CNC theory help

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crash_out
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CNC theory help

Post by crash_out »

I've finally got all the materials to build my CNC cutter, but I'm having a problem understanding something...

When you load your images for a tapered cut, whether it's wing or fuse, is there any other way other than trial and error on each cut to determine how much to enlarge your image and where to position the foam to get your cut the proper size?

Did I type that so you guys can understand it??

My idea is that if you have your root and tip templates the proper size, then each axis will move according to the template...since the foam is probably not right up against your carriages, your wing is going to actually be smaller than your template or image size...is there a constant mathematical formula one can use to determine the % to increase your template size in relation to where your foam is actually going to be, or is this set up in the software itself? I planned on using the Foamworks software, but other than the online manuals and tutorials, I haven't actually used the program yet.
mark s
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Post by mark s »

Nick,

I use GMFC for my CNC foam cutter and all these settings are done in the software.

Thanks,

Roid
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o1moregil
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Post by o1moregil »

I use foamworks, you load your dat.(airfoil) then you tell it your span , root, tip size you want, and then ill tell you where to put the block.
crash_out
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Post by crash_out »

Great, thanks guys. I was hoping it would be handled in the software.
Hat Trick
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Post by Hat Trick »

Some people place the blank in the middle of the table and some position it on the left for a right core and to the right for a left core. I prefer the later. I use a piece of angle iron to be sure I get the core in the same place each time. To make the angle iron removable I put 2 screws into the table and drilled coresponding holes in the angle iron. I think it's more important to get the root right so the cores match up as well as possible. You don't really notice much if the tips are a little off!

As you figured out placing the blank in the correct place is important!
crash_out
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Post by crash_out »

I am trying to find a sheet or cover that is marked off in 1" grids to cover the table with before I set the machine up on it. I thought that would help greatly in placing the block, but so far I haven't found anything. Still have a couple of places to look.

The angle iron is a good idea, Mike, I hadn't thought of that. Yes, I was more concerned about the roots than the tips..I would assume if the software has your span and taper input, then as long as your root cut matched up, the tips should be close enough for government work.
THend
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Post by THend »

Check out a cnc wing cutter video somewhere. It is all handled in software. But, placing the foam properly is important, and is addressed when you go to the cut screen in GMFC if that is what you plan to use.

TH
crash_out
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Post by crash_out »

I assume when you are setting up your foam position in the software that you measure from the center of the drive screws, yes?
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o1moregil
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Post by o1moregil »

this is the way I do it in foamworks Nick, I measure it from were the wire starts, in other words the distance from tower to tower is really the wire distance, thats the way I been calculating it in foamworks and its right on the dime, Capish?
Vapor
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Post by Vapor »

You want to measure it from the attachment or pivot point of the wire.----------rick
THend
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Post by THend »

Distance is pivot point...

Foam placement is important...
crash_out
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Post by crash_out »

Ok. I was making the assumption that since the motor centerline was what was actually moving, that that was where you'd base your movement from. Now that I think about it, it does make sense that the attachment point of your wire would be the reference point...

Thanks for all the help guys!!
THend
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Post by THend »

You're getting there...

Keep asking questions, and we'll do our best to help.
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