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Unread 02-10-2013, 10:24 PM   #1
msleeper
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Gravity Gun (Half-Life 2)

Too many words? Just want pretty pictures? Check out my Imgur album!

I began working on a Gravity Gun prop from the game Half-Life 2 in the first couple weeks of December, 2012 as the first in a series of props for a few accompanying costumes. After about 2 months of work (with some time off around the holidays), I'm probably around 70% finished.

The gun breaks down into two distinct halves, and the majority of parts were either laser cut acrylic or 3D printed plaster which was then molded and cast in resin. The very front barrel "fans" were simply laser cut acrylic. The crystal bars are 3D printed plaster, and the bar "cages" are stacked acrylic. Both of which were molded and cast to create the 6 copies required for the weapon. The rear base of the gun is entirely 3D printed plaster, which is being molded to create a hollow resin casting.

Having a background in 3D editing, I started out with a game model. Unfortunately, the original models from the game are hopelessly, hilariously low resolution. The two available models in the game are either missing 70% of the model, or so low resolution that it's nearly impossible to discern anything. Good thing for me there is a user made high resolution model available! (Original model source here.)



The plan was to break the weapon down to the individual components, re-model each of them in higher resolution, and then export whatever was needed. Below is the final version of the 3D model for the rear base which would be 3D printed.



And here's the whole thing put together, for context:

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Unread 02-11-2013, 09:57 PM   #2
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Once I had the 3D model sorted out, I created 2D vector templates for the front barrel parts, which were then sent off to the laser cutter. A week or so later, this is what arrived.



Because I needed the parts to take paint and glue, I sanded down all of the surfaces. The laser cut edge also has a distinct pattern from the laser - it's not perfectly straight. So that needed to be sanded down to be level as well.

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Unread 02-15-2013, 05:57 PM   #3
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Well I posted like 2 more things but either the moderation queue isn't going through or the mods decided it was spam or something.
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Unread 02-16-2013, 02:33 AM   #4
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With new accounts, they limit your ability to post some things until you hit a certain submission count. It looks like amazing work so far.

What software do you tend to use? What job do you do that gives you access to a laser cutter? I'm quite jealous. I work for a govt contractor myself, so I get to see all sorts of similar wonderful equipment, but since the govt technically owns it, I don't get to play with it
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Unread 02-17-2013, 03:56 PM   #5
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Quote:
Originally Posted by verdatum View Post
With new accounts, they limit your ability to post some things until you hit a certain submission count. It looks like amazing work so far.

What software do you tend to use? What job do you do that gives you access to a laser cutter? I'm quite jealous. I work for a govt contractor myself, so I get to see all sorts of similar wonderful equipment, but since the govt technically owns it, I don't get to play with it
Yeah I understand why accounts are limited, that's just weird that some of my posts made it through moderation queue and others didn't.

For the 3D modeling I used Blender. It's a free program, but the interface is a little dense for total newbies getting into 3D design. That said, there are a ton of really great video tutorials available online, I strongly recommend the ones on 3dbuzz.com. There are also other modeling packages that may be easier to get into if you've never done it before.

For the 2D laser cutting stuff, I used Inkscape. It's a free design programmer, kind of similar to Illustrator. You can very easily create vector images, which you will eventually use in your laser cutting. I do not own or have personal access to a laser cutter. I got all of my stuff done through a member from therpf.com who has access to one. But, I have also used ponoko.com for laser cutting services and they are extremely affordable.
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Unread 02-18-2013, 02:18 AM   #6
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That's great info. I started learning CAD using AutoDesk, but my license is about to run out on that. I played with Blender a little, but the interface was a bit unfriendly. I'm sure I'll switch to it when I start to learn CAD more seriously. For now, I've got too many other things I want to learn first.

I'm glad you're familiar with therpf, I'm pretty sure they're gonna love this project.
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Unread 02-18-2013, 05:38 PM   #7
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After the acrylic barrel parts had been worked, I received the first of 2 sets of 3D printed parts - here, the crystal "bar" and the rear grip plug which will fit into an accompanying socket in the 3D printed rear base (more on this below).

My plan was to make a 2 part mold for the crystal bar, but unfortunately I didn't seem to have put down enough mold release and instead I created a giant silicone brick. It's not a total wash, I was able to cut along the sides to make a usable mold. It's sloppy and it meant there was a lot of cleanup work needed for the final parts, but it worked.



Here are the pulled casts of the six crystal bars, cast in Smooth-Cast 325 which cures a slightly amber colored clear. Since I will be lighting the bars and sanding them to get a "frosted" look, the slight color is not a big issue. I also pulled casts for the 1 part mold for the crystal "cages", but I didn't take any progress photos of that. Sorry.



Lastly, here is a mock-up of everything. Most things are held on with tape here, I had purchased some screws to hold together the front parts but I had to buy more because I didn't account for a few things.

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Unread 02-21-2013, 03:47 PM   #8
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At this point the cast "cages" and "bars had been sanded and were ready for paint. I also went and purchased all of the fasteners needed - something like 60 tiny nylon nuts and bolts. Definitely a small fortune in little plastic bits! The upside is that the entire barrel assembly is sitting together under it's own power for the first time, which really makes me feel like we're almost there.



I also received the 3D print of the rear gun base. If I had to do things over, I likely would not use plaster printing again. The benefit is that the printing is amazingly cheap, but the negatives is that the plaster is incredibly soft and difficult to clean up. There's also a very distinctive texture on it that needs to be worked out - but, you can't, because again the plaster is so soft that you can't really fill it with putty or filler or anything. So, I'm going to go ahead and primer it and cast it as-is, and then work down the texture once I have a resin copy.



Of course, I did take a few mock-up photos of everything for good measure!

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Unread 02-25-2013, 01:32 PM   #9
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Oh my glob, I am nerding out hardcore. It looks amazing! Can't wait to see the finished project.
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Unread 02-25-2013, 05:37 PM   #10
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Good news for you then, because we're getting close!

Things have been going really quickly, so I don't have as many progress photos of the last few steps as I'd like.

I molded and cast a resin copy of the rear grip. Fun fact: resin is about 30% lighter than the plaster is! So maybe this thing won't be as heaving as I was fearing.



I also built the claws for the prong arms, and the cages that hold the actual arms. Here they are with a coat of primer and the first layer of rattle can paint. The arms themselves are in the same stage, but they're presently drying from their paint so I don't have them out to display.





Speaking of paint, I've hit all of the laser cut acrylic and most of the cast parts with primer and a first coat of silver. I am going to lightly sand the silver down and then go over each bit in varying light layers of light and dark silver. The goal is to get them looking metallic without looking too uniform. Then after that we'll get to detail painting (though I may wait until the rest of the parts have caught up before I get there).

I also decided to make the heatsink on the bottom of the gun akin to Volpin's build. Being a terrible hand fabricator, I had it 3D printed and pulled a resin copy from it. I didn't spend remotely enough time cleaning it up before molding, but time is kind or running out. The master is PLA and it didn't seem to like being sanded down, and I'm more comfortable working with the resin anyway. Here's the pull straight out of the mold.



Speaking of the rear base, I've been working on it a bit. The plaster really doesn't like being sanded, it is soooo soft. So I've hit it with a few layers of a high build primer and worked that some. Like the heatsink, I'm going to do more work with the resin copy. But overall I'm not entirely happy with how the whole rear base has come out, and I may revisit this in the future when I have access to better quality 3D printing.



And lastly, here is everything altogether. There's... a lot. In the plastic bag are all of the nylon nuts and bolts after being dyed. I used a gray dye, but it came out a little blue. Which isn't the end of the world because I am planning on making all of the bolts look rusted, and a blue or purple base makes painted rust really stand out.



I am about to get started on the 2 part jacket mold for the rear base. I'm kind of nervous, I've never done a 2 part mold with a mother mold before. Sometimes you have to walk before you can crawl, right?
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Unread 03-05-2013, 02:05 AM   #11
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That is looking very awesome.
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Unread 03-05-2013, 05:00 PM   #12
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Oooh, I do declare!
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Unread 03-14-2013, 07:57 PM   #13
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Whoops, forgot about my thread here! The spam filter eating my posts kind of discourages me.

So last I posted, we were about to mold and cast the rear base. That didn't go so great. My inexperience has caused me some problems that made fixing interesting.

To try and conserve some silicone while filling in the big gaps (namely, between the "drums" where there is a deep valley) I shredded up an old silicone mold and put it in one of the layers. Well, that was apparently not the smartest idea after all because the two silicones didn't stick to one another, and actually caused the silicone immediately around the shreds/chunks to not cure at all.

(I have since found out the cause for this: tin cure silicone will not stick to platinum cure silicone. This is really interesting as I've never heard this before, all I've ever read is "silicone always sticks to silicone". So take notes, true believers!)

What this caused is these hollow spots along these areas where resin got into. Not the end of the world, but definitely a problem I didn't want or plan on having. The bigger problem is that when trying to demold this part I had no choice but to cut out some of the silicone here. So, any further pulls are going to immediately have this awful cleanup needing to be done in these spots.

That wouldn't be as much of an issue if I wasn't going to need at least 1 more pull from the mold. There were some minor alignment / sagging problems, mostly due to thin sections of silicone, at the "top" of the mold where the 3" pipe section is, and on the actual drums. My second pull had less problems and I've decided to go ahead with using it.

It's not a complete disaster, but this whole fiasco is definitely the sloppiest and most expensive mistake I've made thus far on the project. I'm not super happy with the results, but I have got to continue moving forward. Unfortunately the only way to fix the problem is to remold it the master, and if I'm going to remold it then I might as well just remaster it too. Since I'm not made of money that won't happen right away, but I would like to eventually. My coworker has offered to let me use his 3D printer (which printed the heatsink) for other parts, so maybe if I can break things down small enough to fit into his machine.

What's absolute brilliant news though is that the entire rear section is only 1.5 pounds, which is about 80% lighter than the plaster. Weight was going to be a major factor here so having things be as light as I can get them is great.

So, on to the picture show. Here's a montage of building up the silicone and the mother. I can only post 6 images, so check out my Imgur album for lots more.





Here's the first casting that I've made. You can see the pockets where the silicone chunks were filled in with resin.



Here's the the "front" part where the silicone was too thin, so the whole thing sagged in on itself in the mother. The upside is that all of the hard edges are still square, so I can fill in the sagging with putty and not have it be a total bust. Still, it sucks that it could have been an easily fixed problem by buying/using more silicone.





But it's not an entire wash I guess . . .



. . . I still have a Gravity Gun now.

The next step is to clean up my (far superior) second casting, and then start assembling and painting this mother.
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Unread 03-16-2013, 03:53 PM   #14
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Grinding up cured silicone to use a filler does in fact work, but as you discovered, it needs to be similar cure-type. Additionally, you want the silicone to be as clean as possible.

Vacuum degassing after mixing everything up is also a really good thing to do if you have the resources. Small air-bubbles like to cling to the chunks, weakening the mold.

I have a 5-gallon bucket full of dead molds and flashing scrap. One of these days, I'm gonna buy an old-timey meat grinder and use it only for grinding up junk silicone.
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Unread 03-18-2013, 06:00 PM   #15
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The second cast out of the mold (which I unfortunately don't have any pre-cleanup photos of to show that it faired quite a bit better, sorry) had cleanup go pretty smoothly. The little nubs were easy enough to get rid of with a dremel and a coping saw. A few of them left little holes which needed to be filled in, but nothing extreme.



I could have spent a week fixing all of the imperfections but my time table didn't allow for that. The upside is that the piece is supposed to look worn and used, so I can mask some of the minor problems with paint. Here is the cleaned up second cast with primer on it, and the laser cut backplate attached with binder clips while I drill out the corresponding bolt holes. I rotocasted it a little too thick along the top so those ones won't be used.

Now on to paint for the rest of the parts. Again I didn't get too many progress shots here as I was in a serious hurry to get it finished for my deadline. Here are the front barrel parts, the back plate, and the under side heatsink all with their paint.



The paint was varying layers of light, medium, and dark metallic gray on top of the bright silver base coat. I then did a couple of washes in black and brown to make everything look dirtied up. The rust was made using lightly stippled layers of dark purple, then terracotta, then a light orange, and finally a bright yellow.





Also, it's gigantic.

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