Instructables

Using Your 3D Printer to Injection Mold Tiny Objects

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This is an offshoot of another Instructable that documents the development of a previously unrecognized capability of fused deposition 3D printers.

Rather than subject readers to endless babble, dull research and boring experimentation, this Instructable will take you step-by-step from making a mold to the production of an extremely small, detailed part on your own 3D printer.   A part, well beyond the normal resolution of your printer, moving it closer to the rarified atmospheric capabilities of DLP and similar technologies.

This new capability does not give you the ability to print small and detailed parts on your printer directly from stl files, but it will allow you to reproduce an existing small and detailed part, using PLA plastic, with your own printer, at will... Over and over, any time you want. 

Extraordinary claims require extraordinary proof... Here's a video, taken in 1 shot of me producing an "Injection Printed" part on my printer:

 


Step 1: What You'll Need:

1. 3D printer:  Any fused deposition printer will work.  You will NOT be modifying this printer, so don't be afraid of ruining it.  Also, you'll need a reel of PLA. -  ABS might work, but it's higher melt temperature makes it more difficult to keep fluid.

2. RTV Rubber: Room Temperature Vulcanizing Rubber is one of the most popular mold making materials available.  It's a stretchable rubber that can be fast curing, forgiving about undercuts and readily available.  You'll also need the catalyst to cure it, a rubber to rubber mold release, mixing sticks, mixing container and a brush.  I get my RTV materials here.  You can also pick up good quality polymer clay here as well.

3. Knives:  Assorted knives to cut, clean and sometimes separate the mold halves will come in handy.

4. Dowel:  I use plastic blocks to build small RTV molds and make my sprews from those, but a short piece of 1/4" dia. wooden dowel will do just as well.

5. Modeling Clay:  You can use clay made specifically for mold making, or the clay your kids use at school.  Both will work, but The better the quality clay you use, the better your results will be and the easier time you'll have.

6. Something to make a mold with:  For this application, you'll need a ceramic container to make your molds in.  A few years ago, I picked up several boxes of Ikea candle holders for $4.04.  At the time, I hadn't a clue as to what they were, but knew I'd be able to use them someday.  I was right.  If you can find these, it's like they were custom made for the job... More on that later.  

If you can't find them, a ceramic demitasse cup should work.  Be creative.

7. Something to make a mold of:  Any small object you'd like to duplicate.  Keep it small... Money is a no-no.

8. Silicone Lubricant:  If you want your molds to last longer, silicone lubricant will help.

9.  Patience:  RTV takes hours to cure.. And you'll need to cure things twice.  There's also a high chance of an "iffy" result.  Depending on the quality of your mold, the item you choose, the length of time for the extrusion, the temperature and the equipment doing the work.

Excellent results are possible, but patience is an absolute requirement.

 
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Lkymama1 year ago
I am absolutely blown away. Your bio is AWESOME. It sounds like you've had a wonderful life and is paying off 10 fold! I have no idea what you did except the end result which I am in awe over. I know in 2-3 years, heck, maybe less...3D printing will be in all homes! I saw them create an ear out of stem cells and 3d. BRILLIANT to me...probably expected by you...keep having fun and creating!
bfk (author)  Lkymama1 year ago
Wow... You make my head swell. Thank you for that, but you're waaaay off base about me... Just ask my wife :)

I'd written that within 2 years the technology will be available in big box stores, but I see a 3D printer can be picked up at Staples right now ( Staples is a large North American office supply chain). I'll bet it won't make much of an impact because of limitation and cost, but it's a first step. And unless another, more efficient technology happens to come along, layered home cmanufacturing will most likely be the means of future instant shopping gratification and a center of medical advances.

Thank you again for your undeserved comments and open-minded clarity of what the future will be.

bfk
bfk (author) 1 year ago
Sorry, don't know what the problem is... My computer is down so I have to look at the world through my iPod for a day or two. I'll straighten it out then. Until then, here's a direct link:

http://m.youtube.com/watch?v=IGhbVCdYD0Y
BrittLiv1 year ago
The video seems to be private :-(
qwixel1 year ago
Seems to me, you could skip the expensive part of this build and just use a high temp hot glue gun to inject into the mold for similar results.
bfk (author)  qwixel1 year ago
Hey Qwixel:

Have you tried this? I know there have been attempts at hand-held extruders for 3D printing on the fly, but they use motor power to be able to produce an even thread of plastic. If you use, as you say, a hot glue gun, modified to accept plastic filament, then a hand-powered version, while not very good for 3D printing, may work exceedingly well as an injection molder. This should be looked into. Great idea.... I think you're my hero.
qwixel bfk1 year ago
No, I have not tried a hotglue gun with PLA or ABS filament.

I would just use the high temperature hot glue. It can set up pretty firm, and since you just appear to be injection molding a plastic bit, it seems like using high temperature hot glue would be just as effective, a lot cheaper and a lot simpler.
bfk (author)  qwixel1 year ago
Turns out, Reactive urethanes have been out for about 5 years and is the technology I was referring to. Go figure. These LOW temperature, air curing resins would probably work great, if I could afford the equipment to use them... However, I came across a polyurethane, 1/2" gun loading stick that just might do the trick. I don't know if this is the same stick you use, but it appears to have attributes I need. I'm trying to find a source where I can order a few for experimentation.
bfk (author)  qwixel1 year ago
Thanks for your response.
You're the first person to give me a valid critique. I need more responses like yours to help me improve this idea.

What you suggest certainly is true and would also allow the pressure to be controlled. The problem for me is, I make models for museums (the reason for those guns) and hot-melts are wax based polymers. Not so good at longevity. Wax based things, especially small ones, are also susceptible to large amounts of shrinkage (heat-shrink tubing is wax based). Wax is also difficult to paint with water based paints, which is what I use, for a long list of reasons.

I may try your suggestion just to see what happens with one of my silicone molds. If you know of a non-wax based hot melt, please let me know.

And now that I've thought about it, I might attempt to modify a hot melt gun to accept PLA filament. That would be the best of both worlds, don't you think?

If someone else has or has had the same thought, it would be interesting to see what's been done in that direction. I know there's at least one product being prepared, but that has both the heating element and extruder... I like the idea of a hand controlled extruder better. Hmmm.

Maybe this is something you could do as well? Seeing as it's your idea.
qwixel bfk1 year ago
I think you are I get much different hot glue sticks. My hot glue sticks are thermoplastic, not wax.

http://en.wikipedia.org/wiki/Hot-melt_adhesive

I have not used them for injection molding, but I have succesfully used them in a number of structural places including car body repair. I would skip the low temperature materials and go straight for the high temperature sticks - they have a LOT of mechanical strength once cooled.

As for a hot glue gun using PLA - http://www.kickstarter.com/projects/1351910088/3doodler-the-worlds-first-3d-printing-pen?ref=live

already exists.
bfk (author)  qwixel1 year ago
I believe this gun (I remember when they were developing it) uses an extruder that's motor driven. That's how they can get it to produce a consistent thread of material coming out of the nozzle. The idea of using hand pressure, as the glue gun does is what's different and unique. Hand pressure as a means to produce a consistently "perfect" thread would be impossible. but to fill a mold with plastic, there is no need for precision... Only pressure.

I'll check out the glue sticks, thank you. if they are as you say they are, then I'll try them. The nice thing about PLA is, it's hard and tools like nylon. I'll order a different color other than clear, which is giving me fits under the magnifier trying to clean parts up.
bfk (author)  bfk1 year ago
Sorry... I just re-read the first two paragraphs in your comment above (I was going out the door and just caught your last point). I know there has been on hot melts with modified polyethylene waxes that "cure" after being heated allowing for stronger bonds. Eastman Kodak is one of the companies that was involved in the experimentation. I'm not a chemist, but the extremely low molecular weight of polyethylenes is probably their big weakness, and may be what gives them their wax-like properties. I don't think natural wax has been used much since the 1970s, but man-made wax still has all the characteristics that prevents me from using it for models. I'll check around to see if curable polyethylenes are being used. Possibly in those high temperature sticks you use for body work. If they are curable, I'm going to thank you again, make some models for the Parris Island Museum and put them to use on my fiberglass car as well :)
oldmicah1 year ago
That is just awesome!
bfk (author)  oldmicah1 year ago
Sorry to have the reply above your comment oldmicah. AutoDesk's new instructable app seems to only allow new comments and no replies. Back at my computer so I can correct that... Thanks for the kind words :)