Revit export to .maj developed lengths not correct

[Anonymous]

We're seeing that when we create an .maj file from revit, then open it in autocad and look at developed lengths, that on straight duct there is some length added to pieces - in some but not all situations. If we delete the part in autocad, and redraw, the problem corrects itself. There seems to be no reason / method to the parts that have a longer developed length than expected.

We're using Revit 2019. Any idea what causes this? 

[Mike_Arcari]

Hi Shane

have you optimized the lengths in Revit before you save it to an .maj? 

I would check the fabrication specifications to see what the standard length is set at for straights and if the straight duct part has auto length switched on

Are they decoiled straights? if they are then there is also a setting within database for decoiled straights standard lengths, and that may also be a cause of the issue

[Anonymous]

Hi Mike, thanks for your help. 

Optimizing straights in revit has no effect on the issue. We are using "auto" length when straight length = standard length for the part. 

Here's a few things we've determined since this post. 

The fabrication part has this issue when a tap is connected (Revit connected), I'm not sure of other conditions that causes this. 

If we remove the database setting value for the "straight" in the connectors for the part, the issue goes away.

Disconnecting the tap from the straight in Revit, and exporting MAJ's also resolves the issue. 

The length added to the straight piece resulting in the error is 2x the "straight" value for the connectors on the part (TDF/TDC) in our testing. If the value is set to 0.875, we get an additional 1.5" added to the seam length of the part when developed. I've attached some photos to illustrate the difference when the straight value is modified. 

[craigjonnson]

Its likely that the tap is telling the straight to be sent as a machine cut. There is a wastage on the machine which is shortening the straight. This is normal. If your straights are sent to the decoiler with the taps cut in manually you can turn off the dynamic holes within pattern options.

[Mike_Arcari]

Hi Shane

I have 35mm straight set on my TDF and tried to re-create the problem from Revit to fabrication but mine came out correct length

I use CID pattern 866 for my straights

I don't normally use dynamic holes but even switching this on all lengths came out standard with or without a tap connected

Unfortunately that's about as much help I can offer you but i will keep thinking if there is anything else i could suggest to help

Thanks

[Anonymous]

With the help of Autodesk I was able to figure out the problem. There is a known issue with straights, and developed lengths. From Autodesk support - 

When dynamic holes are set to not develop, this issue can pop up. Our options are:

• Develop the dynamic holes:
• Under Database>Fittings>Patter Options>Holes> Dynamic branches section, check on "Draw Holes" and "Develop Holes"
• Once the holes are set to develop, the straight in the connector will not be added incorrectly anymore
• Export as a TXT and then import (This will need to be done in CAMduct)
• If Dynamic holes cannot/should not be developed, the workaround is to export as a TXT and bring the items back in
• Select all items in the job
• Run the EXPORTJOB command in CAMduct (Use CTRL+SHIFT+C to pull up command line)
• Name the file and save as a TXT
• Delete all items in the file
• File>Import>CAD/JCM Items
• Select the TXT file that was created, and select Open
• Items should import again, and now should show correct developments

I'm going to be doing some testing in the next couple of days, and will report back. I appreciate the time everyone took to help troubleshoot this! 

[craigjonnson]

Hi Shane,

What version of CADMEP are you using. We're still on 2019 without this issue, our configuration is set as per our duct manufacturers. All we send out  maj files & I have never come across this issue, except for the information i provided earlier re: machine cut.

[Anonymous]

Hey @craigjonnson,

We tried this with FabricationCAD MEP 2019, 2020, and 2021, as well as with the matching versions or Revit. The issue was persistent on all versions. 

It is likely an anomaly with our database that is causing the issue to persist. Do you have dynamic holes set to develop? If this option is set, it does not seem to be an issue.

[craigjonnson]

Dynamic holes are off. Our shop cut them in manually as its quicker to send all straights through the decoiler. The insulation doesnt cut properly if dynamic holes are set too. 

[Anonymous]

Do you have straight length added to connectors? Maybe that is the difference? If we eliminate the straight length from the connectors in the database, the problem disappears. 

[craigjonnson]

Hi Shane, No we have the straight added into the connector. Our coil width is 1500mm (5ft) Our TDF connector will knock off 50mm each side (2"). Therefore TDF Std Straight is 1400mm (4'6")

If i remove the straight off the connector my straight lengths will be incorrect.