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I am wondering - of course if the 3D printer's bed big enough - printing multiple copies of the same print could save me significant amount of time in a small production line, excluding minor wastage such as setup time, post-processing time, etc.

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e.g. if my foo print takes 10 hours, printing 2x copies at the same time would take 2x times more, increasing linearly or it would be significantly less?

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    $\begingroup$ This depends. Are you printing everything from one extruder, or do you have multiple extruders working in parallel? $\endgroup$ – Davo Aug 2 '17 at 14:40
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    $\begingroup$ Both. The Beast with 4 and a maker $\endgroup$ – Mehrad Aug 9 '17 at 5:13
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Actually no. It will take slightly more for each addition. You also then have the point of failure, where one gets knocked off and ruins all the prints.

The fastest way to print multiple objects is one at a time. In fact slic3r lets you do just that with their sequential printing feature.

The reason is, the time it takes to lift 0.5mm, travel the few MM over to the next object, lower the 0.5mm back down.. Repeat for inner shells, outer shells, infill.. all add time. Doesn't seem like much till you do it 14,000 times.

In the case of your example, it would be negligible. In more complicated or well spaced prints its another story.

For extra extra fast, look into loss PLA casting...

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    $\begingroup$ What does "loss PLA casting" have to do with this? How does it allow you to speed things up? $\endgroup$ – Tom van der Zanden Feb 28 '17 at 5:38
  • $\begingroup$ You might add to your answer that the user is pretty much responsible for verifiying that the required X-Y clearance for the extruder head after a few objects have been printed is set properly. And of course for those not using slic3r, the advantage of printing everything at once is that we can walk away from the setup and come back when everything is done :-) $\endgroup$ – Carl Witthoft Feb 28 '17 at 15:09
  • $\begingroup$ @TomvanderZanden They want to make a bunch. 3d print and make a casting. $\endgroup$ – StarWind0 Feb 28 '17 at 16:15
  • $\begingroup$ That's not the right terminology then. "Lost PLA casting" refers to a process where a PLA print is encased in plaster, then burned/melted out, and then molten metal poured into the void left. The mold is then broken, and a metal part extracted. This doesn't help for making a bunch of parts, since both the master part and mold are destroyed. The idea to look in to (silicone) mold making and casting in resin is not a bad suggestion though, but not really related to the question (and there is no indication OP is looking to print that many copies of this part). $\endgroup$ – Tom van der Zanden Feb 28 '17 at 19:42
  • $\begingroup$ Yup, thats why it was a foot note and not the answer $\endgroup$ – StarWind0 Feb 28 '17 at 20:37
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Yes, and no. It depends.

For FDM printing, the printing time mostly scales linearly with the number of objects. However, some printers have a "minimum layer time" whereby smaller layers are printed more slowly, to ensure each layer takes at least this minimum time. This gives the print enough time to cool.

Since the model shown in your example is quite small, it's quite likely that it will hit the minimum layer time. This means that printing one copy will take exactly as long as printing two copies, which will take exactly as long as printing three copies, until you hit the minimum layer time. At this point, adding more models will just add some constant number of minutes to your print time.

If the model is large enough for minimum layer time not to be a factor, then printing the objects one at a time is generally faster because you save on travel moves between the layers of the two objects (and also results in better quality print, since the inter-object travel moves may leave behind stringing).

This only holds for FDM printing. For DLP printing, the printing time for a (set of) models only depends on their total height and thus the number of layers required, since each layer requires the same amount of time regardless of the amount of material printed. Thus, the time for 1, 2, 3,...n models is exactly the same.

There are many other types of printing process where the number of layers is much more important than the amount of material used, such as binder jetting, SLA and SLS,... Here there usually is some time cost involved for material printed, but the main factor in the print time is the number of layers (and for SLS, the amount of time it takes for the build volume to cool down after each print, which is quite significant.).

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Printing multiple parts can save you time.

The issues pointed out by the other posters are all bang on, but one factor that has been neglected is the time it takes you to clear the build plate and restart the print. I found for smaller parts (under 1 inch cube) printing several parts at a time was more convenient, and minimally faster. The time saved came more from the fact that I could leave the printer for several hours and work on other tasks without having to babysit the printer waiting for it to finish each part. I printed about 100-200 parts in this manner. I did end up losing one 'batch' when one part came loose and started causing problems, but I found that was a small price to pay for being able to get a lot of other things done.

It'll come down to the criticality of your deadline on the parts. If you're making parts for giggles and you don't need them done immediately, then i'd say one at a time. Less risk of failure, less wasted material and the time isn't super critical. If you're making parts for a prototype product that needs to be field tested in a few weeks, then i'd go with small batches of multiple parts. It'll give you more time to work on other things, less releveling, and you can check in once in a while to confirm it's okay usually without having to do anything assuming all is going well.

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The proportion of production improvement is dependent on the size of the items being printed, generally speaking. Unfortunately, it's variable enough to make a precise answer difficult.

Consider a single unit print. I'll use my printer as an example. Other printers may have similar sequences. The print is begun and the bed has to heat up to temperature. Once the set level is reached, the print head(s) also have to reach temperature. Ignoring for the moment the print duration, one then considers that the printer bed has to cool to release the print.

If you have ten items to print, you gain nine times the above elapsed time. That can be a substantial portion of production time.

On the flip side, there isn't going to be much benefit in time from ten prints opposed to one. You may lose some post-processing time if you have stringing between the items.

Directly related to quantity printing is yet another complication. If you have a single print fail, you've lost that time. As an example, one print may take 18 minutes. Twelve minutes into the print, you have a nozzle clog and have to abort the job. That's an unfortunate loss.

With ten prints on the bed, you are two hours into the print and have a failure. Much worse loss of time and productivity.

Obviously, one would prefer to have a properly fully working printer and be able to operate with the confidence that these failures won't appear.

Hobby grade printers can't provide that level of confidence, but industrial/commercial grade printers should, further improving the productivity time for printing multiple items on a bed.

If you have hot-swappable print beds, maybe combined with the ability to pre-heat the incoming bed, you gain time-wise. I don't know enough of the commercial grade printers to suggest that such a feature exists. My printer bed is attached with magnets and could be hot-swapped if I exercised care. The bed would begin to cool quickly, making a pre-heated plate all the more valuable. I'll just print multiple items and hope for the best, instead.

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