Wall thickness versus cost and print time
How wall thickness drives FDM print time and cost, with a comparison of 1.2, 2.0 and 3.2 mm shells on the same enclosure part.
When customers ask why one version of a part costs noticeably more than another that looks almost identical, the answer is usually wall thickness before it is infill or even overall size. Perimeters and solid top and bottom layers are traced at full extrusion width regardless of what is happening inside the part, so they scale print time in a very direct way that is easy to estimate and easy to overspend on without noticing.
What actually drives print time
For most parts with typical infill densities of 15 to 30 percent, the shell (perimeters plus top and bottom solid layers) makes up the majority of the toolpath length, not the sparse internal lattice. Infill patterns move fast and cover ground efficiently at low density, while perimeters print at a controlled speed for surface quality and top and bottom layers need multiple passes to fully close over the infill pattern below. This is why doubling wall thickness on a part often adds far more time than doubling infill density would.
Comparing 1.2, 2.0 and 3.2 mm shells on the same enclosure
Take a mid-size electronics enclosure, roughly 150 by 100 by 40 mm, printed in PETG with a 0.4 mm nozzle and 20 percent infill. Moving the wall thickness from 1.2 mm (three perimeters) to 2.0 mm (five perimeters) to 3.2 mm (eight perimeters) changes the part in a predictable, non-linear way across weight, stiffness, print time and price.
| Wall thickness | Perimeters | Relative stiffness | Relative print time | Relative price |
|---|---|---|---|---|
| 1.2 mm | 3 | Baseline | Baseline | Baseline |
| 2.0 mm | 5 | Approx. 1.8x | Approx. 1.4x | Approx. 1.3x |
| 3.2 mm | 8 | Approx. 2.6x | Approx. 1.9x | Approx. 1.7x |
The pattern worth noting is that stiffness grows faster than price up to about 2.0 mm, which is where wall thickness is earning its cost. Past that, going to 3.2 mm keeps adding weight and time at a steeper rate than it adds usable stiffness, because the enclosure is by then well beyond what its actual load case (screws, occasional drops, panel mounting) requires.
Where extra wall thickness is worth paying for
Extra wall thickness earns its cost around fastener bosses, snap arm roots, hinge points and any surface that takes repeated mechanical contact, because failure there is expensive in a way that a slightly heavier part is not. It also earns its cost when it lets you remove a secondary part such as a metal insert or a bonded stiffener, since the wall is then replacing an assembly step rather than just adding bulk.
It is generally not worth paying for on large flat cosmetic panels, decorative housings, or anywhere the load case is genuinely light. In those cases the money is better spent on a rib pattern, a slightly better material, or simply left in the customer's budget.
Reading a quote with wall thickness in mind
When you get a price back that looks higher than expected, wall thickness is one of the first things worth checking before assuming the quote is simply expensive. A part with unnecessary 4 mm walls quoted against a part redesigned to 2 mm with local ribbing can easily differ by 30 to 50 percent in price for the same functional performance, which is exactly the kind of adjustment we flag during DFM review before a job goes to print.
Frequently asked questions
- Does wall thickness or infill drive FDM print cost more?
- For most parts printed at typical infill densities, wall thickness has a bigger effect, because perimeters and solid top and bottom layers make up most of the toolpath length. Infill density matters, but doubling it usually costs less than doubling wall thickness.
- Is a thicker wall always worth the extra cost?
- No. Stiffness gains taper off past a certain thickness while cost keeps climbing at roughly the same rate, so extra wall is worth paying for mainly at fastener points, hinges and other high-contact areas, not across an entire part.
- How much can redesigning wall thickness save on a quote?
- It varies by part, but going from an unnecessarily thick uniform wall to a thinner wall with local ribbing commonly saves 30 to 50 percent on that part's price without reducing functional performance.
- Should wall thickness change between a prototype and a series part?
- Often yes. A prototype can afford a heavier wall to de-risk early testing, while a series part benefits from being optimised down to the minimum that meets the actual load case, since the savings multiply across every unit produced.
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