View Full Version : CNC Foam Cutter
9th March 2012, 06:35 AM
As already mentioned, I'm gonna build my own foam cutter, CNC. After having numerous cutting bows, a perpendicular cutter stand and a vertical/90 degree cutter, I am looking for consistent results.
I spent the last 2 months on gathering the info and looking at several machines. You could buy some "cheap" off the shelf stuff but it has it's true handycaps. They start at about 2k$US if you want something with a useful size. Most of them are cantilever design, so don't expect any rigidity, hence a full frame design. Mine is about the same price, but comes in super-rigid frame design and the dimensions are twice the size.
I nailed down the choice of chopper boards, the best board for my purpose is the hobbycnc board. This one will come with some steppers, provide 4 axis cutting for tapered and swept wings. My total cutting area will be 1100mx1000mmx600mm. A massive thing. The table is longer than 2m and 1.4m wide. I'm gonna use the GMFC - software as it can be combined with a handy USB interface (called GCC).
The software is proven to be reliable and offers outstanding cuts. I talked with Gilles Muller and the support is truly exceptional: fast and accurate. Because I intend to use limit switches for the stepper motors, I ordered the expert version instead of the pro.
I designed the whole frame in CAD, ProEngineer.
Now I'm waiting for the leadscrews to come and the table to be manufactured out of aluminum profile 30x30mm.
Enjoy, if you are interested in having your very own cutter, or just for the sake of enriching your knowledge.
Thanks and regards,
PS Pics coming soon, need to transfer from other computer :)
9th March 2012, 07:09 AM
Does this mean you have some bow cutters to sell cheap?;) Our homemade bow could use an upgrade!
9th March 2012, 07:42 AM
Sweet. Check out www.cnczone.com. Lots of great info there. I am building a 4x8 cnc cutter myself.
9th March 2012, 08:18 AM
Thanks for pointing out the links. Could you also provide some info on your cutter like pics and material & software involved and on which issues you ran into when building. Much appreciated. Take care :)
9th March 2012, 08:19 AM
@tracks: eh, my bow is no more than 20$us :) you want me to wrap in gold foil and ship it over to make shipping costs worthwhile :) Seriously, there is no magic in those. I'm gonna shoot a pic, u'll see.
Thanks and regards,
9th March 2012, 08:46 AM
Still working on it..
9th March 2012, 10:41 AM
I think we're just going to build a crude cutting table. We just want something so we can cut wings quickly: Sorry for the crappy MSPAINT drawing. I'm at work. ;)
11th March 2012, 10:01 AM
That thing is huge, ernie!
Cool that you got access to a welder + the necessary skills. I have no access to welding. Keep up the good work!
11th March 2012, 10:11 AM
I enjoy it. I have lots of money tied up in it so far but once done will be able to cut pretty much whatever I need to out. I will be able to design and cut out my own planes, pan tilt devices, tracking parts. Whatever I want to make. Maybe I can help people out on here too. We will see.
Thanks for the encouragement!!!
11th March 2012, 08:19 PM
Just curious, what are you going to use to keep the wire tight? A spring?
11th March 2012, 08:42 PM
Slightly off topic, but I'm interested in making my own stuff too but instead of removing material with a cutter I'm gonna grow it 3d printer style. I recently discovered this kickstarter.com project called printrbot (printrbot.com).
It's a reprap design but super simple. When the kits are available I should be able to make some cool fpv stuff.
11th March 2012, 09:58 PM
I bought a machine from HubbardCNC on ebay, it's not a full frame, but plenty sturdy for hot wire cutting. I would like to eventually build a CNC router table for cutting ply/plexi/coroplast parts, so I will keep an eye on this thread.
11th March 2012, 11:07 PM
Just curious, what are you going to use to keep the wire tight? A spring?
... I thought of 2 ways which still have to be tested:
1. The spring mechanism as you suggested. This is pretty standard, you will have 2 limiting factors. When cutting highly swept back wings, the spring possibly won't give you the "extended" wire length you need, only a few cm. That may require you to cut swept wing differently. Also, if your stepper motors needs to pull the spring real hard, it may just send a smoke signal.
2. The "new" way is using a roll with a counter weight (water bottle) on which the hotwire if fitted, tensioning you wire strong enough to cut but not overloading your steppermotor. This way you will maintain the same tension regardless of how swept back your wing is. Of course this adds to the complexity of the structure, possibly not a good solution for a cantilever design.
Thanks and regards
11th March 2012, 11:11 PM
so this is my design....
I decided to have proper swiss made lead screws to ensure precision even at this length.
I cannot insert a bigger pic, any suggestions?
11th March 2012, 11:50 PM
I made my CNC cutter out of wood and drawer slides (around $250), so I wasn't able to use a spring because my frame was too weak.
I ended up using a bow to keep the wire tight. Its hard to explain, but each of the Y axes has an eyelet on it, and the wire of the bow is held in the eyelet. This lets the bow slide back and forth in the machine.
Your lead screws either have to be perfectly straight or you have to make something that will absorb the unwanted movement. I did the latter
You need to have at least manually adjustable heat for your wire. I used a computer power supply and made a PWM controller. (A brushed ESC would have done the exact same thing)
On a subjective note:
Don't make a fancy CNC machine if you don't plan to make a LOT of wings with it. It takes a lot of effort to get it to work right. I made my machine the cheap way, so I don't regret only using it once in the past three months, but it sounds like you're going to spend even more money and effort. If you're going to make less than 50 cores, its easier to just pay someone else
12th March 2012, 11:30 AM
looks good hmfpa!
Well I understand your concern about alignment, but that's what good coupling are there for. I used Huco Oldham couplings, they can offset a few degrees of misalignment. The leadscrews are properly mounted in bearing housings, one end attached the other one floated. All parts that need precision will be CNC milled.
I use 50v DC 500W for the cutter. It's regulated, so when you cut a spar or that alike the software automatically adjusts the heat. The stepper motors are very large, I also bought a huge PSU for those, right I can't remember the size.
Well, I have tons of use for this so it'll be ok - I guess - we shall see.
22nd March 2012, 01:48 PM
tomorrow I will start cutting the pillars of the alu frame...
22nd March 2012, 02:03 PM
22nd March 2012, 02:08 PM
how is yours progressing?
16th April 2012, 03:35 AM
I managed to get the frame structure cnc milled. These big cnc milling machines are a true blessing. I tried to manually lengthen the pillars, besides taking ages because of the wrong tool length (too short), it was very difficult to mount those rectangular hollows in the vice. Pictures coming soon, a big thank uuuuu :-) to my malay friend who did most if the cnc operations. He did an awesome job!
11th May 2012, 07:59 AM
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.
I bought the heck of a lot of wires. hehee :)
15th July 2012, 11:09 AM
it's done and I am very happy about it. have a look:
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.
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.
15th July 2012, 11:24 AM
Wow this is one boss of a machine, nice work.
15th July 2012, 11:41 AM
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...
15th July 2012, 01:12 PM
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. :(
19th July 2012, 09:38 AM
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.
19th July 2012, 03:03 PM
Yeah the axes move independently.
21st July 2012, 02:10 PM
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.
21st July 2012, 04:00 PM
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.
23rd July 2012, 09:39 PM
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 :D
Are you using ballscrews or Acme?
23rd July 2012, 10:19 PM
I am using timing belts.
24th July 2012, 12:54 AM
I use eichenberger precision lead screws, 12x4mm . That was the most expensive item of the whole project... After having it tried out, it was worth the money...
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