Model complex solid shapes with cardboard.

Step 6 Sand, add plastic putty, sand, paint, finish

Sand corners, add plastic putty, sand some more. I use Zeocar or Tersuave (brands you can find here in Argentina), its the type of putty to fix car scratches. Add a thick layer of putty until you can't see the cardboard anymore, otherwise when you apply the paint it will be absorbed differently on the surface.

I recommend you apply some primer before you paint to even the surface.

Practice a few times because it's a technique that gets better with it. Share your experimentations with others. Thanks for reading and the best of luck!

Comments

[Sneyk]

Excelente, muy útil para realizar prototipado.

[Mike McGill]

This is very similar to a method that was once known as 'bread and butter' . It was used as an alternative to plank on frame to build hulls for model yachts. You use the lines of the yacht to produce sliices which are hollowed in the middle, and then when they are glued together you carve and sand the outside. It is possible to produce a very accurate hull using this method, because the bottoms of the notches made by the sandwich provide a guide when carving. Must say I never thought of applying it to circular saws though. Nice one !!

[ononal]

thank you for this helpful instruction, layering is a really good technique for creating solid shapes.

i may add something that may helpful for shelling with this technique. wooden sticks may be used on layered cardboard, which will be helpful for having stronger shell and sanding model into precise dimensions.

t

[mario59]

I was thinking a way to properly align the sheets once separated from the printed paper you used to cu them. since the cut borders are always rough since you've to sand them after, do the glue gives you time to make this alignement?
I tried it, but the tholuol is almost like an INSTANT GLUE!
also after brushing it to the sheet, it gets dry almost instantly!
can you be clearer on this?
thanks!
ciao
Mario

[piaferre]

 m yes more or less but remember this: thoulol is the dissolvant of the high impact polystyrene so to have a better "glued" model you can take a piece of the plastic to use as a spatula, dip it into the tholuol and add the dissolving plastic of that tip in the edge you are trying to unite. The plastic will the solidify again leaving your a bit more time to arrange your parts. Hope this helps =)

[mario59]

Grat idea!
I think is *the idea* to make modeller's creations, otherwise very hard to get!
In the meantime, maybe would be a good idea, also, to find a way to get "lighter" objects, to "epty the inner parts in some way (personally I dunno how!)
Also I could not find any indication of how, so many "layers" could be glued together without adding a considerable thicknes from the glue itself...
maybe you have to "miss" some of the slices to compensate it?

who knows?
anyway: congratulations!
ciao
Mario

[Dentroman765]

 How about assembling some slices, then dremeling? That might be a good way to get some material out.

[agis68]

yeah actually this is what is called Industrial design and modelling....is a very well paid position or the elite of 3D modelling everywhere in the world

[piaferre]

When I have to do empty shells for models I use sheets of high impact plastic (its a type of polystyrene). If you apply the glue with a brush almost nothing is added to the total thickness. I forgot to say that on the Instructable, I'll add it. You have to make sure the cardboard is as thick as you think with a caliber or something, so you can slice your model precisely.

[bill2009]

When I have to do empty shells for models I use sheets of high impact plastic (its a type of polystyrene).

I'm not sure I follow you, how do you use the styrene? Instead of the cardboard?

[piaferre]

At my faculty I can buy sheets of high impact polystyrene, this is the plastic generally used for back light signs. I spend a few hours thinking how to build the model and then print out on paper the surfaces that form my model (you have to take in account the thickness of the polystyrene). You "glue" it with toluol (highly toxic so wear a mask), this dissolves the plastic and welds it. This method is really neat since when you sand off the corners of your model it looks like a whole piece. I will write an Instructable of this method some day.

[bill2009]

Sorry, I'm still not sure I get it. It sounds like that would work best for something with flat surfaces so, for an open sided cube you'd be making 5 surfaces? What about something with rounded corners like a hemisphere?

[Honestinwilkesbarre]

I realize your comment was made a year ago, and you may already understand what this instructable is about.
But.....

Actually, you could make a hemisphere with this process. And a sphere would take just about the same number of slices as a cube (or a box). The problem is your under-thinking it. You don't slice along surfaces, which in the case of an open sided box would be 5, you make dozens (or hundreds or thousands) of parallel slices. Think "Cat Scan". They already have 3D printers that work on this principle. 

[piaferre]

Exactly, it would be the best solution for an open sided cube. For a hemisphere you would have to termoform it (I'm not sure I spelled that right but the idea is to transform it with heat). Here's a great Instructable about that: http://www.instructables.com/id/Make-a-good,-cheap,-upgradeable-sheet-plastic-vacu/. You can replace the oven with a 1000w lamp like on this video: http://www.youtube.com/watch?v=KAsEAyuMNeQ&feature=PlayList&p=B43E612A278826F4&index=0&playnext=1
You can also try with modeling epoxy, a few strips of plastic for the skeleton and a mold to copy. That's how I did the other part of the spoon. But you can only get to about 2mm thick and the surface will allways have imperfections.

[declan12]

Cool technique! Will have to try this soon, Thanks!

[padriacnewton]

haha, estudio diseño industrial, hago ésto todo el tiempo, y con tu tutorial que leí en un par de minutos aprendí lo mismo que todo un semestre de clase de modelos de estudio!... se lo mostraré a todos mis compañeros de generaciones que no hayan llevado esa asignatura, les servirá mucho.. y se dice "Epoxy modelling clay".. pero los gringos lo conocen más como "Sculpey"... suerte, y gracias!

[piaferre]

Gracias! Ahi lo cambio, contame de tus experiencias, siempre sirve mas información. Exitos!

[kalikatik]

Very nice!Good work.The program You used on your PC, what's it called?

[alvbarrett]

it seems to be rhinoceros... bien esto me puede servir... estoy estudiando diseño industrial y me serviría para entregar modelos... gracias

[kalikatik]

Thank you buddy

[i_made_that]

I thought you were going to use the saw to cut the cardboard. Then I read through your well-written ible and was amazed that you'd modeled the circular saw! And the spoon! So real!! Great job, thanks for the info.

[electroaire]

Excelente che!!! Soy cordobes y me tope con tu instructable que ta barbaro. Un abrazo y segui pa lante.

[piaferre]

Gracias! saludos desde bsas!