Originally Posted by danfield

Yes you should have and glad to see you are a Happy Camper once again.

Thanks for the help Dan.

Nauga,
power cored

Hi Everybody,
I have been using GMFC for a number of years, its great software am always learning something new or a different way to do a cut.

But the other day I cut a scale glider wing for a friend, the half span was 2400mm and my table can only cut 990mm wide, usually I split the pannel in the cut menu if they are too big
but this time I wanted to split the wing pannel into 3 sections with a different root profile and tip profile.
I couldnt find a way of doing this in GMFC, so the question is, can this be done, as in split the current pannel into more than 2 pieces ?

Thanks, Kev

Certainly and more than one way to do it. Since you already have a "project" set up with your dimensions, root and tip airfoil, sweep and anything else you want to do except it is one panel. So, I would...:

First "View" select also Wing View so you can see the panels.

Back to the Main screen, click Project/ panel management/ split current...
IF you want 3 equal pieces, first split 33% or uncheck % and enter length.
Current panel is always in Blue, click on the outer panel if not already Blue
Project/ panel management/ split current again but this time 50% and you should now have 3 equal panels.

Again "Current" panel is always highlighted Blue, if you want new airfoils at the intermediate chords, just enter the project and select and change the Tip airfoil of the first panel, OK,, select the middle panel and change the Root airfoil to match the Tip of the first panel. Same for the Next panel break.

When you "Split" the panel the intermediate chord length and a Blend of the original Root/Tip airfoils were auto sized for you.

Plan B - The above method would or should be the easiest but you can also Build your planform first panel, then Panel Mgt, Add to Current but this way you have to figure out Sweep and the new Tip chord.

When cutting, back to the Main screen and just click on the Panel you now want to cut.

Thanks Dan,
plan A would be the way to go, I used plan B to cut then glider wing and had to use CAD to sort out the sweep and the cords.
Next time will try the split current way.

Cheers Kev.

Hi everyone,

GMFC version 3.90.2 is online. There are many bugs corrected everywhere.

For GMFC Expert, the main novelty is about new functions for spar
alignment in separated cutting.

Enjoy,

Gilles

I've read the GMFC help files and searched through this thread and also googled, but still a little confused about kerf correction. I guess I'm a slow learner

Q1) In GMFC, under foam management, where it asks for "Kerf for speed S", is speed S the same as the "Max Speed" on the same dialog ?

Q2) Should the kerf measurement at speed S/2 be done with the same heat % as the kerf measurements at speed S ?

Q3) If the previous question is true, then how does GMFC decide what kerf to allow for when running at a different heat % (or does it always cut with the heat % specified for speed S) ??

Thanks for any guidance.

Originally Posted by Geoff_S

I've read the GMFC help files and searched through this thread and also googled, but still a little confused about kerf correction. I guess I'm a slow learner

Q1) In GMFC, under foam management, where it asks for "Kerf for speed S", is speed S the same as the "Max Speed" on the same dialog ?

Yes, that's the speed at which calibration is done. Try to select a speed that maches the max speed at which you will be cutting

Q2) Should the kerf measurement at speed S/2 be done with the same heat % as the kerf measurements at speed S ?

You have do that using rectangle profile whose tip is half the size of the root. The tip will be cut at S/2

Q3) If the previous question is true, then how does GMFC decide what kerf to allow for when running at a different heat % (or does it always cut with the heat % specified for speed S) ??

That depends if you are using the "computer controlled mode or not". In computer controlled mode, you also have to do calibration at a low speed so that GMFC has a line with the heat for differing speeds.

I know I should do a video tutorial... but that's not easy...

Gilles

Originally Posted by gm.cnc

That depends if you are using the "computer controlled mode or not". In computer controlled mode, you also have to do calibration at a low speed so that GMFC has a line with the heat for differing speeds.

Maybe this is my problem - I am using computer-controlled heat, but can't see anywhere to put a second kerf measurement ?? Screen shot below is from my computer:

Originally Posted by Geoff_S

Maybe this is my problem - I am using computer-controlled heat, but can't see anywhere to put a second kerf measurement ?? Screen shot below is from my computer:

You don't have to enter a second kerf measurement, only a second heat value.

The kerf should be the same as the previous one, if heat is correctly adjusted.

Gilles

Sorry, forgive my stupidity, but where do I enter the second heat value - at the "min" speed ?? Does min speed need to be S/2 ??

The help file, under Foam Management, says also "Note that the kerf is always the same whatever the heat value" - I really don't understand what this is trying to say.

Perhaps I'm making this more difficult than it really is....

Hi Geoff

I would suggest to uncheck that Computer Controlled box, learn to use a single speed/heat first before trying this option. Much easier and less confusing.

You have back in Table Config a box "Hardware interface with heat acquisition", such as an MM2001 or a hobbycnc foam pro board or any board with a GGC interface this allows GMFC to control your heat.

Many think because they have such an interface they ALSO have to check this computer controlled box in Foam Library for GMFC to control the speed/heat.

Gilles promised to put this on the "TO DO" list years ago, change the name of this box to some thing else, like Computer Variable Speed/heat or something that describes what it does. :-)

Unchecking "Computer Controlled Heat" in the Foam Library and now you have just one speed one heat percentage to worry about, GMFC will still control your heat.

This function can be useful with a slow machine as you set up a Max Speed AND a low speed. IF your machine can't cut say a taper at the Max speed , GMFC will auto calculate at what speed/heat the machine can cut at, somewhere in between what you say is the Max and the Min. Problem is, it's difficult to get right over the entire max/min range you choose.

The max speed is wire speed through the foam. On a Taper or a taper with a narrow panel on a wide machine, the root side motor has to go much faster to maintain the wire speed, if your machine can't go faster or as fast as needed, GMFC will give you an error to speed up "X". Well, you can't as it's going as fast as it can already. You have no choice but to use a slower cut speed. OR, you set up the variable speed/heat you are trying to do now and GMFC will automatically lower the cut speed.

I don't know what the max speed of YOUR machine is. I would recommend no more than 3.5 mm/sec even if your machine will go faster and you have enough wire power. 3.2 to 3.5 is a nice speed, not so slow like watching paint dry and not too fast which can cause errors in the profile with some foam types.

Assuming your wire diameter is around .012 to .014, leave the default kerf values at .8 and 1.5 ( because it works well ) and adjust the heat to that first and only change the Kerf if you find it is needed rather than adjust the kerf to some heat value. Most seem to cut too hot and then adjust the kerf up to compensate. Too hot can cause issues usually on the tip side.

IF you are set on using this option, Gilles is telling you the Kerf Value remains the same for both Max and the Min. You have to find the correct percentage of YOUR machine at both the Max and the Min.

So how are you going to do that. One way is...

You could uncheck the box, I see in the pic you have selected 4 mm/s and 70%. I assume this works for you. So set up a Foam Type with this setting, 4mm/s and 70% and test that. Set up a new foam type and use 1 mm/sec, now find the percentage with the same default kerf value that works with testing . Let's say it's 30% of your available power, then set up one more foam type and now check the box and enter it exactly like the picture you provided for an example. :-)

In theory, if your 4mm/sec at 70% works, then 2mm/sec should be very near half the heat or 35%. At least that gets you close for further testing.

Originally Posted by Geoff_S

Sorry, forgive my stupidity, but where do I enter the
second heat value - at the "min" speed ?? Does min speed need to be S/2 ??

Yes, you enter it in the min speed.

The min speed is a speed which will be used for slow cutting. In fact it should be labeled slow cutting speed.

The help file, under Foam Management, says also "Note that the kerf is always the same whatever the heat value" - I really don't understand what this is trying to say.

Perhaps I'm making this more difficult than it really is....

If the heat is correctly setup, you will find that the kerf is always the same whatever the speed. These are value for the root.

You are making a confusion with the kerf at tip for a chord/2 and then Speed/2

Gilles

Originally Posted by danfield

...IF you are set on using this option, Gilles is telling you the Kerf Value remains the same for both Max and the Min. You have to find the correct percentage of YOUR machine at both the Max and the Min.

Ahh, thanks Dan, I think I get it now. The above sentences were the key. I had been slavishly following what the GMFC help file said about adjusting the wire heat ("right heat value will be found when the foam block is closed to be moved by the wire, but still does not move") without realising that the real objective is to tweak the heat values that ensure the kerfs at the min and max speeds are identical.

Just one closing question about "min" speed then. Is there any benefit in choosing a min speed which is much less than half of max speed, given that it is very difficult to cut a wing with taper ratio greater than 2 ?

Originally Posted by Geoff_S

Ahh, thanks Dan, I think I get it now. The above sentences were the key. I had been slavishly following what the GMFC help file said about adjusting the wire heat ("right heat value will be found when the foam block is closed to be moved by the wire, but still does not move") without realising that the real objective is to tweak the heat values that ensure the kerfs at the min and max speeds are identical.

The real objective is the one described in the GMFC documentation. But you will find that is you adjust heat correctly, then the kerf value is always identical.

Just one closing question about "min" speed then. Is there any benefit in choosing a min speed which is much less than half of max speed, given that it is very difficult to cut a wing with taper ratio greater than 2 ?

These are not directly related. The max cutting speed is related to the shape of the project and the bloc placement. You will find that some projects can't be cut at a speed higher than 0.5 mm/s.

The next version will come with better names for the foam dialog.

Gilles

Originally Posted by danfield

Thought I would post a pic of the "Kit", I know I like to see pics.

GGCv2 on the left of course.
1 ea Backlit in Blue Large character 16x1 LCD
3 ea Toggle Switches
3 ea Push Buttons
3 ea LED's, Red, Yellow and Blue
1 ea Double ended for 2 ea 14 Pin Flat Ribbon connector. 18" Lg, you cut to length you need.

Regards
Dan
Update: Also now included.
1 ea 2K resistor - Needed if the Text is too bright.

2 ea 180 ohm 1/4 watt res. for the Yellow and Red LED's
1 ea 100 ohm 1/4 watt res. for the Clear LED, that is actually Blue

Do you think the GGCv2 will work with Mach 3 and a HobbyCNC 4 Axis pro board? I don't relish the idea of building another machine and hobbling it with a 32 bit copy of Windows 7 that won't see over 4 gigs of ram just to run an LPTx port... Saves me putting up a second PC and controller since my table converts to a Mill...