Making a Plunger for a Chocolate Syringe

My latest project is a 3D printer that will produce chocolate objects.  Like many other chocolate printers, it will include a syringe to dispense the chocolate.  Unlike those other printers, the syringe in my printer will have 3.5 liter capacity to enable printing large objects.

The syringe is made from PVC pipe using mostly standard fittings.  One piece that wasn’t standard was the plunger that fits inside the syringe tube and pushes on the chocolate contained therein.  I had to design and fabricate the plunger.  PVC pipe isn’t perfectly smooth or perfectly round inside, so I needed something compliant enough to ride out the pipe’s bumps and constrictions while maintaining a seal.  The seal needed to be tough, yet safe for use with food because it will be in contact with the chocolate inside the syringe.  I found some food-grade silicone casting material and ordered it.

While waiting for the silicone to arrive, I designed a 3D printable core for the plunger and a mold and jig.  The core fits on the end of a linear actuator that will provide the push.  The jig centered the core a few mm above the bottom of the mold.  The mold was tapered and the widest part -the bottom- was a few mm larger diameter than the pipe, and several mm larger diameter than the core.  The silicone envelops the core and is locked in place by holes that connect top and bottom side of the core.  The plunger squeeze-fits into the pipe to maintain the seal against the uneven inner surface of the pipe.

Mold, jig, and core for syringe plunger

Mold, jig, and core for syringe plunger

Mold, jig, and core for syringe showing core inserted into jig.

Mold, jig, and core for syringe showing core inserted into jig.

 

 

 

 

 

 

 

 

 

Mold, jig, and core assembled for silicone over-molding.

Mold, jig, and core assembled for silicone over-molding.

I measured and mixed the silicone, coated the core with it and then set the core and jig in/on the mold and let it cure for 24 hours.  Then I removed the jig and broke the now silicone covered core out of the mold.  Result: a perfect, tight fit inside the syringe tube.

Core in mold with silicone.

Core in mold with silicone.

 

 

 

 

 

 

 

 

 

 

Finished plunger removed from the mold.

Finished plunger removed from the mold.  The mold had to be broken off by design.

 

 

 

 

 

 

 

 

 

 

 

Plunger mounted on linear actuator.

Plunger mounted on linear actuator.

 

 

 

 

 

 

 

 

 

 

 

 

The assembled syringe.

The assembled syringe.

Mechanized Cylindrical Sign Build for Parade Joy (Update 1)

The Milwaukee Makerspace has agreed to participate in one of Milwaukee’s finest traditions, the “South Shore Frolics Parade”.

The “South Shore Frolics” formerly known as the “South Shore Water Frolics” is a Bay View institution. The current celebration of summer & joy starts on Saturday July 16th at 11:00 in the morning with a parade leading to South Shore Park, after which there is a festival and a variety of activities including fireworks for the remainder of the weekend. The Frolics is an event that I have participated in as long as I have been alive, and it is a very integral part of my summer. Of course I was thrilled when the Makerspace agreed that this was a worthwhile use of our time and talents.

Our goal for Milwaukee Makerspace’s representation in the parade is to produce some electric vehicles, ride some previously produced power wheels racers, as well as present a unique parade float. 

Thus far the main work was completed by Tom Gralewicz who re-powered the Makerspace’s “pots of gold” (two electric vehciles that have a parade heritage) with new motor controllers. Now that we have two functioning platforms, we of course wanted to turn one of them into an 8′ mechanized cylindrical sign. (that will resemble a beverage container) 

The build on that commenced last evening. Here are some photographs from the madness & joy:

 

 

 

 

 

Matt N. always measures twice and cuts once. 

 

I don’t know how many times these guys measured, but they always made the right cut!

 

Here the team cuts the circular bases that will anchor the piece. In the background, there is a serious discussion about logicstics…or something. 

 

Matt G. shows us the pride that comes with making.

 

Kevin B. tests out the fit and finish of the first circular support on the vehicle platform.

So far so good! I can’t wait to see how this comes together!

Come and see us at the South Shore Frolics Parade!
Saturday July 16th, 2011
Parade starts at KK & Lincoln at 11:00am
Joy will be had by all!
If you consider yourself a Milwaukee Maker, you are welcome to walk the parade rout with us & represent making in Milwaukee!