S235, S235JR and 'steel'. To you and your colleagues, that is the same structural steel three times over. To Inventor, they are three different materials, each with its own name, its own density and its own row in every list you pull out of the system. As long as everything stays inside one project, you barely notice. Until the BOMs of a few projects land on one pile at purchasing.
Suddenly the same plate exists under three names, nobody can add up the kilos of steel in one go, and the ERP connection dutifully creates three articles where there should have been one. Managing your material library in Inventor is, at its core, a naming problem: one managed name per material, in every library, in every model. In this article you will see how to clean up the material library, how to agree on that single list of names and how to convert existing models in bulk, among other things with a toolbox like Thundercad.
Why three names cost more than one
A computer groups by exact text. Sort or filter a BOM by material and S235 and S235JR form two separate groups, with 'steel' as a third. The work planner who wants to know how many kilos of structural steel the project contains adds up three rows by hand, every single time. If the BOM flows on into an ERP system, three material records appear there, followed later by three stock positions and three purchase lines for exactly the same plate.
The second bill hides in the properties behind the name. Whoever creates a material 'real quick' types in a density by hand, and that goes wrong more often than you would like. Three variants of the same steel means three places where that mistake can live, without anything looking off on the drawing. What happens when masses start drifting through your project as a result, and how to check for it, is covered in Weights and materials in your BOM that are actually right. Here we tackle the root cause: the names themselves.
How the sprawl creeps in
Nobody decides on purpose to run three names for the same steel. It creeps in along a few well-worn routes:
- Templates with an old library. A new part inherits the material and the library link from the template, including names that should have been retired long ago.
- Copying from old projects. A copied part brings its material along, from the library of that era. That is how a retired name lives on through many more projects.
- Local libraries per workstation. Without a shared library, every engineer creates their own variants, with their own spelling and their own properties.
- Rush jobs before a deadline. The right material is not in the list, so someone creates 'stainless' on the spot and keeps going. Understandable, and exactly how variant number four is born.
- Imported files. STEP files from suppliers arrive with a generic material and tend to stay that way.
If you recognise two or three of these routes, you also see why a memo forbidding it will not work: you have to make the standard route easier than the shortcut.
One managed list of names as the foundation
The heart of the fix is a short, managed list: exactly one name for every material you actually use. That list is not a document for a drawer, it is the content of the shared material library. A few agreements keep it healthy:
- For each material, pick the designation you buy and produce against, the standard notation that purchasing and the shop floor recognise, not a pet name like 'steel' or 'regular stainless'.
- Record what each name is for, so nobody has to guess which variant is the right one.
- Appoint one owner. New materials only enter the library through that person, with a verified density and verified properties.
- Make the shared library read-only for everyone else, so the list cannot quietly expand again.
The shorter the list, the better the odds that everyone uses it. Twenty materials that are correct beat two hundred of which half are duplicates.
Cleaning up the material library in four steps
- Take stock of what is in circulation. Export the BOM with its material column from a handful of recent projects and collect all unique names. Chances are you will wince: dozens of variants for a handful of real materials.
- Pick a winner per cluster. Group all spellings of the same material and choose, per cluster, the name that goes on the managed list. Verify the winner's density and other properties while you are at it.
- Build the clean shared library. Put only the winners in it, link the library into the project on every workstation and adjust the templates so new parts draw from it automatically.
- Archive the old libraries. Do not delete them right away, just remove them from the project configuration. Old models remain readable, while new models only ever see the clean list.
Curious how many material variants are drifting around your own assemblies? With the toolbox you can set up that check in a few minutes, right inside your own Inventor environment.
Try 30 days freeConverting existing models in bulk
With a clean library, new work is covered, but your existing models still point to the old names in droves. Opening and converting part by part is not an option: on an assembly of four hundred items you lose a day and are guaranteed to miss a few.
So work per assembly instead. With Assembly iProp Menu from Thundercad you see the properties of a complete assembly in one list, including what each part carries as its material. Filter on the old names, select the whole group and update it in one bulk action to the name from the managed list, instead of clicking through file after file. The same approach works for project numbers, descriptions and other fields, by the way; how to organise that is described in Updating the metadata of a complete assembly in one pass.
Do not try to convert your entire archive in one weekend. The order that works in practice: first the assemblies currently being worked on, then each old project at the moment it is opened anyway for a change or a repeat order. The clean stock grows along with the work, without dedicated clean-up weeks.
Keeping it clean
Cleaning up is a project, staying clean is a habit. Three things keep the list in shape. New materials only enter through the owner, with a short note on why the existing list will not do. Imported STEP files get a real material from the list on arrival, or an explicit marker that the mass was entered by hand. And at release time, someone glances at the material column of the BOM exactly once.
After a few projects the check becomes boring, and that is exactly the point: no more surprises in the material column, weights you can trust and an ERP without triplicate articles.
Frequently asked questions
Do I have to convert finished projects retroactively?
No. A finished project that never opens again does no harm with old material names. Only convert what comes back into active work, for instance for a repeat order or a revision. That way the effort goes into models that still have a future.
Should the winning name be S235 or S235JR?
Pick the designation you actually buy and certify against; in most workshops that is the full standard notation such as S235JR. More important than the choice itself is that there is exactly one winner and that purchasing and work preparation use the same name. Record the decision in the list, and the debate happens only once.
How much work is a clean-up like this?
As an assumption, count on half a day for taking stock and building the clean library, and after that on minutes per assembly once you convert in bulk rather than per file. If you want to see that bulk work with Assembly iProp Menu on your own models, you can try Thundercad free for 30 days.