Follow-up on the CNC machine

I changed the name of my idea from the X-Y plotter to the CNC machine. I believe it is a description of what I’m trying to accomplish; a computer-controlled 3-axis multipurpose machine. This reflects a shift in thinking from having a machine optimized for each task by changing out components to a machine that is a good comprise of all roles. The later idea would only require a change in tooling.

As the result of much research, I have settled on a design similar to the Fab @ Home project. Here are the main differences:

• In my design, the tool itself will move in the z-axis, instead of the table. My reasoning for this decision is weight; if I put anything heavy on the table, the stepper motor may not be able to move it.
• The second main difference is in the ‘walls’ of the machine; they choose to use Plexiglas, I plan to use four 1/2″ rods for vertical support. In the FAQ for the Fab @ Home project, they cite the Plexiglas as a weakness for turning it into a CNC machine. However, the seemly over-building of the rest of the machine impressed me since the machine exerts little lateral force. This largely inspired my design.

After viewing a page on assembling the RepRap Darwin, my CNC machine will look similar to this picture. (scroll down to the first picture) Again the biggest difference is the table will be stationary.

I’m glad that I spent some more time on the RepRap site, they use some components that could really make my life much easier. If I can buy plastic pieces that allow me to make the X and Y axes square, that would be a wonderful advantage. I hope they are available cheaply; from the quoted price of the whole machine, I think they will be. Upon closer inspection, that may not be the case, anyhow its past bedtime.

Update from the next day - Unfortunately it seems the corner pieces I wanted to use aren’t commercially available. I will either ask the RepRap people If I can get something similar or go back to drawing board.

More applications:

Fabber/Rapid Prototype/3D Printer – These three are similar concepts but yet each is different in it’s own way. The basic idea here is to squirt material out of a nozzle, and use this stream to build-up objects.

Wood Engraver/Router – Use rotatory tool to mill designs into wood, or just about any material. I don’t have too much to add here, so I’ll leave the reader with some Wikipedia links.

• Wood router
• Laminate trimmer
• CNC wood router

Computer Controlled Welder – This idea, in my uneducated opinion, is the most challenging application idea I have come up with yet. I think it’s little more than a pipe dream, although it’s one of the most intriguing. Please don’t even remotely consider doing this unless you know -and can take- the necessary safety precautions.

What makes this hard is the X, Y, and Z axes must move with precision and the correct speed for a good weld. Not to mention numerous other factors involved in getting good welds such as metal thickness, metal type, welding rod type, amount of current, and welding wire/rod feed speed. Speaking from personal experience, it’s hard enough to get consistent welds by hand.

Developing a computer program to do evaluate all of the variables would a “challenge” at the easiest. I imagine, however, the quality of desired the welds would determine the complexity. To me, the ability to produce relatively quality welds in all different sizes and thicknesses of metal would make all the efforts worth while.