Hi, newbie to cnc here...
I'm making a very very basic CNC foam cutter to apply towards my metalcasting hobby. In fact, it will be less than two feet long or wide (Reason being my metalcasting equipment can only cast about 1lb or so at once).
For cutting foam I guess the recommendation is slow and cool, so it doesn't have to move super fast. For some reason I'm having a hard time getting my head thru this part of the project to come up with something. It almost seems like overkill to use rollerblade bearings and rods since the machine won't be very big. I'd really like to use belt drive if I could (less backlash hassle). So far the only thing I can think of is taking apart some old printers and using their mechanical guts?
Just wondering if you guys might have any ideas.
The basic design I'm shooting for is one X slide, and one Z slide (NOT TWO like most foam cutters) The Z Slide holds the hotwire in a copying saw type bracket about 8" deep or so. This way I only need two motors and two slides. For example, the foam is mounted on its edge in the machine. X moves back and forth horizontally, and Z moves up and down vertically off of the X plane, and has a horizontally mounted wire protuding off it, and the other end of the wire is held by a bracket arm the comes over the top like a coping saw, with some throat depth. Granted it won't be able to cut very large pieces, but for now I Just want to get it up an running to see how well it will work.
I've also looked at drawer slides but they seem a bit heavy to use with belt drive. Actually, I'm thinking I'll probably end up with belt drive for the X way and screw drive for the Z no matter what I do, because I don't know if a belt will hold the hotwire arrangement in place or not (if the motor torque will be strong enough to hold the wire and the Z way both).
The thing is the hotwire really doesn't undergo any large mechanical forces, so the ways don't have to be heavy duty.
Perhaps there is also a better gantry design than what I had in mind? I'm just trying to avoid using more than 2 motors since I only have so much in the "recycle" area if you know what I mean...
Another thing I found interesting as I was searching the web last night was the theory behind how to draw a straight line - the linkages that they came up with long ago in the 1800's. I wondered if this could somehow be applied to a lightweight foam cutter machine. In other words, use a linkage for the X axis movement rather than a traditional linear bearing. Have a look at what I mean:
http://www.math.cornell.edu/~dwh/cou...aucellier.html
The linkage forces a straight line. Wonder if anyone ever measured its precision?
Nice to be here!
-niko