I have merged an ifc file into AC12 made in autocad mep and the model gets scaled down randomly. The mep model was made off of my AC12 background so I know it started at the right size. We have tried to remerge, (the idea of 'do it again if it doesnt' work initially') and no luck. We have merged this model earlier in the design process and didn't have this problem. Are we over looking something simple?
What is the scale factor? It could be a drawing units problem. If it is 24.5 (or the reciprocal) it is probably a mm to inches issue. If it is 12 then it's feet and inches (etc.). When I was beta testing the AutoCAD MEP to ArchiCAD MEP connection there was a similar problem. I assume this was corrected in the shipping version but perhaps this is related.
Is the scale change something set on the exporting application or on the archicad side? I am dealing with a similar issue with autcad architecture and without changing the "units" in autocad from inches to millimeters I can't get archicad to open it at the correct scale. I do see in the options drop down menu for IFC in archicad but changing the units there has no effect on the scale of the opened IFC file. Am I doing something wrong?