Hot Wire Foam Cutter w /SB controls

[birdsofplay]

Hey guys Long time No See.
Yep I'm back for a while again.

In the Model Aircraft hobby, cutting Wings sections from a solid block of foam
with a single Hot Wire Bow is a way to achieve the end result.

Several CNC Hotwire designs are available for these but the Software
is a PAIN.

They are basically two X&Y stages with the hot wire between them.
The X and X' as well as the Y and Y' axes are all independent.
That way a Tapered wing can be cut.

Since I already have a Bot I was thinking the following.

A program called Profili Pro is available from Stefano Duranti.
It been around for some time and fairly mature.
His latest version creates the G-codes for cutting wings with a Hot Wire.
He also has built in a terrific 3D sim.

I have taken HIS exported G-codes and used Bot Software to generate
the SBP file. The result is all M4, J4 type of commands.

SO this gave me an idea !!!
I have this NOTION that I could Unplug my current Shopbot motors
and PLUG the control box into a NEW CREATION of mine that embodies
the 4 axes as described above.

Then Just RUN the sbp file after redoing the calibrations for all four axes
since I'm planning on using ACME 1/2"-10 threaded rod for motion.

Has anyone ever done this ?
I searched but either didnt look hard enough or I used the wrong key word.

If this were to work it would mean that I would NOT have to purchase any
other SW packages, like MACH3 et al.

I already HAVE Profili for airfoil design and it exports DXF for my Router work and Rib cutting as well as Former cutting for fuselage parts.

ShopBot could market this as another PLUS for their SW and Electronics.

Anyone ?

If you want to write to me via e-mail rcneitzke@centurytel.net

[myxpykalix]

Bob,
I don't know much about foam cutters but from what you describe it sounds like your X and X and Y and Y would move independant of each other and as it stands the two X motors work in tandem with each other and it sounds like you would need a controller for each motor. Then i could see how each motor could move indenendantly but i'm not sure on how you could mount them.

Bottom line is how much time do you save vs how much money you spend to make the other axis, and could you accomplish the same thing with a regular router?

But look what others have done, made cardboard cuttings, quilting machines and other "hacks" to make something cool so who's to say you can't do it? Go for it!

[birdsofplay]

Jack,

Um... My old controller HAS 4 stepper drivers.
I assume that SB uses all four controllers independently
as if you had TWO Z axes.
SB does have M4 commands so I figured it would be a natural.

I do worry about slowness.
Everytime I've done 3 axis Sculpturing with mine it runs very slowly.
Not the speeds in set up but Lots Slower.

Yes All four axes of the foam cutters are independent.

Here are a couple of examples of what I am talking about.
http://www.drayconstruction.com/foamstuffs/
http://www.8linx.com/cnc/

Yes I know what you mean re saving Time vs Money.

But this is hobby stuff not for immediate use in a business opportunity.

Anyway - all replys are good :-)

Thanks for the input

[myxpykalix]

Bob,
I think i left something out regarding the steppers,ect. Like with the X steppers they both move in the same direction to move the carriage. Wouldn't you need to move both of the X steppers independant of each other in order to be able to make the various designs which would necessitate seperate code I think. Most of this is over my head but it is interesting.

[ken_rychlik]

The two X's are NOT controlled apart from each other.

Most controllers have another (5) outs on the board and the last output could be driven seperate from the others to give you 4 outputs.

How would you get past the length of the cutting wire changing as the distance between the motors will change??

If you have four outputs, and you control two x's and two y's, that leaves you no way to raise and lower the wire. Only a way to run it back and forth.

I am thinking you will need 6 motors all running on their own.

Anything is possible, but there are some challenges ahead.

[beacon14]

I think the four outputs would be sufficient, the two X would run the length of the table and the two Y would raise/lower the wire at each end of the gantry as it moves, there would be no need for a conventional Y axis movement. Maybe a spring-loaded assembly for tensioning the wire?

Wish I could help more on the electronics, but that is way above my head.

[dana_swift]

Bob- a zillion years ago I was an RC enthusiast, and made foam wings using the manual version of what you describe. I see exactly what you are trying to do and if I was the guy wanting to cut foam wings would have it running already.

The bot will do 5 axis synchronized motion, so getting your four axis result should be trivial. For each XY at one end of the wing you can know what the XY is at the other end. The control electronics on the bot knows nothing about the geometry of the bot, only the tool pathing software needs that knowledge. Since you have a toolpathing tool and have adapted it to SBP files, there isn't much to do but set up the geometry you need and cut some parts.

As to the question about the varying length of the cutting wire, that problem occurs as the wire heats up, a spring is required to maintain the tension on the wire, and should be adequate for most changes in length from one end of the cutter to the other. If not, rig a cable over a pulley with a weight, so as the length changes drastically the same tension will be maintained. Ni-chrome wire is not cheap, so avoiding breaking the wire is a good idea too.

When you get this gadget going I would love to see photos of both the cutter and shapes you make-

D

[birdsofplay]

Um , lets see here ...

The X axes go back and forth across the Cord of the Airfoil.
That is to say Leading edge to Trailing edge.

THE Y axes go up and down or top to bottom pf the airfoil.

There is nothing else needed to achieve the shape desired.

The block of foam is held in place and the Hot Wire starts at the
Trailing edge, moves up across the airfoil then around the Leading edge
and finally back across the bottom of the Airfoil and OUT at the Trailing edge.

You get a Smoothly cut uniformly blended Root to Tip, with Washout
if desired , with different airfoils at either end if desired at whatever
aspect ratio you wanted.

examples here http://www.profili2.com/eng/default.htm


The wire, on at least one end is, is either sprung or constant tensioned
with enough to allow for that needed extra length when doing tapered cuts.

The X axis is NOT Slaved permanently to TWO outputs or Drivers.
At least NOT the way Mine is built. Over 10 years old Bot stuff.

As long as I can figure out how to set the Calibrations for all 4 axes
I should be able to get this to work.

C U L8r

Bob

Dana I believe you have figured out what I am trying to do.

There are several examples of this thing running out there.
They simply used OTHER SW and Drivers to get there.

I thought I'd try to REUSE my SB equipment in this alternative way.

Nichrome is good But most guys are now using Stainless steel Leader line. 20 - 30 thou size.
It expands/extendeds LESS and takes a bit less power.

Complex cuts even allow for cutting in Spar Slots top and bottom and INTERNAL Lightening Holes.
The Foam gets Covered in Balsa Sheet or sometimes very thin ply 1/32 or 1/64" stuff.

[ken_rychlik]

It is making more and more sense.

Still there is no way on the board to run x1 differently than x2

It is true that they are not connected to each other, but they share the same input to the drivers.

You will need to use the fifth A output to accomplish what you are getting at.

[birdsofplay]

here is a screen capture of the SIM that is doing what I want

http://www.balsabuddies.com/Duster/Profili.mwv

BTW Look Quick ! I wont be leaving it up on my site for long !

The original capture I did was AVI but too large IMHO ( 14 mb)
SO please forgive the vid Rez of this wmv file ( ~ 5mb)

Watch the White line ( The hot wire ) as it 1st cuts the Lightening holes
then the Slots then the Whole Airfoil then chops off the Trailing edge
to be used later as the Aileron or Flaps.


NOTE: MY OLDER Shopbot Controller board my be different.
It only has 4 channels and 4 separate driver boards.
Back then it was optionally for the 2nd Z axis, if I 'm remembering right.

I assume that the NEW boards are hard wired to provide the extra UMPH
for the Second X axis Stepper.
With yet another (5th) Channel for 2nd Z axis et al.
Regardless of the end electronics decision or outcome,

I'm headed to the ship to start cutting steel for the table NOW !

L8r

Bob

[Gary Campbell]

Bob...
Almost 3 months...PICS???