CNC hot wire cutter?

[dave siegler]

So many of you have some powerful tools in your shop.  Milling machines, laser cutters, lathes and vinyl cutters.

For foam,I use templates and cut by hand and it is an inconsistent process at best. 
I can build a 4 axis hot wire cutter for about $300, and am torn if I should.  I don't need another hobby (building CNC tools) , i just want to cut foam. 
Do any of you have one?

If so are they worth the time and effort? 
Are you fiddling with it a lot? 
Would you build one again? 

[Tony Drago]

There's a small one for sale on Ebay. 18in wide with a depth of 13in.
 Its made by Wing Mfg. Which has been out of business for a while. They pop up on Ebay from time to time. They made different size's. Here is the item number: 362532496298

[TDM]

I built one and they are awesome. Programming knowledge and set up is a must. But depending on what software you are planing to use it is not necessary. My machine was 99.96% accurate.  I sold it to someone else as i didn't use it that much. The thing is that it will be the most accurate way to cut cores and nothing can beat it in precision and accuracy.
I would not build one unless I plan to make a lot of parts, for example combat wings that if you fly combat then you might go through a lot of them. If I was Bob Hunt in the past ans made the wing cores I would have invested in a a machine like this one.
There is a learning curve for sure and it may take some time to set a job up. Some cuts with low taper or straight no taper wings can be easy to make but the more taper you add the more complicated it becomes but also it depends on the material you cut. But like with anything else you will learn and once you do you will love it.
Another cool stuff here is if you want to test something out like similar wings with geometry that varies slightly then this machine is perfect because you can cut a bunch of wings quickly make them all at same time and then go fly and see what you like.
If you need answers I might be able to help.
This is the machine I built and of course if i was doing it again it would not look like this one at all. https://www.rcgroups.com/forums/showthread.php?1022533-My-first-CNC-Foam-Cutter

[dave siegler]

My background is factory automation and embedded systems so the programming is not an issue for me.  The issue is the mechanical system, how much it is adjusted, backlash issues etc. 

Also my shop doesn't have a lot of extra space, so I will have to be creative. 

I am worried that the CNC will be a hobby onto itself, and not a thing to make parts. 

[Chris Sarnowski]

Hi Dave,

You might reach out to Buzz Wilson to see how much fussing is required with his homebuilt machine.

-Chris

http://flyinglines.org/buzz.foamcutter.1.html

[Tim Wescott]

Phil Cartier also does CNC foam cutting, and recently rebuilt his machine -- there's a thread on here someplace.

You could check with him, too.

I think that even if you spent a bunch of $$$ and bought a foam-cutting machine, there's still a lot of knowledge you'd need to use it effectively.

[Lyle Spiegel]

Get in touch with John Duncan- he has his hotwire foam wing setup for sale. It is old school. not CNC.

[Chris Sarnowski]

Phil wrote some about his new machine here: https://stunthanger.com/smf/core-house/hitting-the-21st-century/

-Chris

[Tony Drago]

Get in touch with John Duncan- he has his hotwire foam wing setup for sale. It is old school. not CNC.

 Check out the classified section.
 John post his setup for sale in the classifieds about a month ago.

[Alexey Gorbunov]

Scratch built CNC-foam cutter.

[Istvan Travnik]

I can tell my "fairy tales" about only "bluefoam" cutting, since I work with that wonderful material for 37 years.
I never planked it with Balsa or Obechi, etc.  but only glass & epoxy  (sometimes carbon).
I cut with not too hot* wire, but using significant longitudional,  "sawing" movement.  As I observed, the CNC cutters cannot do** that, so I did not steps to that direction, sorrowfully.

*voltage and current is carefully adjusted and kept in 1/100 V  and mA accuracy, by laboratory power supply unit.
**If you see somewhere some "sawing" CNC hotwire cutter, links/infos are warmly welcome!

When interested, here is my post on it:
https://stunthanger.com/smf/building-techniques/the-bluefoam-model-or-how-to-build-a-stunt-plane-without-a-bit-of-balsa/

Istvan

[TDM]

When you cut with CNC the wire never touches the part. You use the radiant heat around the wire to make the cut. There is a curf which is dependent on the wire diameter and temperature at which it cuts and how fast the machine moves. So basically you cut the bottom, let the part drop the curf thickness and cut the top which technically gives you target dimension.  The program also is asking you what is the curf to make compensations if you cut top first then bottom. I preferred the other way around. Take in consideration what wire size you use, how is the wire attached, how is the power getting to the hot wire because if it drags on the table or snags even the slightest bit you scrap the part. Also think about tensioning of the wire because it gets longer and shorter with taper cut plus from the heat.
The machine looks well designed with the linear bearings. It will be a good one.

[Istvan Travnik]

Dear TDM,
Thanks for the precise description of CNC moved "non-sawing" hotwire's working principles!
Regarding to my works, I cannot tell that I got happier*.
Thanks again: Istvan

*no idea now, how to handle the several millimeters melting around the wire... 

[Keith Renecle]

Hi Dave,

Two years ago, we and an airshow at our club which is a big model flying club, mainly R/C but has a decent control-line section with two circles as well. The airshow was a Warbirds day and we were asked if we could fly some combat. I had an old .15 glow powered Zero fighter and I found an extruded foam ceiling tile lying around so I figured that I could make a cheap and nasty fighter fuz out of this stuff. I used paper covered Styrofoam wings and it worked so well that I thought that I could use the method to build some simple stunt trainers. The prototype was also cut with a hot wire bow in conventional fashion and worked great, so I figured that if I had a cnc foam cutter I could slap models out much easier and quicker. I also always wanted to see if I could build one of these things.

I did some Googling and there are plenty of websites with info. The most useful one to me was http://www.https//www.rckeith.co.uk/ This British guy is really helpful and his machine looked doable. I often use my WHIGLA system........ What Have I Got Lying Around. I already had two old slide systems from an old drawing board and I made the vertical mechanism using some rectangular aluminum tubing with hardware store drawer slides. There is very little drag on the system because as was mentioned, the hot wire does not, or rather "should not" drag in the foam. This means that you can use small stepper motors. You do need an older PC with a parallel port to run most of the stepper amplifiers and what is called a break-out board.

Then it comes down to software and I looked at everything that's available. Most folks use Profilli to generate G-code and then run this into Mach 3 software. There is also the old French package that runs cnc cutters but I can't recall the name. I then found a freeware French program called Jedicut https://www.jedicut.com/en/ They have a forum that is mostly in French but the writer or creator whose name is Jerome, will always try and help you in his best English which is more than understandable. He showed a way to use the popular Inkscape to draw the shapes and right now after many months of fiddling I have it down pat. I export the drawn shapes to a dxf file and then use that in Jedicut to create the Jedicut files. If you like I can provide the details if you send me a PM.

Here are a few pics of my machine.

Keith R

[Keith Renecle]

Here are some of the models which I have cut on the machine.

[Chris Sarnowski]

Hey Dave,

Just wondering what you decided to do? Build a CNC system or not?

-Chris

[dave siegler]

First of all thanks for all the ideas. 

I am still on the fence about it. 
The technology ist a problem, shop space is a problem a little. 

Some one (my brother tom) keeps telling me that I'll spend more time screwing with it than cutting foam. 
They are always out of calibration and you end up wasting just as much foam as templates methods. 

[phil c]

I strongly recommend building a box frame cutter.  A full x-y frame at each end.  The T-shaped frames do work, but they are very sensitive to bumps and vibration because they have little support for stiffness.

If you're not planning to cut hundreds, the x-axis can be horizontal and as long as needed.  If the machine isn't extremely stiff just bumping it will leave a mark.  I'd recommend the Gecko G540 4-Axis driver.(geckodrive.com).  It's not particularly cheap but they have very good instructions and have a settings page for Mach 3 that sets everything up in about 2 min. Mach 3 is typically a free download for up to 512 individual moves.  I literally spent months try to get the Arduino and other cheap 4 channel driver boards to work.  It was a waste of time and money(several hundred $$$$), unless you are an electronics expert.

It is very important that the  foam gets firmly clamped over as much surface as possible.  Depending on the quality and density of the foam, 1# foam can wiggle all over the place when being cut.  The melted foam puts enough stress on the foam to warp it.  If the block is uniformly clamped it can't bend and the final cut will be closer to what you drew.

There are quite a few CAD and cutter driver softwares out there.  I'd recommend keeping it as simple as possible and drawing each airfoil as a polyline.  The software can't mess up the point to point coordinates  and it's relatively easy to make detail correction if needed.  I'd also recommend FoamWorks
David Mrozinski
848 W. Borton Road
Essexville, Michigan 48732

Website: http://www.foamwork.net
General Information: info@foamwork.net
Technical Support: support@foamwork.net

It works well on DFX format files.  In this case older format DFX files are better.  With all AutoCAD's updates the files have gotten very complicated and hard to parse.  Dave has been very helpful getting things going.  He also doesn't care how many computers you put it on, as long as it is registered to the machine.

I've got a BUNCH of 0.010 Inconel wire for cutting.  It requires about 5-7volts a foot to cut 1# foam.  It's about the same strength as high strength steel(the label  says 233,000 psi).  A 36in. length stretches about 3/4in. when heated to cut 1b foam.

The problem is that it came as a basically loosely wound donut held to gether by shoelaces.  It's gotten messed up enough that I can't afford to give it away.  So, 50 cents a foot in ~10 ft lengths plus a buck or two for postage, as time us available.