Molds directly from a 3d printer to an injection molder

Picture of Molds directly  from a 3d printer to an injection molder
In this Instructable I will document the process of an experiment i have been working on to test fairly low pressure injection molding using 3d printed molds.

You should be able to find everything you need for this project laying around your house:

-An initial concept and the ability to execute it in a digital format capable of exporting to a 3d printer

-a high res 3d printer

-an injection molder

-a handful of pelletized thermoplastic

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Step 1: Part design

Picture of part design
My teeny, tiny, cute, little injection molder is only capable of squirting out about 1/4 ounce of molten plastic at a time so i had to design a test part no larger than that. I was far more concerned with testing the process than actually making something useful so i just grabbed an existing 3-d file of my logo and converted it to a moldable form.

I used solidworks to extruded the shape in two directions with 7 degrees of draft  on both sides from the parting line.
the final part came in at a volume of 0.238268398 ounces.

Step 2: Mold design

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for this particular test i went with a really simple mold design, the mold would be split equally front to back with a few keys and a single direct injection point.

Step 3: Printing the mold

Picture of printing the mold
I exported an stl file of my mold pieces and set them to a high gloss option for printing thorough an objet 3-d printer.
The out put is an acrylic photo-polymer mold.

Who knows if this is even going to work?
I might just crush the mold while trying to clamp up?
Or burn it up with molten plastic durring injection?
I might lose an eye?
ruisantos107 months ago

This is really cool! Can't wait to be able to try it out ;)

After finishing my 3D printer, an home made injection molder would be just awesome! I'll try to find out if it's possible... and if so, a new instructable will be born!

But one step at a time...

Congratulations for this very sucessfull experiment!

rgarrido091 year ago
Nice!!! Do you think we can use ABS or PLA material coming from a CubeX or Makerbot2?
Ruben , Lima, Peru
bryanbrutherford (author)  rgarrido091 year ago
Your molding material will need to melt and flow at a temperature lower than the temperature at which the mold begins to soften and deform. With ABS and PLA molds you'd probably have more luck if you inject an RTV liquid resin using a plunger.
apappano1 year ago
Fantastic work! which mold injector are you using? I'm about to do some injection molds with my students.
pashakun2 years ago
great tutorial ~

the process layering of 3d printing + molding has a lot of promise

case in point, this amazing pneumatic robot tentacle

r_harris22 years ago
Wow, this is a really great result. And your idea to extend the process by using an aluminum frame will, if successful, make it a small-shop/short run production process, not just an experiment.

I could imagine a small machine shop with a setup like this might have a mold for producing the odd part that is needed in small quantities, with a freshly RP'd mold ready to replace it if several orders come in a row.

Thanks for sharing your results. Now I am even more anxious to get an injection molder!
bryanbrutherford (author)  r_harris22 years ago

I've gotten a lot of criticism and questioning about why i wouldn't just 3d print all the parts in the first place.

There are countless businesses that require small volume high quality parts with finish and material options that just aren't available in 3-d printing and this solution could be incredibly useful in those situations.
lfiore2 years ago
That is a creative way to make a mold! I see that you were having trouble with overfilling the mold. I may suggest a possible solution.

You could integrate relief passes into your mold. I am attaching photos of a similar epoxy mold, where plastic is allowed to pour from the sides before building up pressure.

This way you could produce parts without stressing the plastic mold, and trim off excess material to get a finished part. For the box, you could make your mold round and fit it inside sections of cut up pipe.

Levon Fiore @ Medium Machinery LLC, see our
Small Manual Benchtop Plastic Injection Molding Machine
bryanbrutherford (author)  lfiore2 years ago
further to my previous response, i just spent a bunch of time poking around your site. That is a fantastic machine you've designed.
bryanbrutherford (author)  lfiore2 years ago
thanks for the tips, i think my biggest issue with over or under filling is simply the part size vs. shot capacity of my small machine.

I think my part was little too big so i had to use every last bit of possible shot so i was doing a lot of tricky things to get as much material as possible in to the mold which meant that some times i ended up getting a little too much.

I think with a little more experimentation and adjustments in my part size i could get good repeatability.

This project is awesome. Now, if only there was an option for a cheap injection molder....

The main advantage of injection molds over 3D prints is speed, right?
bryanbrutherford (author)  willrandship2 years ago
speed, material selection, tolerance, cost, durability
all depends on the requirements of the individual project.

also, i could buy quite a few injection molders for the cost of my 3-d printer.

Really? Where!
bryanbrutherford (author)  thekendall2 years ago
are you asking where to buy an injection molder?
ebay, a manufacturing equipment vendor, equipment auctions, the internet.
Yeah one thats about the same cost as a 3D printer!
bryanbrutherford (author)  thekendall2 years ago
we have two 3-d printers in my office, one cost $30,000 and the other $160,000
the injection molder in my garage cost me about $500. There are options for both printers and molders that fall everywhere in between and some that go even higher.

Wow, I had no idea injection molders were that cheap! First one I saw was only $1700, not bad for industrial-quality results.
What make/model of 3D Printer do you use?

What make/model of manual injection molder do you use?
yeah ... that printed mold looks really clean. I would like to know what printer do you have as well........Did you clean the 3d printed part after it was printed or did it come our of the printer like this?
bryanbrutherford (author)  omkarkarve2 years ago
that part is directly form the printer on the glossy setting no post printing cleanup at all.
bryanbrutherford (author)  roystonlodge2 years ago
i'm using an objet eden 350v printer and an old emco table top injection molder
Thank that is great, I think I will take it one step further, and take the mould to a foundry and get them to cast it in aluminium Then it will be bullet proof. I could then use it to cast silver or die-cast materials. fantastic instuctable !
poofrabbit2 years ago
I think your mold idea is great, but I really dig your "skeleton key", very very cool!
bryanbrutherford (author)  poofrabbit2 years ago
thanks, i though i was making a witty skeleton key reference when it was just a two dimensional logo but once it was on my key ring i realized the reference had come full circle.

It is 100% fantastic, I'd buy one :) LOVE IT! Voted for ya and 5 stars (but the start system seems a little wacky lately)
bryanbrutherford (author)  poofrabbit2 years ago
You need to make a second flute in the key for air. There will be two entrances for the material your pouring to enter but only fill one side. Once you see material in the second hole you most likely got the air out.

This is a great idea BTW. With some molding experience backing you the ideas are limitless.

I have made tons of molds and I can tell you AIR IS YOUR WORST ENEMY!
Maybe u should fab an aspirator and lose the air!
This is the method I use now for molds, Just watch how he does the flutes
this video is for casting with rtv resins, which is an incredible process that i use a lot but in this particular experiment i am actually injection molding liquified molten plastic that has been heated to it's melt tmeperature and injecting it under significant pressure.

I used the term "low pressure" because i am using a small manual injection molder rather than an industrial machine capable of 100's of tons of clamping and injection force.