I'm asking people with experience - Is my big project even possible?

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To start, I have no experience of my own, only what I have learned from YouTube videos.

I’m asking for your opinions before I bite into something I cannot chew.

I want to make a big statue, that is also very detailed using 3d printing while maintaining a reasonable cost.

The way I intend to make it, is by utilizing an onion like layer structure. In the center, there will be a steel column with a bunch of welded steel rings to distribute the weight of the filler.

I will surround the metal “skeleton” with a rough 3d printed inner shell and fill the space between the skeleton and the inner shell with “SOMETHING”(concrete/plaster)

The last 2 layers will be an outer shell made of photopolymer resin 3d prints and Polyester resin to bind the inner and outer shells.

To summarize: Steel Skeleton > “SOMETHING (concrete/plaster)” filler > rough plastic 3d shell > Polyester resin > 3d printed outer shell.

Amazing visual representation here: https://gcdnb.pbrd.co/images/zpcK0guPgP0O.png

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zpcK0guPgP0O1737×787 12 KB

Why this layout?

I want the statue to be both big - 15 feet(4.5 meters) and detailed - Something that only resin 3d can do, however the prints are very small. And before you suggest, at this scale it would be cheaper in man-hours to make it in resin, than to make it in plastic and have every nook and cranny filled with plaster and smoothed.

The way it would be assembled is like layering a cake.

1st, the base would be poured and the metal skeleton welded. After that, I will work on 40 centimeter increments. Put the plastic shell >pour concrete and let it dry >Assemble the outer shell >Pour resin and let it dry >repeat until finished.

Plaster >polish the joints of the outer shell and primer>paint.

Alternatively, I was thinking about removing the rough 3d plastic shell after the concrete sets and have the Polyester resin on top of the concrete.

Ok now let’s dig in into the calculations.

I have skipped the Base and the metal skeleton parts because they will not be that expensive compared to everything else.

The average human body is 180 by 50 by 30 centimeters if put into a rectangle box. In order for the statue to remain proportionate, I am multiplying the dimensions of the rectangle by 2.5. Giving new dimensions of 450 cm by 125 cm by 75 cm.

Note this is an overkill. Realistically, both the surface area and the volume are about 40-50% less, since the space around the head and legs is mostly empty. But It’s better to plan for the worse and hope for the best.

I’m using ChatGPT to help me with the calculations because I am bad at math. I try to double-check them myself, but since I have no experience, I just try to spot the chat’s mistakes.

The volume of a 450x125x75cm rectangle is 4,218,750 cubic centimeter

How many tons of cement do you need in order to fill 4,218,750 cubic centimeters?

ChatGPT:

The density of cement can vary depending on the type and manufacturer, but a common density is around 1440 kilograms per cubic meter. Converting 4,218,750 cubic centimeters to cubic meters: 4,218,750 cm³ = 4.21875 m³ To find the mass of cement required, we can multiply the volume by the density: 4.21875 m³ x 1440 kg/m³ = 6075 kg Converting the mass to tons: 6075 kg ÷ 1000 = 6.075 tons

For a 6-ton concrete mixture using a 1:2:3 mix ratio, you would need 1 ton of cement, 2 tons of sand, and 3 tons of gravel.
I would skip the gravel and replace it with more cement and sand.
Based On the prices where I live, I’m looking at about 2-400 USD for everything.

For the inner plastic shell, I’'m getting a bit lazy with the calculations. It will not have to be pretty, and it would be mostly hollow, with the exceptions of some supporting cables to keep it from expanding/deforming when the concrete is poured. However, I’m thinking that those cables should be made from wire, so the concrete doesn’t just melt them. The shell will be made out of modules that fit into each other and are about half a centimeter to one centimeter thick.

How much would it cost to 3d print a sheet that is 125 centimeters wide, 1400 centimeters high and 0.5 centimeters thick?

ChatGPT:

As a rough estimate, we can assume that the sheet will be printed using FDM (Fused Deposition Modeling) technology, which is one of the most widely used 3D printing technologies. The most commonly used material for FDM 3D printing is PLA (Polylactic Acid), which is relatively inexpensive compared to other materials.

Assuming a printing speed of 60 mm/s, and a layer height of 0.2 mm, the estimated printing time for the sheet would be around 58 hours. The amount of PLA filament required would be approximately 8.75 kg, assuming a filament density of 1.25 g/cm³.

The cost of PLA filament varies depending on the quality and brand, but a rough estimate would be around $20-$30 per kilogram. Therefore, the total cost of the filament would be around $175-$262.

I don’t know how accurate that is. Probably not that much. This guy did a 6-foot master chief for about $850. https://www.reddit.com/r/3Dprinting/comments/wmj42o/my_3d_printed_life_sized_master_chief_is_finally/ However, his statue is solid, and I want just a shell. So I am putting a round $1500 for the shell as an estimate.

The next 2 calculations are about the resins. For the 3d printed shell, I’m using a thickness of about 4 millimeters. For the polyester resin, I will double that.

So here is what I calculated for volume:

450x175x4 = 22500 centimeters3 = 22.5 liters x 2 sides = 45 liters

450x75x4 = 13500 centimeters3 = 13.5l x2= 27l

125x75x4 = 3750 centimeters3 = 3.75l x2 = 7.5l

=77.5 liters total

x2 = 144 liters polyester resin

This is what ChatGPT had to say

Unsaturated Polyester Resin (UPR) typically has a density of about 1.1 to 1.3 grams per cubic centimeter (g/cm³) when it is in liquid form. However, once it cures or dries, its density increases and can vary depending on the type of UPR and the curing conditions used.

Assuming a density of 1.3 g/cm³ for the cured UPR, a ton (1000 kg) of UPR would occupy a volume of approximately 769.23 liters (1000 kg / 1.3 g/cm³ = 769230.77 cm³ = 769.23 liters).

So based on this calculation I will need about 200 kg in order to fill 150 liters of volume. At a price of 1.5 USD per kilo, I am looking at 360 USD plus some unknown shipping.

That is for the 3d photopolymer resin. I have read that it has a conversion rate of about 1 to 10. For every 10 liters of liquid, you get 1 liter of solid. Again, I’m not sure if I’m right here, but if the calculation is correct, I will need 780 liters of resin. They sell it in kilograms for about $20 at Alibaba, so I will need 850 kilograms, since I have read that a kg is about 0.9 liters. That is 17 000 USD + about 20% vat. So 20 000 USD plus some shipping cost.

Now for the printing I made calculations using Phrozen Sonic Mega 8K Large High Resolution Resin 3D Printer

It has a Print Volume: 33 x 18.5 x 40 cm

I made my calculations with the following assumptions: Since the sculpture is so big, most of the parts will be largely flat with a little curve. I gave them a bit of space on both sides, so I imputed 16 centimeters width 32 centimeters height and about 4 centimeters depth accounting for curvature and supports. (the parts themselves are 4 mm thick as stated)

So I made the assumption that I can fit 8 on the plate at the same time.

What is the surface area of a rectangle that is 16 by 32 centimeters, 32 cm * 16 cm = 512 square centimeters.

How many of those rectangles can you fit on 199,500 square centimeters,

Number of rectangles that can fit = Total area / Area of one rectangle = 199,500 cm² / 512 cm² ≈ 389.06

If a 3d printer prints at a speed of 70 mm/hour, how many hours would it take it to print 32 centimeters?

ChatGPT

To convert 32 centimeters to millimeters, we can multiply by 10: 32 cm * 10 = 320 mm

To find the time it takes to print 320 mm at a speed of 70 mm/hour, we can use the formula: time = distance / speed

time = 320 mm / 70 mm/hour = 4.57 hours

Therefore, it would take approximately 4.57 hours to print 32 centimeters at a speed of 70 mm/hour.

/ 8 pieces on a plate = 48 prints 1 print = 5 hours = 10 days

This is without any rest or leeway. And obviously I need to calculate the cost of the 3d printers $2700 + $400 and Base plus steel another 1500-$2000 and paint probably few hundred bucks.

One of my worries is that the concrete will deform the 3d shell while curing. But I am assuming if I spray the outside of the shell with water, it will prevent deformation.

So I’m asking you. Are there any big flaws in my logic or calculations?

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I’m worried that the resin calculation speed might be off. I saw a video of a guy who printed a 30ish centimeter tall helmet, and it took him 30 hours, which would bump my printing time to 60 days

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Two big questions reading this:

  1. Where will this statue be placed? Will it be inside or outside? If it’s outside, then I think you need to rethink your approach as UV from the sun coupled with precipitation and temperature swings will tear it apart in short order.

  2. How will you pour in the filler and hold it in place and shape while it cures?

From a practical perspective, you need to explain how you will assemble, mount and connect the 3D pieces followed by how you will pour in the filler. I can’t image that you’re going to assemble everything and then pour in six tonnes of concrete from the top and expect it to be held in by the 3D printed parts before it cures.

Rather than asking people here about the 3D printed skin, I would suggest that you first talk to people who make 4.5m tall concrete statues for a living.

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Hi there, thanks for reaching out!

Some good points have been raised by other people here. It certainly sounds like you have put a lot of thought into this.

You may be able to coat the outside of the print in some sort of epoxy/ sealant to add some structural rigidity while also giving it some uv/ weather protection. I’m guessing that this is going outside based on the size of it, the outside conditions can present some problems when dealing with 3D Printed parts, especially resins which can degrade in the sunlight.

I agree with @mykepredko that it may be helpful to ask some professional sculptors about this as well. I used to do some sculpting but it has been probably 7 or so years since I last really did that so my memory of all of it is a little foggy (Now I just get machines to do it for me :wink:).

Just out of curiosity what are you looking to make a sculpture of? Depending on what it is you may find it helpful to start with something a little smaller and then move on. This project seems pretty daunting, even to people who know a lot about printing this isn’t an easy task to undergo. So especially when you are just starting out you may find it useful to experiment on a smaller scale, this will help you to learn about 3D printing and find out what works and what doesn’t without wasting lots of material.

It may also be a good idea to try to prototype different designs and mixtures on smaller scales before going to the big piece, you could leave them all in the conditions you plan to leave the full statue in for a while and see what happens. That way you could see if there are any combinations that work better than others before putting it all together.

Good luck with everything, please keep us updated on your progress. I am very curious how this turns out!

Happy Printing,
Matthew

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Outdoors, but it would be shaded. I also plan to use UV coating to seal it after painting.

I assume you mean the resin filler. Well, I intend to have the outside shell designed in such a way that the places connect like a puzzle so they will hold the filler resin.

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In regards to being outside, you’re going to have issues with heating and cooling (regardless of whether or not it is in the shade) along with rain, ice and snow. This will be compounded by having two materials in contact with one another that have different coefficients of expansion (due to heating/cooling).

In your image you have “Concrete / plaster filler”. A column of freshly poured concrete (which is what you basically have) 4.5m high will have a side pressure at the bottom of roughly 128kPa (calculated as the product of 19.8 kPa pressure for 1m of water at atmospheric pressure x 1.44 concrete to water density x 4.5m).

Resin pieces that are 16cm x 32cm at the bottom of the statue (from your original post), they will be holding back 6,553 Newtons of force (1,473 pounds-force). The force along the column is linear, so at 2.25m up, it will be half the force or 3,277N (737lbf).

If you fill the whole thing with resin, then you can rerun the calculations with 1.11 (the density of resin compared to water) rather than your value of 1.44 for concrete (just FYI, when I looked up the density of concrete, the value that came back is 2.4x that of water). Taking these numbers your pieces, that “fit into each” other, will have to hold back force in the range of 5,051N (1,135lpf) and goes as high as 10,922N (2,455lpf), when you use the density of concrete that I found.

Maybe my assumptions are way off but I’m going by what you’ve presented and the numbers make sense and are easily verifiable.

Again, rather asking a bunch of guys who fool around with 3D printers along with a somewhat experimental AI program, you really need to talk to people who are paid to mould large concrete statues, pillars, columns, etc. as they will have the specialized knowledge you need.

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That’s why I’m installing additional metal rings, and i’m pouting at 40 cm increments. You have misunderstood me a bit the concrete would be poured into the PLA inner shell not the resin outer shell.

After reading a bit more, I’m starting to think that PLA prints that are smoothed and then cast with iron would be more suitable and cheaper at the end.
Do you have any experience with that process, does the PLA shape need to be removed or does the metal just melt it off?

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Hi there,

I have never tried using PLA to cast iron, but given that the melting point of iron is ~ 1500°C it should be able to melt it off pretty well. I do know that people often use Styrofoam for casting metal as it melts off very well. If you were interested in casting you may want to look into sculpting the figure yourself.

See the attached links below for 3D printing metal molds. If you were to go this route I would still highly advise you to seek help from a professional first, especially when dealing with dangerous molten Iron. Stuff can go wrong pretty quick. It may also be a good idea to get a second opinion on how this stuff actually works since I know basically nothing about casting metal.

Hope this helps,
Matthew

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Hi, i am sculptor with 40 years experience, (forgive my bad english)

1- First, the desing of your project place a lot of weight at the top standing on one leg only. If you are going this way you need an engeneer to calculate the size of the steel column for your security and the security of public.
2- Friend of mine use to pour concrete in 3D printed molds that have a lot of parts, he print mold 2 to 3 inches thick, and parts are bolted together to stand the pressure ot concrete even on 40 cm high.
3- A plastic shell filled with concrete will not stand weather changes unless you live in a country where there is no winter (as mentioned in the comments expansion of materials are not the same) .
4- this is a way to do that kind of project : The Making of 30' 3D Printed Statue - YouTube

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