I finally got the courage to load 16.6 SP3 and start a new design with it. Having to duplicate an existing layout with respect to many keypad switch placements, I thought importing some simple mechanical info from a client provided "dwg" might save me some time - - should have know better! Ranting aside - -
I converted the client's dwg to a dxf (2000-2002 format). Then with autocad viewer determined which of the 100 un-named layers of content contained the features that might actually be helpful for component placement. Using the Import>>DXF functionality, I selected and mapped the desired two layers of the dxf into board_geometry/assembly_notes and assembly_detail subclasses of a new blank board file.
Theimport onto assembly_notes subclass mostly imported OK except for line and arc line widths being weird. However, the import onto assembly_detail subclass was a disaster. Essentially 27 separate squares managed to import on top of one-another in a location not even close to their actual location (in the dxf) or relative to the location of the other features from the first layer import.
I used "incremental addition" and "use default text table" selections for the import process (thinking that one of the dxf layes did have some text on it). The dxf2a log only reports a few "illegal character substitutions" for each of the layers imported.
Any clues to what I'm doing wrong?
You are not the only one having problems with DXF import. I have had the same experience.
I cannot gurantee that what I suggest can help, but here's what I do:
Open the DWG in AutoCAD.
Delete every non essential drawing element.
Use menu command "Purge" to get rid of any empty layers.
Zoom out and issue command "UCS" and then "Extents" in order to reduce the DWG to cover only the drawing elements that you want. You may also want to use UCS in order to move the DWG origin (set "0,0" somewhere in the center of the file)
(If you want imports to be shapes, you have to use command PEDIT and from there create polylines - but this is another story).
Export as DXF.
(So far I have still had occasional problems, so I have had to import the .DXF into Agilent's ADS and make a re-export from there. This odd way is when the Cadence Tool fail to import curves. It seems that the .DXF importer can only recognise perfekt circle elements. Why it can import Agilen ADS-created DXF's with curved elements I cannot say)
The approaches above generally works.
In reply to UlfK:
Thanks for the tips, but unfortunately I do not have access to a full version of Autocad for editing. I'm using their free DWG TrueView to open and display. I found a free (trial) converter to convert the dwg to a dxf, but again I have no editing tool at the moment for M-CAD.
Spent all my money on Cadence tools <grin>.
In reply to Roger BFS:
I have Autocad if you would like me to try something for you.
In reply to TH Designs:
But I'll open a support case with Cadence and see what they say first (besides its broken). I'll let you know - -
Plus you get to take advantage of some of those maintenance $$.
Hey Roger, it could be that the DXF format is the issue. I have seen lots of wierdness with dxf imports, mainly scaling issues.
Anyway this might be of help to you.
Dassault systems offer a free cad tool that works great with dwg and dxf files. It is not crippleware : ) I have had good success using this to export dwg drawings to dxf format for import to Allegro.
The program is called DraftSight and is available here.
In reply to ScottCad:
Thanks for the pointer, I'll have to give it a try. I've been looking at various M-CAD tools over the past few months (in my spare time) trying to find something sufficient for my "occasional" needs for 3D modeling and package layouts and such. Solidworks appears to be one of the best, but as with most high-end tools they aren't cheap.
For update - I opened a support case with my Cadence reseller on this issue and got good fast response. They quickly duplicated my problem and got the same "import" response on the last three versions of the tool at their end. Conclusion - there must be "something" in your dxf that's confusing the Cadence importer - REALLY? (I thought that's why I opened the case). Guess the good news - there wasn't something that I was doing wrong to goof things up.
Our joint conclusion was I would be best off to look at the dxf, get the coodinates/measurements of stuff I needed then manually re-create the features in PCB editor. In this particular case, I only have 20-30 things to create as opposed to 1000's. <grin>
Oh BTW - I reran my DWG-DXF converter to create the dxf in two other newer "formats" for AutoCAD 12 and 14. No improvement, the import to Cadence did the same screwy stuff. The dxf2a log files just reports a few "illegal characters" being replaced for whatever reason. Curiously though when I try to use the "view selected layers" button on the importer, it does error out, with several reports of
(SPMHDB-70): Buffer contains overlapping segments. ERROR: Failed to add (LW)POLYLINE.
I haven't found documentation of this error code yet. It may be a clue, but I best be getting on with the job at hand.
Two key suggestions with dealing with importing DXF files into Allegro is to save the DXF file to the lowest possible version, normally version 12.0, and to explode all elements prior to export or load the DXF file into a third party tool to explode everything. Doing this will yield the best results getting the DXF file into Allegro.
I normally add a couple of dimensions or measure a couple of elements in the DXF file so I can spot check the measurement after loading it into Allegro to make sure the units are correct, if it doesn't match I can change the units and load the DXF file again. In some rare cases, I take the fastest / easiest path and just scale the data inside of Allegro so the scaling is correct and move on. You can use Manufacture > Drafting > Create Detail and File > Import > IPF to scale the elements in Allegro.
I start out with a blank Allegro database with the units set to MILS with the import units of the DXF File set to INCHES which most of the time works without an issue. Loading a DXF file in incremental mode does work but if I have scaling issue or other file problems it is just easier to reopen a new blank database to do the import again. Once you get it right you can always generate sub-drawings (File > Export > Sub-Drawing...) to cut and paste the elements you want into the master database or generate a plot file (File > Export > IPF...) and load plot files back into the master database.
Check out this thread - it may help:
Good luck,Mike Catrambone