to: biancy

General rule: If you get a Revit Arch model, then use RMEP; but if you get an AutoCAD arch file (or any other CAD) then do it in AutoCAD MEP.  You are correct, much of the RMEP is "face based" and so the Revit Arch model provides those faces that the other CADs will not.  Othe CADs in Revit are 'pretty pics' and as you have found, you have to model the arch to be able to place MEP objects.  I really discourage MEP engineers from model architecture, that is the arch-designers' jobs.  Yes, if you are modeling architecture to do your RMEP work, then when there are changes to the arch model, you will have to fix your model.  Too much work from my point of view.

 

So, with your workflow, you are either going to be doing alot of extra work modeling the arch, -or- (taking your final workflow idea) you will be reworking alot of families to make them 'free floating' rather than 'face based'.

Message 3 of 6
TonyVav
in reply to: biancy

I just completed a five story apartment building  in Revit MEP. I only had Architectural CAD files. First I had to find out what the levels were then I placed each AutoCAD background at the appropriate level. When I had wall hosted fixtures I put a wall in just for that fixture. I was not going to build the whole building in revit as I did not have time. Worked pretty good.

Message 4 of 6
AnmarieJames8335
in reply to: biancy

You've probably figured out already that working in 2D isn't the most affective use of Revit, so I won't go there. But because your architectural is 2D, using Revit for MEP is more of a challenge.

 

1. On the Manage tab, you can use the Coordinates and Position tools to locate your project exactly on top of your linked CAD file. Just remember to pin it in place so it doesn't accidentally move. And, when you update the architectural, make sure to use the same insertion point (center, origin, shared coordinates).

 

2. If you can get away with it, I like the other reviewer's suggestion of only drawing portions of the walls you need. Use the architect's dimensions if there are any at this point, to maintain their "intent".  You could use reference planes for this, but that seems messier to me. Might be faster, though. Do what works best for you.

 

3. Create a Level for each floor level, and adjust the spacing to match the architectural. You could create additional levels for ceilings (diffusers, lights), but sometimes that gets crowded and confusing. For ceilings, I would create reference planes. Each one can be named in the Properties box, which can be helpful, but isn't required.

 

4. Yes, you would want to turn off any architectural modeling that you've done before you print or export a CAD file. It's probably a good idea to make a Duplicate of the plan view you work in to send to your architect. The idea is to use the Visibility/Graphics (in Properties) for this view to turn off what you don't want to send. That way, you can work in one view, and the other always has the correct entities showing for the architect. (Sort of like setting up a viewport and layer manager to print in Acad.)

 

5. You COULD draft your MEP completely in 2D in Revit, but it's not recommended. Detail Views are for taking a view of the 3D model and adding 2D graphics to create a detail. Drafting Views are meant for things like diagrams, sketches, and details that have nothing to do with a 3D model. So, technically, it could work. I don't see how that's different than doing it in CAD, though.

 

Good luck!

Message 5 of 6
biancy
in reply to: biancy

Thanks to everyone for your help, I think I will be trying TonyVav's method and seeing how I go from there.

Thanks.

Message 6 of 6
CVMN0501
in reply to: biancy

I have experienced working with Cad backgrounds in RMEP2012. We normaly have a rule that we are not to use hosted families since there are times that there is no architectural model to work on but there is structural (which is better than nothing) yet there is nothing to host to, the reason for having that so. There was one instance that we made a project in full CAD background but we did partial detailing in plant rooms so we created partial architectural model on said areas. We showed sections and isometrics in plantroom areas then after that, in the common areas we just used placeholders for ducting and piping and we didn't bother managing clashes in common areas(which is kinda lame and loses the essence why we are using revit).

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