Multi-Body Parts in SOLIDWORKS Weldments / Structure System – Problem and Solution | DSTV Assistant

Multi-Body Parts in SOLIDWORKS Weldments / Structure System
From Design to Manufacturing - is it really that easy?

The Multi-Body Problem

SOLIDWORKS Weldments / Structure System create so-called Multi-Body Parts – a single part file containing multiple solid bodies.
For design purposes, this is a clever solution: all structural profiles remain in one file, changes can be managed conveniently, and typical problems associated with conventional assemblies – such as numerous mates, external references, or circular dependencies – are largely avoided.

Strictly speaking, Multi-Body Parts are the way SOLIDWORKS enables parametric steel structure design within the part environment. For many design tasks, this concept works remarkably well and offers an easy entry point into weldment design.

The trade-off, however, becomes apparent in downstream processes and in the absence of dedicated steel construction features – such as those offered by SolidSteel parametric for SOLIDWORKS.

While the designer views multiple bodies as a single part, manufacturing, CAM systems, and machine controllers require individual parts with their own distinct properties. A Multi-Body Part, however, shares only one common set of file properties. Material, part numbers, and other part properties apply to the part as a whole – not to the individual bodies within it.

To address this limitation, SOLIDWORKS introduced the Cut List. It provides individual information for each structural body – such as length, profile, or material – and serves as an important basis for bills of materials and manufacturing documentation. For many use cases, this concept works very well.

However, as soon as native manufacturing data needs to be generated – such as DSTV, DXF, or other NC files – this approach reaches its limits. These export formats operate at part level, not at the level of individual bodies within a Multi-Body Part.

The Equal Parts Problem

A direct consequence of this is the lack of automatic geometric equal parts detection.

If a design contains, for example, six identical posts within a Multi-Body Part, a conventional DSTV export will produce six individual NC files – even though a single file with a quantity of 6 would be the correct and desired result.

For the machine operator, this means unnecessary files, more administrative overhead, and a higher risk of errors. The actual information – "this part is manufactured six times" – is lost in the export process.

Without equal parts detection, a separate NC file is created for each body

Why This Is Not a Bug in SOLIDWORKS – But a System Boundary

This limitation is less a bug and more a consequence of the underlying architecture. Multi-Body Parts were primarily designed to enable weldment structures to be modelled efficiently within a single part file. For design purposes, this is a sensible trade-off – but it is not always the ideal data foundation for downstream manufacturing processes.

Alternative approaches – such as those taken by specialised steel construction solutions – work with their own parametric logic at assembly level. This allows individual parts to be managed independently, without incurring the typical drawbacks of conventional SOLIDWORKS assemblies with numerous mates and external references. The result is high-performance models where every part exists as a standalone manufacturing object from the very beginning.

For those who deliberately rely on the flexibility of SOLIDWORKS Weldments, however, an intelligent bridge between design and production is needed for the manufacturing step.

Our Solutions for Both Workflows

DSTV Assistant – Equal parts detection from Multi-Body Parts

Geometrically identical parts are automatically detected and combined into a single NC file with the required quantity specified.

Even with SOLIDWORKS Weldments, users do not have to go without a convenient DSTV export. The DSTV Assistant can analyse Multi-Body Parts directly and output the structural bodies contained within them as DSTV NC files. A prior decomposition of the Multi-Body Part is therefore not required for the export itself.

If, however, geometrically identical parts are to be automatically detected and combined into a single NC file with the corresponding quantity, the structural bodies must first be converted into individual parts using the SOLIDWORKS "Save Bodies" function. It is only at this assembly level that geometric equal parts detection can operate reliably.

Those who would prefer to avoid this intermediate step altogether will find a different approach with SolidSteel parametric. Here, steel structures – including profiles, steel-specific connections, stairs, and railings – are created from the outset as individual components within an assembly. Thanks to its own parametric core, parts are managed intelligently without relying on a large number of conventional SOLIDWORKS mates or extensive external references. As a result, even large steel structures remain high-performing, and all downstream processes – from bills of materials and PDM through to DSTV export – work directly with individual parts.

Whether working with existing Weldment designs or fully parametric steel construction: we offer a solution for both workflows that makes the transition from design to manufacturing significantly more efficient.

You have additional questions about this topic? Our experts are pleased to help you. Just send us a Message or give us a call at +49 271 23167 0.

Multi-Body Parts in SOLIDWORKS Weldments / Structure System
From Design to Manufacturing - is it really that easy?

The Multi-Body Problem

The Equal Parts Problem

Why This Is Not a Bug in SOLIDWORKS – But a System Boundary

Schedule an online product demo

Try the software free of charge for 7 days

Contact us

Our Solutions for Both Workflows

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Multi-Body Parts in SOLIDWORKS Weldments / Structure System From Design to Manufacturing - is it really that easy?

The Multi-Body Problem

The Equal Parts Problem

Why This Is Not a Bug in SOLIDWORKS – But a System Boundary

Schedule an online product demo

Try the software free of charge for 7 days

Contact us

Our Solutions for Both Workflows

YouTube: Products in action

LinkedIn: Updates for professionals

Facebook: News at a glance

Multi-Body Parts in SOLIDWORKS Weldments / Structure System
From Design to Manufacturing - is it really that easy?