There is a mechanism for controlling that using a weighted bar and a little bit of math. http://charlesriverrc.org/articles/tools/brengmancutter.htm This is next on my agenda. I built the wire power supply yesterday. I already have a 'foam table saw' ie a small table with a hot wire coming out of it at 90 degrees for cutting simple shapes.
It kind of hard for me to make out, but that lever arm looks over complicated. Here is one similar to what I made: http://www.parkflyers.org.nz/modules/ne ... st_id=3254
I have a Feather Cut foam cutter that uses a counter weight to slowly draw the bow across the templates for an even cut.. The templates work better if they are cut from phenolic or formica so that the hot wire doesn't get caught on or burn the templates. The Phlatprinter would be ideal for cutting the airfoil templates. I was too impatient to cut out perfect templates so I bought a foamlinx FC3920 CNC 4 axis Hot Wire along with Foamworks. Foamworks is an easy to use CNC package for cutting wings. It has a DXF converter that codes your file for Foamworks, but I've never had a successful conversion. Foamworks does take care of all of your calculations. You enter in the distance between the towers, the root and tip chord and length and type of planform and it does the rest. Bill Hobby Central
So I have played around with this idea in the past. EMC2 will handle 4 axis, but I am not sure how it will render it in the visual display, it's not important if it works, the visual display is not really necessary. This is what more time into the project looks like, it's exactly what kwok has posted with more detail. The yellow areas indicate cutting area or what we see in sketchup as the "safe area." You should know however that the foam must be located in the correct spot in both X, Y, and Z to have a good cut. It's not impossible to setup, but needs to be precise. 1/4" will make a difference when making two wing halfs. Attached files
Take a look at this http://www.8linx.com/cnc/day1.htm. That's where I've got the idea to use drawer slides.
Yup! Perfect cheap linear slide, that was the plan for what I had drawn, only I was at the stage where I needed to start actually buying stuff.
What's the biggest block size you think this needs to be able to cut? I am thinking there isn't any need for more then 6-8 inches in the vertical axis. and maybe 24 inches in the horizontal. Then the distance between of course can be made to suit whatever size is needed. Keeping the towers short seems to have value to me, I don't like tall unsupported things. Plus the shorter it is, the easier to build. Any comments?
Bert, I'd tend to agree with you that a person would seldom, if ever, need to work on a plank that was more than 6" thick, and probably most of the time they'd be working with 2" thick planks.
I guess since the easiest stuff to find is the pink stuff at HD, that seems to be 2" thick mak. So maybe a 4 inch stroke is plenty?
