Designing the new extruder

In order to minimize the design of the extruder, it is necessary to outline what is needed.

A Supply of plastic

A Device to transport the plastic to the extruder

A Device to liquefy the plastic

A Device to direct the molten plastic into a fine stream in a precise location.

- I have ideas swimming around my head as to how to solve thiese problems, so it's hard to prevent what I BELIEVE to be an intriguing design path from influencing the bare-bones minimum description of what's needed.

- Let's look at the extruder component list above and think about it - is everything needed? is there anything missing?

supply of plastic - seems pretty general to me. could it be something else? perhaps its not plastic, ok so "SUPPLY OF MATERIAL"....

A Supply of Material

A Device to transport the plastic to the extruder

A Device to liquefy the plastic

A Device to direct the molten plastic into a fine stream in a precise location.

Perhaps this is too specific still... if we change to "Material" then perhaps there is no need to liquefy the material... what if it is liquid already (e.g. epoxy, or silicone, or frosting)...

OK so -

Simplest version is

A Supply of Material and a way to direct the material to a Specific Location.

I think something's missing...

A Supply of Material and a Pathway to Direct a Specific Volume of Said Material to a Specific Location at a Specific and Variable Rate.

--- I like that....

One last thing - that's optional is processing the raw material.

A Supply of Raw Material(s) and a Pathway that includes any Processing, and Directs a Specific Volume of the Processed Materials at a Specific Rate to a Specific Location...

So - interesting - Specific - means that's an important aspect to control, either through design or actually on the fly needs to be controllable.

1) Raw Material Supply (Hopper for Pellet Plastic, a Spindle for a Spool of Filament, a Chamber for Frosting-Like Materials, a Pair of Chambers for a 2-part epoxy)

2) Processing

• Pellets need to be dried, melted, degassed, and homogenized, possibly colored, then if they are thermoplastic, then they need to be made molten by heating or perhaps by u/s vibration, or pressure. Injection molding uses a combination of pre-heating and pressure to inject the plastic and retain the best mechanical properties. Melting plastics with heat is not necessarily the ideal way to liquify them, but it's working - so we can use it for now... but consider there may be better ways that produce superior output.
• Filament might need to be dusted/cleaned, possibly pre-heated, possibly oiled (for materials like PLA) - similar to above the filament needs to be liquefied, but we don't have the opportunity to compress it and use pressure the way we can with a screw. However, nothing says we can't use u/s pressure. we'll see... ( I just had a thought of sandwiching the filament between an ultrasonic plate, and a a stationary plate that contains the nozzle-outlet... feed the filament into the u/s pressing chamber and vibrationally smash it through the nozzle a droplet at a time. -
  
  
u/s extruder head - just a thought


• Frosting-Like materials might need to be mixed to a smooth consistency, and perhaps degassed as well, perhaps coloring as well, but that would essentially make it a 2-Part material - see below.

• 2-Part materials would need thorough mixing, possibly coloring, degassing?

3) Specific Volume of Material

• Pellets would need some drive mechanism that accounts for their granular nature, and the fact that they will need to be degassed... the "specific" part would mean it would probably need to be a mechanism AFTER the processing, so either the hopper is gravity feeding into the dryer aparatus, etc... or there are 2 feed mechanisms... possible more
• Filament needs to be driven either by a pinch-wheel, pax-style, or some other mechanism. Perhaps though, there is another method that is more controllable - this could use more thinking - keeping in mind tolerances and avoiding situations where precise construction is required. Best design = Design that anyone with half a brain and limited tools can make it.
• Frosting - I'm going to stop considering frosting, it is a much larger task than I care to take on right now.
• 2-Part Materials, same as above - both of which I may come back to in a later post.

ok time to get back to work - will work on this post later - feel free to leave comments if you think of anything to include... certainly I'm open to suggestions.