At Thursday 9.30 pm, we have concluded our first, complete, UltiCast. As our emotions of joy welled up like the silicons did in the overflow valve, we were tossed into an historical perspective that only Neil Armstrong could adeptly describe. This is a small step for one hacked UltiMaker 2+, but a huge step for UltiCast.
In all seriousness, we are stoked that we finally made UltiCasting work. Previously we have had major issues with the silicons curing inside the system, and consequently blowing up the tubing and covering our print head in silicons. This is why we redesigned the entire set up all over.
We have removed the right fan of the print head, to use that space for the nozzle. We had concluded that the mixed silicons settle faster when subjected to heat and one of the main reasons for our system to get clogged was the fact that our casting nozzle was right next to the heating element of the first extruder. Also we have once more increased the diameter of the mixing nozzle, and seeing we can now start mixing closer to the bed, we have shortened the mixing nozzle as well.
Not only the silicons proved to be though to work with, also the PVA had a will of its own. Getting the PVA to stick to the print bed proved to be a really big deal. After trying alcohol, window cleaner, vinegar and prayer, we found ye good old Pritt stick. The rest is history, we finished our first print and are waiting for the PVA to dissolve in water to see the final result. All in all, we did it, and we’ve got it on film.
Well the experiment did not fail, but it sure did not provide the desired results. “An absolute mess” it has been called, but from the gooey remains of our set up we have build the foundations of our new set up.
So what happened? Our initial UltiCast fears were confirmed when we tried to cast the silicons in our first full scale test. Due to the high viscosity (18,000 cps) of our silicon components, we had a huge pressure buildup when trying to use the second extruder. In reality we tried to push molten chocolate through a 1 meter flexible tube with a diameter of 4 millimeters, but you could imagine it to be like pushing wet concrete through a garden hose.
Needless to say soon we were all covered in silicons. Our tubes had burst under the pressure that was being build up. Due to a then discovered syringe flaw that lead us unable to retract the plunger and release the pressure from the tube, we discovered that the only thing we had created was a ticking silicon bomb. Luckily the silicons are skin safe so the damage was contained to a bit of clean up.
To counter these problems we have redesigned the UltiCast set up. First of all we now use bigger tubes and static mixing nozzles to reduce the friction created by the highly viscous silicon components. We have tried mixing the silicons in these wider pipes and they proved very successful.
.To be able to reduce the pressure on the pipes if needed, we have remodeled a part on the plunger to enable it to retract. This part still has to be tested in a full scale test, but also seems to be functioning correctly.
We are currently waiting for our final components to finish printing so we can do a second cast with UltiCast.
From moment one we were experiencing problems with our valve fittings. Turns out: our valves were to big for our fingers to handle. In the picture below you can see our first type of valve rupturing one of our fingers.
But then christmas came early! Our expert Rob Scharff supplied us with a bunch of different kind of valves we could test. He even tossed in some glue to make the seal as airtight as possible.
Below you can see the smallest valves glued to test prints. It turns out that not only the material does not rupture, but the seal itself is also completely airtight. This leads to most of the air leaking through the valves themselves. Turns out it’s not all about size on this one.
And that’s what she said!