Filament Sizing Solutions
Filabot has had many questions pertaining to the sizing and tolerancing capabilities. From watching videos on youtube, surfing the internet, reading comments, and talking with engineers in the plastics industry, we have three possible solutions to the sizing problem. This update will outline the solutions that we have conjured up.
After the Filament leaves the nozzle of the extruder, the plastic will pass two rollers for sizing. The filament then will run through a small water tank to cool and harden. This method is what we are going to test first. We are working on this right now, making the rollers and tank. In the picture below the two front rollers will pinch the filament and will form it into the right size. These two rollers will also be geared and powered to pull the filament through. This is a very promising design, it is simple and easy to make.
The next design is a simple needle bearing idea is used. This method is similar to rolling clay on a table so that it becomes a smaller diameter. The "bearings" will be tapered to the desired size (3mm to 1.75mm diameter). Here is a quick drawing. Please excuse the bad drawing, we are not artists.
The last design will be used with the roller system. This design will have a cutting unit that will be heated to a low temperature to cut and shape the plastic. The cut plastic will fall back into the hopper to be reprocessed into more filament. The rendered photo is what the system will look like it this is the solution that is needed.
This is some more test plastic that was made from another green and yellow HDPE detergent bottle. Some parts of the filament are very smooth and have plus or minus an average of 0.031 of an inch within a 4inch long sample. This filament was made on the extruder without the refined nozzle and without a roller system. It was extruded directly out of the nozzle. A better nozzle, and the roller system will make the tolerances even better.
(Please note, number on paper is wrong. 0.0031in is supposed to be 0.031in)
All in all the tests show that even with this basic system, without all the modifications, the Fialbot can produce usable printing filament. While still in the prototype stage we are producing results that are needed for the system to work.
I hope this clears up some questions for sizing of the filament.