I made a new version of my original ziploc extrusion machine. The main updates were adding additional heat capacity, water cooling, metered pulling of the extrusion out of the die, and better thermal isolation. Below is an in progress photo, showing most of the barrel components. Inspiration for the thrust bearing and live center came from Russ Gries.
The barrel sections are 4130, TIG welded to their end plates.
The three heaters are sections of 26 gauge nichrome wire, electrically isolated with ceramic beads and contact cemented to the barrel.
This extrusion is roughly a factor of two smaller than the zippers I've made with embossing.
There is a lot of iteration to do with die design and closer cooling control, but this first test of the machine gave me a consistent seal longer than my wingspan.
Next up, tests with combination air- and water-cooling to slow solidification and try tot get less warpage.
In this project, I wanted a machine that could extrude melted polymers through custom electric-spark machined dies. As the first example, I machined a die on our EDM to make ziploc seams that could be heat sealed to the edges of panels to make reversibly-assembled inflatable structures.
A stepper motor drives an auger, forcing pellets from the hopper into the heating chamber. An AVR tiny44 microcontroller PWMs a nichrome wire to control the temperature in the chamber based on feedback from a 300C thermistor. In my first tests, I hit controlled temperatures up to 300 degrees Fahrenheit, well into the melting range of polypropylene.