Lava Bot

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Lava-Bot Documentation


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Lava-Bot

Release status: concept

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Description
A buoyant environment liquid extrusion printer
License
Author
Contributors
Based-on
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CAD Models
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This will eventually become a development page. Please comment on the discussion page if you have any thoughts on the ideas here.

Introduction

At the moment it is just to store a couple of ideas that I have.

This relates to an idea that grew out of limitations of extruding runny waxes (the forum member gmerz triggered the association for me). So far wax fabrication has mostly been traditional milling, drop on demand printing and hot needle vacuum machining. In production situations wax patterns are traditionally cast into master moulds to make positives for investment/lost-wax casting.

Most waxes do not have a suitable plastic phase and most plastics are not ideal for lost-wax casting. They do not melt out as cleanly and can contaminate the work flow of a production foundry that only want wax in their wax melt-out tank.

The new innovative concept is to use a surrounding carrier liquid to buoy the extruded melted wax and keep it in place for long enough for it to set (freeze) without having it run down the sides of a part.

Think of a Lava lamp.

Benefits

  • The benefits are a low force deposition system that can make a wax part directly
  • Standard extrusion software should work with minor modifications
  • Layer heights maintained with light nozzle contact like plastic printing, no layer levelling required like drop deposition
  • Existing wax fluid combinations exist to test
  • Potential for long bridging with slow extrusion rate as thread is 'weightless'
  • Could be used to print etch resist on copper clad PCB
  • Buoyancy fluid could be a fine powder of a molten salt
  • Could potentially print other materials like metals, caramel, chocolate or ice
  • Buoyancy fluid can have fluxing properties to protect surface from contamination or oxidation.
  • Buoyancy liquid can be cooled to speed up deposition process
  • Large nozzle diameters may be possible for fast build speeds
  • Dye injection or multi extruders may be possible for multi colour artistic models
  • What if we had a non-polar liquid with a specific density close to 1? We get an ice sculpture Bot

Drawbacks

  • Needs a tank for the printed part
  • Extruder needs to pump liquid at elevated temperature
  • Tank must fill with build progress to avoid submerged extruder assembly
  • Tank should be stationary due to increased mass and sloshing liquid, XY gantry printer
  • Material choices will need to be compatible with the process and the buoyancy liquid
  • Sealed voids will remain filled with buoyancy fluid

Challenges

  • Have a system that maintains adequate wax at printing temperature
  • Use a positive displacement pump to dose melted wax, compensate for roller pulses in peristaltic pumps
  • Select suitable wax and buoyancy liquid that is low-toxicity and compatible with investment casting process

Relevant Forum Threads

  • The Under Water Printing thread considered water and oil as a warm printing bath for plastic printing to minimise warping, it covers some of the same concepts almost a year ago and refers to earlier thoughts on printing in liquid as well. Adhesion was considered the largest hurdle to overcome. Forum user tprime also pondered on the buoyancy and rapid cooling as a means to assist with the plastic bridging.
  • In the Wax Printing thread many of the Lava Bot ideas have been first mentioned with a focus on the quick setting and buoyancy of liquid wax.
  • Metal-print Reprap thread has ideas of printing with molten metal that is done submerged in liquid molten salts or flux powder.

Other links