Hi Folks,
I am an engineer working on my own design for a CNC hotwire machine for my own use. I have been talking to a couple of people in my area about their hotwire and router machines and have received some great input with regards to my machine. Let me first lay out my goals:
I am designing and planning to fabricate my own composite homebuilt airplane (You know, use those silly Aero/Mechanical degrees I got). I am more interested in the journey than the final product, so I do not mind taking time along the way to get it right (obviously safety is #1). One of the ways I hope to get it right is by using hot wire CNC. Here's what I'd like my machine to do.
I want a machine that can cut full sized tapered wing panels that will be build up to a full-scale wing. These panels would be probably 3 feet wide at a time, with a maximum chord of 5.5 feet (at the root of the wing). I will likely put a linear twist into the airfoil, so I think this will require 4-axis control. Each 3 foot section will be placed into reference fixture, finish sanded, then glassed up into molds. Since the airfoil shapes are the most important, it is paramount that the XY coordinates be very close to the actual airfoil contour.
I also want to be able to cut my fuselage out on the hot wire machine. I will have a compound curvature fuselage, and so I envision taking the 3D contour, and cutting it into pie slices, then having the CNC cut out 4 inch long cross-sections and then I stack them longitudinally. Again, the same general desciption for the wing cores should suffice for requirements. The fuselage could get as tall as 5-6 feet.
I also want the machine to have 2 independent sets of carriages so I can unbolt each side (X and Y) and move them. Also, I designed the box beam assemblies to easily accept lengthened X-axis travel in case I want to upgrade length.
With that in mind, I have consulted with the people I know, and they seem to think the Probotix HT23-280-8 Unipolar motors, and the standard driver kits that come in the 4-axis pack for $410 should be sufficient to drive the machine using Mach 3 as the computer software.
I found a box beam cheap for $25 at a steel scrap yard that was in good condition. It's a solid 3X6 X 1/4" thick and 64 inches long. I designed my first pass at my X-axis (Horizontal) carriage assemblies off the fact that I can get 4 15" sections out of that rectangular box beam. In the presentation I describe my current approach to this carriage design.
What I am hoping from you, the community, is honest and civil feedback on my current design. I am particulary interested in any lessons learned with this configuration, and I am open to suggestions : ). One thing I have not sorted out yet that I know of is how to secure the ACME threaded rod end on the side without the motor. I have it supported by a bearing, but don't have anything restraining it axially. Thank you so much for your time, patience, and advice! I am really excited to finish a good design and start cutting metal for my hotwire device!
-Chris Z.