Plant 3D Practical Knowledge
Clash detection and plant origin point in AutoCAD Plant 3D
Civil works, steel structures, equipment, existing plant and pipes come from different programs and different partners. For everything to fit together, you need a common plant origin point – and clash detection before construction starts.
With us you will find solutions for your tasks.
The task: bringing the disciplines together
In a plant project, several disciplines supply their models. Every program has its own origin, its unit and its axis direction. Only when all use the same reference do the models lie on top of each other in the right position in AutoCAD Plant 3D and in Navisworks.
| Discipline | Typical source |
|---|---|
| Build | Buildings and foundations, often from Revit |
| Steel construction | Platforms, pipe racks and scaffolding, e.g. from Advance Steel |
| Machines and equipment | Manufacturer models, e.g. from Inventor or as STEP |
| Existing plant | Point cloud from the laser scan |
| Piping | AutoCAD Plant 3D |
Setting the plant origin point at the project start
Checklist for the project start – defined once, valid for all disciplines.
- Position of the plant origin point: a clearly defined point that can be found on the building, e.g. intersection of two building axes
- Axis direction: X and Y axes aligned with the building or plant grid, reference to north recorded
- Height reference: which elevation is Z = 0, e.g. top of finished floor, and its value above sea level (NHN)
- Unit: millimeters or meters – explicitly agreed for every supply
- Site plan coordinates: only as a converted offset; drawing is done close to the origin
- Exchange: which discipline supplies in which format and how often
- Documentation: all values in one sheet that every discipline receives at the project start
You define these points before the first model is created. Models moved afterwards cost time in every exchange.
Check the coordinates of supplied models
From our questions from practice on AutoCAD, Plant 3D, ReCap and Navisworks.
- Objects end up in the wrong place – very large coordinates make AutoCAD and Plant 3D inaccurate – work close to the origin. Go to the question
- Drawn with the real site plan coordinates – better draw close to the origin and output via elevation mark and north orientation. Go to the question
- Survey points in the wrong unit – in ReCap, the coordinates of survey points are entered in meters. Go to the question
- Point cloud does not match the floor plan – set the origin of the point cloud to a grid coordinate of the plan – once, in the master project. Go to the question
- Models moved in Navisworks – after the next exchange, measurements and clashes no longer match – correct the position in the source. Go to the question
- The isometric should show plant coordinates – enter an offset in the advanced isometric settings – the model stays where it is. Go to the question
You attach drawings from other disciplines as references instead of copying them. That way, changes arrive the next time you open the drawing, and the position is preserved. Transfer in the same position: Transfer content into a new drawing in exactly the same position.
Clash detection with Navisworks
Navisworks combines the models of all disciplines – including the point cloud – and checks them against each other.
- Assemble the overall modelAppend the drawings of all disciplines in Navisworks and save them as an NWF. The NWF only references the original files and stays small.
- Create search setsCreate groups such as “all pipes”, “steel structures” or “insulation” as search sets. They remain correct even after refreshing.
- Set up the testIn Clash Detective, check selection A against selection B – hard or with clearance, e.g. for insulation and installation space.
- Evaluate the resultsFilter out irrelevant results, assign genuine clashes and pass them on to the disciplines as a report.
- Fix it in the source modelClashes are always resolved in the source model, for example in AutoCAD Plant 3D. Then refresh Navisworks and run the test again.
- Combine many Plant 3D drawings into one overall model Go to the question
- Set up a meaningful clash test in Clash Detective Go to the question
- Reduce hundreds of irrelevant results Go to the question
- Why clash tests are built on search sets Go to the question
- Create and distribute the clash detection report Go to the question
How we support you
Navisworks training
Live with a trainer, online or in Frankfurt: combine models and check for clashes.
Project start with us
Together with you, we define the plant origin point, units and exchange and set up the Plant 3D project accordingly.
Configuration training
Project setup and isometric settings in AutoCAD Plant 3D, including isometric coordinates with an offset.
Support
Models do not line up or the test returns too many results? Via Teams, billed by actual time.
Looking for support in an ongoing project?
Self-test exercises
For studies, vocational training and induction – with a solution to expand.
Exercise 1 A supplied equipment model appears 1,000 times too small in the piping model. What is the most likely cause?
Show solution
Different units: the model was supplied in meters, the project works in millimeters. Define the unit for all disciplines at the project start and check supplied models on receipt.
Exercise 2 The isometric should show plant coordinates. Do you move the model to achieve this?
Show solution
No. You draw close to the plant origin point and enter the offset in the advanced isometric settings. The model stays where it is – otherwise references and supplied models no longer fit.
Exercise 3 Where do you fix a clash that Navisworks finds between a pipe and a steel beam?
Show solution
Always in the source model, for example in AutoCAD Plant 3D or in the steel model. Then refresh Navisworks and run the test again.
More exercises and a guide to the modules in your studies: For teaching and education.
Frequently asked questions
What is a plant origin point?
The plant origin point is the common reference point of all disciplines in a project: position, axis direction and elevation Z = 0. If all disciplines supply their models referenced to this point, civil works, steel structures, equipment, point cloud and pipes fit together without moving anything.
Why not draw directly with site plan coordinates?
AutoCAD and AutoCAD Plant 3D become inaccurate with very large coordinates. So draw close to the plant origin point and output site plan or plant coordinates as an offset – on the isometric via the advanced settings, without moving the model.
What do I use to check clashes between AutoCAD Plant 3D and other disciplines?
With Navisworks. There you combine the models of all disciplines and check them against each other in Clash Detective. Fixes are always made in the source model; then you refresh Navisworks.
Before you go …
Don't miss any training dates, C³ invitations and news on AutoCAD Plant 3D and P&IDR&I – Piping and instrumentation diagram Flow diagram showing all pipes, valves, equipment and instrumentation of a plant (P&ID, Piping and Instrumentation Diagram). Background and sources ›.
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Terms, background and sources 1 term on this page
Brief explanations for reference. They do not replace the standard or code itself.
- R&I – Piping and instrumentation diagram
Flow diagram showing all pipes, valves, equipment and instrumentation of a plant (P&ID, Piping and Instrumentation Diagram).
Symbols and drawing rules: DIN EN ISO 10628-1 and -2. Identification letters for instrumentation: DIN EN 62424 or ISA-5.1.