3D Printing Question
by John
3D printing is really slow. So slow, that the machine is left unattended to continue the print, overnight in many instances. The print head is set at 205ºc and the table at 60ºc, and it does bother me that this hot machine is left unattended, unwatched. I do not know if any fires have resulted, but fires are of some concern, particularly here in Oz.
A substantial component of the printing time is the hidden, internal structure of the object being printed, the “infill”.
In this photo I set the infill at only 3%, but to compensate for that I increased the wall thickness. The result was a nicely rigid article, but it was a 24 hour print.
My question. At this point in the print job could I have paused the printing, and filled the cavities with a substance which set hard. It would have to be done carefully of course, and keeping the level below the printing edge. It would also have to be cool or cold, so the PLA did not melt or distort. It would also need to be able to be poured, or injected. Plaster of Paris comes to mind. Car filler bog would be too viscous.
Any suggestions?
johnsmachines 
If you add something that is not at the bed temperature the part will probably release from the bed, so probably better to do the filling after it is off the printer.
With the fire issue you should check that the thermal protections are enabled. Specifically runaway, if one of the sensors separates from the heaters or has a bad connection it sees that the heater is just staying on and stops to prevent fire. Sadly a lot of the printers coming from china and other places have disabled this. There are a couple of known issues with specific printers, but you would have to search for your printer.
Depending on your concern and the flammability of what is around your printer there are self actuating fire extinguishers such as the ‘fire extinguisher ball’ and some other ‘Automatic Fire Suppressor’ devices that have magnets for stoves.
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Good information, thanks Chris. See another reader has suggested an enclosure might be safer.
If I was going to add a filler, the thermal shock would be reduced by warming the filler, and using thicker walls on the print which tend to insulate the filler from the heated bed. I could even dispense with the heated bed because I am using only PLA at this stage.
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Hi John;
Just an idea: Instead of pausing prints & filling cavities… Would it be helpful to enclose the printer in some kind of heat insulation? This would serve a double purpose of more efficiently keeping heat in to improve the print, as well as preventing any possible heat spread to nearby flammable materials..
Ben
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Yes, good thought. I have been thinking about making an enclosure for energy conservation reasons, particularly now that we have a spell of cool weather, at the tail end of summer.
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