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Old Dec 10, 2012, 12:35 AM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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How do I CNC cut a foam fuze from cross-section drawings?

I am interested in using a CNC Hotwire to cut foam sections of a fuselage with the aim of creating a full fuze to either modify and fly, or make a plug with to ultimately pull moulds from.

I have a set of accurate cross-sections and a 1/2 plan and elevation drawings that show me where each cross-section needs to be placed to create the full fuselage.

While I could probably get the result I need by cutting and filing the cross-sections out of 3mm ply etc, then using these as templates to hand hotwire each individual fuze section, I'm interested in using a CAD/CAM solution to run a 4 Axis CNC Hotwire cutter instead. I figure if I can get it to work, it should save heaps of time in the long run. As well as produce a really good quality cut fuze to either modify and balsa sheet/glass etc. to fly as is, or take the next step and produce moulds from for a full carbon/glass ship.

The added advantage is that once I get the hang of it, the possibilities are almost limitless as far as quickly producing different aircraft would be concerned.

My biggest dilemma so far is: what software to use?

There are so many CAD and/or CAM applications out there. 2D. 3D. Fuselage-specialist software. CNC capable... the list is almost endless.

And while there's a few threads around in RCG and elsewhere that broach the subject, a lot of them are fairly old and out of date with what's out there these days.

I've had a look at DevFus, DevFus Foam, DevCad, TurboCad, AutoCad and a few others. Both 2D and 3D.

The closest one to my needs so far seems to be DevFus Foam, which will generate a 3D sectioned model. The software can then export the cutting instructions for each section to something like Mach3, which will in turn run the CNC Hotwire to perform the cutting.

The only problem is, the software is going at it from the other direction i.e. start with a 3-view and end up with cross-sections.

I already have the cross-sections. I just need to load them into something that will allow me to orient them correctly and then arrange them at the spacing they need to be in order to create the final fuselage to scale. Each pair of cross-sections representing one cuttable fuselage block.

I'm hoping that there is someone out there who has already done this (or something similar) and who can point me in the right direction regarding what software I need to get to do the job.

Some of this CAD/CAM can be quite pricey, and often requires a steep learning curve before you actually start producing results. I don't need the massive power of something like AutoCad where I can design a whole football stadium down to the last nut and bolt. Just something reasonably priced with the capability of going from cross-sections to finished fuselage would be ideal.

I've thought of trying Profili2 - but using my own templates instead of it's vast list of airfoil choices. The principle would still be the same - a suitable aligned template at each end to cut a chunk of foam from.

Any recommendations, discussion, or advice would be most appreciated.

BJ
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Last edited by BJ64; Dec 10, 2012 at 03:50 AM. Reason: put "CNC" in the title - for clarity
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Old Dec 12, 2012, 09:40 AM
Launchpad McQuack
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Netherlands, Moordrecht
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BJ,

Been there, done that.

After trying several programs, nothing seemed to fit the bill. So I wrote my own spreadsheet which generates the G-code for the fuselage sections. It's really build for my own use, and not really user friendly.

But boy, does it works wonders.

















Vincent
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Old Dec 12, 2012, 11:52 AM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
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OMG!

How on Earth did you manage that, Vincent?

What a superb effort

BJ
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Old Dec 12, 2012, 01:14 PM
Launchpad McQuack
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Netherlands, Moordrecht
Joined Sep 2004
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Well, I'm quite at home with the CAD software Rhinoceros3D.
You've seen the 4 blocks of foam.
Each piece of foam has 4 cutting paths. (Fuselage outside, inside, and this on both sides of the foam block)

So I've drawn the 16 cutting paths in Rhino. The curves are then converted to points. The points coordinates are saved as a text file. This text file is opened in Excel, and the Z-coordinate column is deleted.
From here, the coordinates are saved as a text file again, but with .DAT file extension.

The DAT files are imported in the spreadsheet, and from there, G-code is created.

It is a lot of work, but very rewarding.

Tip: Please have a look at the great and free German software "SchnApps":
http://scehandball.de/SCHNAPPS/publish.htm

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Old Dec 13, 2012, 02:25 PM
Build it again, Sam!
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Germany
Joined Oct 2004
4,091 Posts
Cool!

Something like I did .... I set up a " virtual Cutting machine" in Rhino which ich place the part in and the machine then creates the g code file directly....

But same as with yours ... it works for me but is still not debugged

DIY Hot Wire Cut (1 min 13 sec)


and some samples...

TYPHOONxx (1 min 30 sec)


MIG 3 Maidenflight (1 min 9 sec)
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Old Dec 14, 2012, 04:37 PM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Just been having a play with DevFus Foam, and I might be onto something.

I'll have to do a fair bit of 'manual tracing', but it looks promising so far

Once I get the basics entered in, I think I can then edit formers and move things around etc.

Off to OfficeWorks to get them to scan the 2m long top and side profiles..

BJ
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Old Dec 14, 2012, 11:30 PM
Firecracker!
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San Francisco & Santa Cruz
Joined Oct 2004
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Quote:
Originally Posted by Prop-er View Post
Well, I'm quite at home with the CAD software Rhinoceros3D.
You've seen the 4 blocks of foam.
.....
It is a lot of work, but very rewarding.
Very nice! Vincent, I am very interested in this method of construction as well. Can you tell me what kind of foam you used? I've been using extruded polystyrene (like for bagged wings) and it changes shape after you cut it due to internal stresses in the foam. Thanks!
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Old Dec 15, 2012, 05:12 AM
Launchpad McQuack
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Netherlands, Moordrecht
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The shown plane is a prototype, and like you, I have used Styrodur. (XPS)
I'm switching to EPP soon, after I've changed the design to my liking.

I'm cutting with a razor thin (0,08mm tungsten from ebay) wire. For a block width of 40mm, I'm using only about 1 Watt of heat. Cutting speed is very slow (70mm/s)

When cutting a block from left to right, the upper part will deflect upwards due to heat deforming / internal stress. It hasn't been an issue for me so far. Wings and fuse are straight.
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Old Dec 15, 2012, 04:34 PM
Firecracker!
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San Francisco & Santa Cruz
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Thanks -- well maybe I'll just give it a try with the foam I have then...
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Old Dec 17, 2012, 08:21 AM
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Russia, Moscow, g. Moskva
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Originally Posted by Prop-er View Post
BJ,





Vincent
bravo!
this is a very good cutting quality.
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Old Dec 24, 2012, 08:21 AM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
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Merry Christmas and thanks for your feeback.

Amazing work that some of you have done - gives a fog-brain like me some hope

BJ
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Old Dec 28, 2012, 12:05 AM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Anyone been doing anything exciting over the break?

BJ
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Old Jan 02, 2013, 02:05 AM
The wheels touch down FIRST??
BJ64's Avatar
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What....no GREAT Chrismas prezzies... nada?

BJ
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Old Jan 02, 2013, 02:47 AM
Build it again, Sam!
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Germany
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Nothing I did not tell---- But already thinking about molds
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Old Jan 02, 2013, 04:56 AM
The wheels touch down FIRST??
BJ64's Avatar
Australia, VIC, Melbourne
Joined Jun 2009
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Just trying to get this Thread off Page 1 - sooo many pics to wade through... LoL

BJ
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