I have a number of…um, fairly ambitious projects I’m working on right now that I’ve hit roadblocks on. Since the Internet is a marvel of modern technological accomplishment that allows instantaneous access to not only the entirety of human knowledge but also domain experts in every conceivable field of human endeavor, I’m throwing out a request for ideas and suggestions here.
Project 1: The Alien Pod
I have, through a strange set of circumstances, come into possession of an old “bod pod,” a medical scanner designed, I’m told, to measure BMI. It doesn’t work—it’s just the pod without the computer software and such to drive it—and my goal is to turn it into a gigantic alien egg, like the kind in the Alien movies, but large enough to hold a person.
So the plan is to cover this thing with silicone, to make it look like one of the eggs from the Alien movie (which were basically garbage bags and chicken wire covered with silicone). The effect I’m looking for is something like this:
My thought is to cover the pod with silicone (probably condensation-cure rather than the medical-grade platinum-cure silicone I ise for sex toys, whcih is more than $200 a gallon).
Why silicone and not paper-mâché? The pod weighs more than 400 pounds, so it’s very difficult to transport, and the egg needs to be strong enough to survive handling and moving in a truck. My goal is to use it for a photo shoot, with a model halfway out of it, being dragged back in by tentacles.
The problem is that silicone won’t stick to the surface, like, at all. Not even a little bit.
The pod is a stainless steel shell overlaid with fiberglass and with some sort of textured polymer layer on top. Up close it looks like this:
My first thought is to epoxy a whole bunch of short pins to the pod, to give the silicone something to grip. Many years ago, I remember seeing a product that would be perfect for this: small steel pins, about a centimeter or less long, with a ball on one end and a flat base on the other, kind of like so:
They’re quite small, and a whole bunch of them sticking out of the pod like spines on a porcupine would give the silicone something to hang on to mechanically. Trouble is, I don’t know what they’re called or what they’re used for (I vaguely recall that they’re used in aviation, maybe?), so I don’t know how to search for them.
Alternately, any small, cheap, epoxy-able pin or whatever I can glue to the pod might work. I’m also open to other suggestions. Keep in mind it has to stand up to rough handling—this bloody thing is almost unimaginably heavy and hard to maneuver!
Project 2: Machining Molds
I’ve started making alien xenomorph hiphugger strapons and alien xenomorph facehugger gags for sale.
Right now, I’m 3D printing the molds, a 6-part mold for the hiphugger and a 7-part (yes, seriously) mold for the facehugger.
I’d hoped to get maybe ten castings from each mold. In fact, I’m getting 2-3 before the mold is ruined and I have to print a new one. The facehugger mold takes two weeks(!) to print on my 3D printer. Obviously this isn’t sustainable.
I’ve been planning for a while to move to machined wood or aluminum molds, and I have a 4-axis desktop CNC machine:
I’ve been teaching myself CNC milling, but the learning curve is a cliff; I’m getting reasonably good at 2D and 2.5D machining, but man, the molds are complex.
Here’s a 3D model of one part of the hiphugger mold. This is what I’m looking to machine, either in aluminum or even in wood:
As you can see, it’s a complex shape with aggressive undercuts.
I have not been able to make a CNC program to carve this. (One person online looked at this mold and was like “um, yeah, you’ll need four years of trade school plus at least four years of apprenticeship to even think about machining something like that.”)
So, hey, I have the machine but not the skill, why not hire someone to design the CNC program, right? I’ve talked to a few folks online who are like “yeah, pay me and I’ll do the program for you,” then when they see that part they’re like “oh hell no. Hell. No.”
If anyone reading this knows a skilled CNC machinist who can create a program to mill this part, and parts like it, on my machine (a Makera Carvera with a 4th-axis module), send them my way! This is a paying gig.
In the meantime, I’m also exploring ways to treat the 3D printed molds with resin or epoxy or something to make them more durable. Right now I’m only making one facehugger and one hiphugger per month, and even at that slow rate of production, the process I’m using is unsustainable.
So yeah. I have an eclectic set of friends out there with some highly unusual skills, so I’m hoping that some of you might have insights or ideas to offer.
Those pins look like hair brush pins! I am curious how you would go about sticking them to the surface when it doesn’t seem to want to adhere to anything else though. If you have something that will join the pins to the pod why not skip the middle man and just use the miracle adhesive for the end product!?
Epoxy sticks well to the pod. Silicone doesn’t, but that’s not unusual–silicone doesn’t like sticking to anything but itself.
Instead of pins, why not use steel pad eyes? They’ll give better “grip” because the silicone will pass through the hole. Topographically, it’ll be interlocked with each pad eye. And pad eyes have screw/bolt holes which give more topography for the epoxy to latch on to as well.
That would absolutely work, if I can find them small enough! Ideally they’d be quite small; the silicone layer should be relatively thin.
How about lots of tiny self-tapping screws screwed into the surface, leaving the heads sticking out a couple of mm? But wear a mask in case of fibreglass fibres.
That actually sounds like a fantastic idea!
I don’t know how thick the stainless steel under the fiberglass is, but if it’s of significant thickness (like more than 1mm) you will want to pre-drill a hole because the self tapping head won’t have the power to penetrate anything thicker. These are meant for thin sheet metal. It would save a lot of time and frustration trying to directly drill into a thick shell. Fiberglass won’t hold it, the stainless base layer will. Just make sure you cover or cut off whatever’s behind.
If you are able to 3D print your molds, you might consider making a four axis pantograph and use it to duplicate the plastic molds into aluminum.
A usual pantograph does a size reduction, but the same idea could be used for a one to one copy.
See: https://www.youtube.com/watch?v=vtm4u583YOQ for a simple three axis pantograph.
Huh. I hadn’t even considered doing something like that. Clever!
I thought it clever when I saw it roughly sixty years ago.
There was an attachment for a Bridgeport milling machine that had a hydraulic piston under the table (the Z axis) and a probe above the table that was parallel to the spindle. The model was placed on the table under the probe. The workpiece was on the table under the spindle.
As you manually traversed the table in the X and Y direction, the table moved up and down to cut a steel copy of the aluminum model.
What are the dimensions of your 3D molds?
How does it handle undercuts or sharp vertical walls? Because the milling table exerts a heck of a force, and if the probe gets stuck you’ll just break it. If I have to guess at the dimension, it’s probably fairly large, as it’s for a xenomorph strap on. It looks to be fairly large, probably just about stretching the work envelope of the Makera machine. I doubt it will fit on the 4th axis attachment because that only allows 9cm maximum. May have to do the undercut portion by hand.
Just some ideas (I’m not actually sure if you will read this).
Undercuts are a pain and I think you’re asking a lot from your machine. I’ve said it before and I will say it again: Even if your parts will fit into the work envelope of your machine, with the 4 axis module, you’re still asking a lot of your machine. As far as programming the machine goes, Mastercam does it fine. They do these 3d scanning type machining all the time, and doesn’t bug out like Fusion does, however the license costs about 10,000 dollars.
I am not sure a 4 axis module is going to cut it, what you are asking requires a 5 axis machine, and not a desktop one either. Reason being that some of the undercuts requires a very long tool to get at, long tool means more flex and higher chance of breaking them. So what you’d need is a long tool with a large shank, that tapers down to the size you need for the job. Your machine can’t take those tools. We’d want something that takes 1/2″ shank, that is tapered ball nose, like this one (but longer): https://www.ebay.com/itm/355858322480
The machine rigidity is critical for this kind of machining operation, and I am not sure your desktop machine can cut it (it seems more intended for wood after all).
You should redesign your mold so that you can eliminate the undercut, or at least drastically reduce it. Make the mold multi piece to do this. It sounds like your mold is meant to be 3D printed, and machining a mold/die is completely different than 3D printing it.
Another option is like Kenneth said, a copy carver of some kind, or just do it by hand with a Dremel/Foredom type tool.
Can you contract the job out to a tool/die maker? I think this is the best way. They may ask you to redesign it to eliminate the aggressive undercut however. At least get it so that you can use a lollipop end mill to get at them with a 3 axis machine. This would significantly lower the complexity of machining it. Either way regardless of the part size you really want a large CNC machine, not a desktop one. Otherwise you’re going to spend days machining it, and then ruin the part because you broke an end mill.
When I said redesign, I meant break it up into more pieces so that those undercuts don’t become a problem. I doubt you can metal 3D print it with Elon Musk’s machine (whatever they use to print rocket engines), so you will have to design it for machining.
I need to add: I have a friend who has several large CNC machines, 3 axis that machines aluminum parts with perfect finish all day long. If you can get it designed so that it can be done on a 3 axis, using a lollipop end mill, my friend’s machine could possibly do it.