Ran the snot out of my needle cutter this weekend. I've been experimenting with fiberglass and composites lately and a local guy hooked me up with some really nice epoxy so I could see what a difference high quality epoxy makes over the hobby grade stuff I've been using. Well, long story short I'm now sold. The stuff he gave me is not only FAA (and German FAA) rated for fabricating manned aircraft and WAY easier/nicer to work with...it's also half the price of the "cheap" epoxy from the hobby store. Only catch is you have to buy at least a gallon of resin and quart of hardener (and more realistically 2 quarts of hardener because the fast is too fast and the slow is too slow so you have to blend them to get a better cure rate) plus there's a hazardous material shipping fee...so it ends up being $150-$200 to buy it...but the per oz price is about half what epoxy in the little 4.5oz bottles goes for at the LHS or online.
Anyway, he hooked me up with a nice big bottle of the resin and enough blended hardener to go with it. And then mentioned that his grandkids were interested in building the Alpha/Bravo/Charlie jets from FT if I could cut them on my MPCNC. And another local guy did me a favor and I offered to repay him will a FT Dart and FT Arrow. So I had some cutting to do this weekend.
Got off to a rocky start Friday evening. Pulled out my vac table and found it had warped again. Didn't really want to wait for it to flatten out under weights so decided to cut myself the
Long-EZ jpot1 has been working on in the Mad Scratch Builders section. I've been kind of gung ho about composites lately because a good friend of mine recently bought a used Velocity XL which is a composite aircraft very similar to the Cozy MarkIV which is in turn based on the Long-EZ only modified for 4 passengers. So I figured cutting jpot1's experimental build would be a good warm up for the weekend.
I've been experimenting with cncjs on a pine64 (kind of like a RaspPi only cheaper) instead of using the LCD lately - so after I created my gcode in estlcam I loaded it up in there and gave it a go.
Unfortunately after just a few operations I saw and heard the machine do something odd. It was almost like it skipped a few steps...except it didn't skip - it actually moved backwards then continued. The end result was the same as skipped steps with it getting out of position...but I swear it didn't skip it actually moved backwards. 95% of the sheet came out ok...but due to that issue one of the B folds on the fuselage was too wide and the other too narrow. So the long-EZ came out a bit crooked and there was no way to install the motor pod because one of the mounting slots was partly covered. Oh well...it's still a halfway decent chuck glider and gave me a feel for how the plane will go together.
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With that done I called it a night.
Saturday I ran up and bought 15 sheets of foam...then dug in on the cut fest.
I cut the Alpha using the LCD/SD like I usually do. But the Bravo and Charlie I cut using cncjs. They all came out great except for two minor issues. One sheet of the Bravo I didn't quite position correctly and a tiny bit of one wing fell off the edge of the foam...oops. It will be ok...just isn't perfect. And on one sheet of the Charlie cncJS did the same thing again suddenly backtracked loosing position. Thankfully it did it at time that didn't really affect anything. Just left one score cut a few mm short and the rest of the parts on the sheet nested a few mm closer together.
So that was 9 sheets of foam back to back with only 2 very minor issues. I did notice my cuts are getting a little less clean...guess it's time to finally sharpen this needle...it did seem to be getting a little dull.
But first I have the Dart and Arrow for the other guy.
I cut both of them with cncJS and only had one issue. On the last sheet of the Arrow cutting out the motor pod part it only cut 1 of the 4 sides. It cut that side 4 times though. No clue what caused that. The preview on CNCjs looked correct and the CAM looks correct. So not sure if it was a cncjs issue or a marlin issue. No big deal because he's going to use a 3D printed motor pod on this build anyway but still kind of crazy and hard to explain. I guess cncjs is still not 100% with marlin...or at least not with the 2 year old version of Marlin I'm still running. I really need to upgrade to the latest beta of Marlin since there are some really nice upgrades for CNC use I want to try.
But 15 sheets of foam in one weekend is a new personal best...and I could tell the needle was getting duller as the cut quality on the 15th sheet was not as nice as on the 1st. But...doing all those planes gave me the itch to build and the Alpha jet looked kind of fun.....
So I just fired it up to cut an alpha for myself. 1st sheet went great. 2nd sheet went great for the first half....then...suddenly the machine seemed rather quiet. I looked over and sure enough I couldn't see a needle on it anymore. Oops.
Shut it down...and sure enough the needle is gone. The bit around the bearing was still there but the rest was nowhere to be found - it broke off right where it bent around the bearing. I wonder if it would have lasted longer if I had sharpened it so the forces on it were a bit easier.
Still...it lasted almost a year (I made that needle in July of Last year and have totally lost track of how many sheets of foam I've cut with it. I've made almost 20 planes for myself (explorer, arrow, dart, mini-dr1, x29, mirage chuck glider, a couple beta gliders from Sponz, tinywhoovs, the vactable, simple scout, 2 mini scouts, xb-70 chuck glider, 3 sparrows, ft cub with floats, baby bugatti), even more for friends (almost every plane I cut for myself I also cut one or two for friends), my ink organizers, my solar projectors, a few dinosaur skeletons, a few cardboard projects, and a couple of other random DTFB projects....that needle had a good life
I should be bending up a new one right now to finish cutting my Alpha....but...I think I may give moebeasts needle holder a try instead. So going to fire up the 3D printer and crank one of those out and give the MPCNC a rest for the rest of the evening