Iterating a Part with FDM: v1, v2, v3
Running a prototype loop with FDM: what each version should test, which material to use, and what to change when a part doesn't fit or breaks.
Very few functional parts are right on the first print. A hole is a little tight, a clip snaps, a bracket flexes more than you expected. That's normal, and it's the main reason FDM printing is so useful for development: each version costs little and arrives quickly, so you can learn from it and move on.
This guide is about running that loop well. What each version is for, what to change between them, and how to set up your files so v2 and v3 take less effort than v1.
A simple plan: three versions, three questions
Each version should answer one main question. Trying to settle everything at once is how you end up on v7.
| Version | Question it answers | Typical material | Focus |
|---|---|---|---|
| v1: fit check | Is the shape and size right? | PLA | Critical dimensions, clearances, mating parts |
| v2: function check | Does it work under real use? | The intended material, often PETG | Strength, flex, heat, snap fits |
| v3: release candidate | Is it ready to use or batch? | Final material | Small tweaks, cost, consistency |
Simple parts may only need two rounds. Complex mechanisms may need more. The principle is the same: one main question per version.
v1: get the geometry right
The first print is about fit. Will it slide onto the shaft, clip into the housing, line up with the screw holes? PLA is ideal here. It's the cheapest material, dimensionally accurate and quick to print.
Before you send v1
- Export cleanly. Check units, close any gaps and keep walls at 1.2 mm or more. Our guide to preparing STL files covers the common mistakes.
- Or skip the conversion. You can upload STEP or IGES straight from CAD and we convert it on our side. If you do want an STL, converting STEP to STL explains the right tolerance settings.
- Build in clearance. Holes typically come out 0.1–0.2 mm undersize and overall tolerance is ±0.2–0.5 mm. Design for that rather than hoping.
- Tell us the critical dimensions. "This bore must fit a 22 mm bearing" is far more useful than a perfect model with no notes.
What to check when v1 arrives
- Measure critical dimensions with calipers, not by eye.
- Test-fit against the real mating parts.
- Note what's tight, what's loose and by how much.
- Mark up a screenshot or photo with the changes. It makes the next round faster.
v2: test it under real conditions
Once the shape fits, switch to the material the part will actually use and test it properly. A PLA bracket that fits perfectly tells you nothing about how a PETG or Nylon one will flex, or how either survives a hot car.
Choose the material for the job
- PETG for most everyday functional parts. Tougher than PLA, handles heat up to about 80 °C.
- ASA for parts outdoors or in the sun.
- Nylon for gears, hinges and snap fits that flex repeatedly.
- PA-CF or another carbon-fibre material for stiff, hot or chemically harsh jobs.
Orientation and strength
FDM parts are weakest between layers. A clip printed standing up may snap along a layer line, while the same clip printed flat can flex happily. If v1 broke in testing, look at where it broke. A clean break along a layer line usually means orientation, not material. Our guide to how strong 3D-printed parts are goes into this in detail.
Infill: strength vs cost
For most parts, walls do more for strength than infill. Adding perimeters often helps more than pushing infill up, and costs less. Moderate infill suits most functional parts, with higher values reserved for parts under heavy load. See 3D printing infill explained for numbers by material.
v3: refine, then lock it down
By v3 the part should work. This round is about polish and making the part easy to repeat.
- Trim cost. Hollow out solid sections that carry no load, avoid unnecessarily thick walls and reduce overhangs that need supports.
- Fix the small things. A slightly loose fit, a sharp corner that could crack, a chamfer to make assembly easier.
- Lock the settings. Once you're happy, keep the same file, material and orientation. If you plan a batch, order one sample print at the normal price to confirm it before ordering the rest.
What to change between versions
The most common problems and the usual fix:
| Problem | Likely cause | Change for next version |
|---|---|---|
| Hole too tight | FDM holes print undersize | Enlarge by 0.1–0.2 mm, or ream after printing |
| Parts won't slide together | Not enough clearance | Add clearance on mating faces |
| Snapped along a layer line | Load pulls layers apart | Change orientation; add fillets at the stress point |
| Clip cracks when flexed | Material too brittle | Switch PLA to PETG or Nylon; lengthen the flexing arm |
| Part bends under load | Too thin or too flexible | Thicker walls (1.6–2.0 mm), ribs, or a stiffer material such as PA-CF |
| Softened or warped in use | Too much heat for the material | Move from PLA to PETG, ASA or a carbon-fibre material |
| Small screw threads strip | Printed threads below M6 are weak | Use heat-set brass inserts or self-tapping screws |
Change one or two things per version where you can. If you change the material, orientation and wall thickness all at once, you won't know which one fixed the problem.
How we help between versions
Every model is checked by hand before it prints, on every version. If we see a wall that's too thin, a feature that will need awkward supports, or a material that won't survive what you've described, we tell you and suggest a fix before it goes on a printer. We don't redesign parts for you, but we will tell you what to change.
Re-quoting is quick. Upload the revised file and the price appears in seconds, with no waiting on a manual quote. If you sign in, your files stay in a file library, so you can come back to v2 months later. Paid jobs can also be reordered at today's price while the model is still on file.
Quick FAQ
Should my first prototype be in the final material?
Usually not. PLA is cheaper for checking fit. Switch to the final material once the shape is right.
Can I send a STEP file for each version?
Yes. We accept STEP and IGES directly, as well as STL, 3MF and OBJ, up to 100 MB per file.
How fast can I get the next version?
Most orders are ready in 24–48 hours, and short prints can often be collected the same day.
Will you tell me if my design will fail?
We flag any risk we can see before printing and suggest a fix. We print what you send, so the final call is yours.
Got v1 ready? Upload it and see the price in seconds. Get an instant quote.
