Wednesday, August 20, 2008

Welcome to cncFDM!

My goal is to make an FDM (Fused Deposition Modeling ) toolhead that can be bolted onto a typical 3-axis cnc milling machine, and used to make rapid prototyped parts.

cncFDM Goal:

Build an FDM toolhead for a cnc machine, which:
  1. Allows interchanging a cncFDM toolhead with a traditional spindle on the same (3 or more axis ) cnc machine without mechanical rework ( reconfiguration of software is ok ).
  2. Uses standard 1/8" diameter ABS welding rod as input material.
  3. Keeps construction cost inexpensive
  4. Has good reliability. The heater shouldn't need rebuilding/replacing every 20 hours of runtime, for example. I'm willing to sacrifice more difficult construction to achive this goal.
  5. Leverages Gcode and other common cnc tools to save work. No need to re-write motion algorithms, acceleration profiles,etc etc, they are already available.
  6. Has accuracy deviating by no more than 0.010" on x and y axes, and 0.020" on z axis. This will require melt flow compensation and other techniques used by commercial vendors.

Assumptions and goals that contrast RepRap ( and are one of the main reasons I started this blog ):

  1. Line level power is ok, since cnc machines already have it available.
  2. ABS plastic is the main material, other materials that are more environmentally friendly can be accomodated but are not the focus
  3. Use existing tools that are commonly available, even if they are not GPL/free. For example, I do not care which solid modelling package is used to create the STL, as long as it works.
  4. It is ok to have parts that require a lathe or a mill to make. Of course, avoiding work is good, but "assemble with hand tools" is not all that important.

One other point I'll mention is that this is a problem that has been solved by many commerical vendors, most notably Stratsys. Their patent literature describes in some detail the many challenges ( and solutions, woo hoo! ) one might encounter along this journey.

Since I'm not intending to sell or in any way profit from this project, ( at best others may follow this path and construct one themself ), I do not have any problem learning from and employing the patented techniques that commercial vendors use.

Of course, the RepRap project is the best source of inspirational ideas :)

More later.

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