Custom Python Scripts for AutoCAD Plant 3D – Part 3

By David Wolfe (Contributor)

Get start with Part 1 and Part 2 of this series.

Expansion Joint Script

This article will look at creating a completely new script, an expansion joint. The script should look like this:

from varmain.primitiv import *
from varmain.custom import *
@activate(Group="Sleeve",
          TooltipShort="Expansion Joint",
          TooltipLong="Expansion Joint with Bellows",
          FirstPortEndtypes="FL",
          LengthUnit="in",
          Ports="2")
@group("MainDimensions")
@param(D=LENGTH, TooltipShort="Pipe OD", TooltipLong="Pipe OD")
@param(D1=LENGTH, TooltipShort="Flange OD", TooltipLong="Flange OD")
@param(D31=LENGTH, TooltipShort="Bellows OD", TooltipLong="Bellows OD")
@param(L=LENGTH,
       TooltipShort="Length of the ExpansionJoint",
       TooltipLong="Overall Length of Expansion Joint")
@param(L31=LENGTH,
       TooltipShort="Flange Thickness",
       TooltipLong="Flange Thickness")
@param(T=LENGTH,
       TooltipShort="Bellows thickness",
       TooltipLong="Thickness of a bellow")
@param(B=LENGTH, TooltipShort="Number of Bolts", TooltipLong="Number of bolts")
@param(B1=LENGTH, TooltipShort="Bolt Size", TooltipLong="Bolt Thickness")
@param(B2=LENGTH,
       TooltipShort="Bolt Length (greater than L)",
       TooltipLong="Bolt Length")
@param(OF=LENGTH0)
#(arxload "PnP3dACPAdapter")
#(testacpscript "EXPJOINT1")
def EXPJOINT1(s, D=4.5, D31=5.5, D1 = 9.0, B=4, B1=0.75, B2=9.5,
              L=9.0, L31=0.25, T=0.5, K=1, OF=0, **kw):
    NumOfBellow = round(((L - (2*L31)) / T)/2)-1
    #set a default hole size
    fhole = .95*D
    #create a hole in the flange
    if OF > 0:
        fhole = (D-OF)
    #create our first flange
    Flange1=CYLINDER(s,R=D1/2, H=L31, O=0).rotateY(90)
    bellowlength = (T*2*NumOfBellow)-1
    nb = 0
    #overall length - belows length / 2 plus 1/4 the width of the bellow
    offset = (((L - bellowlength - (2*L31))/2)+L31)
    expBody = CYLINDER(s,R=D31/2, H=L-L31, O=D).rotateY(90).translate((L31,0,0))
    #union the first flange and main body
    Flange1.uniteWith(expBody)
    expBody.erase()
    while (nb < NumOfBellow):
        #create and offset our torus
        b=TORUS(s,R1=D31/2,R2=T/2).rotateY(90).translate((offset,0,0))
        #increment our offset distance
        offset = offset + T*2
        #union as we go
        Flange1.uniteWith(b)
        b.erase()
        nb = nb + 1
    #create our end flange and offset it
    Flange2=CYLINDER(s,R=D1/2, H=L31, O=0).rotateY(90).translate((L - L31,0,0))
    Flange1.uniteWith(Flange2)
    Flange2.erase()
    #see if we need to create bolts, if there is a bolt cound and it's greater than 0
    if B > 1 and B1 > 0 and B2 > L:
        anglesplit = 360/B
        startangle = 0
        if B%2!=0:
            startangle = anglesplit/2
        intbolt=0
        incangle=startangle
        platewidth=3*B1
        platelength=4*B1
        plateheight= 0.75*L31
        #make the bolts the length of the object + 2 flange thickness
        boltlength = L + 4*L31
        #calculate our offsets
        #plate on flg one offset
        pof1 = (L31 - plateheight/2,D1/2+platewidth/2,0)
        #translate the bolts
        bof1 = (-(B2-L),D1/2+platewidth/2,0)
        #translate the second plate
        pof2 = (L - (L31 - plateheight/2),D1/2+platewidth/2,0)
        #create a cylinder to subtract for the opening
        boreCy = CYLINDER(s,R=fhole/2, H=L, O=0).rotateY(90)
        Flange1.subtractFrom(boreCy)
        boreCy.erase()
        while (intbolt < B):
            #create a plate for the bolt, rotate it, and then move it to the edge and back to face of flange 1
            p = BOX(s,L=platewidth,W=platelength,H=plateheight).rotateX(90).translate(pof1).rotateX(incangle)
            #unite with flange 1 so we have a single body
            Flange1.uniteWith(p)
            p.erase()
            #create the bolt
            b = CYLINDER(s, R=B1/2, H=boltlength,O=0).rotateY(90).translate(bof1).rotateX(incangle)
            #join the flange and bolt
            Flange1.uniteWith(b)
            b.erase()
            #create our plate on flange 2
            p2 = BOX(s,L=platewidth,W=platelength,H=plateheight).rotateX(90).translate(pof2).rotateX(incangle)
            #merge the last plate
            Flange1.uniteWith(p2)
            p2.erase()
            incangle = incangle + anglesplit
            intbolt = intbolt + 1
    return

Metadata

The most interesting part of this script, other than the geometry, is the metadata.

Note that the group defines where the script shows up in the spec editor.

The tooltips show when the dimensions are hovered over in the editor as well.

Script Testing

While creating the script, you must be able to test it to see if your geometry can be generated. Because these scripts are designed to be processed within AutoCAD, currently there is no IDE that you can use to debug the shapes. The process of testing the script looks like this.

1. Create your script file at C:\AutoCAD Plant 3D 2025 Content\CPak Common\CustomScripts (or wherever your Shared Content folder is for plant (MODIFYSHAREDCONTENTFOLDER).
2. Create your geometry functions, and metadata sections.
3. Start Plant 3D
4. Use PLANTREGISTERCUSTOMSCRIPTS. If there is an error in the script, you will get a warning at the command line with the line number. For most errors line of the script with the error will be listed. If no errors are shown, the script compiled.

   

5. Load the PnP3dACPAdapter.arx. You can do this by pasting this at the command line:
   

   (arxload "PnP3dACPAdapter")

   
   
6. Test the script. You can test with the default parameters by pasting this at the command line:
   

   (testacpscript "EXPJOINT1")

   
   

   Fill in your script function where EXPJOINT1 is.You can also test the script from one of the other following options:

   
   

   (TESTACPSCRIPT "CPFLR")
   (TESTACPSCRIPT "CPFLR" "D1" "300.5")
   (TESTACPSCRIPT "CPFLR" "L" "40" "D1" "300.5" "D2" "88.9")
   
   (TESTACPSCRIPT1 "CPFLR")
   (TESTACPSCRIPT1 "CPFLR" "D1=300.5")
   (TESTACPSCRIPT1 "CPFLR" "L=40,D1=300.5,D2=88.9")

   
   
7. If you need to make changes, make them before closing Plant. That way you can try to register the script again to see if you still have breaking code.
8. If the script has been changed and registered, you must close Plant 3D in order to test the geometry again. Once the script is registered or run, the Python processor stores that script in memory until Plant 3D is closed, so starting a new session is the only way test new script changes.