Rapid Prototyping with Epoxy?

Has anyone done any rapid prototyping with epoxy resin? This would have the advantage of not requiring heated material, and would produce a more heat-resistant product. Also, the extruder head(s) could draw from a reservoir of liquid instead of solid material, which I think has some advantages.

The problem would be getting the componts mixed, and keeping it flowing without curing epoxy clogging up the extruder head. Maybe something could be worked out with twin extruder heads applying stacked very-thin layers of liquid epoxy components that would mix after they were extruded. But the layers might be too thin, and the proccess of building an object could be really slow.

theres is definitely some interest in this area. we have two very knowledgeable people you can bounce ideas off here: fernando and ohiomike (sorry if i forgot anyone!)

basically, we already decided to go the thermoplastic route for v1.0, but looking forward to the future, resins are a very attractive area to pursue. for example we could do something like have the shell of the object printed in HDPE, then fill it in with resin. there are a tons of things we could do and its a very exciting future once we have the initial print head and machine working in the wild.

hey there!
I've been summoned i think?
well i am now actively experimenting with resins and epoxys are definitely in my list.
i have started with polyester as they are cheaper then epoxys and very easy to find in shops, but epoxys have very attractive possibilities indeed!

I am now busy defining cheap resin/catalyzer mixes that can be stored indefinitely and don't clog the conduits of pumps and nozzles but once deposited will be activated through UV light. It's already working fine but i'm looking to improve hardening times.

As for dual composites, the products are even more readily available in the market. The only iffy point here being the mixing devices, ratios and procedures. I think (ohio)mike has been working on this side of the issue, with very interesting results.

One idea i had on dual components was the use of one depositing head that would drop a layer of resin, then a spray nozzle would atomize a thin layer of low viscosity monomer (like styrene, a common solvent monomer) mixed with the activating catalyzer (usually an organic peroxyde like MEK peroxide or Benzoin peroxide in case of Epoxys but it could be an acidic or basic activator for other resins).

The question here is the speed of hardening between layers. You don't need the layer to harden completely before you deposit the next one, just enough to keep it's shape when receiving the next layer on top. This is called setting time. The dual composite mixes keep on hardening after being mixed, so eventually the whole body of the piece would get set and hardened... many things here to be tried out! If you want to, you can join us both experimenting this line of research!

You rang?

I too have been experimenting with epoxies but not so much the UV versions as the composite versions. My employer has a toll-production setup with a line of Huntsmen's structural adhesives that have a selection of activators, 45min, 60mins and 90mins, if memory serves. I imagine the activators are syrene/peroxide blends although I dont recall off-hand. With those at least I am not so worried about interlayer adhesion, but more with being able to control viscosity enough to prevent serious part deformation.

A small syringe of high viscosity epoxy (or perhaps a low viscosity with a low filler load) with an open time of 45 minutes could be a wonderful way to make high performance parts, but the specs of pure epoxy are a little overkill for what we need. The materials are not difficult to mix, google "static mixer tube" which is basically a helix that splits and recombines two liquid streams using the flow of the stream as its energy source, $0.50 each in bulk. I have actually discussed getting some new plunger designs from a supplier that would control the ratio precisely but would still fit into a standard caulk gun. The two syringe-like cavities are in line and act as plungers for each other. He seemed less than crazy about the idea of me wanting refillable plungers however. My hope was to make a 3d pen that would function as a repstrap for those of us that really dont understand robotics, but still want to test material properties.

Epoxy is rather expensive so I have been concentrating on suspensions of polyurathane in filler, since that is much cheaper. But anything that works with the poly will work with epoxy, most likley without modification.

I discovered some time ago that if you mix 30% epoxy onto low density refractory material you get an reasonably priced (about $0.01/cc) concrete strong composite (600psi tensile!), and very light material (0.75G/cc, it floats!) but it is an incredibly difficult to push or move material. I cannot imagine extuding it in a controlled manner. But if I can extrude a mold out of thermoplastic, this material can be cataysed and rammed into a mold very easily, set aside and pulled out after it has hardened slightly. More importantly there is a method called cold-box core making where the material is air-fluidized and blown into a mold, then instantly cured using a gas catayst. Turn the mold over, give it a good smack, pull the finished part out, and then blow another one.

Thats my answer to the whole cost/time/production problem. Make molds out of extruded thermoplastics, blow in thermosets with heavy filler loads to reduce cost (furans in particular interest me) and then flash cure (furans only need hot dry air, no chemicals required). Use the mold until you start to lose dimensional stability then recycle it. As soon as I get a reprap going I am starting on a coreblower.

Furans are much cheaper than epoxies and are biopolymers which makes them more attractive to me. But the extreme strengths of epoxies, epecially in high filler situations means that they might be an excellent starting point.

Mike

The thoughts and ideas expressed in this post do not reflect those of my employer and are intended only as communications between individuals. Any attempts at implement are at your own risk

Edited 1 time(s). Last edit at 09/12/2007 09:21PM by ohiomike.

I'm digging up an old thread here, but I had an idea which might have legs. What if you combined epoxy with the powder printing approach described here. What I'm envisioning is a bed of resin, perhaps mixed with filler to reduce costs and increase the viscosity. An inkjet printer would deposit hardener in the desired cross section. Finally the build table would drop and a blade would spread a new layer of resin paste. Ideally the resin paste would be thick enough to support the material even if each layer hasn't fully cured, and to limit the amount of diffusion of the hardener. Thoughts?

... when using an UV-laser instead of an inkjet with hardening agent, then you described exactly the common stereolitho-process which was the breakthrough fro 3D-printing in the 1990s

An interesting sidepath could be printing an acid or acetone on waterglass (=sodium silicate) - it will instantly harden, while the surrounding still fluid volume will support overhangs ...

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Viktor
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I know about stereolithography, but this is different. What I'm describing is something closer to what z-corp does with plaster, only using the two parts of epoxy as the "powder" and the binder. UV-curable resins are very expensive, and aren't as strong as epoxy.

The acid / sodium silicate thing is interesting too - but I think it's pretty brittle isn't it?

... all curing ingredients are costly - especial when low viscouse, so it can be ink-jetted

Pure sodium silicate is brittle, but when mixing with fine mineralic powder and additives that will add some elasticity (as in Prestogum car-exhaust-paste), you should get something more rigid ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Quote
vdx
. all curing ingredients are costly - especial when low viscouse, so it can be ink-jetted

Costly is relative I suppose. Epoxy resin & hardener is about $6/lb, which isn't much more than the abs used by and FDM reprap, and about 10 times less expensive than UV-curable SLA resins.

... i don't know any of the 2K-resins with viskosity low enogh, so you can ink-jet one of the components.

One alternative would be dispensing through a fine nozzle (should go with 0.1mm ID), but then it's much slower than laser-curing ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

i ask if any one work to make rapid prototyping by powder
my problem :- i can`t separate the powder with high accuracy please if any one can help me send to my email

i work on 3d sand printer but worked by polyester to make rapid prototyping and sand mold used to AL casting
what you need exactly ?

I have a inkjet hardener + powder based design that prints at ~0.5L/hour with only one printhead. I should have open plans for it later this year.

Inkjetting water based epoxy also works. Micro valves will work for slightly higher viscosity epoxys.

2shedsJackson, Could you drop me a line? ericdwilson [AT] yahoo [dot} com

2sgedsJackson, Could you drop me a line too? tome77[at]gmail[dot]com

I am interested in learning what kind of inkjet printhead you are using and how you control it.

Thanks

I've been thinking about this a lot, and I was wondering if it would be possible for an desktop inkjet printer to print a 2 part epoxy resin. I was thinking the tricolor cartage would be used. One part of the epoxy would be put in the cyan ink chamber and one part would be put in the magenta ink chamber. Now magenta and cyan make blue. Print a blue circle from the computer and you get an even 50/50 mix of the epoxy. Different colors produce different mixes. A piezoelectric inkjet might have to used rather than a traditional inkjet. Do any of you think this could work?

The issues with thermal inkjet cartridges "TIJ" are:

They only work with low viscosity fluids <3 cps

They are compatible with fluids within narrow range of surface tension.

There is only one older HP Gen1 with open specs. There are many other cartridges available but expect a sh*tstorm of complaints from the makers if the specs get out in the wild.

They are only good for a couple of Litre's of prints before they drop nozzles due to heater failures.

They clog with most any particles over 1-5 microns dia. so fluids have to be filtered really well.

Industrial Piezo Printhead Issues:

They work with slightly higher viscosity fluids than TIJ and many have heaters.

They can print for hundreds or thousands of Litre's before they wear out piezo elements.

They clog with most any particles over 1-5 microns dia. so fluids have to be filtered really well.

They are compatible with fluids within narrow range of surface tension.

They cost anywhere between $250-10K ea. There are some new 16 nozzle MEMS heads that are going for ~$100ea. these might be a good fit for DIY.

There are many heads available under strict NDA or licensing requirements, but expect a sh*tstorm of complaints from the makers if the specs get out in the wild. Most are licensed for particular applications in a given location. Printing only barcodes and markings, no labels, graphics, images etc for say the USA and can't be resold unless it's for repair of the licensed printer.

The two part epoxy idea does work. It's only with low viscosity epoxy and it doesn't mix perfectly, but it does mix after jetting.