Sound familiar?
- The toolmaker will not quote without a STEP file
- You have a physical part that is no longer made and need a model to remake it
- Parts that looked right in your head clash when they are assembled
- A supplier's 3D file is a 'dumb' solid that nobody can edit
- You need a model for printing, machining and marketing images, and keep paying three times
Key facts
- Parametric models with a logical feature tree, so dimensions can be changed later without rebuilding
- Neutral exports as STEP (AP214 or AP242) for suppliers, IGES on request
- STL or 3MF exports for 3D printed prototypes
- Assemblies with a bill of materials and interference checks before anything is made
- 2D manufacturing drawings produced directly from the model, so they always match
- £45 an hour + VAT, or a fixed quote for a defined scope
Parametric or direct modelling: why it matters to you
There are two broad ways to build a 3D model, and the difference shows up when you need a change.
Parametric modelling (the approach used in SolidWorks, Fusion and Inventor) records the model as a history of sketches and features driven by dimensions and constraints. Change the wall thickness or hole spacing and the model rebuilds around it. It captures design intent: a hole stays centred because it was defined as centred, not because it happened to be in the middle. This is the best choice for parts that will go through several versions.
Direct modelling pushes and pulls the faces of a solid without a history. It is quick for concept work and for editing imported STEP files from someone else's system, where no feature tree exists. We use whichever suits the job and often both: direct edits on a supplier's imported part, parametric modelling for your own design.
What we can model from
- Sketches and notes: hand drawings with key dimensions.
- Existing 2D drawings: old paper or PDF drawings rebuilt as 3D (see CAD conversion).
- Physical samples: measured with callipers and gauges by you, or posted to us for measuring where that is practical. Freeform shapes may need a 3D scan, which a scanning bureau can supply as a mesh for us to model over.
- Supplier files: STEP, IGES or STL from a component maker, used to design around bought-in parts.
- A brief: where nothing exists yet, which is product design.
Assemblies, clearances and fit
Modelling every part together as an assembly catches the expensive mistakes early. We check for interference (two parts occupying the same space), confirm clearances for fasteners, tools and hands, and make sure moving parts can move through their full range. Bought-in components such as bearings, fasteners, hinges and motors are placed from the manufacturer's own CAD files where they publish them, so their sizes are right.
The assembly produces a bill of materials listing every part, quantity and material, which becomes the basis of your purchasing and costing. Changes to one part update the assembly and its drawings, which is why we model the whole thing rather than drawing parts in isolation.
Modelling for the way it will be made
A part designed for CNC machining, injection moulding, sheet metal or 3D printing looks different, because each process has its own limits. Machined internal corners need a radius at least as big as the cutter; moulded parts need draft angles and even wall thickness; sheet metal parts need realistic bend radii. We ask how a part will be made before modelling it, and flag features that will add cost. Read more on sheet metal and design for 3D printing.
Hand-over files and STEP versions
Every 3D job ends with a set of files named so you can tell what each one is and which revision it belongs to. STEP comes in several application protocols. AP214 is the long-standing choice and carries geometry, colours and assembly structure. AP242 is the newer protocol and can also carry product manufacturing information (dimensions and tolerances attached to the model), which suits suppliers who work from the model rather than a drawing. If your supplier's software is older, AP214 is the safer choice; we ask before exporting.
Units are set to millimetres unless you tell us otherwise, and each part is exported both individually and as part of the full assembly, so a supplier quoting one component does not have to dig it out of a large file. Native files come too, so you or another designer can carry on later.
Price
3D CAD modelling is £45 an hour + VAT. A simple bracket or spacer might be an hour; a multi-part assembly with drawings is a larger job that we usually fix-price once we have seen the inputs. Need images from the same model? Our 3D rendering uses it directly, so you are not paying to model twice. See prices.
What you get
- Native parametric part and assembly files
- STEP exports of each part and the full assembly
- STL or 3MF files for 3D printing
- A bill of materials (BOM) for assemblies
- Dimensioned 2D drawings as PDF and DWG
- Screenshot or rendered views for approval
How it works and what it costs
Logos from £150, brochures from £295, photography from £295 a half day and CAD at £45 an hour, all + VAT. You get a fixed price before we start.
Tell us the brief
What it is for, who will see it, where it will be used and any examples you like. Rough is fine.
Fixed price
We confirm the price and what you get, in writing, before any work starts.
First designs
We design, shoot or model it and share the first version for your comments.
Refine
We make the changes, check every detail, and prepare the files properly for print, web or manufacture.
Final files
You get the finished files in the formats you need, ready for your printer, website, social channels or manufacturer.
Frequently asked questions
What is a STEP file and why does my supplier want one?
A STEP file is a neutral 3D format defined by ISO 10303 that almost every CAD and CAM system can import as an accurate solid. Machine shops use it to measure and program toolpaths directly, which is quicker and less error-prone than re-drawing from a PDF. dijitul supplies STEP with every 3D job.
Can you model a part from a physical sample?
Yes, for parts made mainly of flat faces, holes and simple curves. You can measure it, or we can discuss posting it to us. Complex organic shapes are better 3D scanned first by a scanning service; we then build a clean, editable model using the scan as a reference.
Can you edit a STEP file someone else made?
Usually, yes. STEP files carry no feature history, so we edit them with direct modelling tools: moving faces, adding holes or changing lengths. Larger redesigns are often quicker to rebuild parametrically, and we will tell you which is cheaper before starting.
Can I have the native files as well as STEP?
Yes. dijitul hands over native files and neutral exports, so you can make changes yourself or use another designer later. Native files only open in the same software family, so STEP remains the safer format for sending to suppliers.
How accurate is a 3D model?
The model itself is mathematically exact. Its real-world accuracy depends on the information it is built from, which is why measured dimensions, drawings and tolerances matter. Where inputs are uncertain, we mark the dimensions you need to confirm before anything is made.
Related
Get a fixed price
Send a rough brief. You'll know exactly what it costs before we start.