CAD <-> Revit Linking Issues; Scale

[Anonymous]

Hey ya'll, 

Thank you very much for reading through and helping.

I have been struggling with linking an AutoCAD MEP file into REVIT. Initially I was linking and only seeing the drawing block load into Revit, and not the plan from model space. I then deleted the drawing block layer, and have it as a default Layout1 that comes standard with CAD. This helped REVIT decide to pull the plan from model space.

I set all line work to layer 0, color black, explode all, remove blocks, run PURGE and purge all, then run SETBYLAYER, then run AUDIT. 

Scale: 1:1 inches

Revit scale inches, drawing at 3/8"

I set the CAD scale to match the Revit scale, save as copy, and link to Revit.

I have tried setting the import scale to .0375 (3/8. The decimal factor is just through testing and seeing that hundredth scale is relatively the closest) But either way the scale is not lining up. it is not .01, .02, .03, .0375 or any other predictable number. What the heck is going on here. I have not seen any online forums clearly outlining a procedure, and nor is it hosted by Autodesk. They simply advice to change the scale in properties. I'm not even seeing that. Attached is screen shot. 

[RobDraw]

There should be no need to scale the .dwg. I could be a units thing...

[Anonymous]

Thank you for trying to answer the question. The units selected in both programs are identical and still the drawing does not import scaled correctly. How does one reconcile scaling in this situation? Surely there is a format?

[cbcarch]

Just checking your post carefully---3/8" is .375, not .0375.

Scale factor is 1/32xp.

[Anonymous]

What do you mean scale factor is 1/32xp. What is xp? Why is it 1/32? 

[barthbradley]

32 3/8ths in one foot (=32 scale). 48 1/4ths in one foot (=48 scale). 96 1/8ths in one foot (=96 scale). Etc. 

..."scale" as in LTSCALE

[andybrack · Accepted solution]

Samuel,

The golden rule of AutoCAD is to always draw your building at full size in model space. Then, in paper space create a view port and use the zoom command to zoom in or out to get the drawing to the correct scale on the sheet.  This is called the scale factor and is found by taking 12 and dividing by the drawing scale. For example, drawing at 1/8" = 1'-0" results in  a scale factor of 12 / (1/8) = 96xp.

To help figure out your issue, need to confirm a few things.  Is the CAD file drawn at the correct size?  Meaning measure the width of a room in Revit and measure the same room in your AutoCAD file (model space). Do you get the same thing? If not, you have a bigger problem and your drawing is not true size.

Are the units the same between Revit and AutoCAD?  Check the units in your CAD file with the UNITS command. Is it set to Architectural, Engineering, or Decimal? When importing CAD in to Revit, you sometimes have to set the 'Import Units' drop down box to make it work correctly.  If your CAD file is set to Architectural units, then the Import Units in Revit can be set to either Auto-Detect or inches. This is assuming your Project Units in Revit are set to Feet and Fractional Inches.

Let me know then we can point you in the right direction.

Andy

[RobDraw]

Again, there should be no need to scale the CAD.

I looked at you screen shot again and realized that you are linking directly to a sheet in Revit from model space in the .dwg. Don't do that. Avoid the confusion (and math errors) and link to a drafting view 1:1 then place that view on a sheet. You can then set the view scale as desired.

[Anonymous]

Andy-

The units are set to inches in CAD. The drawing is exactly precise as well. I do not have anything in the paperspace, so it is importing from the model space. You're saying to set it in paper-space to the proper scale?

[Anonymous]

Thank you for the solution. I made sure everything was measured correctly in the model space, set to the scale I wanted, and then I deleted and remade my paper space. When I linked this new file set to auto detect, it was to the accurate scale. Great!

[andybrack]

No. Revit allows you to import from model space or paperspace. What you described previously is best, where there are no elements in paperspace and the import comes from the CAD model space. Now that you've figured it out, I suspect that what happened was that you had a viewport in paperspace that was scaled incorrectly. When you were importing it was bringing in the improperly scaled paperspace view. By deleting the paperspace view tab and recreating everything was set back to ground zero. Glad I could help.



Andy