CNC Foam Cutter

[Dionysos]

Hi,
I m lagging a little behind with updating this thread.
I'm currently working on the electronics side, the hardware is almost done. Almost because it was done already, but I under-dimensioned the guiding rods. That translates into too much sagging when the traveler is in the middle. It's not much, like 2mm, but in terms of my CNC world, 2mm is a life.

So I need to change bushes (haven't lathed them all, lucky me) and increase the hole diameter. That sounds easy but have you ever tried drilling a 24mm hole with a precision of 0.1mm? that's quite impossible to do is manually, so that's when a proper CNC milling machine comes in handy but it just takes time. I'm hoping to get the stuff done by next week.


I have installed auto-heat control features, i.e. the computer regulates the heat of the bow automatically, but it can also be switched to manual mode.

I placed an LCD display to view parameters and
a bunch of swichtes for safety and a couple of fuses to make it secure.

The hardware part is quite tricky if you wanna make it rigid, but so far it has been an experience. I'm not an electronics guy at all, but so far they haven't given me any problems. Reducing play, drilling or routing the holes, creating proper drawings was and is the main tone of this project.

When I see other people just using normal screws as lead screw, some hombrew ballbearing linear travellers, it works, of course, but I aim for something a bit more solid. This is really tricky to achieve.

So if anyone is doubting whether to get a cutter, be prepared to really really spend some time on the structure.

A big thumbs up for Gilles Muller, the creator of the GMFC software (cutting software) and Dave Rigotti. Now that's what I call outstanding / jumping jacks support.

Dio



I bought the heck of a lot of wires. hehee

[Dionysos]

Hi all,

it's done and I am very happy about it. have a look:

View this video on YouTube

It took me about 4 months on/off to build it, now cutting foam is just an ease, no more nasty template cutting and a left wing that looks just identical to the right wing. I am lagging behind a few posts in other threads, I am sorry for that.

Feel free to ask any question you like if you are interested in building your cutter.

Thanks for your interest in this thread.

Dio

PS it's not perfect yet (that's the German engineer talking) but after sorting out the last issues, I am very delighted to have this beautiful machine.

[volto]

Wow this is one boss of a machine, nice work.

[Dionysos]

thank you Sir

how is the spar cutting with the specter, i mean do you cut spars there? Straight spar in a tapered wing is not easy... It works here, ie in a second pass, but adjusting is quite tricky. I'll go for Profili2. I guess it makes it easier...

Dio

[volto]

Yeah that was a bit tricky, I had to draw the whole foam cutter and the wing with the proper taper in autocad and then project the strait spar out onto the actual path on the axes, I couldn't find a program out there that would do it for me, but after doing it on autocad it's pretty simple. I can send you a screenshot or the drawing file if you want.

My foam cutter is out of commission at the moment, I was building a bigger table for it so I can have a longer wire, and I bumped the computer while it was running, the hard drive started chirping, and lost the file system. I think I recovered some of it after running chkdsk /r for about 3 days strait, but the Mach3 config is gone, so I will have to build that again from scratch, major bummer that I didn't make a backup.

[aeryck]

Great project! Looks like it works great. Although, I will admit, the sound of the stepper motors does sound like somebody that desperately needs bagpipe lessons.

Does your design allow you to control just one side of the gantry for tapered wings? When I cut cores for flying wings by hand, I anchor the wire at one end as a pivot and draw the wire around a template from the opposite side to achieve the tapering effect.

[volto]

Yeah the axes move independently.

[Dionysos]

@aeryck
The 2 axes move independently, i.e. you can create and kind of washout you like. even stuff like 20 degrees is not a problem. It's cutting with about 8mm/s, that's quite fast, then I cut a circle. I like that sound. reminds me of: Terminator 1, production hall, end of part 1. hahaa

The tricky thing is placing the foam block at the right position, i.e. for making straight spar cuts and that stuff. Even tough it's CNC, not everything is automated and it still takes some time to fiddle around and make things. When it works, it's very easy to duplicate the result, that's the beauty.

To be honest with you guys, I am not very happy with the spring tensioning mechanism, I'm being a little perfectionistic here. Even though it's very standard, I don't particularly like it. You can "go diagonal" only for a limited distance (stretch the wire/spring) because at some point the wire may break, or the motors will start loosing steps. Didn't happen so far, but it's a drawback. After my current projects I will try to build a counterweight tensionig mechanism, ie. constant force on the wire not matter how stretched it is because I will be using rolls.

@volto: I'm not sure if I understand you correctly regarding the spar cut out. Could you explain again?
FYI: The bigger your table, the more tricky it will be to cut something tapered, but I guess you now that already.



Thanks,
Dio

[volto]

Yeah I have a solution for that, I will have two wires I can exchange, one the length of the full width of the table, and one the old length, with rigid extensions, essentially making the table narrow again without having to move the axes closer together (I haven't actually tested this, still fixing my cnc computer). I think it will work though.

As for the tapered spar thing, I'll have to get a screenshot and show you.

[noxnflame]

Wow That looks cool! I tried converting my home built 3 axis router to hold the and of a wire so I can do the "pivot" technique for forming wings. I had a lot of trouble with the tensioning. I was able to get some alright cuts but I had to hold the other end of the wire with my hands! I ended up scrapping teh idea and keeping the router a router

Are you using ballscrews or Acme?