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.

Applications for X-Y plotter

In regards to my last post, I didn’t discuss any applications of the X-Y plotter. I’m sure that people can come up with additional ones, these are the ones that I came up with however:

Printer – graphs, charts, documents, etc

PCB creation – using a special pen, have the plotter trace out the circuit layout on to a copper-clad board. This can then be etched normally.

Plasma cutting – combine a plasma cutter and the X-Y plotter to create a crude CNC machine. The plasma torch would be connected where the pen would go. Special design precautions would have to be taken due to the plasma cutter and the relatively heavy weight of the torch head.

Oxy-MAPP torch cutting – similar to the plasma cutter, but instead a small cutting torch. The main disadvantage is the crude cut produced by an oxy-torch, this may be offset by being roughly 20 times cheaper than a plasma cutter. The torch that I am referring to is available at Home Depot for less than 50 dollars. The torch head is very light as well.

PCB hole drilling – By replacing the pen with a drill/Dremel tool, the user can precisely drill holes in circuit boards. In my opinion, this would greatly simplify board creation.

With significant modifications in the z-axis:
Some kind of an arm as well as a third stepper motor would have to be added for this to work.

Milling machine – Computer controlled milling machine capable of cutting metal. The milling machine I link differs from the typical X-Y plotter, this will take analysis to figure out a good compromise.

Drilling through thicker material – Similar to the above idea, something along the lines of a computer controlled drill press.

My goal in this post has been to provide ideas for the reader to be hopefully interested in and possibly build. I have been rather vague in details since I don’t have a working plan designed, and I think it best for the reader to design the plotter that best meets their needs.

My tips on designing a plotter are: make it both modular and robust. By modular I mean able to accept different attachments, pens, torches, small drills, etc. I would also make the components easily changeable. Let’s say the milling attachment will have beefed up X and Y axes to handle the weight. Let’s also say the regular printer needs to have as little mass as possible in-order to move quickly. The user could then switch out components for ones that are more suitable to the task. By robust I mean the design is able to handle a variety of tasks, it’s not optimized to just print paper.

Post project z80 idea: z80 X-Y plotter

The basic idea here is to take a normal pen and have a computer control it. This is done by attaching the pen to a set of movable arms, the X and Y axes. The arms are controlled by stepper motors, allowing precise control of the pen. The computer will drive the stepper motors, and will also control a mechanism that raises and lowers the pen. Since this is nothing new, I found some links that go more in depth on the subject.

Examples:

• http://www.sentex.net/~mwandel/tech/plotter.html
• http://opax.swin.edu.au/~jtoms/index.htm
• http://lims.mech.northwestern.edu/~design/mechatronics/2005/xyplotter/