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Old Dec 23, 2012, 02:29 AM
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Quote:
Originally Posted by Geoff_S View Post
0.4mm (0.016") stainless steel wire (fishing trace - very easy to get from the fishing shops around here, in any number of sizes). I was using thicker stainless wire (around 0.6-0.7mm I think) but thought the smaller diameter would help bring the kerf down, and I had plenty of spare capacity in my power supply to drive it.
Interesting. I expected you to say something much finer than .016 on the basis of your Kerf(s) shown in the screen shot. You also mentioned a bit of Angel Hair.

As you said the French did a lot of testing and hence the default kerf of .8 & 1.5. This works very well with wire of say .012 to .014. I used to use .014 Inconel but got some .012 Inconel and it's much much better. Everyone was saying how well .014 Rene works so I bought some to see for myself. It actually mics closer to .015 avg. Nice rugged wire but if you are used to .012 it's Huge. I made a few cuts and took it off. If I could find .010 Inconel I would be in heaven.

I know you're way down South but maybe you can find some of this locally. .012 Inconel
http://webpages.charter.net/mnemesh/

20 feet for $ 10 USD's will last a long time. You're not going to break it though I see you have lots of Heat left in your power supply so you could if you mess up and hit with all you have. But same for the SS Fishing Leader, I remember trying a number of Fishing Leaders of which usually broke in the middle of a cut. :-(

I would say just looking at the screen shot you're cutting a bit Cool,maybe one or two more percent in GMFC and therefore a little small on the kerf setting.

Congrats though as most seem to cut to hot and then chase the Kerf Up. Much better to cut as cool as you can. They are fine until doing very thin airfoils. I prefer to leave the Default Kerf and adjust heat to it rather than chase the kerf to the heat.
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Old Dec 23, 2012, 07:49 AM
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I've always been curious about why people use inconel with hot wire bows. What is so good about it ??

Yes, it has excellent high temperature strength, but our temperatures are really quite low compared to those in the sorts of applications normally associated with inconel (eg engine exhaust, turbochargers, gas turbine discs)
Old Dec 23, 2012, 08:44 AM
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Still us NiChrome and cut at 1mm per second...It's where I get the best quality...
Old Dec 25, 2012, 04:57 AM
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Originally Posted by danfield View Post
Welcome Geoff

Yes they did do a lot of testing and for ever grateful, Vive la France.
Merci,

Merry Christmas to everyone :-)
Old Dec 25, 2012, 05:06 AM
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Thanks Dan. My understanding is slowly increasing...

I've managed to do some testing with various heat and cut speeds (after first discovering and then fixing my PWM hot wire controller which had been going berserk).

1. Firstly, I did straight cuts at a number of different cut speeds. For each speed I tweaked the heat setting until the foam block was just on the verge of sliding along the cutting table, as per the GMFC help file. I also checked and the surface of the cut foam had just a few very fine hairs, so I was happy that this was a sign of non-contact cutting by radiation. I've put the results into Excel and produced the following chart. Interesting that it is not a linear relationship.

Really good. The result for your foam is not a full straight line, but close.

I think that approximating it as as line is sufficient for most case. If you want more precision, just create two materials with the intermediate measurement as the medium point.

Quote:


2. Now even though the maximum speed that my cutter is physically capable of running at is 4 mm/sec, I settled on 3.3 mm/sec as my "maximum speed" for the foam management screen in GMFC, and also chose 1.5mm/s as my "Minimum speed". I did some kerf test measurements on a 2:1 tapered block and entered the corresponding values in the "Kerf for speed S" and "Kerf for speed S/2" boxes.
looks good to me.

Quote:

3. Now, I also did a kerf measurement at my "minimum speed" of 1.5mm/s with heat at the ideal value of 30% (as deduced from step 1 above). It did NOT match the kerf for my maximum speed - it was greater (0.825mm vs 0.635mm at max speed).

So, do I:
a) decrease the heat at min speed BELOW the ideal value, and accept that this will give more wire drag than ideal
b) increase the heat at max speed ABOVE the ideal value, and accept that this will give more kerk than ideal
c) get a life, and stop worrying about 0.2mm differences in a piece of foam...
0.1 mm is the best you can achieve with foam. A precision of 0.2mm is perfectly acceptable.

As Dan said in his other posts, if you know the cutting speed, you can also create a fixed cutting speed material.

Gilles
Old Dec 25, 2012, 06:26 AM
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Geoff,

I tried to reproduce the crash problem in the foam management menu, but no luck...

Please could you email me privately what you did exactly and your .bd files.

Gilles
Old Dec 30, 2012, 05:10 AM
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GMFC version 3.90.5


Hi all,

This new version allows to quickly switch from the complex shape mode to wing mode using two icons in the "wing" toolbar.

Enjoy,

Gilles
Old Jan 20, 2013, 04:02 AM
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Bugs in GMFC software


Is there any page about knowen/removed/pending bugs?
I found several problems while panel cut/ block trimming/before,while,after
I got step losses when the wire was returning from LE back to its home position.
Another problem is the shape of the trailing edge. It always looks like the shape as with Accelerated Positioning
Wolfgang
Old Jan 20, 2013, 05:09 AM
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Originally Posted by wattsi View Post
Is there any page about knowen/removed/pending bugs?
I found several problems while panel cut/ block trimming/before,while,after
I got step losses when the wire was returning from LE back to its home position.
Another problem is the shape of the trailing edge. It always looks like the shape as with Accelerated Positioning
Wolfgang
Hi Wolfgang,

There is no page about known bugs. If you gets a bug, just mail me the project and a description of how to reproduce it.

Gilles
Old Jan 21, 2013, 05:53 AM
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Merci beaucoup, Gilles
je l'esserai
Last edited by wattsi; Jan 21, 2013 at 06:01 AM.
Old Mar 06, 2013, 08:30 AM
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GMFC version 3.90.6


Hi all,

This version introduces TE prolongation using the lower surface. In fact, this is useful when cutting a wing with an inverted profile for putting spar entry on top. Since lower and upper surface are inverted, this is equivalent to a TE prolongation using upper surface.

Bug corrected:
- The spar menu is disabled when in complex shape.

Happy cutting,

Gilles
Old Mar 07, 2013, 01:52 AM
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Straight TE


Can you put a check mark to make a wing with a straight TE wing core?
Old Mar 07, 2013, 02:22 AM
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Originally Posted by Kevin Matney View Post
Can you put a check mark to make a wing with a straight TE wing core?
There is already a icon in the wing toolbar for this purpose.

Gilles
Old Mar 08, 2013, 03:30 AM
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Originally Posted by gm.cnc View Post
There is already a icon in the wing toolbar for this purpose.

Gilles
The icon is for a LE not TE
Old Mar 08, 2013, 04:26 AM
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Quote:
Originally Posted by Kevin Matney View Post
The icon is for a LE not TE
Just look at the attached picture

GIlles


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