# Polyurethane mix-on-the-spot system

3d printing is a slow process and for my solution I need fast printing. So I print with no infill and I fill inside with a two part, 10 min drying polyurethane resin. I mix them in a disposable cup and use a syringe to put it inside. It gives super results as it is both sturdy and lightweight so I recommend this method.

My problem is that if the print has a high volume, the mixture begins solidifying inside syringe. So I need a device which can mix parts and apply it on the spot. Below is a crude drawing of what I need. Is there a name for such a device readily avaible or will I have to build it myself? Or any other advise is appreciated.

What I have tried so far:

• If I use a slower drying formula then most of the solution leaks from small holes in printed object. In faster drying formulas it is managable.
• If you have a mixing tank, wouldn't there be a problem with the residual mixture curing in place and destroying the device? There are epoxy syringes that are side by side but have no mixing chamber. I was unable to locate a source for that product, but plenty of sources for pre-filled epoxy twin syringes. Lacking the mixing chamber makes it academic. Sep 7 '18 at 17:16
• Do you need to apply the resin infil layer-by-layer? It's not at all clear from your description what the problem is. Sep 7 '18 at 18:18
• searched for two part epoxy syringe with mixing nozzle found: ebay.com/i/222048583062?chn=ps Sep 7 '18 at 18:42
• I get the impression you might need a mixing system with a timer in it, where a certain amount of both resin part is injected every "required time period", instead of having a continuously injecting system. I don't know if such a system exists.
– Fred
Sep 7 '18 at 21:10
• Use temperature to your advantage. Mix and inject 50F material then allow it to warm to cure temps in the piece. Another way is to use a fast tack, but slow cure resin. Basically it is 25% fast resin, which bumps the viscosity very quickly, followed by a slower agent that manages heat buildup and allows cleanup and secondary bonds. Another simple method is to use a thixotrope such as Cabosil or Aerosil to produce a non-self-levelling dooky. Both are brands of fulminated silica. Add the thixotrope last in you mix steps. Sep 8 '18 at 13:36

there is a device called a mixing tube or mixing nozzle which is used with industrial-duty epoxy dispensing systems. it clips onto the dual-nozzle outlets of a pair of syringe tubes that are molded together into a single unit and filled with the 2-part glue composition of your choice.

This assembly then snaps into a hand-operated ratchet dispenser which forces the two parts into the mixing tube, which contains a series of twisted baffles that fold together the two substances so by the time they emerge from the other end of the tube, they are thoroughly mixed and ready to apply.

the tube is a single-use device as there is no way to clean out the mixed epoxy from the baffles and re-use it. However, the way you use it is by staging up a whole series of things to be glued and then dispensing the mixed glue until there is none left in the syringe tubes- at which point you remove the empty tubes and the mixing nozzle and throw them all away.

• Great idea. I am sure this will work. Thanks a lot. Sep 10 '18 at 8:52

in the construction industry, there are many companies which sell two component epoxy and its applicator. which happens to be a double cylinder pump with a mixing nozzle.

These pumps do exactly what you need, they mix the two components at the final stage in a mixing nozzle. Some are hand operated, some have work with air pressure and some are electrical. I add the battery operated epoxy gun by "Read Head" Co.

The nozzle is a plastic cone with spiraling inside blades designed to mix the two components and deliver to the fasteners.