How can a custom part be made?
Most one-off parts come from one of three families of process, and a fabricator who owns the machine can tell you which suits yours.
- 3D printing builds a part up layer by layer, usually in plastic or resin. It handles complex shapes and single copies well. A printed part is not as strong as a machined one in every direction, and its surface shows layers unless it is finished.
- CNC machining cuts a part out of a solid block or sheet. It is the usual choice for metal parts, tight tolerances and surfaces that must be flat. It costs more to set up for odd shapes, and some shapes cannot be reached by the tool.
- Laser cutting follows a flat outline in sheet material such as wood, acrylic or leather. It is quick for flat parts and for anything built from several flat pieces that fit together. What a laser can cut depends on the machine, so ask.
Other services exist, such as decals and UV printing, which put graphics on a part. What a particular fabricator offers is up to them, so check each profile in the directory. If you are not sure which process fits, say so and ask. A good fabricator will tell you if another process would do the job better, even if they do not offer it.
How do I describe a part so any fabricator can quote it?
Start with the job, then the details. A fabricator who knows what the part does can choose the process and the material, which is often better than naming them yourself.
- What it does and where it lives: indoors or out, hot or cold, loaded or not, near food or skin.
- A drawing or a model if you have one, with the key dimensions and their units. A STEP file is the most flexible for machining, and an STL is fine for printing. If you have neither, a sketch with measurements and photos is a start. See 3D print my idea.
- Which dimensions really matter. Mark the ones that must be tight, such as a hole for a bolt or a surface that sits against something else, and say the others can vary.
- The material, if you have a preference, and what you will accept instead.
- How many, and whether you will want more later.
- The finish: raw, sanded, painted, anodised, polished. Say what is actually needed.
- Your deadline, and whether you will collect or want it posted.
How do I compare quotes?
Do not just look at the total. Put the quotes side by side and check:
- Is it the same part? Same material, same size, same finish, same quantity.
- What is included. Setup, programming or design time, finishing, packing and shipping can all be inside the price or on top of it.
- The time, counted from the day you pay.
- What happens if it comes out wrong. Who pays to make it again, and what counts as wrong?
- How clearly they wrote it. A quote that is short and vague today often becomes a dispute later.
The cheapest quote is not always the best deal. A fabricator who asked you two sharp questions before answering often has understood the job better than one who sent a number in a minute. Ask both to explain how they would make it. You will learn something either way.
What if the part does not fit?
It happens, especially with mating parts and first orders. Ask before you pay what the plan is. For something that has to fit, order one piece or a small test piece first. If you collect locally, you can try it in front of the fabricator and agree a fix on the spot. Prepare your first local pickup lists what to check before you accept the order.
Keep what you agreed in the offer on PrintCommons: the material, size, finish, quantity and date. If something is wrong later, that record is what a fair outcome rests on. How PrintCommons works explains your options.
Where do I start?
Write the brief once, then find a fabricator and send it to two or three. If you suspect the part already exists as a design, check the marketplace too. For printed parts, see custom 3D printing service and finding a 3D printing service near you.