Dealing with acad files/turning them into dgn files

This may not give you an answer - If I remember correctly, Coincident lines up the design plane coordinates and Coincident World lines up the Global Origins. DWG files will only attach Coincident, never Coincident World.
Hopefully someone who is very well versed in coordinates, units and Global origins will come along to set the record straight!

I've found it much easier to open the DWG file and simply save as DGN. This will retain whatever coordinate system was used in the DWG. The new DGN file should be very easy to work with.

Thanks Robert. What about the global origin I need from the seed file?

You should not need to mess with the global origin. If the AutoCad file is in correct coordinates, the results SaveAs DGN file will retain those coordinates. When working with other files, everything will align at scale 1:1. If the original AutoCad file is not in correct coordinates, I would address that first, then do a SaveAs. My goal/strategy here is simplicity.

I had  issues with acad DWG conversions  or even just ref attach dwg to dgn and they never came into the right coordiantes..

part of the problem is we workin civil and use meters and  coodinates in meters.. acad is unitless and even though acaders treat the coordinates system xy as if they were in meters so I the  options for open acad I set it to meters  and now they  come in perfect...

I alway pretest out of habit  by creating a  new dgn with the seed file set to our datums and then ref attach the acad coincident and then merge the ref or  copy it through and detach.. I prefer the merge as I doenst  take on the the acad colour table  like save as  or  convert does  so I can then just rename levels and use our dgn lib to resymbolise to standards colours.. this seems to be the most efficient way I've found so far... the acad colour table thing  really bugs me as I ahve to then attach the standards or client msnt  colour table to it ! these are extra steps and it all adds up at the end of the day...

Another Trick is to open the dwg  first with microstation and  label a point with coords that  you know exist in the  your dgn world then  when you convert or ref attach you can check the known point... the only other thing is when acaders have drawn the acad as if they were in mm then its trial and error  changing the ref attachment 1000 times scale etc...thats why  I prefer to ref attach rather than convert...

If I have to do lots of them then I random check a few with ref attach and if all good then I use the batch convert with the meters option in the dwg open option...

havent had iny  more issues for 11 out of the last 12 months since I found the setting and I use acad files all the time everyday from our local 12D  road designers... 

I'm the lone mstn guy in the team the other acad drafters just use the acad dwgs no issues for them but I'm there for the DGN prefered clients  like DOTs etc...so I had to figure out how to adapt... so far so good....

I had  issues with acad DWG conversions  or even just ref attach dwg to dgn and they never came into the right coordiantes..

part of the problem is we workin civil and use meters and  coodinates in meters.. acad is unitless and even though acaders treat the coordinates system xy as if they were in meters so I the  options for open acad I set it to meters  and now they  come in perfect...

I alway pretest out of habit  by creating a  new dgn with the seed file set to our datums and then ref attach the acad coincident and then merge the ref or  copy it through and detach.. I prefer the merge as I doenst  take on the the acad colour table  like save as  or  convert does  so I can then just rename levels and use our dgn lib to resymbolise to standards colours.. this seems to be the most efficient way I've found so far... the acad colour table thing  really bugs me as I ahve to then attach the standards or client msnt  colour table to it ! these are extra steps and it all adds up at the end of the day...

Another Trick is to open the dwg  first with microstation and  label a point with coords that  you know exist in the  your dgn world then  when you convert or ref attach you can check the known point... the only other thing is when acaders have drawn the acad as if they were in mm then its trial and error  changing the ref attachment 1000 times scale etc...thats why  I prefer to ref attach rather than convert...

If I have to do lots of them then I random check a few with ref attach and if all good then I use the batch convert with the meters option in the dwg open option...

havent had iny  more issues for 11 out of the last 12 months since I found the setting and I use acad files all the time everyday from our local 12D  road designers... 

I'm the lone mstn guy in the team the other acad drafters just use the acad dwgs no issues for them but I'm there for the DGN prefered clients  like DOTs etc...so I had to figure out how to adapt... so far so good....

Thanks Lorys........again
This very good stuff! Luckily all I haven't had any problems with the acad files being in meters. I was concerned that I might be creating files in the wrong location but using your method seemed to work for me.
Cheers!