Post by chuck26287 on Dec 30, 2015 22:59:21 GMT -5
I get a little dissappointed with as often as I stop by here and there's nothing new on the board. So, I figured I should upload a little content myself before I complain. So, I've got three different projects to share... not much by any means, and only in the 2D realm so far. This first project is why I went shopping for a CNC router... to prototype/develop a specific multirotor UAS body (more commonly known as a "drone"). This is a true "scratch build", prototyped with 1/8" Baltic Birch plywood before cutting the expensive carbon fiber sheet stock.
I even designed a few pieces of hardware needed for specific function. I found I could design/prototype a custom part with Corian (acrylic solid surface counter top material) very easily for the initial build and flight trials, then I'll make production pieces out of aluminum after the designs are finalized. Acrylic solid surface material is great stuff for things like this as it can be drilled and tapped and holds pretty strong.
Not finished with this by any means, but it was incredibly rewarding when I started with plywood, aluminum square tubes, and flight parts, and saw it fly the first time. The best part was designing something, assembling it, and when it wasn't exactly what I had in mind or wanted, or was a little off in its functionality, I changed the design and made it again right then and there. These CNC routers are a maker's dream come true.
Last Edit: Dec 30, 2015 23:51:31 GMT -5 by chuck26287
Thanks, Chips. It provides all kinds of versatility. Sometimes too much. It's real easy to let yourself get sidetracked and start down a path that has you redesigning things. I'm now looking into some weight reduction, and design changes that will shave grams off. Challenging, but fun.
I have a potential upcoming project for a friend who is basically requesting a similar project: Drone body + carbon fiber. Have you gone all the way to carbon fiber with your project yet? If so, i'm curious what bits you used and what feeds/speeds settings... etc.
any pointers would be helpful
For the sake of some brief (5 minute) google-fu research i did just before posting a reply... some other forums/threads (some quite old/2011 etc) mentioned...::
"Start with a .125" cutter at full depth, 7500 rpm at 15-20 ipm. This isn't very fast and I would start with the Feedrate override down at 50% and ramp it up with a little air or vacuum in the zone. After you get a feel for the cutting action, I would say you could triple the speed and feed without splaying the material if the machine is rigid enough."
someone else on the same forum mentioned the next bit... although the full method probably isn't going to happen:: (submersing the piece.... yikes)
"Material Sheet Thickness 2.0mm Rotary Burr Cutters - normal single 2 flute 3 flute etc end mills can cause delamination and pull fibre strands
1.4mm 1.5mm 1.6mm 3.175mm cutter diameter we run at 100mm per minute 3.0mm depth cut - 20,000rpm (1.0mm below material thickness)
Material spaced 3.0mm above milling table with 3.0mm plates in each corner - this allows 2.0mm material to drop below the lowest part of material and cutter depth - t-bolt clamped in each corner
Material submersed underwater for cutting - not cutting fluid. "
A third site basically says... mill at a relatively high RPM... but at a relatively slow feed rate.. Regarding bits... "carbide and polycrystalline diamond (PCD). Carbide provides good wear resistance, but is more applicable to smaller jobs. PCD cutters offer better wear resistance and are the cutter of choice for several composites machine shops. However, the benefit of PCD cutters does come at a significantly higher cost compared to carbide. "
for the most part it seems the problem with Carbon fiber would be the risk of de-lamination due to thermal issues... so a creative tool path to avoid that might be necessary.. (i suppose thats why the middle post said they submerged the piece for the job)
in any event... anyone else have tips/experience/pointers besides the submerging the part is not healthy for the machine if stuff goes where it shouldent? :-)
Secondary point, carbon fiber is aparently conductive so the vac will be on for the job needless to say...
I order Amana Tool #46260 for cutting the carbon fiber sheet stock, but haven't cut any yet. Still fine tuning the prototype, and don't want to change the body design after cutting over $300 worth of cf plate. These bits look reasonably priced, but I don't expect they will last real long.