Which file format should I send?
The format matters less than people think, but a few rules help.
- STL is the format almost every printer workflow accepts. It describes the surface as a mesh of triangles. It has no units and no colour, so you have to say whether the size is in millimetres or inches.
- 3MF does the same job and keeps more information: units, colours, and several parts in one file. Many fabricators like it, and it removes the unit guessing.
- STEP is a CAD format. It describes the part as exact shapes instead of triangles, so a fabricator can change a hole or a wall if they need to. It is the one to send when the part might need editing, and it suits machined parts too.
- OBJ is a mesh format too, often used when colour or textures matter. Ask before sending one.
If you can, send the STL or 3MF for printing and keep the STEP ready in case the fabricator asks for it. Do not convert a mesh back into a CAD file and expect it to be editable. It does not work that way.
What file problems cause failed or bad prints?
These come up again and again. Most can be caught in a minute before you send the file.
- The model is not watertight. If there are holes or gaps in the surface, the slicing software cannot tell inside from outside. Many modelling programs have a check or repair function.
- The walls are too thin. A wall thinner than the printer can lay down will vanish or come out fragile. The limit depends on the printer and the nozzle, so ask.
- The units are wrong. A part drawn in inches and read as millimetres arrives the size of a grain of rice. Tell the fabricator the longest dimension in plain words as well, so they can check.
- Loose pieces. A model made of separate floating bodies can print as separate floating bodies.
- No allowance for fit. Two parts that are drawn to meet exactly will rarely fit. Plastic printing leaves small variations, so mating parts need a small clearance. The right amount depends on the printer and the material.
- Tiny detail. Text and features smaller than the printer can resolve will blur or disappear. Raised text usually survives better than very fine engraved text.
- Awkward orientation. Overhangs and flat faces printed in the wrong direction look rough or fail. A fabricator can usually choose the orientation, but tell them if one surface must be smooth.
Be honest about how far you have checked. "I have not tested the fit" is useful to know and costs nothing to say.
What should I ask before I send the file?
- Which formats do you accept? And would you prefer one?
- Will you check the file before printing and tell me about problems? Some will, and some print what they are sent.
- What material and layer height would you use, and how will it look?
- If the print fails because of the file, who pays for another try? Agree it before you start.
- Will you keep or reuse my file? You can ask that your design is used only for your order. If it is private, say so.
Messaging a fabricator first is easier than sending a file cold. You can find a fabricator who lists 3D printing, ask these questions, then send the file with your agreed offer. Keep the conversation and the file on PrintCommons so there is a record of what was agreed.
Can I have a design made if I did not draw it?
Maybe. A design you downloaded comes with a licence, and the licence says what you may do. Some allow personal use only, some allow you to have it made, some do not allow selling copies. Read it before you ask anyone to print it. If the design is published on PrintCommons, the project page tells you what the licence allows, and you can browse the marketplace to see designs that a fabricator can already make for you.
If the design is your own, there is nothing to check. If it was drawn by someone else for you, make sure you have agreed that you can have it made.
What if I do not have a model yet?
Then you need a design step first, and many fabricators will quote for it separately. Describe the part, give measurements, and attach photos with a ruler or a coin in the frame for scale. For a first order, expect a back and forth. The guide to custom 3D printing explains what a fabricator needs from you and how quoting works, and how to find a 3D printing service covers choosing one. Orders are explained in how it works.