Upload STL for 3D Printing: Quote Checklist

To upload STL for 3D printing without delays, send the STL plus the units, one known dimension, what the part does, any critical fits, and photos of anything it must bolt, clip or slide against.

The STL is only the shape. A quote also needs the intent. Two identical-looking brackets can need very different handling if one sits inside a cupboard and the other lives outdoors on a vibrating gate.

If you are ready, you can upload your STL here. If you want a little more context first, use this checklist before sending the file.

Upload STL for 3D printing: the short checklist

Send these with the file if you can:

• The STL file, ideally as exported from your CAD rather than re-saved through several tools.
• The intended units: millimetres, inches, metres, or something else.
• One known dimension, for example: “overall width should be 72 mm”.
• Quantity needed: one prototype, a spare pair, or a small batch.
• What the part is for: bracket, cover, knob, jig, spacer, enclosure, clip, adaptor.
• Where it will be used: indoors, outdoors, in a car, near heat, near water, under load.
• Any faces that must look tidy.
• Any faces that must be accurate or flat.
• Holes, slots, clips, hinges, snap-fits or threads that matter.
• Photos of mating parts, preferably with a ruler or calipers in shot.
• Preferred material if you know it, or the conditions if you do not.

That sounds like a lot, but it is usually a two-minute message. It saves the annoying round of “is this in inches?” and “does this hole fit an M5 bolt or a printed peg?”

STL files do not store real-world units

An STL file contains triangle positions, not a proper unit system. A model that opens as 25.4 units wide might be 25.4 mm, or it might be a one-inch part exported from inch-based CAD.

So always write the intended units in the message. Better still, give one check dimension:

“This part should be 118 mm long overall.”

That single line catches most scale mistakes before quoting. It is also useful if the model has been downloaded, scanned, repaired, or converted between apps.

If you are unsure whether your model is correctly scaled, include the dimension you care about most. For a bracket, that might be hole spacing. For a replacement knob, it might be shaft diameter. For an enclosure lid, it might be the outside width of the box it fits.

Tell us what the part is actually doing

A quote for a display model is different from a quote for a working clip. A part’s job affects material, orientation, wall thickness, infill, supports and whether the STL should be changed before printing.

Useful context includes:

• “This holds a 1 kg sensor under a desk.”
• “This covers a hole in a campervan cupboard.”
• “This is a drilling jig for five holes in aluminium sheet.”
• “This clip snaps over a 12 mm tube.”
• “This gear is for a hand-turned mechanism, not a motor.”

That kind of note is more useful than saying “strong material please”. Strong in what direction? Against heat, bending, impact, abrasion, UV, or creep over time? PLA, PETG, ASA, TPU and nylon all fail differently.

For general parts, PLA is easy to print cleanly but can soften in a hot car or near a radiator. PETG is tougher and more forgiving around damp garages and sheds, but can be stringier and less crisp. ASA is a better outdoor candidate than PLA because it handles UV and weathering better, though warping risk is higher. TPU is for flexible parts, not rigid brackets. Nylon can be tough and wear-resistant, but design and moisture matter.

If you are choosing between materials, the 3D printing materials guide is a useful starting point. If you do not know the material, describe the use and we can suggest sensible options.

Mark the dimensions that matter

Most STLs arrive with no drawing. That is fine for many decorative covers, spacers and prototypes, but it is not enough for close-fitting parts.

Tell us which dimensions are critical. Examples:

• “The two mounting holes must line up with existing M4 screws.”
• “The tab must slide into a 6.2 mm slot.”
• “The outside surface is visible; underside is not.”
• “The bore fits a 10 mm shaft and should not wobble too much.”
• “The lid needs to push-fit, not snap permanently.”

For FDM printing, holes often print slightly undersize and outside corners can be a touch rounded. Clearance matters. A peg modelled at 10.00 mm will not usually slide nicely into a hole also modelled at 10.00 mm. Depending on size, material and orientation, a clearance of around 0.2–0.4 mm may be a more realistic starting point for a sliding fit, but the right number depends on the job.

If you have a proper drawing, upload it with the STL. If you only have notes, that is still useful. A photo with “this hole spacing is 64 mm centre to centre” written in the message can be enough to avoid a bad assumption.

For more on what affects cost and quoting, see how 3D printing pricing works.

Orientation can change strength and finish

A printed part is not equally strong in every direction. Layer adhesion is usually weaker than continuous roads of plastic within the same layer. That means the way the part sits on the build plate can matter more than the material name.

A hook printed flat may resist load differently from the same hook printed upright. A clip might snap if its flexing direction pulls layers apart. A bracket with screw holes may need orientation chosen around the load path rather than the prettiest surface.

Orientation also affects finish. Supported faces can have marks. Curved top surfaces show layer stepping. Tall thin parts may wobble or warp. Large flat faces can pull at corners, especially in materials like ASA or nylon.

When you upload the STL, say what matters most:

• strongest direction;
• neatest visible face;
• flattest mounting face;
• most accurate holes;
• lowest support marking.

You cannot always optimise all of these at once. If the visible face and the strongest orientation conflict, it is better to know that before quoting than after the part is in hand.

Send photos of mating parts

For replacement parts, brackets and fixtures, photos are often as important as the STL. A model can look correct on screen while missing the awkward truth: a screw head fouls a rib, a cable exits where the support material would go, or a clip needs room to flex.

Good photos show:

• the broken or original part, if it exists;
• the place the printed part will fit;
• nearby screws, clips, slots, lips and obstructions;
• a ruler, tape measure or calipers for scale;
• the direction of load or movement.

Do not worry about studio lighting. A clear phone photo on a bench is enough. If the part mates with something heavy, hot, electrical, moving or safety-related, say so plainly.

When the STL itself needs fixing

A quote can be delayed if the STL is not printable as a solid object. Common issues include open edges, inverted normals, paper-thin walls, intersecting shells, separate bodies that only touch at a point, or decorative details smaller than the process can resolve.

A few practical checks before upload:

• Make sure the part is meant to be a closed solid, not just surfaces.
• Avoid walls thinner than about 1 mm unless they are cosmetic and non-load-bearing.
• Check tiny text, pins and clips; very fine details may not survive handling.
• Export at a sensible resolution. Huge triangle counts do not automatically mean better parts.
• If the part has exact engineering features, consider sending STEP as well as STL.

STL is good for quoting many printable parts, but STEP is better when design help, hole resizing, fillets, threads or tolerance changes may be needed. You can also browse example printable parts in the 3dp6 print library.

When 3D printing is the wrong answer

Some uploaded STLs should not become printed plastic parts without a rethink.

Use another process, or redesign, if the part is:

• safety-critical, such as a load-bearing vehicle, climbing, braking or lifting component;
• exposed to high heat, flame, boiling water or exhaust temperatures;
• required to be optically clear like glass;
• a long, flat, perfectly straight panel where warping would ruin it;
• a pressurised fitting or sealed vessel;
• a precision bearing surface needing machined tolerances;
• a production part where injection moulding would be cheaper at higher quantity.

Sometimes the answer is CNC machining, laser cutting, an off-the-shelf metal bracket, a bought spare, or a small design change before printing. Saying that early is part of quoting properly.

Ready to send the file?

Upload your STL and tell us what the part is for so we can check printability and quote it with the right assumptions: upload your STL for a 3D printing quote.

If you have multiple files, label them clearly: left_bracket.stl, right_bracket.stl, cover_v3.stl. If there are choices, tell us which version is the one to price. If you only have a rough model and need help turning it into something printable, start with the quote form and explain what you want the part to do.

FAQ

Can I upload more than one STL for a quote?

Yes. Send all the files and state the quantity for each part. If parts assemble together, say that too, because fit and orientation may matter across the set.

Is STL enough, or do you need STEP?

STL is often enough for a straightforward print quote. STEP is better if the model may need editing, accurate holes, changed wall thicknesses, added fillets or proper engineering features.

What if I do not know the material?

That is normal. Describe the use: indoors or outdoors, hot or cool, flexible or rigid, loaded or decorative, wet or dry. The use case is usually more useful than guessing a material name.

Should I repair the STL before uploading?

If you can, yes: make it watertight, remove stray shells and check scale. But do not spend hours fighting the file. Upload it with a note about what you are unsure of, and we can tell you whether it is quoteable or needs work first.