iLogic or a ready-made toolbox? When to choose what

You know the moment. For the umpteenth time you run through the same string of actions in Autodesk Inventor: filling in iProperties, turning drawings into PDF and DWG, exporting a bill of materials to Excel. And you think: there has to be a smarter way. The obvious route is iLogic. You write a few lines of code, hook a button to it, done. But then it grows. One script becomes ten. A colleague asks if you can quickly fix his variant. And one day, usually right when you happen to be on holiday, something grinds to a halt and someone asks: who actually maintains this?

That is exactly the point at which many engineering departments start looking for an iLogic alternative. Not because iLogic is bad, it is a powerful piece of tooling, but because building it yourself has hidden costs that only become visible once the script is already deep in your process. In this article we lay out the two routes honestly side by side: automating yourself with iLogic and standalone scripts versus a maintained toolbox such as Thundercad. No sales pitch of "scripting is dumb", because it is not. Instead a sober trade-off of maintenance, Inventor updates, team dependency and coherence, so that you make the right choice for your situation.

What iLogic is and is not

iLogic is the built-in rule engine of Inventor. You write rules (essentially VB.NET) that drive parameters, suppress features, read and write iProperties, or build complete configurations. For parametric, product-specific logic that is worth its weight in gold. Think of a stair manufacturer who enters height, width and number of steps and lets a complete model roll out of that. Or a machine builder with a standard conveyor belt that is supplied in lengths of 1 to 12 meters, where the frame, the number of support legs and the drive adjust themselves automatically. That is iLogic at its best: knowledge about your product, captured in rules.

What iLogic is less suited for is generic, recurring production work that is the same on every project. Publishing all drawings of an assembly in one go. Managing metadata consistently across all your document types. Opening an assembly of 200 parts at lightning speed and then closing it neatly again. Getting a bill of materials into a fixed Excel template that purchasing can read straight in. Those are not product-specific rules, but workflow actions that are largely the same for every Inventor user. And that is precisely where building it yourself often starts to chafe.

The difference lies in the nature of the problem. Product logic is unique to your product and belongs with you: no one else knows your configurations and build rules. Workflow automation is generic; every Inventor department struggles with the same export dialogs and metadata fields. If you build that yourself, you are reinventing the wheel, and you keep maintaining it yourself afterwards too.

The hidden costs of building it yourself

Writing a script is cheap. Maintaining a script is not. That is the heart of the trade-off, and the reason so many departments consider an iLogic alternative as soon as their first collection of scripts has grown into a tangle that no one fully oversees anymore.

Maintenance creeps into every corner

The first script works perfectly. The second one too. By the seventh you discover that they get in each other's way: one user runs a modified version, another the original, and no one knows anymore which one is the "real" one. Someone changes the folder structure on the server and half the export scripts trip over a path that no longer exists. A template gets an extra iProperty field and your BOM script suddenly spits out empty columns. Maintaining home-built automation is not a project with an end date: it is a fixed cost that never goes away. And it gets in the way precisely at the busiest moments, because errors only show up when you have to deliver a set under pressure.

Inventor updates break things

Autodesk releases a new Inventor version every year. Sometimes the API changes, sometimes a method behaves slightly differently, sometimes a function disappears. With a maintained toolbox that is the vendor's concern: they test against the new version and ship an update. With your own scripts it is your concern, and usually at the worst conceivable moment. Suppose the whole department has just switched to the new version because a customer asked for a model in it, and then it turns out your publish script no longer runs. Now you are stuck with production waiting and a colleague who has to figure out, between his own deadlines, which API call has changed. That bill is hard to estimate in advance, but it comes back every year.

Team dependency: the bus factor

This is the quietest and most dangerous cost. Often there is one colleague, let us call him the script hero, who built everything and is the only one who understands how it fits together. As long as he is around, it runs. But what if he is on holiday for two weeks, gets sick, or finds another job? Then there is code in production that no one dares to touch, with variable names only he understood and without a single line of explanation. We call that the bus factor: how many people can get hit by the proverbial bus before your process grinds to a halt? With many home-built solutions the answer is: one. And that is a risk no engineering manager would consciously choose if he saw it spelled out in black and white.

Coherence is missing

Standalone scripts are exactly that: standalone. Each script has its own button, its own logic, its own assumptions about folders, names and settings. There is no shared configuration, no consistent interface, no overarching management. A new employee has to learn one by one which button does what, which order is correct and where the pitfalls are, usually by getting something wrong once. A toolbox designed as a coherent whole offers one way of working across all tools: the same settings, the same logic, the same behavior. That saves enormously on onboarding time and on the kind of mistakes that arise because one tool works just slightly differently from another.

iLogic alternative in practice: the direct comparison

Enough theory. Let us lay the two routes side by side on the points that matter in daily practice. The table below summarizes what you get and what it costs you: not only in euros, but in time, risk and peace of mind.

The table makes one thing clear: it is not a question of good versus bad, but of the right tool for the right problem. iLogic wins on product-specific logic. A toolbox wins on generic, recurring production work where coherence and maintenance weigh heavier than custom work. The mistake departments make is not that they use iLogic, but that they also deploy iLogic for generic work where it offers no advantage and does create a maintenance burden.

Do the math: what does building it yourself really cost

Let us take an example, clearly presented as an assumption. Suppose an engineer spends two days building a batch publish script that turns drawings into PDF, DWG and DXF. That seems like a one-off and therefore "free after the first investment". But do the math further. Every new Inventor version costs, say, half a day of adjusting and testing. A changed folder structure or a new template costs another few hours. A colleague wants an extra format added: another afternoon. And when the builder leaves, onboarding a successor, or rebuilding the script from scratch, quickly costs several days.

Add that up over a few years and "two days" is no longer two days at all. And these are engineering hours: the most expensive and scarcest hours in the building, which you would rather spend on design than on repairing a PDF export script. With a toolbox such as Thundercad you do Batch Publish in one click instead of twelve steps, and you save, for example, 48 PDFs in 6 seconds, including collaboration with Autodesk Vault. No maintenance, no version stress, no dependency on one person. Whether the subscription is worth it depends on your situation, but the sum often works out very differently from the gut feeling that "building it yourself is free".

What a maintained toolbox covers in concrete terms

To make it tangible: a toolbox takes over precisely those generic, recurring actions where building it yourself demands the most maintenance. At Thundercad it concerns, among other things:

• iProperty Menu: manage metadata and iProperties through one configurable data card per document type, instead of per script or by hand.
• Batch Publish: all production documents in one step: PDF, DWG, DXF and STEP, working with Vault.
• BOM Export: bills of materials to Excel in a fixed template, without having to maintain the export logic yourself.
• Batch Open & Close: open files in assemblies quickly and close them neatly again.
• Quick Save / Load: park work and bring it back exactly as you left it.
• Model Cleaner: remove leftover geometry and tidy up the browser.
• Sheet Buttons: scale the sheet size up or down and rotate.
• Dashboard: activate and manage tools, and link them to your ERP or other software.

That last one, the Dashboard with a link to ERP, shows where the two worlds meet. A toolbox does not close the door on custom work; it gives you a maintained foundation on which you can hook your own integrations. So you keep the freedom to build your real product logic with iLogic, while the generic work around it is covered. Companies such as Little Giant Europe, Van Egten, Banzo and Mannen van Staal already work with it to take exactly that repetitive work out of their engineering process.

On the roadmap, by the way, there are even more tools that are now typically solved with home-built scripts: Batch Flat Pattern, Find Item, a Drawing Checker/Cleaner and a Drawing Updater. Not available yet, but they show the direction: more and more generic manual work is shifting to a maintained whole.

So when do you choose what?

The honest conclusion is not "always this" or "always that". It is a trade-off, and it works out differently per type of work. Below is a rule of thumb you can apply directly to your own collection of scripts.

Choose iLogic / building it yourself when:

• it concerns product-specific logic that is unique to your product: configurators, parametric families, build rules that no one else knows.
• you structurally have someone in house who can build and maintain this, and you consciously accept and document that dependency.
• the problem is so specific that no existing product covers it and custom work truly delivers a distinguishing advantage.

Choose a maintained toolbox when:

• it concerns generic production work that is the same on every project: publishing, exporting, managing metadata, opening and closing assemblies.
• you would rather not carry maintenance, Inventor updates and team dependency yourself.
• you consider coherence and a consistent way of working across your whole team important.
• you want a new colleague to be productive quickly without someone having to come explain the pitfalls first.

In practice many departments choose both: iLogic for the real custom work that sets their product apart, and a toolbox for everything around it. That way you spend your scarce engineering hours where they make the difference, on the design your customer buys, and not on a PDF export script that can break with every update. The nice thing is that you do not have to prove that in advance on a spreadsheet: you test it on your own projects before you change anything about your process.

Frequently asked questions

Is a toolbox a replacement for iLogic?

No, and that is not the intention either. iLogic is strong in product-specific logic such as configurators and parametric families; a toolbox such as Thundercad covers generic, recurring production work such as publishing, exporting and managing metadata. Many departments use them side by side: iLogic for the custom work, the toolbox for the daily workflow around it.

What happens to my existing iLogic scripts?

You can simply keep using them. A toolbox does not replace your product logic, but takes over the generic actions you now maintain standalone scripts for. So you can switch over gradually: start with the scripts that cost the most maintenance or pose the greatest bus factor risk, and let those go first. You do not have to rebuild everything in one go.

What if I want to link to our own software or ERP?

That is possible via the Dashboard, with which you manage tools and link them to ERP and other software. That way you keep a maintained foundation for the generic work and hook your own integrations and custom work onto it. Want to experience it yourself? You can try Thundercad free for 30 days without a credit card, on your own Inventor environment and projects.