Short version: you do not have to do any of this. Send the file and we will check it, and the fixes below are part of the print price rather than an add-on. But if you would rather hand over something clean — or you are designing the part right now and want to get it right the first time — this is what we look at when your file lands.

Is the mesh actually closed?

A slicer needs to know what is inside the part and what is outside. That only works if the surface is watertight: no holes, no faces pointing the wrong way, no edges shared by three walls at once. Models pulled from a marketplace or scanned from a real object are the usual offenders, and the damage is often invisible until you slice it.

Most CAD and mesh tools have a repair or analysis command that will find these for you. If yours reports errors you do not know how to clear, stop there and send it anyway — repairing a mesh you downloaded is on our side of the line.

Wall thickness

Resin resolves fine detail, but a wall still needs enough material to survive being washed, cured, and shipped. Very thin walls print — they just arrive fragile, and they warp as they cure. If a feature is thinner than about a millimeter, it is worth asking whether it needs to be, especially on a part that will be handled rather than displayed under glass.

The tell is usually in the original model's intent: something drawn for injection molding or for a screen render often has surfaces with no thickness at all.

Hollowing and drain holes

A solid part uses more resin than it needs to, and resin volume is one of the things that drives price. Hollowing the interior cuts both. It also introduces the single most common way a resin print fails.

A sealed hollow shell traps uncured resin and a pocket of air. As the build plate lifts between layers, that pocket becomes a suction cup pulling against the part, and either the supports tear off or the shell implodes. The fix is drain holes — at least two, placed so liquid can leave from one while air enters the other. One hole is not enough; it just makes a different suction cup.

If you hollow it, tell us in the notes. If you would rather we did it, that is included too.

Orientation and where the marks land

Every supported surface leaves a mark. The craft is deciding which surfaces get to be perfect and which can carry the evidence — the underside of a base, the inside of a shell, a face that will be glued to another part. A miniature's face and a jeweler's ring shank are worth protecting; the flat bottom they stand on is not.

You do not need to add supports yourself. If you have a strong opinion about which face must come out clean, say so in the notes and we will orient around it.

Scale and units

This is the error that wastes the most time, and it is almost always the same one: a file exported in inches and read as millimeters, or the reverse. A part arrives at 25.4 times its intended size, or a 25.4th of it.

STL files do not carry units at all — the format simply stores numbers, and the reader decides what they mean. STEP and 3MF both do carry them, which is one good reason to send those when you have the choice. Either way, put the intended real-world size in the notes. One dimension is enough for us to catch a mismatch.

Will it fit on the plate?

The Form 4's build volume is 200 × 125 × 210 mm. Larger models are not a problem — they get split into printed tiles that bond cleanly, and we plan the seams to land somewhere they disappear. But it is worth knowing before you design a single-piece part at 300 mm.

What to send

STL, OBJ, STEP, or 3MF, up to 8 MB through the quote form. Bigger than that, drop a shared link in the notes or call and we will sort it out. No file at all? Describe the part — we design it with you, quoted flat before we start.

Either way a person opens it the same day, checks every item on this list, and sends you one number. If something on the part will not print well, you hear about it then, not after you have paid.

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