What maintenance costs and what happens if you ignore it

Of every field in this calculator, maintenance is the one most people leave at zero. It makes sense: when you buy the printer you spend nothing on it, and for a few months you still do not.

Then a nozzle wears out, a tube degrades, a belt stretches, and it turns out the machine was not just what you paid for it.

This article is about putting a number on that. And it starts with a confession: the value this site uses in its guides is too low.

What that field actually means

First we need to clear up a misunderstanding that changes the answer by a factor of four.

The maintenance field in this calculator is not what you spend in a year. It is what you will spend over the machine's whole service life, exactly like the printer price. The two are added together and spread over the hours it will last:

Machine cost per hour = (price + maintenance) ÷ service life

With the values this site's guides use — a $400 printer, $50 of maintenance, 4,000 hours of service life — that is $450 spread over 4,000 hours, or 11.25 cents per hour of machine time.

If what you have written down is an annual figure, you have to convert it before entering it. And that is where the problem shows up.

Why this site's value is too low

Let us do the sum backwards. If you print 1,100 hours a year, which is what two hundred parts like the reference one come to, the 4,000 hours of service life last you 3.6 years.

Spread over that time, the $50 of maintenance the guides use is $13.75 a year.

Thirteen dollars seventy-five a year. That is one nozzle, one PTFE tube and not much else. If you have had a printer genuinely running for three years, you know that does not stretch as far as it sounds.

The figures normally quoted for a home or semi-professional machine are between $50 and $150 a year in spares and consumables. Converted to a full service life, that is not $50, it is between $182 and $545.

In other words, the default this site's guides use may be underestimating by a factor of four to eleven. I say it here because it is the honest thing to do, and because it helps to know which way a figure is wrong before you price with it.

So why not change it across the other guides? Because every figure on this site comes from the same scenario, and moving it now would break the comparison between articles. The value stays as it is, and you already know which way to correct it when you run your own numbers: upwards.

What it does to your part

Now the important bit: how much this changes the real cost. The same 60 gram part in 5 h 30, varying only the maintenance budget for the service life.

From the first row to the last there are 83 cents a part. On a cost of five dollars, that is 16%.

And between what the guides use and a realistic $50 a year there are 20 cents: the part goes from $5.11 to $5.31. You can open both and compare: with $50 and with $182.

Twenty cents a part sounds like nothing until you put it next to something else: it is double what you would save by moving all your printing to the cheap electricity band, which is 10 cents. That contrast is the reason for this article.

What wears out, and how often

To estimate your own number you need to know what goes in that bucket. I am not going to give you prices, because they depend far too much on the brand and where you buy, and in six months they would be out of date. I will give you the list and the frequency, which is what does not change:

• Nozzles. The thing you replace most often. In brass with PLA they last a good while; with abrasive materials — carbon fibre, glitter, wood, anything with filler — they wear out in a fraction of the time. It is the cheap part you buy most often.
• The PTFE tube on machines that run it all the way to the nozzle. It degrades with heat and starts causing jams that look like something else. It is one of the replacements people take longest to connect with the problem they are having.
• Belts. They stretch slowly, last years, and when they fail they do not snap: you see it in print quality before anything else.
• Fans. They start getting noisy long before they die, so they usually give you warning.
• The build surface or sheet, which is a consumable even if it does not look like one. It gets scratched, loses adhesion and ends up causing failures.
• The small stuff that adds up: rail grease, cleaning alcohol, hex keys, unclogging needles. Little money each time, constant over the years.

The frequencies normally quoted as a reference are a nozzle every 3 to 6 months, PTFE or hotend every 6 to 12 and belts every 1 to 2 years, always with the caveat that they depend enormously on what you print and how many hours you put in.

The maintenance you do not pay in money

There is a second half to this line that never shows up in any order: the time you spend maintaining the machine. Levelling, cleaning the bed, swapping a nozzle, tensioning a belt, clearing a jam.

This calculator pays your time at $12 an hour. At that rate:

An hour a month is $144 a year. That is nearly three times what the spares cost on a normal machine, which we were putting at $50 a year.

And here is the awkward part: that time does not go in the maintenance field, and it should not, because the calculator already charges your labour in the 15 minutes per part. Putting it in both places would be charging it twice.

What is worth knowing is that it exists. If your machine gives you trouble and you spend two hours a month on it, the problem is not the nozzles: it is the 24 hours a year you are not printing or selling. That is a far better argument for changing machine than any other.

Getting your own number in ten minutes

There is a way to do this that requires guessing nothing, and it is to look backwards instead of forwards. Three steps:

One. Open the order history wherever you buy spares and find everything that is not filament from the last year. Nozzles, tubes, sheets, fans, whatever. Add it up. That number is already better than any estimate.

Two. If you have had the machine less than a year, add what you have spent so far, divide by the months you have had it, and multiply by twelve.

Three. Convert that annual spend to the service life: divide your service-life hours by the hours you print in a year, and multiply the result by the annual spend.

With this site's numbers: 4,000 hours of service life divided by 1,100 hours a year is 3.6 years; times $50 a year, $182. That is the number that goes in the field.

And if you are new and have no history, put $182 in and move on. It is a conservative estimate and it is infinitely better than a zero.

What changes over a full year

Per part, twenty cents comes to nothing. Across a year's output, it changes the conversation.

If your real maintenance is $100 a year and you have the field at $50, you are failing to charge $86.35 a year. Not a fortune, but it is money leaving your pocket without appearing anywhere, because you never put it in the price.

And it is money you do not see coming: it does not arrive as a monthly bill, it arrives as a nozzle here and a fan there, each one a few dollars, and none of them big enough to make you stop and add them up.

Is the expensive machine that breaks less worth it?

This is the question behind the whole article when it is time to buy. If a more expensive printer needs less maintenance, does it pay off?

With the formula in front of you it answers itself, because price and maintenance are added in the same place. What matters is the sum of the two, not each one separately.

The result is blunter than I expected: the purchase price weighs far more than the maintenance. The $200 machine that needs twice the spares still comes out cheaper per part than the $800 one that needs none.

You can even work out how much it takes: the $200 machine would have to spend $782 on maintenance — about $215 a year — to match the $800 one. That is far more than any home machine spends.

Which does not mean you should always buy the cheapest. It means the saving-on- maintenance argument almost never justifies the jump in price. If you pay for an expensive machine, pay for what it does give back: speed, reliability, fewer failures and, above all, fewer of your own hours fighting with it. Those hours, as we have just seen, are worth more than the spares.

Compared with what people usually worry about

This is the part of the article I find most interesting. Let us put side by side the things people try to optimise and see which one moves most.

Plenty of people spend time scheduling overnight prints and have never touched the maintenance field. The second moves nearly three times what the first does, and you do it once in your life.

If you want the full breakdown of where every dollar of a machine hour goes, it is in what an hour of 3D printer time costs. And the detail on how little the electricity tariff moves is in printing at night.

Why zero is the worst option

Leaving the field blank has one concrete consequence: the part comes out at $5.03 instead of $5.31. That is 28 cents you are not charging and are spending.

You can see it with the field at zero, which is how a lot of people have it.

At two hundred parts a year that is around $55 that disappears. And the worst part is not the amount: it is that it disappears quietly. A failed print is visible and it stings; a seven-dollar nozzle every four months nobody notices, until you look at the year's accounts and they do not match what you thought you earned.

The printer is not what you paid for it. It is what you paid plus everything you are going to pay to keep it running, and your parts pay that second number too.

Put something in that field. Even an estimate, even a conservative one, even one you work out from the list above. Any reasonable number beats zero, because zero is the only one we know for certain is wrong.

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