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Author Topic: Laser Cutting Problem  (Read 414 times)
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rederfi
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« on: October 27, 2021, 09:40:09 AM »

Hi my friends,

Last year, I built a Rc plane using foam material. Now, I want to built a plane using balsa. But I have a problem. This site have a lot of beautiful plans. Firstly I feel we are lucky for that. But all plans are pdf format or converted jpeg to pdf. I want to laser cut balsa material. For this reason, I need CAD format.
how can i convert these plans to cad format ? or  How can I convert it to a format that can be laser cut?

Please help me.

Thank you
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Konrad
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« Reply #1 on: October 27, 2021, 09:53:54 AM »

Redraw the plans in a format that can be read by your cutter. I've use Corel Draw. Some have tried to use the raster function but this results in a lot of machine time and burned wood! It is best to stay with vector lines. This means you have to redraw the plans.
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pedwards2932
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« Reply #2 on: October 27, 2021, 10:10:32 AM »

I use Inkscape because you can pull a pdf in and then trace it.  Then you can save it as a .dxf or .svg depending on what your laser uses.  There are some auto trace programs but they are a bit sketchy and you have to clean up the trace.  For me it is just easier to trace the pdf.
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TheLurker
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« Reply #3 on: October 27, 2021, 10:44:02 AM »

I use Inkscape because you can pull a pdf in and then trace it. ...
+1   and the Bezier line tool is your friend.
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rederfi
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« Reply #4 on: October 27, 2021, 12:14:38 PM »

Thanks for reply. Probably, I should work a little.
 
So, Do you have a suitable plan for laser cutting of a trainer model? While learning these programs, I wammt to start the bıild of a model at the same time.

I'm waiting for your help
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Konrad
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« Reply #5 on: October 27, 2021, 12:22:17 PM »

I use Inkscape because you can pull a pdf in and then trace it. ...
+1   and the Bezier line tool is your friend.
Are you guys making a distinction between tracing and drawing with vectors (Bezier)? I'm saying that a bit map is not the desired way to use a laser program to cut. It can be used to etch but a bit map does not result in nice cut lines.
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Konrad
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« Reply #6 on: October 27, 2021, 12:25:43 PM »

Thanks for reply. Probably, I should work a little.
 
So, Do you have a suitable plan for laser cutting of a trainer model? While learning these programs, I wammt to start the bıild of a model at the same time.

I'm waiting for your help
Some great laser cut basic RC Trainers.
https://www.stevensaero.com/product-category/laser-cut-model-airplane-kits-balsa-wood/model-airplane-kits/radio-control-rc-primary-trainers/
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pedwards2932
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« Reply #7 on: October 27, 2021, 12:37:08 PM »

Konrad, Inkscape allows you to pull in the pdf then trace the pdf as a vector so you are just using the pdf to get the patterns.  You can save as a .svg which my craft cutter uses or a .dxf which my laser uses.  You do have to "flatten" the bezier curves before you convert to .dxf......Inkscape has a tool that will flatten the curves.
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Konrad
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« Reply #8 on: October 27, 2021, 02:51:44 PM »

Don't most drawing programs allow you to put a transparent sheet (layer) over another layer (pdf, jpeg, etc.) to allow this kind of "tracing". But in the end it is still up to you the user to trace with vectors (Bezier curves or other vector tools). This is still a lot of work (read hours of work). I'm not aware of any click conversion of a bit map to vector output program. My laser will cut a jpeg drawing if it the lines are one pixel wide. Adobe illustrator and Coral Draw does this without the issues associated with most open sourced code (read few undocumented bugs).
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TheLurker
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« Reply #9 on: October 27, 2021, 03:03:58 PM »

Quote from: Konrad
This is still a lot of work (read hours of work).
Nahh.  It's not that bad.  If you're just after a set of ribs and formers you can knock out the file for those in an evening*, perhaps two.   Depends a bit on the model.  A constant chord wing is easy, trace one rib and copy/paste as many times as required.  Tapered wings? Trace the largest rib and use the scaling tool to shrink each one in turn.  Once you've got the knack of it, it's not that slow.

Tracing and cleaning up a whole plan is a bit more time consuming. That can take a good long while depending upon how scruffy the original is.

Cheers,
Lurk

*My evenings for aeromodelling purposes are about 1.5 to 2 hours long.
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Konrad
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« Reply #10 on: October 27, 2021, 04:58:44 PM »

Going one step further one can import real airfoils rather than redrawing what is on the plans (often originally drawn around a Florsheim size 12 shoe by the kids working for firms like Comet models).

But to redraw a set of plans for a one time laser cut is counter productive by any measure of ones time.  (I can cut out a set of parts in less time with an optically driven #11 blade). It takes an inordinate amount of time to develop a nice clean set of cut files. Just take a look at how slow it is for a new kit to come from guys like Dave Cowell of DPC Models.
http://dpcmodels.homestead.com
These files have a lot more than just the OEM airfoils. They also often have improvements to the parts like the fuselage bulkheads and plans. With the amount of time it take to generate this level of quality in a cut file, it is highly unlikely that you will see a set of cut files given away or even sold!
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lincoln
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« Reply #11 on: October 27, 2021, 07:15:52 PM »

On Outerzone and Aerofred there are some trainer plans that I think are in various CAD formats. Also pdf vector, whatever that is. Unfortunately, it's frustrating to find them. Aerofred has an alleged CAD file for the Telemaster 400, though IMHO it's a bit small unless kept light enough for a motor smaller than a Speed 400. Outerzone supposedly has a CAD file for the RCM Trainer. I think that one might be a bit heavy and fast, though my guess is that it would be fine if lightened up enough. I'm sure their are others, but it would take work to find them.

Any reason you don't want to build a kit? There are some decent ones out there. If time, money, and emotional investment don't matter, Sig's Kadet Senior is really easy to fly. But I bet they do. Maybe the smaller one is good. An electric motor in their Riser might make a good trainer. Their LT planes, which I've seen, but not flown myself, are probably good. Their Kadet Mark II, IMHO, is a bit heavy and fast, but might be good if put on a diet or in windy areas. I don't know if you can get them any more, but I remember Great Plane's PT 40  and Goldberg's Eaglet 50, which I built and flew myself, as good trainers. I'm not really up on the latest, though, because I haven't been training many power fliers lately.
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TheLurker
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« Reply #12 on: October 28, 2021, 01:44:17 AM »

Quote from: Konrad
Going one step further one can import real airfoils rather than redrawing...
Yes, you can even write your own software to generate the section files,  If you poke around in the gallery you will find an example complete with a library of ready-rolled sections, but if you're after "originality" then tracing it is.

Quote from: Konrad
But to redraw a set of plans for a one time laser cut is counter productive by any measure of ones time.
Is it?  Depends entirely on your motives and requirements, it's the sort of thing I'd do.  Anyone thinking that doing something "by computer" will save him or herself time is mistaken.  The time saving is made by others who use the results of your efforts.

Quote from: Konrad
It takes an inordinate amount of time to develop a nice clean set of cut files. ... bulkheads ...highly unlikely that you will see a set of cut files given away or even sold
Sorry, but a clean set of files will not take an inordinate amount of time, especially for an established and proven design.  Bringing a product to market usually involves more than just creating the cut files.  Test builds, repeated test builds for new designs, build notes, packaging, marketing etc. etc.

Bulkheads?  See my point about tapered wings above.  Even better, they're symmetrical so you only need to draw one half and you can copy/paste/flip for the matching half.  No,not slow at all.

Not given away or sold?  Why not?  If you're not running a business why wouldn't you?  People draw up and give away plans all the time, cut files are merely extensions of a plan.

Apologies to the OP for the thread hijack.
Lurk
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Konrad
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« Reply #13 on: October 28, 2021, 08:39:20 AM »

Thread is not hi jacked.  We are discussing the merits of cut files and their limitations.

Lofting fuselage cross sections is not a function of scaling, well not usually.

You are correct in that time valuation is a personal thing. That is why I say for a one off production it is much faster to use a #11 blade. I assume the OP wants to build from a set of plans rather than develop the skills to make cut files.

I have access to a laser and if a cut file is not available I often prefer to use the #11 blade and jig saw to make low count parts. It is just faster and a better use of my time.

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rederfi
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« Reply #14 on: October 28, 2021, 01:10:28 PM »

Thanks for your valuable comments.  First of all, I will not use the plan for any commercial purpose.  There are many plans in PDF format, but I can summarize the part that I do not understand.  usually there are 1 or 2 pages of documents and all parts are drawn on top of each other in these drawings;  that is, how many pieces of each piece I will cut, and there is no clear drawing of all the pieces.  The plans are so complicated and I can't perceive them because the pieces are on top of each other.  I am having this problem as I am a novice.
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TheLurker
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« Reply #15 on: October 28, 2021, 01:45:29 PM »

Quote from: rederfi
...how many pieces of each piece I will cut, and there is no clear drawing of all the pieces. 

OK, if you can pick a plan that you are having trouble understanding perhaps we can, and I can't think of a better way of putting this, translate it for you.   We often forget that reading a plan is something you have to learn and that there are standard ways of showing things that may not be clear if you have never built from plans before.

Cheers,
Lurk
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pedwards2932
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« Reply #16 on: October 28, 2021, 02:05:26 PM »

Another thing that is possible when you are tracing the pdf you can lighten up the model.  Very easy to add some cut outs in the ribs or lighten the formers towards the rear of fuse.  Especially if you are using old Guillows's plans.  I retraced a Guillows Spitfire that I had bought and was able to reduce the weight considerably (still was tail heavy but not near as bad as the kit)  The other advantage I see with this is if I really like a plane I have ready made cut files to build it again.  I have built about 6 Cloudbusters (lost a lot of them to trees or flying it out of the field.)
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lincoln
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« Reply #17 on: October 29, 2021, 03:38:27 AM »

Thanks for your valuable comments.  First of all, I will not use the plan for any commercial purpose.  There are many plans in PDF format, but I can summarize the part that I do not understand.  usually there are 1 or 2 pages of documents and all parts are drawn on top of each other in these drawings;  that is, how many pieces of each piece I will cut, and there is no clear drawing of all the pieces.  The plans are so complicated and I can't perceive them because the pieces are on top of each other.  I am having this problem as I am a novice.
Sounds like the kind of plan they used to have in Modele Reduit d'Avion (MRA). Those can be pretty confusing, and I've done mechanical drawings professionally. If it's too frustrating, there are plenty of plans that aren't like that. It might help if you showed us which ones you're considering.
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rederfi
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« Reply #18 on: October 29, 2021, 04:21:45 PM »

Let me show you a few examples of trainer models I want to build.


https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=7414
https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=8811
https://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=8815


But, When I download the plans here, I see that they are not suitable for laser cutting. I can't start building a balsa plane as I don't know how to convert it to the proper format . I wanted to present these examples to you.

Attached files Thumbnail(s):
Re: Laser Cutting Problem
Re: Laser Cutting Problem
Re: Laser Cutting Problem
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lincoln
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« Reply #19 on: October 30, 2021, 12:40:08 AM »

Although I didn't examine them closely, those look like acceptable trainers to me. One thing to keep in mind is that ground handling will be easier with tricycle gear. Somewhere, I ran into a link for a short kit of a  Junior 60 with tricycle gear. I can probably dig up the link. I've got some others, too.  THere are a bunch of small outfits that make short kits or kits for an unbelievable number of models out there.

Of course, if you want to figure out how to turn plans into cut files, that's another story. I could probably figure out how to do it for myself, but others have far more expertise on that particular task.

BTW, if you just want rib sets of known airfoils, I have a copy of a program called Profili that will do that, with spar notches, etc. I think it may even export to dxf. If you're pretty sure what you want, let me know.
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TheLurker
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« Reply #20 on: October 30, 2021, 04:02:27 AM »

Quote from: rederfi
The plans are so complicated and I can't perceive them because the pieces are on top of each other. 
OK. We'll try to explain how to read a plan.  I apologise in advance if what I say is already known to you.  We'll make start with a couple of fragments from the simplest plan as that has the fewest formers and rib shapes.

Each part shape is usually labelled, for example rib W2.  You find where it is used on the plan and count how many times it is used.  That will give you the number of parts to cut.  To cut the parts trace the shape from the plan and make a plywood or even thick cardboard template (pattern) from it and use that template to cut the parts from the balsa sheet.  There are quick ways of cutting many ribs of the same shape, but we'll talk about that later.  The same is true for fuselage formers.

A plan will often show parts drawn with dashed or dotted lines.  This is because they lie under or behind another part.  Until you've had some practice it can be difficult to interpret this

On some plans only one half of a symmetrical component is drawn to save space.  On this plan only half of the wing has been drawn.  You are expected to copy the drawn half and flip it over to give you the mirror image part.  Very easy these days with photocopiers.

Have a look at the attached fragments and see if it is a bit easier to understand now.  After that, go back to the plan and study it and where you don't understand it come back here and we'll try amd explain what the plan is trying to show.

You should also know that even when you have built many models that you will still need to study a plan in detail to understand how the model should be built

As Konrad says, you really don't need a set of laser cut parts to build a model and almost certainly not for this example.

Cheers,
Lurk


Attached files Thumbnail(s):
Re: Laser Cutting Problem
Re: Laser Cutting Problem
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