ifc export accuracy?

[Anonymous]

I created structural model with columns and beams in Archicad 10. All of the beams are lined up and snapped to the corners of the tops of the columns.

I saved my structural model in the IFC 2x2 format to open in CadWork (we use CadWork to produce automated shop drawings for CNC machines).

When I open the IFC file in CadWork, the beams are 1/64" away from the columns in the x and y planes.

I figured out that Archicad has a 1/64" accuracy in it's model units etc.
Is there a setting in the IFC translation or in Archicad that I can change so that the IFC model will open in CadWork and be as accurate and the columns and beams will be lined up as they appear to be in Archicad?

Thanks!

Manny Jasus

[Anonymous]

Make sure you are inputing dimensions when placing/positioning things in Archicad. Some users will look at the dimension in the coordinates box/traker and assume it represents the actual dimension (makes sense). Unfortunately this is not the case. Another option is to enable the grid snap and set the gird to 1/2" or whatever works in your situation. This will assure everything is where you assume it should be.

[Chazz]

Frightening if true. In fact, this would sort of kill any use of IFC as an interchange standard. Manny, if you look at the relationships in AC, and zoom way way in do you see any of these discrepancies?

[Anonymous]

Chazz wrote:
Manny, if you look at the relationships in AC, and zoom way way in do you see any of these discrepancies?

I zoomed way way WAY in and did not see any discrepencies . . . everything appears to be lined up correctly.

But when I save as IFC and open in CadWork, everything is off. Today it is 3/64" off (see screen shots)

And the 3 1/2" wide beams I created in Archicad are 3 15/32" wide.

The 5 1/2" x 5 1/2" post in Archicad is 5 7/16" x 5 15/32" in CadWork.

[Anonymous]

Any other thoughts on this accuracy issue?
I don't understand why the beams I created a certain width in FrameWright are now not the same size when I open the IFC file I created. I typed the exact dimensions I wanted the members assuming that 5 1/2" is in fact 5 1/2" . . . if it's not, why should we use Archicad? And who's to say that my 90-degree walls are in fact 90-degrees? If I have a 30 foot wall or beam and I open the IFC in CadWork (or other program) and try to send the data to a CNC machie to cut and notch, then everything will be inaccurate and the precisely milled joints will not fit. Besides this obvious fact, it just looks really messy and is not acceptable to open posts and beams I thought were "tight" and find out they are loosey goosey . . .

anyway, thanks for all the help and suggestions . . .

mjasus

[Richard Morrison]

Manny,

Just to check, see if both Working Units AND dimensions are set to 1/64". If you have dimensions set to a "cruder" value than the working units, you may not realize that there is an inaccuracy in the dimension that you are seeing displayed.

[Anonymous]

Hi Richard,
Both my Working Units and Dimensions were set to 1/64 before I started modeling. It's still 3/64" off or misaligned when I import the IFC file into CadWork.

Could it be an IFC setting on the Archicad end? Maybe it's translating to IFC less accurately than it should be? I looked in the "IFC 2x Edition 2 Options" (File--File Special--IFC 2x2--Options) and didn't a setting for accuracy or tolerance.

Thanks again for the suggestion. Is there an official Archicad/Graphisoft support email I should try too?

Manny

[Anonymous]

Manny,
Here are some e-mail addresses and phone numbers
for Graphisoft US in Boston.
Graphisoft US Tech Support 1-800-238-3992
David Tauer dtauer@graphisoft.com
Graphisoft U.S., Inc 1-617-485-4203
Peter Devlin

[Anonymous]

Hi Peter . . .
I sent an email to David with these questions . . . I'll repost when I hear from him.

Thanks for the info . . .

Manny Jasus

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[Djordje]

It is under investigation ...