As part of the gift I'm printing for Doug (dots of paint blog) he also requested two tanks. We will look at some of the challenges of more complex shapes in this post. FDM printers sorta suck with undersupprted overhangs.....which is to say printing in midair works poorly. With an angle you can manage a gradual extension out without problems (such as an arched door). Otherwise you get big droopy loops and poor quality or worse.
Supports, a throwaway structure connected to the ground/build plate which rise up to the unsupported part are the solution. Supports have their own challenge, besides the waste of material and time....they usually leave some cruddy artifacts where they connect. It is therefore key to choose the best orientation to minimize overhangs, or to make them where they aren't going to be seen well. For tanks, and me, that seems to be barrel up.
Our slicer, conveniently, shows in red where the overhangs are. This is based on a setting you tell it where your own printer/settings start to fail. For me it's about 60degrees. Note also that if you printed this without supports it'd fallover almost immediately and be a spaghetti mess in no time. You need a decent amount of contact with the build plate.
Once again, I'm using a 1:100 model which requires me to remember to upsize it, and what percent to use.
After slicing you can (and should) preview the print to make sure the computer hasn't chosen to do something wacky. Here we see the original structure in red (technically the walls are red and inside fill is yellow. We aren't looking at a cross section so we don't see the yellow right now). The blue is the support. It quite clearly illustrates how a throwaway structure is generated which will rise up to support the part of the model which are more than 60degrees off of vertical (such as the bump closest to us there is a pillar)
Printed we see things look pretty decent. The barrel is a bit rough. I suspect this is due to flexing of the tall narrow structure so the small play in the material means perfect alignment doesn't happen and the layer lines are a lot more obvious.
More photos without commentary to follow. Note the final picture gives you a sense of the type of artifact you see where supports contact the model.
Printing it with the barrel up sure seems to minimize the print lines on the top of the turret which is nice as that is what you are going to see the most of when on the tabletop. Do you think there is a solution to the rough barrel?
ReplyDeleteThere are lots of solutions! Everyone seems to have one =p
DeleteA little bit of sanding is probably the best bet here as it's so easy to access. Multiple coats of primer can also work too.
Lol I admit I was hoping for something more hi-tech than good 'ol fashioned elbow grease.
DeleteYah, seriously. There's a ton of solutions people propose but I think sanding does come up with a lot of them. Filler and sanding. Various types of filler. There are some finishing stations that I think use some sort of solvent to very slightly melt the plastic. You lose a touch of crispness for a glossy finish. Seems like a while since I've seen that though.
DeleteWhile I have left the barrel as is, it is a bit rough. Because I plan to have David's nice Valentine as a Russian Lend-Lease, I might paint the barrel white to give the impression the tankers have covered it to give a camouflage effect.
ReplyDeleteHowever I usually remove the 3D barrels (always a bit of a problem for the printer machines) and replace with pipes of some sort. Used ink pen tubes work well.
Really enjoying these examinations into the 'black art'
A fair amount of the roughness and print lines I think do disappear with painting.....provided you don't use a technique like drybrushing which enhances the textures.
DeleteCVA/instant glue works pretty well on PLA (what I print with), so it shouldn't be too hard to change the barrel, though the interior is a semi hollow matrix so might not provide as much support as 'normal'