Props "I Need A Weapon" - CnC Props For Mold Making and Casting [VOTE INSIDE]

[CPO mendez]

Hello 405th! i'm back with another prop project for y'all! this one will have more community involvement, more pictures, and more advanced tech!

So, to start, this entire project came around because my University (previously featured in my 3D Printed Props thread) gave me access to this A B S O L U T E U N I T: (Pardon my Australian)

Boys and girls, say hello to the Multicam 3000, a 3-axis CnC mill!

Starting in January i took up a job as a student workstudy monitor running this beauty, and it got me thinking about all the incredible possibilities...

So, for a little backstory, I always meant for my 3D printed props to be molded for casting to sell, as a way to fund this little hobby of mine, as well as to provide fantastic props to all you lovely armour makers for a fair price. But it ended up getting hit with a couple problems.
1: i lovingly and painstakingly painted these 3D printed props, which isn't a very good idea if you plan on casting something, as the process is very dirty and could potentially destroy the master copy of the prop. and 2: a solid urethane cast of, for example, an Assault Rifle, would weigh a TON! that'd make it an absolute killer to ship, and wouldn't be very fun to carry around a convention for an entire weekend either!

The good news is, there's a solution to this issue. the bad news: It involves sawing the prop in half... or starting from scratch.

So, the solution i came up with to make lightweight yet sturdy props is this:
When you're casting something big that you want to be light, you do a slush cast shell that you fill with expanding foam, which is super lightweight, while also being fairly good at getting smacked around without breaking. But, instead of slush-casting (which would be a pain in the ass for props like this, in my opinion) there's another way. All you have to do is chop the prop in half lengthwise, hollow out the inside until its ~1/4" thick (give or take) then do a two-part mold of each half! all the hollow shell goodness with none of the turning and tumbling and sore arms that you get with slush-casting.

Now, this method could easily be done with my 3D printer and existing files. But do you really expect me to have such a beautiful $80,000 machine at my disposal and NOT make all of you insanely jealous watching me use it to perfectly craft Halo props? i didn't think so! And, more practically, it cuts the fabrication time down from ~1-2 months to a matter of hours. so there's that.

SO! now for the voting! since this project's goal is to sell props, i need to gauge what props you guys want, and how many of you want them. MDF, silicon rubber, fiberglass, and urethane are all expensive, and since this isn't just a personal project i'd like to make sure i'm spending money on things that are worth it. I've compiled a list of what i feel are the most popular weapons in the series (mostly from Halo 5, for now):

The AR is a shoe-in, so that's what i'm gonna start us off with while everyone votes. and once i get some sufficient numbers i'll start going down the list by popularity and working on those.

Now for the actual build process! well, first and foremost, the 3D modeling. we got the game-ripped asset:

which we need to pull all the complicated bits off of. I'm doing this because while the CnC will be very accurate, it can mangle some of the more detailed parts of a model if they're small enough.



these details will be 3D printed and cast separately as well.
This is also partly a little perfectionist nitpick of mine. things like plates and screws and small details like that, in my opinion, look just slightly flat or "off" when they're just a carved or painted detail on a piece, as opposed to being completely separate and attached. It's something so small most people won't notice either way, but the devil is in the details i suppose.

There are also some parts that i want to keep separate for practical reasons. the biggest one is the barrel. after having the barrel of my 3D printed AR smashed off so many times, having one that is a "breakaway" piece that comes off cleanly and can be easily reattached is pretty handy.

Tomorrow i'll separate what goes into the 3D printer and what goes into CnC. for now, get voting!

 

[Lieutenant Jaku]

Wow interesting idea. If your goal is to sell props what do you estimate as the cost.
Also it may not be one of the most popular weapons but I think Missile pod should be in the vote too. (You don't have to listen to me it's just my favorite)

 

[PHCosplay]

I would really love to see a silenced smg from ODST to be done, and then i would love to BUY said smg lol or maybe the assault rifle and again i would BUY said assault rifle for my up coming cosplay

 

[Hein B287]

Hold on a minute. Are you making molds for weapons? I would be very interested if the price is right

Will be following this thread as this project unfolds

 

[CPO mendez]

Wow interesting idea. If your goal is to sell props what do you estimate as the cost.
Also it may not be one of the most popular weapons but I think Missile pod should be in the vote too. (You don't have to listen to me it's just my favorite)

Whoof! the missile pod is a BIG sucker! i don't think you'd like the price if i went through with making it. And speaking of price/costs, I don't have a solid number yet. the MDF wood used to make this stuff is pretty damn pricey considering the volume i'm using (24" by 48" by 3", four boards stacked and glued) then on top of that is the rubber molding (smooth-on's Mold Star 16 platinum silicon, with an additive to make it brush on), then the fiberglass and resin for the mother mold, then the urethane/expanding foam to make the cast itself, and finally paint. I'm estimating it'll be around $400-$500 for everything, which should make 2-3 full molds and maybe a dozen or so full casts. Luckily for you guys i plan on making the money back through volume, which means a lower/more reasonable price.

I would really love to see a silenced smg from ODST to be done, and then i would love to BUY said smg lol or maybe the assault rifle and again i would BUY said assault rifle for my up coming cosplay

I can't make any promises about the ODST SMG, but if enough people ask for it, then i'll be happy to make it! i do know i'll be making the ODST silencer attachment for the H5 magnum, and of course the AR is already in the process of being made.

Hold on a minute. Are you making molds for weapons? I would be very interested if the price is right

Will be following this thread as this project unfolds

Yes indeed! i'll crank out urethane casts of whatever props y'all vote for! and like i said to Jaku, i plan on pricing bast on selling a high volume, which means it should be a very reasonable price. There'll also be a few options, like an unassembled kit (lowest price), assembled, unpainted kit (medium price) and fully assembled, painted, and detailed prop (highest price).

Now! onto the project itself! i planned on updating on thursday, but wouldn't ya know it, the CnC decided to set itself on fire! some settings were funky and the 4 fluted bit being used was dull, so a student's piece got hot enough to ignite, and the student wasn't watching it like they were supposed to. On the bright side everyone on staff that day (me included) got to test our emergency response skills, which were stellar. Unfortunately the CnC has been shut down for repairs all weekend. So we'll be focusing on the 3D modeling and wood prep for now.

So, we left off with the AR prop having all its details (screws, switches, buttons, etc.) being pulled off. now, those details are converted into STLs and put into my 3D printer's slicer so they can be printed:





After that, comes the body itself, which is going into the CnC. our Multicam 3000 CnC machine runs off of RhinoCam, which is an addon for Rhino, so guess who just spent the last month learning Rhino! (i swear, that code line at the top that auto-completes for you is spoiling me rotten!)

Now, one issue that i ran into (that almost tanked the project) was the problem of giving this mesh some sort of thickness. (this might get into some nitty gritty 3D modeling stuff, so hang on tight!) So, technically, a polygon is a strictly 2 dimensional thing. it has a thickness of zero. well, just like with my 3D printed props, this became a problem for this project. i needed the body to have enough thickness to, well, exist in 3 dimensions! At first i tried "Local translate Z" in maya, but too much geometry would come out of the outward face of the mesh, like so:




Now, i was able to clean up the mangled geometry, however the other issues with this were 1: the maximum thickness the model could handle before the geometry just went crazy was WAY too small, 0.025 inches. that would be far too fragile to survive the milling, let alone the mold making process and casting! and 2: this TRIPLED the amount of triangles in the model. it got to the point that when we were doing toolpathing on the computer in the CnC room, every edit would make rhino unresponsive for up to an hour while it processed this bloated, enormous file. I posted on the (super helpful) McNeel support forums for Rhino, and the responses i got were mostly along the lines of "ooh, yeah, that's a tough one. this MIGHT work but i don't like your chances".
The other option was just milling it out as a solid, and then hand-sanding it to be hollow. and while that would normally be what i would do, in this case every mistake made with this master copy will be compounded a hundred or so times since i'll be cranking out casts of it. so if i left a section a bit too thick, or another section a bit too thin, then i'm either losing a TON of money in extra material/weight, or ALL the casted props are going to have a weak spot that could get bashed and easily damaged. Therefore, i figured it would be best to let the machine precision handle things. And thankfully, i managed to come up with a solution.

The solution: Now, i need to explain how the CnC works before this makes sense. So, since it's just a computer controlled mill, that means that it has all the limitations of a mill. the biggest one being that it can only mill in 3 axis. (There are CnC mills that go up to 5 or 6 axis, but neither me nor my school are Baller enough to have a multi-million dollar machine like that at our disposal). 3 Axis milling means that any overhangs or details underneath what's being milled can't be milled. the tool can only go up and down. it can't turn sideways and get under an edge, or flip under your piece to hollow it out. There is away around this, called a "flip cut" which, as the name suggests, involved milling one side of your piece, then flipping the whole thing over and milling the other side to get all the details or, in our case, hollowing it out into a shell. It's the most difficult kind of cut you can do on a 3 axis CnC machine, and of course literally every prop i'm gonna make on this thing, by design, is going to be a flip cut.
ANYWAY! with that explanation out of the way, here's the solution. So, The two cuts are going to be the outside shell (or "top") and then the flip cut, which will hollow it out and also get a few small details around the edges that the first cut couldn't get. Now, if i were to import the mesh with no thickness and cut it, it would mill out the top perfectly fine, but since there's no thickness, the flip cut would hollow it out to nothing and just leave a pile of useless sawdust. HOWEVER, if i were to go into the tool dimensions for the flip cut, when it's hollowing out the piece, and change the tool dimensions to a quarter inch thicker, and a quarter inch longer than the tool actually is, then when it goes to hollow out, it THINKS that it's hollowing out the model with zero thickness according to the set tool dimensions, but its ACTUALLY giving me the quarter inch wall thickness that i want. However there is a downside, which is a massively increased risk of snapping a bit because there's material in places that the CnC thinks are clear. Snapping a bit certainly isn't the end of the world, and happens fairly regularly, but obviously we don't want to needlessly put the machine in danger. The compromise is to just use this method for the roughing (first pass with a big bit before the smaller detail parts with smaller, more fragile bits) and i'll take care of the rest with sanding.

So, with that long rant over, back to the file prep!
First, the meshes are dumped into rhino, then registration is put in so both halves will fit together perfectly:




Then, Supports are added. these supports are for the Flip cut, because once the CnC does the perimeter on the second cut, then it's completely cut the piece out of the surrounding material. For a normal cut this wouldn't matter, since it still has a flat footprint secured to the table underneath, but after the first cut there's no solid footprint left. So, a bunch of support poles are added going through the piece, which keep it secured to the surrounding material so the flip cut can be completed without it moving and getting ruined. They'll be cut off by me once the mill is done:


Next up, is the stock. AKA the block of wood that this piece will be cut out of. This needs to be defined so the CnC knows where it can and cannot go (it doesn't exactly have eyes or a brain, so to speak, so it needs to be told everything by the code its given).


then, the "bounding curves" are added. this is a perimeter around the actual piece you're milling, leaving at least a half inch gap between the line and your piece. this is for efficiency, and basically gives the CnC a more specific area that it can cut into. otherwise it would just mill down the entire block of wood, which would be incredibly time consuming, pointless, and in the case of our flip cut, destroy the surrounding material holding the piece to the table.


Finally, everything is copied, pasted, and the copy is flipped over 180 degrees. This is the "flip" part of the "flip cut". RhinoCam needs to have the "top" of the model, AND the flipped-over "bottom" of the model because they will need to be separate cuts to allow us to go in there and flip the material over. Also, on the right side of the picture, you can see the Layer and sub layer organization (works just like layers in photoshop) which are needed when we get to the toolpathing and need to make some things disappear for certain cuts.


There's also (not pictured) three registration points in the corners of the stock. these will be used to make holes all the way through the material and into the table below (Specifically the replaceable MDF table cover) and special pegs will be inserted into the holes. this works just like normal registration in a mold or casted object, since we'll be flipping it over, and will need to have it lined up PERFECTLY to where it was, otherwise the CnC will ruin the piece, thinking it's in a different position that what it actually is.

Alright, i think that's enough writing for one day, Kudos if you made it this far without falling asleep to my nerdy ramblings about the intricacies of 3D modeling in Rhino. I promise it'll get more interesting very soon. next up: something a little more straightforward, gluing the MDF boards together to create the stock.

 

[Lieutenant Jaku]

Whoof! the missile pod is a BIG sucker! i don't think you'd like the price if i went through with making it. And speaking of price/costs, I don't have a solid number yet. the MDF wood used to make this stuff is pretty damn pricey considering the volume i'm using (24" by 48" by 3", four boards stacked and glued) then on top of that is the rubber molding (smooth-on's Mold Star 16 platinum silicon, with an additive to make it brush on), then the fiberglass and resin for the mother mold, then the urethane/expanding foam to make the cast itself, and finally paint. I'm estimating it'll be around $400-$500 for everything, which should make 2-3 full molds and maybe a dozen or so full casts. Luckily for you guys i plan on making the money back through volume, which means a lower/more reasonable price.

View attachment 254891

oh pricey, looks like I won't be buying, but still excited to see what you make.

 

[CPO mendez]

oh pricey, looks like I won't be buying, but still excited to see what you make.

the $400 -$500 would be for all the materials needed, which would make a ton of props. this certainly isn't a set price, but i could see the AR going for $150-$175. the smaller stuff like magnum and SMG would be roughly half that, the bigger stuff might hit $200. just some rough estimates since people are curious

 

[Hein B287]

For that price range i would definatly go for an assault rifle and a magnum. Maybe even a socom from odst?

 

[mkshane81]

Wow, what a project! Very impressive work on the separation.

-Matt

 

[BDUB]

I have a nice SMG model i made a while back. Really high poly. I actually intended for it to be CNC'd and produced that way. Parts separate, so it's semi functional. You can use it if you'd like. It is very accurate.

It's in two halves and nearly fully prepped for carving, so you could literally just spit it into your software super fast and easy.

Nice work you're doing thus far. Keep it up!

 

[CPO mendez]

I have a nice SMG model i made a while back. Really high poly. I actually intended for it to be CNC'd and produced that way. Parts separate, so it's semi functional. You can use it if you'd like. It is very accurate.
View attachment 254925
It's in two halves and nearly fully prepped for carving, so you could literally just spit it into your software super fast and easy.

Nice work you're doing thus far. Keep it up!

I appreciate it man! But i already had all the files cut and ready to go, though. if i run into any issues with the SMG, i'll let you know.

 

[CPO mendez]

Jesus... lemme just blow the dust off my copy of the necronomicon and resurrect this thread...

Looks like things got pretty damn busy over the summer and this project got pushed by the wayside (ironically a majority of my free time over the summer that was devoted to this project got eaten up by maintenance and repairs to the CnC machine). That being said, I kept working where i could, and have PLENTY of updates to keep this thread going!

For the sake of catching up i'm going to skip the process of laminating the MDF boards into a block of material. just imagine a bunch of wood boards getting glued together and clamped down, and you got a pretty good idea of what happened. Now, onto the fun part!

First up: calibrating the machine! i'm only including this because whenever i do it i always feel like a xenomorph is about to pop out of a vent and jump me, for some reason...

With the machine calibrated, the material gets secured with double stick tape, and the built in vac-table suction.

Now, like i mentioned earlier in the thread, these milling operations are the most complicated out of all the cuts the machine can do: Flip Cuts. it's certainly not impossible, but it's not exactly easy either. that means that the material needs to be very precisely placed on the table, so when its flipped over, it can be put in the EXACT same spot. any deviation from the original position, and the entire second half of the milling process will be off. Think of a mold without any registration marks. if one of the halves slips even a bit, you got a big seam running along your entire cast.

So, with the material secured, we ran a quick simulation before proceeding with the first cut:

And, seeing that everything looked good, it was time to mill! first, the rough pass:


Then, more precise tools were brought in to do the finishing pass:






Looking DAMN good! here's a close up to show the detail and smoothness:

There are some mill lines that come through, but a bit of sanding will clear them up easily. Before that, though. it's time for the flip! Same as the first cut, it's a roughing pass, then a finishing pass.

And just like that, we have ourselves a milled MDF assault rifle prop! However, we've already run into some very not fun issues, which i'll be going over in the next post...

 

[xXDashIVXx]

That is amazing!!!!

 

[mkshane81]

Wow! I really can't say anything else, just wow!

-Matt

 

[GMer56]

MDF? Sounds like it's gonna have a nice weight to it.

 

[Lt.Dan]

Oh man the potentials for this are pretty endless. I really want to see more of this process!

 

[MajWood]

holy crap man! yes! though it looks like only me and one other person voted for the power of the promethean weapons, LONG LIVE THE DIADACT