In the first post in this series we described the open-book exam: instead of letting an AI answer your visitors’ questions from memory, you hand it the relevant pages of your own website and ask it to answer from those. That post ended with a promise to explain the next piece of the puzzle — how do you know the AI actually read the book? The answer, when it works, is the little line at the bottom of a reply that says Sources.

This week that line has been on our workbench, because we caught it doing something subtly wrong. So this post is about what a citation actually is, why it matters more than it looks, and two real ways a Sources line can mislead — both of which we found in our own product, in our own chat logs.

What a citation actually is

When a visitor asks a public-facing AI assistant a question, three things happen in quick succession. A search runs over the site’s own documents and fetches a couple of dozen excerpts that look relevant. The AI writes an answer, drawing — if all is well — on a handful of those excerpts. And then, underneath the answer, the assistant lists the documents it drew on, each one a link to a real page.

That list is the citation. And a citation is best understood as a promise: this answer stands on that page — go and look.

Which is why citations matter more than their modest appearance suggests. A chatbot without sources asks to be taken on trust. A chatbot with sources can be checked — by the visitor, who can click through and read the page for themselves, and just as importantly by you, the site owner, reading your chat logs over coffee the next morning. Our working rule for the whole product is never take the AI’s word for anything you can check, and a Sources line is what makes an answer checkable at all.

But a promise is only worth something if it’s kept. Here are two ways we’ve watched it break.

The greeting that arrived with sources

Early in development, a visitor to our demo shop typed one word: “Hello.”

The assistant replied, perfectly reasonably, “Hello! How can I help you today?” And underneath that greeting, it printed: Sources: Hello world!, Clan Name Relationships.

It had cited the default WordPress post — the “Hello world!” page every new site starts with — as a source for saying hello.

The explanation is almost funny once you see it. The document search runs before every message, because at that point nothing knows whether the message is a question or a pleasantry. Asked to find pages resembling “Hello”, it dutifully returned the closest matches it had, and the AI just as dutifully listed them. Every one of those documents was real. The search genuinely fetched them. And the Sources line was still false — because the promise a citation makes is this answer is based on these pages, and the answer was based on nothing at all.

That’s the first lesson about citations: a Sources line can be built entirely from real documents and still be a false statement. The fix, once we understood the problem, was plain: small-talk replies now cite nothing, and our quality scoring stopped awarding marks for citations an answer never used. An empty Sources line under “Hello! How can I help?” is the honest one.

Twelve sources for one clan

The second failure is this week’s, and it’s the opposite of the first: not sources that were never used, but too many of them.

Part of every release for us is firing a battery of test questions at the live demo shop and reading the results back through the chat logs. One of this week’s questions was about Clan Cameron — crest, septs, the usual. The answer was good: grounded in the site’s own pages, correct, every link real and working.

But the Sources line listed twelve documents. And on the follow-up question it listed nine — nine clan-map pages, not one of them about Cameron.

Nothing was invented. Every page existed; every link loaded. What the assistant had done was list a large slice of everything the search fetched, rather than the two or three pages the answer actually stood on. And a citation list like that quietly breaks the promise from the other direction: a visitor who wants to check the answer now has to wade through a dozen links to find the one that matters. Cite everything and you may as well cite nothing — the reader can no longer tell which source is load-bearing.

So we did what we always do with a finding like this: logged the evidence, filed the issue, and designed the fix before touching code. The Sources line should list what the answer used, not what the search returned, and it should be capped at a sensible handful. In the interests of honesty — because honest engineering stories are rather the point of this series — that fix is filed and designed but not yet shipped. If you’re watching our demo, you should see the Sources lines get shorter in a coming release.

And the links must exist

There’s a third way a citation can fail, the bluntest of the three: the AI can simply invent a source — a plausible-looking link to a page that has never existed. We told that story in our guardrails post, where our assistant confidently invented two products, complete with convincing web addresses, on our own domain.

That one we treat as a hard stop. Before any answer reaches a visitor, every link in it is checked against the site’s real pages, and an invented link fails the whole answer rather than being quietly served. In this week’s release checks — umpteen scenario conversations fired at the live site — that check had a quiet day: not one invented link, and every single cited page loaded when we clicked it. Quiet days are what good guardrails sound like.

Three questions worth asking

If you’re evaluating an AI assistant for the front of your own website — ours or anyone’s — the citations behaviour is worth probing, and three questions get to the heart of it:

Does the Sources line show what the answer used, or what the search returned? (Asked of AnswerRails today, the honest answer is “the search, for now” — which is exactly why it’s on our fix list.)

Are cited links checked to actually exist before the visitor sees them? An AI that can print an invented link under the word “Sources” has turned the trust signal into a liability.

Can you, the owner, see the difference in your logs? Our chat logs record what the search offered and what the reply cited, separately — so when a Sources line misbehaves, there’s evidence to read rather than a mystery to shrug at.

A citation is a promise you can check. The engineering job — never quite finished — is making sure it’s a promise that’s kept: no sources the answer never used, no more than the answer needs, and never, ever a link to a page that doesn’t exist.

Next in this series: why your AI should tell you when it’s having a bad day — the story of our assistant’s health dashboard, and the afternoon a provider slowdown taught us what an assistant should say about itself.

AnswerRails is a public-facing AI assistant for WordPress, in development at Celtic3d — built compliance-first, with guardrails as the product rather than an afterthought. Follow its progress at answerrails.com.

The post How Do AI Citations Work? (And Two Ways a Sources Line Can Mislead) appeared first on Celtic3d.

At Celtic3d, we make 3D printing simple. Most of our production is handled through our trusted manufacturing partner, giving us access to industrial-scale capacity, a wide choice of technologies and materials, and consistently high quality. Better still, when you need multiple identical copies of a part, you’ll benefit from generous quantity discounts.

There is one trade-off: because of courier transit times, set-up costs per file and a minimum order value, this service is not the best option for once-off small parts. For larger projects, prototypes or batches of parts, however, it’s an excellent fit.

Our core 3D printing technologies

SLS (Selective Laser Sintering) – PA12 Nylon

Our go-to process. SLS fuses fine PA12 powder layer by layer into strong, detailed parts.

• No support structures needed → allows intricate, interlocking or organic shapes.

• A versatile, durable material with a slightly textured finish.

• Great choice for functional parts, prototypes and assemblies.

SLA (Stereolithography) – Resin

The next most popular option. SLA uses a light-cured liquid resin for superb detail.

• Smooth surface finish, excellent for visual models.

• Can mimic some production plastics, ideal for product design prototypes.

• Wide range of resin properties to choose from.

FDM (Fused Deposition Modelling) – Filament

The odd one out. FDM prints by extruding melted plastic (e.g. PLA).

• Best suited for larger, simpler shapes.

• Limited detail compared to SLS or SLA.

• We don’t use this much, but if it’s needed for a project, we will seek a solution through our manufacturing partners.

To contact us: email sales@celtic3d.com or phone +44 (0)7714 790161 (During business hours – GMT+0)

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Effective from 10th April 2025, all new digital downloads will include a choice between two types of licence:

Personal Licence

This option is intended for private individuals and hobbyists. It allows the file to be 3D printed for personal use or as a gift. However, prints made under a personal licence may not be sold, and the original digital file may not be shared or redistributed.

Commercial Licence

This option is designed for makers and small businesses who wish to produce physical items for resale. It permits the manufacture and sale of printed products based on the downloaded file, but does not allow digital redistribution or modification for resale.

What About Previous Purchases?

If you purchased a downloadable file from Celtic3d before 10th April 2025, your original licence terms still apply. These new options only affect new purchases made on or after that date.

Why the Change?

We’ve introduced this new licensing structure to:

• Continue to offer an affordable option for personal, non-commercial use

• Support small businesses and home-based makers who want to resell printed products

• Protect the originality and integrity of our 3D designs

If you have any questions about which licence is right for you, or if you need clarification about how you may use your files, please contact us.

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Using high-resolution digital scans and working with brogenville, a local Ferrari expert and enthusiast, we have been producing parts that are no longer in production and that are very difficult to source.

Producing the parts is made possible by the expertise and hands-on experience brogenville has in converting Ferraris with automatic transmission to manual.   This is a continuation of a fruitful collaboration that started with a clutch pedal for another model of Ferrari.

The original OEM parts are cast in aluminium with selected faces machined flat and threads tapped.   The industrial process to create castings requires minimum production quantities to make it worthwhile.  So, for small batches,  we find it more economical to machine the parts from a solid aluminium block.

Our aim is to produce a part that could simply be bolted in.  To achieve that, we include the press-fit bearings and bushings.  Because the bushings and gearings are already fitted for you,  you don’t have to source and fit these yourself.

We had a number of pre-orders for these parts and, after running a small batch through production, we have some stock that is available for sale and shipping worldwide.

How to buy

If you are interested in purchasing these parts,  contact us here,  or on this thread on the Ferrari Chat forum.

If you are converting your late model Ferrari from automatic to manual, and are looking for parts, get in touch, we may be able to help.

The post Parts for sale- Reproduction right-hand drive clutch pedals for Ferrari 360’s and 430’s appeared first on Celtic3d.

We are often asked what software we use to create 3d models for printing.  The answer depends on the type of project.   This potted guide explains some of the software we use in the production of our 3d models.

The basic workflow for any 3d printing or CNC project is

1. create a digital 3d model.
2. break this down into commands the machine can understand.
3. send the commands to the machine.   

In this article, we are mainly concerned with the first step, creating the digital 3d model.

See also:  An Overview of 3d Printing. 

The right tool for the job

If the model is driven by dimensions, say it has to have a specific pattern of holes, or a specific size,  we use CAD (Computer Aided Design) software.  

Some projects involve more organic shapes, or a highly detailed surface.  For these, we use mesh modelling tools. 

Repairing issues with mesh files is a specialist job for mesh analysis and repair tools.  

Sometimes, mainly for CNC and laser cutting,  we just need the outline, or a path to follow with an engraving or cutting tool.  For these we need drawing software that can create paths or vectors. 

CAD (Computer Aided Design)

CAD software is all about dimensions.  If you know that something has to be a certain thickness, with specifically sized holes in exact locations, these can be created in CAD software in a matter of seconds.   In CAD software, if the dimensions change later in the design process,  you can quickly find the parameter, and change it.   The software will apply the change and update all the downstream characteristics that depend on that parameter.   So,  if you placed a feature in the center of an object, but later change its width or length,  your feature is still in the center.

This ability to drive the design by defining and updating parameters is known as parametric modelling, and it is very powerful.  Especially when working in an iterative design process where changes are frequent.

CAD File Formats

CAD software has been widely used for decades.  Over the years, several industry standard file formats have emerged. It is usually straightforward to import and export files between different CAD packages using these formats.  IGES and the newer STEP format are the most common.  These file formats preserve all the dimensional data in the design.  

For 3d printing however,  files need to be exported in a mesh format. The most common format is  STL (Simple Tesselation Language).  The STL format describes the surface shape like a digital lump of clay.  STL files contain no information about units, colour or materials.  While you can still take measurements,  the STL format does not contain any of the parameter information from the CAD version.  Converting to STL format creates a series of triangles for the surface.  A flat plane can be described using a few of these triangles. A sphere may use thousands.  If you zoom in on a curved surface in an STL file, it will be made up of many small flat surfaces.  If the resolution of the surface is not high enough, these will show in your final print.    

While editing CAD designs by updating parameters is fast and easy,  making changes once it has been converted into STL format is difficult and time consuming. 

At Celtic3d, we use Autodesk Fusion 360 for design work on a daily basis, and occasionally SketchUp which is popular among some of our architectural clients.

Mesh Modelling

When working with organic shapes, say a landscape or a figurine,  it is more important to have precise control over the overall shape and form rather than just be driven by dimensions.   More like digital sculpting than engineering design.     It may also be necessary to make changes to an existing STL file where the original CAD version is not available.   In these cases, you need to use software that allows direct editing of the surface mesh.

Mesh software breaks down into two main categories,  analysis and fixing of issues with the mesh, and authoring tools to create your own mesh from scratch.

What’s a Mesh?

A mesh comprises of a series of vertices (points in space), connected by edges (connecting two vertices) and faces (enclosed by three or more edges).   While the STL file format works with triangles,  Faces with four edges (quads) are easier to work with when editing.   It is also possible to work with faces with more than four edges (polygons). 

For 3d printing,  the mesh needs to have thickness and volume, fully enclosing a space without any holes.    A mesh that successfully encloses a volume is known as watertight or “manifold” and is essential for 3d printing.  If 3d printing software comes across holes in the mesh, or a face that does not enclose a volume,  it will either fail or have unpredicted results when trying to print.

Fixing Issues

Getting the mesh right is critical to a successful 3d print.  This applies equally to files that have been exported in STL format from CAD software and to files that have been created from scratch in mesh modelling software. It also applies to 3d models that might have come from another source – like a 3d scan.  

Scanning software creates thousands of reference points from an object, known as a point cloud.  Many scanning packages can convert these point clouds into a mesh.  Essentially this involves treating the points as vertices and joining them together with edges and faces.  The resulting mesh often needs clean-up to fix holes in the model where the software found insufficient points to join together.

At Celtic3d we use several industrial strength tools to analyse and fix mesh issues prior to 3d printing. 

MeshLab (http://www.meshlab.net) is available as Open Source under GPL licence and is an invaluable tool to find and fixing issues with your 3d model file.  It has features to automatically find and fill holes as well as fix the most common mesh issues.

Creating Your Own 3d Models

While exporting from CAD, downloading STL files from the web or scanning objects are all viable ways to get your 3d model file.  Often 3d modelling from scratch is the best option.  Our go-to software for creating 3d models from scratch is Blender.   It is not just a great tool for digital sculpting and mesh modelling.  It is also a full-featured 3d authoring environment. Blender covers everything from CGI (Computer Generated Images), animation, video editing, physics simulations, materials, textures and lighting.

It has superb 3d modelling capabilities and has an included 3d printing add-in (enabled via User Preferences) to export files in STL format.  Like any software of this breadth of capability, you will need to invest some time to get to grips with it.  However, the payback is enormous.  Health warning:  if you get the bug, it can take over your life.   But, you will be joining a massive online community of artists who have created a large library of tutorials and resources to get you started. 

Blender is Open Source, available at blender.org and is a free download.  We encourage you to make a contribution if you find it useful.    

Celtic3d is a member of the Blender Professional Network.

Quick Tips

Creating a guide to using Blender for 3d print projects is beyond the scope of this article.  For those of you who have already dipped a toe in the water, some quick tips for using Blender specifically for creating 3d printable models.

1. Sort out your scale from the outset.  The STL file format does not include any information about units,  however most software assumes 1 unit = 1 mm in the real world.  Blender, by default, uses it’s own unit scale when exporting STL files.  The easiest way to handle this is to adopt a convention where 1 Blender unit = 1 mm.
2. Pay attention to real-world sizes and thicknesses.  It is easy to get sucked into spending hours on details that turn out to be too small to see in the 3d print.
3. Use non-destructive modifiers.  A quick way to ensure that all your wall thicknesses are 3d printable is to model using planes and add a “solidify” modifier to make them a defined thickness.    (Remember to “Apply Scale” when modelling and turn on the “Apply Modifiers” option in the 3d Print utility.)

Vector Art

Although strictly not relevant to 3d printing,  we frequently combine 3d printed parts with 2d CNC machined components in the same model.  CNC machines and laser cutters need a defined path to follow.   These paths, or vectors, are created in 2d drawing software.  We use Adobe Illustrator for this purpose,  mainly because we can also then use Illustrator for other graphics work.   

There are Open Source vector drawing tools available but unfortunately their functionality generally lags behind Autodesk’s.

Closing

Preparing and creating files for 3d printing involves a whole toolbox of software.  Fortunately, much of what you need is readily available and often free to download and try.  Choosing the right tool depends on the type of job in-hand.  We have hopefully given you some pointers.   If you found this article useful, please link and share.

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