Assembly Cut or Promote Body?

[sam5a1]

I have a small sub-assembly with only 8 parts. The parts have no holes at the part level. This sub-assembly (assy-1) will be used in the next, upper, sub-assembly (assy-2) where each part will have 1 to 2 holes applied. That sub-assembly (assy-2) will be used in the next upper assembly (assy-3) where other parts will be added and located in the holes that were cut in the previous sub-assembly (assy-2). That assembly (assy-3) will then be used in another assembly (assy-4) and that will be used in the next 3 assemblies (assy-5, 6, 7). So you can see that (assy-1) is the foundation for the final, large assembly.

My question is kind of a poll, what is better for cutting the 12 holes in assy-2, a promote body or assembly cuts and why?

 

[KhimaniMohiki]

Not wanting to further complicate the matter but you could also use WAVE linking. Model your 'cutting' tool bodies at the assembly level, WAVE link the part bodies in then subtract the tool bodies. The only downside to that being that you will have model data at assembly level.

Khimani Mohiki
Design Engineer - Aston Martin
NX8.5

 

[JohnRBaker]

The 'Assembly Cut' function is actually based on performing a 'promotion' internal to the feature being created, like having a Boolean Subtract and the Promotion all in one easy to use operation.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[sam5a1]

The opposition to the WAVE application is having the model data at this assembly level since it is so low in the finished assembly process. Personally I much prefer using WAVE but we have had "Out of Date" issues and some maintenance issues with some WAVE parts in the past.

 

[Xwheelguy]

The Assembly Cut because it can be redefined to another body (using Edit with Rollback) - whereas you have to completely re-create the Promotion if the target or tool body is missing.

Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB

 

[sam5a1]

Very good point Tim. That is something that has to be taken into account.

I always thought that was the case John but it seems sometimes that the more complex the assembly cuts are the more unstable it becomes in the upper assemblies. That is one reason I am asking this question, to see if anybody else has seen some problems with either assembly cuts or promotions.

 

[Xwheelguy]

The ONLY problem I've encountered with it has nothing to do with NX, but rather our PDM software not recognizing an Assembly Cut as an NX Assembly when we import the 3D. Make sure you test with PDM if applicable before making the move permanently.

Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB

 

[JohnRBaker]

Assembly Cut was NOT designed as a way of sharing design geometry with other models. Rather it was designed to work ONLY in the context of an Assembly and to be used primarily to create Modeling operations, at the Assembly level, which represented manufacturing steps, in that case, metal removal operations, as in drilling and milling, which could take place ONLY after two or more parts were assembled together, the classic example being where there is some question where one part needs to be attached and so a part is positioned at that Assembly level and then holes are drilled to hold the part where the final position was determined to be, but that these holes would never be drilled, even in future manifestations of this product, while the individual parts were being fabricated. Another example is where there's a need to drill holes for pins which will hold some part rigid once the parts have been positioned and bolted into place, but there is a need for a fixed position, NOT dependent on the clamping force of the fasteners, to prevent it from moving. One example of this is the use of cross-drilled nuts that once tightened, a hole is drilled through the threaded shaft/bolt using the cross-drilled hole in the nut as a guide and then a roll-pin is driven in to hold it. The hole in the threaded shaft/bolt could not possibly have been drilled prior to Assembly and will only be manifested at the Assembly stage of the manufacturing workflow. Assembly Cut is also useful when something like a frame is welded together and then machining operations are performed to square-up faces or to provide something where another part can seal against it, like we used to do with large mixer bowls used to make bread dough (up to 2,400 lbs at a time) where the mixer bowls were welded fabrications of stainless steel which was then put on a machine and the faces of the bowl where doors and shafts had to seal were machined. The model of the welded bowel, which was an assembly of previously fabricated parts, many of them machined parts, did not include any of this secondary machining until is was an 'assemblied' part and welded together.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[Xwheelguy]

Poorly worded....I meant an NX Assembly where an Assembly Cut had been performed on one of the Components was not recognized as an NX Assembly by PDM. Sorry about that.

Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB

 

[sam5a1]

That is close to what we have seen here at times. When an assembly cut is used to cut through several items in an assembly and then that assembly is imported into (or out of) Tc, the assembly cuts were not made and the tool was just solid body. This behavior is not predictable and seems very random.

 

[Xwheelguy]

This wasn't TC which was giving us the issue - the E-word from the D-word company in France.

Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB

 

[sam5a1]

Surprised that it wasn't much worse but when you're using the "End to easy Design" PDM you have to expect......somethings not to work correctly?