Handling Welded Assemblies (e.g., I-Beam with Welded Ribs) and Post-Weld Machining in Onshape

Fladdie

I am working with welded assemblies consisting of multiple individual parts, sometimes including identical parts. For example, an I-beam with welded ribs (identical parts).

• Each individual part requires its own part number and drawing for procurement.
• The welded assembly is treated as a single part with its own part number in the ERP system since it is permanently joined.
• The structured Bill of Materials (BOM) of a main assembly must correctly show both the welded assembly as a single part and all individual components needed for procurement.
• After welding, the assembly requires additional machining, such as milling the top surface to compensate for weld distortion or adding holes as part of the post-weld processing.

My questions:

1. What is the best practice in Onshape to represent both the individual parts and the welded assembly with their own part numbers and drawings?
2. How can post-weld machining (e.g., milling or drilling holes) be integrated efficiently into the Onshape workflow, considering assemblies cannot be directly modified with features?
3. Are there recommended workflows or best practices for managing welded assemblies and their post-weld machining in Onshape?
4. How can I ensure that the structured BOM of the main assembly correctly includes both the welded assembly as a part and all individual components?

I appreciate any advice or tips you can provide.

Pat_Couture

Wow no response since June 11. I have the same need and was hoping to find a solution here.

tabetha_bulnes

Have you tried Composite Parts?

Create a part studio. Derive the components you want to create post-weld machining for. Composite the parts together. Create your machining and bring the composite into an assembly.

The Composite Part can have its own part name and will show as a single "welded part" in the BOM.

Fladdie

Hey everyone,

first of all, thanks a lot for your replies!
@Pat: It’s really reassuring to see I’m not the only one running into this.
@tabetha: I was basically aware of the composite-part-from-derived-components approach – but in my use case it unfortunately comes with a few gotchas.

What does work for me in principle:
I can derive the individual parts into a separate Part Studio, position them there as “pre-weld” parts, weld / further process them, and then turn that into a Composite Part which I use as the “welded part” with its own part number in the assembly.

The real problem, however, is:

• The individual raw parts (e.g. machined parts that later get welded together) no longer show up in any BOM – but I still need them as separate items for manufacturing, purchasing, and inventory.
• I could build an assembly that contains both the welded composite part and all the individual parts, so they appear in the BOM – but then
  • the mass/weight of the assembly is no longer correct (geometry is counted twice), and
  • the structure of the BOM no longer reflects the real physical assembly.

On top of that:
If I want to perform final machining operations (e.g. drilling, milling, facing) on the “finished” welded part, I quickly hit a limitation when using only an assembly in Onshape, because I can’t model those post-weld operations there – that’s only possible in a Part Studio.

So in short, what I’d really need is:

1. a finished, post-machined welded part (ideally with its own part number, e.g. as a Composite Part),
2. all individual parts cleanly and structurally listed in the BOM so they can be manufactured / purchased,
3. without breaking the correct mass/weight and BOM structure of the final assembly.

If anyone has a clean workflow or best practice in Onshape for this, I’d really love to hear it.
In any case, thanks already – I’m genuinely glad we’re finally having a discussion about this.

tabetha_bulnes

I am not sure if this is what you are looking for but have tried inserting the weldment as a rigid part studio in the assembly? This will bring in the parts and composite part so that both show in the BOM. And then as long as you do not set a material to the composite part the mass should be correct.

Below I created a part studio with 2 parts (11111 and 22222) and created a composite part (333333) I then brought in the whole part studio as rigid and then is how my BOM was generated.