3D CAD services explained: from sketch or scan to print-ready model

"CAD services" is one of those phrases that means five different things depending on who's selling it. Drafting bureaus offer 2D drawings. Freelance marketplaces offer quick STL tweaks. Product design agencies offer six-month development programmes. If what you actually need is a part designed, fixed or captured so it can be manufactured, it's hard to tell from the outside who does what.

This post explains it plainly. It covers what a 3D CAD service actually does, the three ways a job usually starts, what "print-ready" really means, and how the work is priced — so you can brief a design job knowing what you'll get back.

The three ways a CAD job starts

Almost every design job we see arrives in one of three states, and the route to a finished model is different for each.

An idea or a sketch. No file exists yet — a drawing on paper, a photo of the space the part has to fit, a description of what it needs to do. This is full design work: we establish the critical dimensions with you, model the part from scratch, and iterate until it's right. It's also the category people most often assume is out of reach. It isn't — a bracket, mount, enclosure or fixture designed from nothing is routine work, not a product-development programme.

A physical part. The part exists but no model does — it's worn out, discontinued, or was never documented. Simple geometry we capture by careful measurement; complex shapes go through 3D scanning. Either way the output isn't the raw capture — it's a clean CAD model rebuilt from it. We've covered this reverse-engineering workflow in detail separately; the short version is that a scan tells you what a part looks like, and CAD work turns that into something you can manufacture.

A rough file. The most common case of all: a file exists but isn't usable. A downloaded STL that needs resizing or a mounting hole moved. A mesh with gaps that won't slice. A supplier's STEP file that needs one feature changed. Mesh files like STL are hard to edit directly — the geometry is thousands of triangles, not features — so small changes often mean partially rebuilding the part properly. This kind of repair and modification is quick, cheap and by far the most frequent job we do.

What "print-ready" actually means

"Print-ready" gets used loosely, so here's the concrete version. A print-ready model is watertight — a closed, manifold mesh with no gaps or self-intersections, so a slicer can process it without guessing. It's dimensioned to the real world, with clearances and tolerances chosen for the manufacturing process rather than left at whatever the sketch implied. And it's delivered in the right formats: STEP or Fusion 360 source for the editable engineering model, STL or 3MF for the print file. If a service only hands back an STL, you've bought a print, not a design.

That last point matters more than any other. We model in Fusion 360 and SolidWorks using parametric pipelines, which means the model is built from named, editable features — not a frozen lump of triangles. When the part needs a second version (they almost always do), changing a dimension is minutes of work, not a rebuild. And once the parametric model exists, the part can never go obsolete: the file is the spare.

Design for the process, not just the shape

A part that's correct on screen can still be wrong for the printer. Wall thicknesses below what the process resolves, overhangs that need a forest of support, holes that print undersize, a strong axis loaded the wrong way — none of this is visible in the model, and all of it decides whether the part works. Designing for the process from the start is what separates CAD work done by a design bureau from CAD work done by a manufacturer.

This is the practical advantage of design and print under one roof. The person modelling your part is metres from the machines that will make it, so design-for-print decisions — orientation, wall thickness, tolerance on a press-fit — are made from direct experience rather than a guidelines PDF. It also collapses the iteration loop: model, print, measure, revise, all in-house. For prototyping work, that loop running in days rather than weeks is most of the value.

What it costs and how to brief it

CAD work is quoted per hour, from £30/hr, with a written estimate before any work begins — so you know the cost before committing, and a small job is priced like a small job. An STL modification or mesh repair typically sits at the bottom of the range; a part designed from scratch depends on complexity, and the estimate will say so plainly.

A good brief is simpler than people expect. Tell us what the part needs to do, and how it fails or what's missing today. Send whatever exists — a sketch with rough dimensions, photos of the part or the space next to a ruler, or the file that isn't working. State the critical dimensions and which surfaces matter for fit. That's enough for an accurate estimate; we'll ask about anything else.

A recent example of the from-nothing case: a commuter's motorbike had an exposed toolbox recess that was never fitted with a cover — no part to copy, because the part never existed. We designed a custom toolbox cover from measurements of the recess, modelled it parametrically, and printed it in a material suited to weather and vibration. Sketch to fitted part, with the model on file for the day it needs replacing.

If you've got a sketch, a worn-out part or a file that won't print, the fastest way forward is to describe the job and send what you have. We'll come back with an honest view of what it needs and a written estimate — usually the same day.