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Old Aug 31, 2012, 07:40 PM
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Joined Aug 2012
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oi a todos! sou novo aqui e gostaria muito de sanar uma duvida.
gostaria de usar o gmfc com 4 driver tb6560 e uma bob. gostaria de usar o arco com controle manual , tenho desenho de uma bob com o timer , gostaria de saber se vai funcionar com o gmfc, e se tem algum erro.
obrigado
marcos soares
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Old Aug 31, 2012, 09:22 PM
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Kevin Matney's Avatar
United States, MI, Monroe
Joined Mar 2000
861 Posts
Quote:
Originally Posted by marcos soares View Post
oi a todos! sou novo aqui e gostaria muito de sanar uma duvida.
gostaria de usar o gmfc com 4 driver tb6560 e uma bob. gostaria de usar o arco com controle manual , tenho desenho de uma bob com o timer , gostaria de saber se vai funcionar com o gmfc, e se tem algum erro.
obrigado
marcos soares
This what he said
hi everyone! 'm new here and would love to remedy a doubt. I would use the gmfc with 4 tb6560 driver and a bob. I would use the bow with manual control, I have a bob design with timer, I wonder if it will work with gmfc, and if there is any error. thank you
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Old Sep 03, 2012, 12:18 AM
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Australia, VIC, Melbourne
Joined Apr 2001
60 Posts
Hi,
I am hoping someone can help point me in the right direction.

I am running gmfc on my 4axis wire cutter using a hobbycnc board going through a gmfc v2 board to usb and control the wire heat.

I have calibrated both while and blue eps foam by setting the lowest heat to cut the foam for a number of speeds as well as set the kerf compensations until I get pretty accurate tapered rectangular shapes cut.

My problem is that when I then try to cut a wing with a tapered airfoil, the smaller end always appears to be cut way too hot. To the point where the foam is actually distorted by the heat.

I have tried various types of wire and see the problem using most of them. Currently I am using 0.5mm nichrome, but it has happened on finer gauge wire as well.

Here are some specs in case they help diagnose my problem:
Distance between cutter axes is 1m
Wing being cut has 160mm root, 76mm tip and panel length is 520mm
Speed of cut is 3mm/sec
Computed heat at this speed is 44%
Voltage to wire is 36v

Any help would be welcomed. Please let me know if a pic of the problem would help and I could post one.

Thanks,
Domenic
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Old Sep 03, 2012, 12:38 PM
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gm.cnc's Avatar
France
Joined Feb 2006
282 Posts
Hi Domenic,

Have you calibrated the kerf for V/2 in the foam management menu? The purpose is to get correct results for tapered wings.

Gilles

Quote:
Originally Posted by Domeno View Post
Hi,
I am hoping someone can help point me in the right direction.

I am running gmfc on my 4axis wire cutter using a hobbycnc board going through a gmfc v2 board to usb and control the wire heat.

I have calibrated both while and blue eps foam by setting the lowest heat to cut the foam for a number of speeds as well as set the kerf compensations until I get pretty accurate tapered rectangular shapes cut.

My problem is that when I then try to cut a wing with a tapered airfoil, the smaller end always appears to be cut way too hot. To the point where the foam is actually distorted by the heat.

I have tried various types of wire and see the problem using most of them. Currently I am using 0.5mm nichrome, but it has happened on finer gauge wire as well.

Here are some specs in case they help diagnose my problem:
Distance between cutter axes is 1m
Wing being cut has 160mm root, 76mm tip and panel length is 520mm
Speed of cut is 3mm/sec
Computed heat at this speed is 44%
Voltage to wire is 36v

Any help would be welcomed. Please let me know if a pic of the problem would help and I could post one.

Thanks,
Domenic
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Old Sep 03, 2012, 05:04 PM
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Australia, VIC, Melbourne
Joined Apr 2001
60 Posts
Hi Gilles,

I used the tapered rectangle project that came with gmfc to calibrate the kerf. One side cut a rectangle half the size of the other side. I managed to get accurate results in the rectangle sizes.

I did use two smaller blocks at either end of the panel rather than one full block, to save on foam. Could this cause inconsistencies?

Thanks,
Domenic
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Old Sep 04, 2012, 06:48 AM
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BMtech's Avatar
Kurrajong Australia
Joined Jul 2005
1,457 Posts
Hi Dom,

as Giles said you need to adjust the V/2 kerf , cutting blocks gets you close but there is nothing like cutting full span panels to get it set up

It just takes time, adjusting the temps ,kerf & speeds till you get what you want . your speeds ,temp & voltage look good to me what currant are you running at 2amps or so ?

I use .016'' SS fishing leader with 18/20kg tension as my power supply doesn't have enough grunt to run thinner Nichrome wire

wings with hight tapers can be problematic at times, I tend to cut with a lot of kerf & some extra length so it can be cut off after doing the foil cut

hope that helps

Rick
Off the Edge Sailplanes
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Old Sep 11, 2012, 04:24 PM
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Australia, NSW, Warriewood
Joined Oct 2011
295 Posts
Quote:
Originally Posted by gm.cnc View Post
Hi Grant,

The problem is located in the motor interface. Which one do you use?

Gilles
Hi Gilles
In regards to my timer value problem, I am using a Hobby CNC controller board.
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Old Sep 12, 2012, 02:51 AM
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France
Joined Feb 2006
282 Posts
Quote:
Originally Posted by Snowy170 View Post
Hi Gilles
In regards to my timer value problem, I am using a Hobby CNC controller board.
I assume that it's an old Hobby CNC board with a timer. I think that the timer value was 8Khz, so 125micro second is the right value.

Gilles
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Old Sep 12, 2012, 02:55 AM
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danfield's Avatar
Fullerton, CA
Joined Nov 2004
1,824 Posts
Quote:
Originally Posted by Domeno View Post
Hi,
I am hoping someone can help point me in the right direction.

I am running gmfc on my 4axis wire cutter using a hobbycnc board going through a gmfc v2 board to usb and control the wire heat.

I have calibrated both while and blue eps foam by setting the lowest heat to cut the foam for a number of speeds as well as set the kerf compensations until I get pretty accurate tapered rectangular shapes cut.

My problem is that when I then try to cut a wing with a tapered airfoil, the smaller end always appears to be cut way too hot. To the point where the foam is actually distorted by the heat.

I have tried various types of wire and see the problem using most of them. Currently I am using 0.5mm nichrome, but it has happened on finer gauge wire as well.

Here are some specs in case they help diagnose my problem:
Distance between cutter axes is 1m
Wing being cut has 160mm root, 76mm tip and panel length is 520mm
Speed of cut is 3mm/sec
Computed heat at this speed is 44%
Voltage to wire is 36v

Any help would be welcomed. Please let me know if a pic of the problem would help and I could post one.

Thanks,
Domenic
Hi Domenic

Just tossing out some stuff here as "I" see it.
1. .5 mm is pretty big wire, nice for Big Blocking Bows. IMHO, Nichrome sucks but many use it. If you can get your hands on .012 Inconel (.3048mm ) I think you will be much happier. A bigger wire gives off more Total Heat which has to go somewhere, usually as the wire goes around the LE the rising heat sucks down the core and it all goes bad from there.

2. I see you say 44% and 36v's. Calculated that should be you have around 81v available from your power supply. You don't say how long the wire is though, do you ever need 80 v's? First you need to be careful but you probably already know that. Reason being, GMFC controls voltage in whole numbers, 44, 43, 42... A 1% difference means .8 v's is the increment for each percentage. IF you can dial down the power supply to say even 50v, the increment becomes .5v. Just saying maybe you drop a percentage and that might be too much and getting wire drag so you go back up.

Or, plan B: If the increment is too large, the vary the speed slightly. Drop 1% heat and maybe 2.9 or 2.8mm/s would work instead.

Plan C: If you're having problems another answer is to slow down. I hate going below 3mm/s but sometimes you have to. Nor do I go above 3.5mm/s anymore, that's another story. 3 to 3.2 is my favorite.

3. Your core of 160/76 is a bit greater that a 50% or 2:1 taper. You're in a grey area as 50% or less is pretty easy, above runs into to issues like you're having. Like the Jet high taper guys. Usually the answer is split the core in half and glue together after they are cut.

An alternative might be worth a try,,, as with real thin DLG tails, it's very helpful to add an inch ( 25mm or so ) to each side of the core block, cut the core and trim off both sides. In your case, you might try adding 25 mm's just to the tip side and trim that after the core is cut.

4. You didn't mention what Kerf values you are at. I would like to know where you're at. Many cut too hot and chase perfection with Kerf rather than being close to the default Kerf(s) and chase with Heat/speed. 36v's sounds like a lot but I don't know how long the wire is. Wire supports at 1 meter, so the Bow is what, 1.2 M maybe?

If you can wait and I don't know if he ships Internationally, but you can get .012 Inconel in small quantities at aerowright's,
http://webpages.charter.net/mnemesh/
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Old Sep 12, 2012, 03:15 AM
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Fullerton, CA
Joined Nov 2004
1,824 Posts
Quote:
Originally Posted by Kevin Matney View Post
This what he said
hi everyone! 'm new here and would love to remedy a doubt. I would use the gmfc with 4 tb6560 driver and a bob. I would use the bow with manual control, I have a bob design with timer, I wonder if it will work with gmfc, and if there is any error. thank you
There's been some personal emails sent already. It is assumed this Break Out Board works with the paired Controllers to run his motors. Gilles suggested if he wants to build this board to also build the Timer on Gilles website. The "Timer" is some version of the 555 Timer, no clue what it actually does. A better solution is to use what works, or get a GGCv2 which is the best solutions allowing GMFC to manage the Heat is much better as well.

Timer schematic here:
http://gm.cnc.free.fr/CNC/timer_quartz.zip

Google translate:
Houve alguns e-mails pessoais enviados já. Presume-se esta Break Out Board trabalha com os controladores de pares para executar seus motores. Gilles sugerido se ele quer construir esta placa para também construir o Timer no site Gilles. O "Timer" é uma versão do temporizador 555, nenhum indício que ele realmente faz. A melhor solução é usar o que funciona, ou obter um GGCv2 que é das melhores soluções que permitam GMFC para gerir o calor é muito melhor também.

Esquemática temporizador aqui:
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Old Sep 20, 2012, 11:13 AM
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gregnapola's Avatar
Italy, Lombardia, Brescia
Joined Dec 2011
75 Posts
Hi there!

I have a few questions about foam cutting, not specifically related to GMFC...but I can't figure out what's wrong with my foam cutter and this is driving me crazy...

Here's my homemade foam cutter:



It's really rock solid , and there's no vibration and no play at all... 4 wooden blocks at the end of each axis make the screws rotating straight. I'm using it with GMFC for more than a year and it does its job perfectly...here's some of my works:









All is perfect... EXCEPT for one thing: I NEVER managed to cut Drela's Supergee wings!! Why? Because of this:



Every time I try to cut a wing panel for the supergee the lower surface is perfect, the top is a !!! It's FULL of big waves , and I cannot understand why. Every time I cut a panel I perform a test with two small blocks (one for the root and one for the tip) to verify if is all right:



and ...it is! Both airfoils are perfectly cut. Then...when I cut the entire panel waves everywhere!!! What the H**L ! is going on ?!?!?!?! I can't see the point....

P.s Waves disappear when I do the same thing with white EPS...and if I remove the foam block while it's being cut (with waves) the wire stops making waves.....

Any idea? resonance? Foam irregularity ?

Help me please, I'm throwing away a lot of foam because of this!
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Old Sep 20, 2012, 09:44 PM
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United States, MI, Monroe
Joined Mar 2000
861 Posts
Change the speed and the heat and see what happens
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Old Sep 21, 2012, 01:40 AM
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gregnapola's Avatar
Italy, Lombardia, Brescia
Joined Dec 2011
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Quote:
Originally Posted by Kevin Matney View Post
Change the speed and the heat and see what happens
Already tried....it changes the size and the "pattern" of the waves. I tried to change block position in Z and the wire tension but nothing happened....
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Old Sep 21, 2012, 02:10 AM
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gm.cnc's Avatar
France
Joined Feb 2006
282 Posts
Quote:
Originally Posted by gregnapola View Post
Already tried....it changes the size and the "pattern" of the waves. I tried to change block position in Z and the wire tension but nothing happened....
Hi,

If you get wawes, this means that the wire starts to vibrate. It usually means that the wire is too cold and touch the foam.

Gilles
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Old Sep 21, 2012, 02:43 AM
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Italy, Lombardia, Brescia
Joined Dec 2011
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Quote:
Originally Posted by gm.cnc View Post
Hi,

If you get wawes, this means that the wire starts to vibrate. It usually means that the wire is too cold and touch the foam.

Gilles
Thanks gilles! Maybe but....I can't understand why the bottom surface of the same wing panel at the same speed and the same heat (I haven't heat control on my board) is perfect. The waves are about 1 per second.... maybe because I'm using AC to feed the wire and this is causing resonance? Thie strange thing is that with other wing cores is all right with the same setup!
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