Re: [decoupe CNC] Getting started

I have the latest version of the software and the wings come out the right size if I add the "X" offset to the chord length. It is not too bad to deal with but it doesn't seem right. I have been able to get some good cores cut and I am happy with them.

I had to go to half step to get to motors to not miss a step. There is still enough power to work and it runs smother now so I like it.

Newest question.
Please tell me there is a way to cut a spar slot that is parallel with the trailing edge on a single taper wing.

Thanks,
Mike

----- Original Message -----
From: Dan Field
To: Mike Bailey
Sent: Tuesday, October 02, 2001 12:25 AM
Subject: Re: [decoupe CNC] Getting started


Mike
You didn't say what the core looked like other than short. Leading edge was ok, and the trailing edge was sharp?

Have you told CNC under project there is a "skin thickness"? If on the thick side, it will cut short.

Same problem with different airfoils? Thinking you may have a bad dat.file :-)

If that doesn't work then I am not sure what the problem is then. Adding extra will be a pain. If it were mine I would adjust the calibration of the lead screws.

I just reread your post...... do you have to add 20 mm no matter what the chord length is? I would think, though not sure, if a calibration problem of either steps or lead screw, it would be a percentage error, not always 20mm.

Are you sure about the amount of steps for your motors? This will change the distance traveled also.

Assuming X and Y motors and the lead screws are the same, check that the calibration is the same for x & y

Check over 400 mm, go to CNC configuration, decrease the number for "lead screw" until it is correct.

When you add 20mm to the chord, is the percentage thickness correct for the airfoil.

You might try a new download of the program.

That's it for now
Dan Field

----- Original Message -----
From: Mike Bailey
To: Dan Field
Sent: Monday, October 01, 2001 5:33 AM
Subject: Re: [decoupe CNC] Getting started


I was using the 20mm offset and had the wire 20mm from the foam. The difference in the wing length ended up being 20mm so I had to add 20 to what I input for the wing chord. This does not make sence but I can live with it. I have almost got the kerf set for the differend foam types. I am still trying to figure out how the cutting speed works. For not I have resolved to cutting test pieces untill I get the wing the right size. As I use it more I will learn all of the quirks.
Thanks for your reply.
Mike

----- Original Message -----
From: Dan Field
To: jbailey@...
Sent: Sunday, September 30, 2001 11:10 PM
Subject: Re: [decoupe CNC] Getting started


Hey Mike
Just a wild guess.... what did the core look like, did it have a nice trailing edge, or too thick. What I am getting at... I believe the default "offset" is 20mm. this means how far away the foam is from the wire at the start. So if you are putting the foam right next to the wire at the start, it would be short, in your example 19mm..... when you calibrate, do it over something much more than 20mm, you might have to fine tune it. Mine uses 6mm x 1mm all thread rod, with out looking, I had to tell the software something like .999 instead of 1mm per turn.

You want the foam away from the wire a little anyway, and you don't want the trailing edge to be cut twice, once up, then down. The hot wire will of course melt more in two passes. When doing tapered wings, that offset will have to be increased to make the angle also.

Plan "B",,,,,, If that doesn't do it. Watch your motors carefully as they turn over say 300 mm, watch for a missed beat or two. This one normally only show up on one side or the other but sometimes both. It was happening to me, as I had the minimun time between steps either too high, or too low for proper motor function. I don't know if this is correct, but I now set the time as high as I can, and still have motors that "sound just right". Play with the time, you will see.

No expert yet, still learning a lot.. buy some cheap 1 lb foam and cut samples.

That is all I can think of right now.

Dan Field



----- Original Message -----
From: jbailey@...
To: decoupecnc@...
Sent: Saturday, September 29, 2001 7:08 AM
Subject: [decoupe CNC] Getting started


I have just got my machine set up and am using the latest version of
the Muller software. I have tried to callibrate the kerf but I do not
know if I am supposed to enter the whole kerf ammount or half. With
the set zero page if I tell it to move 20mm it does. When I cut a
wing I told it the cord is 228 but it cuts the wing 209. I cannot
figuer out what is wrong.
Mike


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