Can you print a huge helmet on a Prusa? – Postprocessing of 3D prints step-by-step

Can you print a huge helmet on a Prusa? – Postprocessing of 3D prints step-by-step

Hi everyone, today we’ll take a look at
post-processing of 3d prints. It means we will take a 3d printed model and turn it
into a beautiful fully colored object. This is the best way how to create
things you can put on display, or how to make amazing cosplay accessories. So let us show you how to do it. Once the object is printed, you need to remove all support and brims. Actually, it doesn’t really matter from which type of filament you print or what color is used, because in the next steps, you will cover the whole surface with another material or paint. However, the best options are PLA or
PET-G. Try to clean all parts from all strings and cut off all “elephant feet” from the print, otherwise you won’t be able to align the parts perfectly. The printed model should be temporarily assembled first. An ordinary adhesive tape is perfectly fine for this task and the tape is also useful once you get to
painting. Let’s say we will need to paint the model with multiple colors and the tape can be used to mask various sections of the model so that the spray paint does not affect already painted parts. Once we know how the model will look and we know which parts will have to be glued together, we can finally start with the proper glue. We recommend using a glue with an activator, which usually comes as a spray. If you don’t have that, any better super glue should be enough to ensure a strong connection. Large and thin surfaces can be reinforced with the polyester resin that improves the structural strength of the whole model. Add a hardener to the mixture according to the manufacturer’s instructions. It’s always better to start with a small amount, so you don’t have to throw the
remaining material away. Also keep in mind that the polyester resin will pretty much destroy the bowl and the paintbrush. Apply the mixture into the
inside of the model with a brush. If you still find the model fragile, use a
fiberglass cloth, which you will press into and already applied polyester resinlayer and then apply another layer on top of it. The resin should be applied in
a well-ventilated room or outdoors, but preferably at temperatures above 20
degrees Celsius. Now we have the models ready for the next step – hiding gaps between parts and sanding. First let’s do a rough sanding of the printed object to find out whether we need to add extra material to hide the gaps between different parts. It is also the first step in the process of creating a nice smooth surface. For this task we recommend the P 100 grit sanding paper. Once the model has been roughly sanded, we can move on to filling the gaps
between single parts. We recommend using a body filler used in the automotive industry. Apply a thin layer on the gaps and let it dry. Once the model has dried, polish it with
a p100 sandpaper. Keep repeating this procedure until the gaps are no longer visible. Once the model is ready, we can apply a layer of a putty / body filler onto the rest of the model, and then send it with a p100 sandpaper. And we basically repeat the step over and over and over again until the model is beautifully smooth. However, be careful not to make a necessarily large scratches or gaps in the print, which would require extra fixes afterwards. On the other hand, if you just grind through the surface into the infill, don’t throw the part away. You can still fix it easily with a putty. Between each round of application and sending of body filler, it is a good practice to spray the model with the filler in a spray that will highlight contours between layers, so we can instantly see whether there is some kind of bulge or defect. Use a marker to mark areas that have visible inconsistencies and require more care in the next round
of sanding smoothing or painting. You do not have to worry that alcohol-based markers would be visible through the base color and multiple layers of the filler. When the model is finally dry, you will easily mask these marks with the first proper color layer. Once we have sanded everything to
achieve the best possible look, the model needs to be spray with a base paint and then finished with a very fine P 400 grit sanding paper to achieve a completely smooth surface, which is ready for applying the last layer of base paint. If you feel that the surface is still not smooth enough, you can spray the model with a filler or a base coat again and then send it with a P 400 grit
sandpaper either using dry or wet sanding methods. Use the spray from a distance of about 20 centimetres which is eight to ten inches at an angle of about 15 degrees. This applies to base colors or colorless varnishes as well. Use smooth long strokes and spray the model from one end to the other without staying in one place for too long this will avoid accumulation of drops of
paint. Now we have the base paint applied, so we can finally move on to the other colors. The best way to apply the paint is to start from the least accessible places or from the largest areas. A good practice is to fix every layer of
paint in place using a clear coat spray glossy or matte to preserve the layer
and prevent any damage to it such as smudging during subsequent work. Than you can proceed with applying other colors either with a brush airbrush or spray. If you use a brush, keep in mind to mix the color within a water to avoid visible brushstrokes on the surface of the object apply multiple layers to achieve
proper coverage. The color will be beautifully saturated and the brush marks will not be visible. If you apply paint using a spray or an airbrush, you may need to use a paper adhesive tape to mask already sprayed surfaces. With regard to color selection brands like: Valejo, Citadel or Model Air will offer you a huge range of shades. Maybe you already have your favorite brands, but we know from our own experience that it’s good to do a bit of experimenting from time to time and discover new products. Once you get to gluing, it may happen
that you encounter parts that will be stressed more. To achieve a better toughness we can reinforce the stressed parts to prevent them from breaking. The best practice is to use metal profiles and drill small holes in the plastic
where we can insert the profiles. You can use various screws, pipes or wires, skewers or plastic boards as a reinforcement profile, or pretty much any
material or objects that will fit the particular model and improve the
strength of the stressed part. So for example this antenna required
reinforcing, because this part was too thin and susceptible to fracturing. We fix that by drawing a small hole and inserting a steel rod in it. And this concludes our video. We took a 3d printed object and through the process of
sending, gluing, painting and coating, we turned it into something you can wear or put on display. Also don’t forget about one of the biggest advantages of 3d printing: if you accidentally damage the model, you can easily print another one. So don’t worry about something like “I’m clumsy, I would ruin it”. Because with a 3d printer, you can always try again. So thank you for watching and remember if you want to learn more about post-processing and other techniques, be sure to check out our blog at

48 thoughts on “Can you print a huge helmet on a Prusa? – Postprocessing of 3D prints step-by-step”

  • Awesome stuff, nice to see some variety, I personally would have wet sanded, it makes the process much faster and less messy, great video overall!

  • P.s. you can use a cheap welding mask for the visor, and don’t forget the “circuit board” behind the key holes in the back!

  • Well done. Very comprehensive. I liked the wide variety of techniques you used. Reinforcing weak parts is really smart. Thanks!

  • The best options are not PLA or PETG. ABS is the best option for props since it's the most easy to sand and is the most heat resistant. I have friends which have printed props in PLA and put in alot of work but they left them in their car on a summer day and guess what happened? They warped pretty badly and had to throw them away. Hours of printing and post processing work in the trash.

  • It would be nice if when splitting the print in Slic3r, to allow adding alignment holes that later can be used to aid in gluing pieces together using toothpicks as dowels. Might be worth suggesting that to the programmers?

  • So. Much. Waste. I don't even mean the support material, that can be recycled. All the plastic tape, tiny filler particles, the spray painted paper that can't be recycled, and the leftover resin.

    Please be conservative when possible. Re-use tape, don't throw out your printed plastic waste. Store it and separate different types. The tiny particles are the worst but you can melt them down into something functional or at least more easily recycled chunk.

  • I recently bought the i3 mk3 kit and I must say, I am absolutely amazed by the entire thing! This is my second 3d printer, my first was one I bought around four years ago, and it is a night and day difference in quality. Right after the build and after fixing one or two things that I did not do perfectly, It has had multiple amazing prints. The layers look amazing and the crash detection has worked flawlessly so far, both with simulated crashed and a crash that was my fault when checking things with my calipers while it was printing. This printer has already done 2 days and 18 hours worth of printing in the less than a week that I have owned it. So far, I must say, this printer is the best I have seen, without even changing from stock settings. I cannot wait to take this into the class I teach to children over the summer. It has also taught me a few things that I did not know which is good because I am at school for mechanical engineering. Thank you for making such an amazing printer!

  • If you happen to damage it, don't worry, you can always print another one and spend another month of work postprocessing it 😀

  • Kind of defeats the point of a good 3D Print. I would just use my Anycubic Chiron as I do and print all in one go. And then for ultimate smooth finish just use Acrylic Spray putty and a light sand with wet and dry. Painting is easy after that. A lot less work.
    Maybe this much work is needed when printing with a Prusa, not sure. 😛

  • It is better to apply one or two layers of spraycan-filler before sanding, you don't have to sand as much and it is much easier to see how many passes you still need for a good finish.
    This is especially usefull for PLA parts which are hard to sand.
    Also don't cover the whole model with putty, apply the putty only to the seam-lines, you could also try to use disolved plastic (sprue-goo) instead to fill the gaps.

  • And once you finished, 3D printers no longer exist….Even after all that post-processing, you can see defects, due to the body fillers and whatnot.

  • In the interest of safety: Most automotive bodyfiller contains styrene (smells sweet) which is a likely carcinogen. Wear proper safety equipment and work in a (genuinely) well ventilated area.

  • All that work and then you use shitty GW paints? 🙁
    I used to work fro GW, if you knew how long those paints sit in storage and how inconsistent they are from lot to lot, you probably wouldn't use it.

  • After priming you want to use a thin layer of guide coat spray. It's much more effective at identifying low spots before you sand. It's commonly used in automotive painting to ensure extremely flat surfaces.

  • I really like this video. It helps showcase how what you can do with a 3d printer. My only question is, where do I find the model for the double light arch?

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