[kcaldwel]

I just got my CNC foam cutter running, and it seems to be working very well.

I used the HobbyCNC FoamPro board, 1/2"-10 ACME screws, linear slides, and Lin Engineering steppers. I use a tensioned wire, rather than a bow, with a vacuum table for foam hold down.

http://www.alltronics.com/cgi-bin/it...-stepper-motor

Kevin
www.sealbayaero.com

[747drvr]

John,

I was planning on buying the French Gilles Muller software . Not sure which version yet . I may give Foamworks a look as well .

Kevin,

Sounds like a nice setup . Those steppers look nice ( and cheap !) What software are you using ? Also, what are you using for power supplies for the driver board and the hot wire ?

Marc

[kcaldwel]

Marc,

I have just started playing with GMFC, although I have Corecutter as well (used to be FoamCutter, but now open source and free!).

http://stealthplaneworks.com/

(Anker has a very nice CNC set-up as well)

I only have a very old computer running my CNC, and Corecutter needs more horsepower, since it doesn't use the board timing circuit from the FoamPro board. You also need a precision controllable power supply, because it does not use the FoamPro wire heat control. So for the moment. looks like I'll have to spring for the expensive GMFC. It does seem to work quite well.

I have a 24V 12.5A supply running the control board and steppers, and a 24V 6A supply on the wire at the moment. I think I will have to find a 34V supply for the wire, since the smaller diameter wires need a lot of voltage to push the current through. I am near the top with just a 650mm long, 0.012" wire. My table is expandable to 1200 mm wide, and I would definitely need more voltage if I used the small wire at that length. So maybe I need a lab power supply that does up to 36V, so I can use Corecutter. Not cheap though.

These guys have good prices on power supplies, and will ship USPS if you talk to them nicely:

http://www.mpja.com/prodinfo.asp?number=17429+PS

Here I am busy trying to precision cut wing cores, and I have someone who wants me to cut foam letters!

I do have 0.012" and 0.018" stainless spring wire, which makes good cutting wire, if anyone is interested.

Kevin
www.sealbayaero.com

Originally Posted by 747drvr

Kevin,

Sounds like a nice setup . Those steppers look nice ( and cheap !) What software are you using ? Also, what are you using for power supplies for the driver board and the hot wire ?

Marc

[747drvr]

Thanks for all the great info ! The Corecutter program looks great and very capable for the price Re power supplies , I guess the thin wire has such a high resistance that you can only get the amps up by increasing the voltage . Why not use the thicker wire ? Does the kerf get a little too nasty ?

What's the max V that the HobbyCNC board can tolerate ?

Marc

[kcaldwel]

Yep, the thin wire resistance needs the higher voltage. The HobbyCNC board says 34 and 35V (two different numbers in the instructions), but at least one person has been running at 36V without issue. The large wire has a bigger kerf which I guess you can compensate for to some degree (more melt to go somewhere though), and you need more tension.

Most of the people on the Yahoo CNC Foamcutter group seem to be using 0.008" to 0.014" wire. They have far more experience than me, and 0.012" to 0.014" seems to be the favoured dimensions. The real small stuff seems to break too often.

One thing I am a bit concerned about with the Corecutter program is support. Gilles, creator of GMFC, is on the Yahoo forum every day, and regularly fixes bugs. You won't get that with a free copy of Corecutter. There are a lot of other users that are very helpful with GMFC as well, and there definitely are a few mysteries to both the software and the foam cutting.

Kevin
www.sealbayaero.com

Originally Posted by 747drvr

Thanks for all the great info ! The Corecutter program looks great and very capable for the price Re power supplies , I guess the thin wire has such a high resistance that you can only get the amps up by increasing the voltage . Why not use the thicker wire ? Does the kerf get a little too nasty ?

What's the max V that the HobbyCNC board can tolerate ?

Marc

[747drvr]

I guess then , the solution is more voltage . Not having the board or access to the HobbyCNC discussion group yet , a lot of this is abstract . Do you set the wire heat through the GM software ? How much amperage are we looking at for 36v and the .012 wire . Just trying to get specs for a PS . Did you go the transformer ,rectifier ,cap route or a switching unit ?

Marc

[kcaldwel]

Marc,

Yep, more voltage seems to be the trend.

With the FoamPro board and GMFC, you can either set the % of heat with buttons on the FoamPro controller (3 to 100%), or GMFC will control the heat and the stepper speed according to the kerf model you have to input (stepper speed for two wire heats, kerf measurements) for each foam type, wire type, etc. And I guess even the temperature of your shop will affect it a bit.

I am debating what to do about a 36V supply. You only seem to need 2A or so, so maybe a transformer and rectifier is the way to go. The 36V switchers are expensive, and controllable supply more so.

Kevin
www.sealbayaero.com

Originally Posted by 747drvr

I guess then , the solution is more voltage . Not having the board or access to the HobbyCNC discussion group yet , a lot of this is abstract . Do you set the wire heat through the GM software ? How much amperage are we looking at for 36v and the .012 wire . Just trying to get specs for a PS . Did you go the transformer ,rectifier ,cap route or a switching unit ?

Marc

[747drvr]

Thanks again for the info. I just got access and am researching the HobbyCNC discussion group . It's good to know that not much amperage is required . I'll have to figure out the same as you . It may not be worth it to source all the parts rather than buy an assembled switching PS . We'll see !

Marc

[kcaldwel]

Marc,

There is a Foam Cutters group as well:

http://tech.groups.yahoo.com/group/CNCFoamcutters

A good friend down the street is a retired British Airways 747 captain, and ex-British Air Force pilot. I love to talk to him about flying, he's a big RC modeler too.

Kevin

[747drvr]

Yep , on that one too ! I'm also a "retired" 747-400 pilot . Actually , Air Canada retired the airplanes . I'm now on the B777 . More power and almost as heavy as the 747 but somehow just not as cool

Marc