What a 3D print actually costs you
Most print shops start by quoting on filament. A spool costs £20, the part weighs 40 grams, so the part costs 80p and they charge £5. That works until the day a part takes eleven hours, and then it does not work at all.
Filament is usually the smallest line in a printed part. Here is the whole bill.
Machine time
The largest cost in almost every part, and the one quoting by weight ignores completely. A tall thin vase and a short dense bracket can weigh the same and take four hours apart.
Work out an hourly rate from what the machine cost and how long you expect it to last. A £400 printer you expect three thousand printing hours from is about 13p an hour in depreciation. That figure is not the whole rate, but it is the floor.
- Depreciation: what the machine cost, divided by the hours you expect from it.
- Maintenance: nozzles, belts, bed sheets, the hotend you replace twice a year.
- Failures: a share of every print that does not finish. More on that below.
Electricity
Smaller than people expect and not nothing. A typical desktop FDM printer with a heated bed draws somewhere around 100 to 150 watts averaged over a print, with spikes at the start while the bed comes up.
At 120 watts and 25p a kilowatt-hour, an eight-hour print uses about a kilowatt-hour and costs around 25p. Worth including, not worth agonising over, and worth checking against your own tariff rather than ours.
Filament
Work it out from mass, not from an estimate of volume. Your slicer gives you the mass the toolpath actually uses, and the price per kilogram turns that into money. A 40 gram part from a £20 kilogram spool is 80p of plastic.
Your time
The cost everybody leaves out, and the one that makes small jobs unprofitable. Levelling, loading, removing the part, taking off supports, cleaning the bed and packing it are all time, and almost none of it scales with the size of the part.
Charge it per plate rather than per part, because that is how it is spent. Four small parts printed together cost one setup, not four, and quoting them as four is how you lose a job you would have been happy to take.
Failures
Some prints fail. The filament runs out, the part lifts, the nozzle clogs eight hours in. If you have never priced for this, every failure comes out of your margin.
The usual approach is a percentage added to every job. If roughly one print in twenty fails, five per cent across everything covers it. Measure your own rate rather than guessing: most shops are better than they think on simple parts and worse on tall ones.
A worked example
A 40 gram bracket, six hours of printing, on a machine you rate at £1.20 an hour, with £1.50 of setup and a five per cent failure allowance.
| Machine time, 6 hours at £1.20 | £7.20 |
|---|---|
| Electricity, 120W for 6 hours at 25p/kWh | £0.18 |
| Filament, 40g from a £20 spool | £0.80 |
| Setup and finishing, one plate | £1.50 |
| Failure allowance, 5% | £0.48 |
| What it costs you | £10.16 |
The filament is eight per cent of it. A shop quoting on plastic alone would have charged about £2 for this and lost £8 on every one.
What you charge on top of £10.16 is your decision. A markup is simpler to explain; a target margin is easier to hold across parts of different sizes. Either is fine as long as it is applied to the real cost rather than to the plastic.
Why this is worth automating
Working this out by hand for one part is ten minutes. Doing it for every enquiry, including the ones that never order, is most of a day a week. PlateDock does the same arithmetic from the customer's actual file, using your rates, and gives them the number while they are still on your page.