3D Printed Syringe Static Mixer


This is a system that allows a person to pre-portion
casting material to allow for quickly filling molds on the spot. It was designed for live silicone casting
demos during soft robotics workshops, where custom blends of silicone could be degassed
and pre-portioned to allow students to gain experience casting molds and building their
own soft robots without spending time degassing The mixer mechanism consists of helixes that
form eight 180 degree turns inside a printed tube. Each turn mixes the two components roughly
50 percent. When the mixture exits, it is almost completely
homogenous. This system was prototyped and printed on
an Ultimaker 2+ in PLA using a 0.6mm nozzle. Print settings will be provided in the video
description and on the Thingiverse page along with the STL files. Most dimensions throughout this project can
vary by up to 0.5mm without hurting the function, but the dimensions on the printed luer-lock
connectors are more critical. If, when printing the luer-locks, you find
they do not fit easily on to the syringes or break, it may be best to separate these
components and print them with finer settings. Begin assembling the system by glueing the
Luer connectors to the mixer using Weld-On 16. Draw a bead of adhesive around the interior
rim of the square recesses in the static mixer. After holding the connectors in place for
several seconds, they should stick well enough that you can let go and they will be set in
roughly 15 minutes. Prepare to fill the syringes by pouring out
and degassing the material you intend to use in your casting. This is an ideal opportunity to mix in pigment,
thinner, or additives to quicken or slow curing time. You will find it easier to fill the syringes
if you portion your silicone into small flexible containers that you can bend to form a pouring
spout. This system was designed for use with 60 milliliter
easy-glide Luer-tipped syringes, which are common and easy to find through online shops. Remove the plungers from your syringes. Attach the Luer plugs to your syringe ends. Add the clips to the opposite ends of the
syringes. There are two sets of clips: one to label
part A and B of your silicone, and another to unify the pair of syringes together. Place the pair of syringes into the holder. Fill each syringe with an equal amount of
silicone. Remember to pour slowly in a thin even stream. If one of your syringes is off by a few milliliters,
you can always bleed some extra material out to even them back up. Once they’re filled (60 milliliters is the
maximum recommended fill level for this model of syringe) push the plungers back into the
cylinders. This will displace most of the air. Invert the syringes in the holder to allow
bubbles to rise up to the tips of the syringes. Remove the Luer plug from a syringe and bleed
out any air bubbles. Begin with the syringe with the lower amount
of silicone. Next, bleed the other one and push out any
excess silicone so that it is at the same level as the other syringe. Clean up any mess with a paper towel, reattach
the lure plugs, and attach the plunger base. In this state, with the Luer plugs attached,
these syringes can be stored almost indefinitely for later use. When you are ready to pour your mold, remove
the Luer plugs, hold the assembly upright, and twist the syringes on to the mixer. Doing this a bit at a time, turning one syringe
a quarter rotation and then the other until they’re snugly attached, will help prevent
them from putting too much strain at the connections on the mixer. Dispense silicone by holding the syringe clip
on the syringe body and pressing on the plunger base. This requires a decent amount of force (which
will vary depending on the viscosity of your particular silicone). The system needs to flush out a small portion
of silicone before it will be consistently mixed, so dispense 5 milliliters from each
syringe (10 milliliters in total) into a disposable container. After purging, you can fill your mold with
silicone directly from the mixer. If you need to pause during the process, attach
the printed cap on the mixer. Take note of the working time of your silicone,
as it will thicken as it sets up which will increase the force necessary to eject it from
the mixer. Once you are finished pouring, you may throw
the mixer away and cap the syringes to retain any unused material. Aidan Leitch, who evaluated this system, found
that it is possible to reuse the mixer, though you will need to pull out any cured silicone
with tweezers and purge it before pouring again. Hopefully this system provides you with more
options to explore mold making, casting, and soft robotics. You can find the source files and documentation
on Thingiverse. Thank you, and have a good day.

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