New to 3D printing? Start here.
A plain-language knowledge base covering how to prepare your files, choosing the right material, and what to realistically expect from print quality and finish.
Choose a topic to see its questions.
Getting Started with 3D Printing
The basics of how FDM printing works, what it suits, and where its limits are.
FDM (fused deposition modelling) melts plastic filament and lays it down in thin layers, one on top of the other, until the part is complete.
Because every part is built from stacked layers, the layers are slightly visible on the surface, and the part is weaker between layers than along them.
FDM suits functional prototypes, brackets and mounts, enclosures and housings, jigs and fixtures, replacement parts, display models and short production runs.
Our estimate tool accepts parts up to about 295 mm on their longest side. If your model is larger, the estimate page suggests a smaller size that fits.
Layer lines are always visible on curved and angled surfaces, so FDM is not the right choice if you need a perfectly smooth finish straight off the printer. We supply parts as printed and do not offer sanding, priming or painting.
Parts are also weaker between layers than along them, and every material has a heat limit (see Choosing the Right Material). Fine detail is limited by our 0.4 mm nozzle.
No. You can send your own CAD model, download a ready-made one from a site listed on our 3D Model Hub, or use our custom design service.
Send us hand sketches, technical drawings, reference photos or a broken part, and our engineers turn them into a 3D CAD model made for FDM printing.
As a general guide, FDM parts are accurate to about ±0.5 mm, or about ±0.5% on larger dimensions. Fit and shrinkage vary with the material and the shape of the part.
If a dimension is critical, mention it in the Additional Project Details box when you send your request.
Preparing Your 3D Files
How to export and send a model so it is estimated at the size and shape you expect.
The quote page accepts STL, 3MF, OBJ, PLY and STEP (STP) files.
- STL, 3MF, OBJ and PLY get an instant estimate from a real slice.
- 3MF is the most useful: it can hold several plates in one file (each plate becomes its own part with its own estimate) and it carries the infill setting from your slicer.
- STEP files are accepted but cannot be sliced, so they are quoted by hand.
Native CAD files such as .f3d or .sldprt cannot be uploaded. Export them to STEP or STL first.
Export in millimetres. After you upload, the page shows your model's size in millimetres, so check it against what you expect.
A model exported in inches comes out 25.4 times too small, and one exported in centimetres 10 times too small. That is the most common reason a size looks wrong.
It means the model is one properly sealed solid, with no holes in the surface, no faces pointing the wrong way and no stray internal walls. The slicing software needs a clean solid to work out what is inside and what is outside.
Models exported from CAD are usually fine. Sculpted, scanned or heavily edited meshes sometimes need repairing in your modelling or slicer software first. If an estimate cannot be produced, the page tells you, and you can still send the request for our team to quote by hand.
Each file can be up to 150 MB, and you can send up to 20 files in one request.
Very high-resolution exports make large files without a visible improvement, so if a file is very large, try exporting it at a lower resolution.
Yes, up to 20 files in one request. Each file gets its own panel, so every part can have its own material, colour and quantity.
If you upload a 3MF with several plates, it is split into separate parts automatically and each part gets its own estimate. Use "Apply to unpriced parts" to copy one part's material to the others, and "Get estimate for all" to price them in one go.
Our 3D Model Hub lists Printables, Thingiverse and MakerWorld (free) and Cults3D, Pixup3D and CGTrader (premium). Before ordering, check that the model's licence allows you to print it, and that it was designed for FDM printing.
Choosing the Right Material
A plain-language comparison of the materials in our quote tool.
PLA. It prints crisp detail and comes in the widest choice of finishes, including basic, matte, tough, silk, metal, sparkle, galaxy and marble. It suits display models, visual prototypes and general indoor parts.
Its limit is heat: PLA's heat deflection temperature is only about 57 °C, so it is not suitable for a hot car, direct summer sun or parts near heat sources.
PETG handles more heat than PLA (a heat deflection temperature of about 69 °C), so it suits functional parts and brackets. We offer PETG HF, translucent PETG, PETG-CF (carbon-fibre filled) and PCTG.
Both handle more heat than PLA or PETG: ABS has a heat deflection temperature of about 87 °C and ASA about 100 °C. ASA is the better choice for parts that live outdoors because it is designed to resist UV light.
Large flat parts in these materials can warp slightly while printing.
Choose TPU when the part needs to bend, stretch, grip or absorb shock, such as gaskets, bumpers, feet and vibration mounts. We offer TPU 95A HF, which is rubber-like and flexible.
For demanding mechanical parts we offer polycarbonate (PC), carbon-fibre filled nylons (PA6-CF and PAHT-CF), PPA-CF and PPS-CF. These are stiffer and stronger than standard filaments and cope with more heat.
Choose them when the part carries real load or sits somewhere hot.
Ask yourself three things: is the part used indoors or outdoors, how hot does it get, and does it mainly need to be strong, stiff or flexible?
Describe the job in the Additional Project Details box, or contact us at info@craftmill3d.co.uk.
Print Quality & Finish
What a finished FDM part looks and feels like.
Because the part is built from stacked layers, horizontal "layer lines" are always visible on angled and curved surfaces, a bit like contour lines on a map. Flat vertical walls and top faces look smoother; sloped surfaces show the steps more.
Thinner layers make the lines finer but never remove them completely.
Layer height is the thickness of each printed layer. The quote page offers 0.08, 0.12, 0.16, 0.20, 0.24 and 0.28 mm, with 0.20 mm as the standard.
Finer layers print smoother but take longer, so they cost more. Coarser layers print faster and cost less, with clearly visible layers.
It will not be glass-smooth straight off the printer. Vertical walls and top surfaces look best, and the underside of overhangs and curves comes out rougher.
We supply parts as printed and do not offer sanding, priming or painting.
Overhangs steeper than about 45 degrees from vertical normally need temporary support material underneath. Where supports touch the part, the surface is rougher than the rest.
You can reduce the need for supports by designing overhangs at 45 degrees or less, or by adding chamfers (see Designing Parts That Print Well).
No. Parts are strong within each layer but weaker between layers. A printed part is most likely to fail by layers separating under a pulling or bending load.
Design with this in mind, and avoid loads that pull the layers apart. If the part carries a load, describe how it is used in the Additional Project Details box.
Each layer has a point where the nozzle starts and stops, and these line up into a subtle vertical seam. It is a normal feature of FDM printing and cannot be removed entirely.
Round holes tend to print slightly undersize, because the plastic is pressed down as each layer is laid and the curve is approximated in small segments.
If a hole must be an exact size, plan to drill or ream it to size after printing.
Designing Parts That Print Well
Simple design rules that lead to stronger, cleaner prints.
With our 0.4 mm nozzle, the absolute minimum is about 0.8 mm (two lines of plastic). For parts that need strength, aim for 1.2 to 1.6 mm or more.
Surfaces within about 45 degrees of vertical print cleanly without support. Where you can, replace flat overhangs with chamfers. Short horizontal gaps, up to roughly 10 mm, can usually be bridged without support.
As a starting point, leave about 0.2 to 0.3 mm per side for parts that must slide against each other.
The right gap depends on the printer, material and part size, so test a small sample first for any critical fit.
The estimate page offers a smaller scale that fits (parts up to about 295 mm on their longest side).
If you need the full size, you can split the model into sections in your CAD software and send each section as its own file.
Yes. A small chamfer or fillet on the bottom edge reduces the slight flared bulge at the base known as "elephant's foot". Fillets on internal corners also spread stress and make the part stronger.
Ordering, Pricing & Turnaround
How estimates are worked out and how long a job takes.
The estimate comes from a real slice of your model: the material it uses and the time it takes to print. Your cart shows the print cost, any bulk discount for larger quantities, a handling fee and an estimated total. Estimates exclude VAT and freight.
Larger, taller, denser and higher-detail parts cost more.
Infill is the internal lattice that fills the space inside a solid-looking part. The quote page offers 20% (standard), 50%, 80% and 100%. If your 3MF was saved with its own infill setting, the page offers that too.
Higher infill makes the part stronger and heavier but uses more material and time, so it costs more.
Use the Get a Print Quote button, upload your model or models, choose a material, colour and quantity, then press Get estimate. Add each part to your cart and send your request with your name and email.
We review it, confirm the final price and aim to reply within 24 hours.
Standard jobs usually take 3–7 working days.
Yes. Single parts and one-offs are welcome.
If the estimate fails, or the part needs several colours, you can still add it to your cart and send the request. Our team will quote it by hand.