AI for CAD Tools
How to get the clearance between two parts during a design review without opening a CAD seat, what the number means, and the limits to keep.
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8 min read
Michelle Ben-David
Michelle Ben-David is a mechanical engineer and Technion graduate. She served in an IDF elite technology and intelligence unit, where she developed multidisciplinary systems integrating mechanics, electronics, and advanced algorithms. Her engineering background spans robotics, medical devices, and automotive systems.
BOTTOM LINE
A clearance question in a design review should take seconds, not a trip through the vault and a licensed seat. Selecting one part shows its properties, and selecting two measures the distance between them. Treat that value as a nominal screening number: name the two parts and the revision, confirm which distance is reported, move to tolerance analysis when the gap is tight, and keep the drawing as the source of the requirement. Used that way, a fast measurement speeds up the review without weakening it.
Somewhere in every design review, someone asks a question that sounds small. How close does the bracket sit to the motor housing? Is there room for a cable clip between the cover and the frame? The answer is one number, the clearance between two parts, and getting it often means finding the right assembly, waiting for it to load in a licensed CAD seat, picking two faces and reading a dimension.
That detour is the cost this article is about. We look at what a clearance number really is, what a measure tool inside an AI assistant can and cannot tell you, how the one-part and two-part modes work, and the habits that keep a quick answer from turning into a wrong one. It is written for design engineers, reviewers and project leads who need a distance during a meeting, not a modeling session.
Why a clearance question interrupts the review
Clearance is the gap between two things that are supposed to stay apart. It matters for assembly access, thermal growth, vibration travel, service tool reach and plain manufacturability. In a review it comes up constantly, and it is almost always asked by someone who does not have the model open.
The usual path to the number is longer than the question. The reviewer needs a seat of the CAD system, which may be shared or limited. The assembly has to be located in the vault, opened at the right revision and rebuilt. Large assemblies take minutes to load, and the person who knows which two parts matter may not be the person with the seat. By the time the number arrives, the discussion has moved on or the group has agreed to look at it later, which in practice means a follow-up meeting.
There is also a quieter cost. When a clearance question cannot be answered on the spot, people estimate. Someone says it looks like about five millimetres, the estimate goes into the notes, and it quietly becomes the working assumption. Estimates made from screenshots and memory are where many late fit problems start.
The goal, then, is not to replace the CAD system. It is to separate two jobs that have been bundled together: modeling, which needs the seat and the skill, and asking a geometric question of a model that already exists, which needs neither. A distance between two selected parts is a question of the second kind.
It helps to be precise about what the reviewer actually wants. Usually it is one of three things: the smallest gap anywhere between the two parts, the gap at a particular feature such as a mounting face, or confirmation that a required minimum is still met. These are different questions, and a good answer says which one it is giving.
Teams that treat the clearance question as a routine lookup, rather than a small modeling task, tend to hold shorter reviews. The number arrives while the group is still looking at the same screen, and the decision follows from it immediately.
IN PRACTICE
We're less dependent on outsourced engineers. We do it all in-house. We get answers in a few minutes instead of a few days.
- Harel Oberman, CEO, Oberman Industrial Designs
What a distance measurement returns, and what it does not
A distance between two parts is a geometric fact about a specific model in a specific state. Before relying on one, it is worth knowing what is inside that fact.
Most distance tools report the minimum separation between the two bodies: the shortest straight line from any point on one surface to any point on the other. That is usually what clearance means, but it is not the same as the distance between centers, between two named faces, or along a chosen direction. A bracket and a housing may be 12 millimetres apart centre to centre and 0.8 millimetres apart at the closest corners. Both numbers are correct. Only one answers the clearance question.
The number also depends on the state of the model. The distance in a collapsed, exploded or partly suppressed assembly is not the distance in the fully assembled product. Moving parts, flexible components and configurations can all shift it. A value read from a design that has since been revised answers a question nobody is asking anymore.
Finally, a distance is nominal. It reflects the modeled geometry, not the manufactured part. Tolerances, thermal growth, deflection under load and assembly stack-up all move the real gap away from the modeled one. If a clearance is tight, the nominal distance is the start of the analysis, and our guide to AI for tolerance stack-up analysis covers what comes next.
The same caution applies to every number taken from CAD data. Our look at reading measurements out of CAD files you already have explains why a value that is derived from geometry can disagree with one typed on a drawing, and why you should know which of the two you are quoting.
For quick questions, this is fine as long as the answer carries its context. A distance of 3.2 millimetres between two named parts in the current released assembly is a useful statement. A bare 3.2 is not.
One part for properties, two parts for distance
The simplest design for a measure tool follows how people already think. Pick one thing and ask about it. Pick two things and ask about the space between them.
In Leo's measure tool, selecting one part shows that part's properties. Selecting two parts, with Ctrl and click, measures the distance between them. There is no separate mode to learn and no dimension to place. The selection itself is the question.
This matters because the two requests tend to arrive together. A reviewer who asks how far apart two parts are often asks next what one of them weighs or is made of. With one tool covering both, the follow-up does not need a second trip through the vault.
A typical use during a review looks like this:
Open the assembly in question, at the released revision, and note which two parts are in doubt.
Select the first part and check its properties, to confirm it is the part you meant and not a similarly named one.
Hold Ctrl and select the second part to read the distance between the two.
Say the number aloud together with the two part names, so the notes record what was measured.
If the value is close to the limit, mark the pair for a closer check in the CAD system or a tolerance review.
The last step is the important one. A fast number is a screening tool. It tells you which pairs are comfortable and which deserve attention, so that the group spends its modeling time where the gap is genuinely tight.
Used this way, the tool also works as a sanity check on a design decision. Before agreeing to add a feature or move a component, the reviewer can confirm the neighbours are far enough away, and a single question is enough to keep the discussion moving. Pairs that show a comfortable margin need no further attention. Pairs that come back close to the limit go on the follow-up list with their part names and the number already recorded, which makes the later check shorter. For interference between parts, a different tool is the right choice, and how AI catches clashes in CAD assemblies explains where that line sits.
Where Leo fits in the review
Leo is an AI assistant built for mechanical engineers, trained on more than one million pages of standards, books and articles. It connects to an organization's knowledge base, including PDM, PLM, local and network directories and ERP, and sits on top of those systems as an intelligence layer instead of replacing any of them. Leo offers integrations with leading PDM and PLM platforms such as SolidWorks PDM, Autodesk Vault, PTC Windchill, Siemens Teamcenter and Arena PLM, among others.
The measure tool was released in the Sept 29 to Oct 4, 2026 update, and it is described there simply: select one part to see its properties, or select two to measure the distance between them. That is the whole claim, and this article keeps to it. It does not change the model, it does not replace the CAD system for modeling work, and it does not by itself judge whether a clearance is acceptable.
What it removes is the detour. The question is asked where the engineers already are, in a conversation about the design, instead of waiting for someone to open a seat. For teams with a limited number of licenses, that also means the seat stays free for the people who are modeling.
The wider value is that the answer sits next to the rest of the product knowledge. The same assistant can find the drawing that states the minimum clearance, the past design note that explains why the gap was set, and the standard that applies. A number is more useful when the requirement it is checked against is a click away.
Because reviews often touch controlled files, security belongs in the evaluation. Leo is SOC-2 certified and GDPR compliant, no AI is trained on customer data, and customer intellectual property is protected. Ask any tool you assess for the same statements in writing before connecting a vault.
It is also worth knowing what an assistant cannot do for you. An assistant that cannot read your CAD files will guess, and our piece on why general chatbots cannot read your CAD files shows how that goes wrong. A tool that works on the actual model avoids the guess, which is the reason to prefer one.
Limits to keep in place
A quick number is only as good as the habits around it. Five are worth writing into the review routine.
Name the pair and the revision. Every recorded clearance should say which two parts were measured and in which released revision.
Know which distance you are quoting. Minimum separation, centre distance and distance along an axis are different values, so confirm the tool reports what the question needs.
Treat the value as nominal. If the gap is tight, move to tolerance and stack-up analysis instead of settling the matter from the modeled geometry.
Re-measure after changes. A clearance that was comfortable before an engineering change may not be afterwards, so repeat it when either part is revised.
Keep the drawing in charge. Where a drawing states a required clearance, the drawing is the requirement, and the measurement is only evidence about the model. See model-based definition versus 2D drawings for how that relationship is changing.
None of these slow the review down. They take a few seconds each, and they are what separates a useful screening number from a confident mistake.
It also helps to keep a short record of the pairs checked. A line in the review notes with the two part names, the value and the revision is enough, and it saves the next reviewer from repeating the question. When a design later fails a fit check, that record shows quickly whether the clearance was ever measured, and by what method.
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