Engineering guide
How to Specify a Custom Ceramic Part on a Drawing
A drawing that specifies ceramic as if it were metal guarantees a quotation revision. This guide covers what to put on the drawing, what to leave off, and which details actually change the price.
Starting point
What changes compared with a metal drawing
The geometry language is the same. What changes is which tolerances are reachable and what a sharp feature costs.
| Item | Metal practice | Ceramic practice |
|---|---|---|
| Sharp internal corner | Common, easily produced | Not producible; radius required |
| Thin section | Flexes, can be straightened | Chips; needs support during machining |
| Tolerance on a whole part | Often uniform | Feature-specific; costly if generalised |
| Edge specification | Usually implicit | Must be explicit; edges are the defect site |
| Surface finish | Often overall | Specified per functional surface |
The questions that come up most often before an order is raised, and the answers to them, are collected in the frequently asked questions. Where the drawing describes a shape that has to be machined rather than ground, the component family that covers it is custom complex ceramic parts. The recurring ways a drawing makes a ceramic part harder to make than it needs to be are listed under design for manufacture problems. What happens to the drawing once it is approved, from the first article to the repeat order, is set out under prototype to production.
The nine items a drawing should carry
Missing any of these is the most common cause of a revised quotation.
- Material and grade, or the operating conditions if open
- Units and drawing scale, stated explicitly
- Datum scheme, even on a simple part
- Tolerance class for non-critical dimensions
- Functional tolerances, with the feature each applies to
- Surface finish by surface, not as a general note
- Edge break and corner radius requirements
- Inspection report type required with the shipment
- Quantities separated into prototype and production
Where tight tolerances belong
A tight tolerance is only worth its cost where something depends on it.
| Question | If yes | If no |
|---|---|---|
| Does another part mate against it? | Tolerance it | General class |
| Is it measured at incoming inspection? | Tolerance it | General class |
| Does its position affect function? | Tolerance with a datum | General class |
| Is it a visual or reference dimension? | Leave it nominal | – |
What to send and what comes back
Send the 2D drawing and the 3D model together when possible: the model carries geometry, the drawing carries requirements.
The part and the process
Frequently asked
Do I need a 3D model as well as a drawing?
A drawing alone is enough to quote. Send the model too when you have it, because it removes ambiguity about surfaces that are hard to describe in two dimensions.
Can I specify a tolerance the process cannot hold?
You can, but it will come back as a query. It is better to state the functional requirement and let the manufacturing route be proposed against it.
What if the design is not finished?
Send it anyway with the open points marked. A review on an incomplete drawing is faster and cheaper than a rejected part.
How detailed should the application description be?
Two or three lines are usually enough: what the part does, the temperature, the load and the medium. That context often changes the recommended material.
Have a drawing that this guide applies to?
Send it with the material and the quantities. The review confirms what is achievable before any price is issued.