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Author Topic: Laser cutting UK  (Read 683 times)
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tctele
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« on: September 27, 2018, 03:53:55 AM »

Hi

Looking at getting some  ribs in 1mm balsa cut. Does anyone know who does this now in the UK and would I have to source the balsa and send.

Thanks in advance

Tony
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SP250
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« Reply #1 on: September 27, 2018, 04:26:20 AM »

http://www.belairkits.com/
https://www.sarikhobbies.com/
A google search threw up about two dozen more as well.
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tctele
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« Reply #2 on: September 27, 2018, 06:17:58 AM »

Thanks for looking I'll inquire. I did get some sheets cut about 6/7 years ago but can't remember who with unfortunately

Edit. You prompted my memory it was Leon from Belair and it was 9 years ago. Where did that go! Thank you
« Last Edit: September 27, 2018, 06:45:39 AM by tctele » Logged
Bryanair
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« Reply #3 on: September 27, 2018, 08:55:21 AM »

I was told by Belair kits that they will only laser cut from the customer supplied CAD files. 

I got the ribs for my latest project laser cut by SLEC.  I sent them the rib profile copied from a plan and they did the rest.  They supplied the balsa.  Very pleased with the results.

Bryan
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kiwibrit
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« Reply #4 on: October 26, 2018, 02:50:19 PM »

If you are on Facebook: https://m.facebook.com/groups/197778064270550. Tim Hobbins offers a bespoke cutting service from your drawings.
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DavidJP
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« Reply #5 on: October 27, 2018, 03:25:52 AM »

I too found SLEC very good - and in my view very reasonably priced.  They will do it from scratch (they have balsa mill by the way) or to suite you. 
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Buster11
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« Reply #6 on: October 27, 2018, 08:08:15 AM »

Could I make a slightly alternative view regarding laser cutting? I may be a bit of a luddite (moi? luddite??) but here's how I see it. Decent quarter-grain 5lb balsa is pretty rere now and if I want ribs cut from it I'll use a template and lay it out for each cut to use the grain of that wood as efficiently as possible. On an undercambered rib, for instance, I'll lay the template so that the grain follows the curve of the rear half of the airfoil, rather than having it run more or less diagonally across the rib and weakening it. From what I've seen of laser cutting it seems to regard the wood as a uniform material and takes little account of the grain. I'll stick to a scalpel, thanks.
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Andrew Darby
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« Reply #7 on: October 27, 2018, 09:44:34 AM »

The laser cutting has nothing to do with the grain direction, per se, so I don’t quite get your point Buster.  if you want specify the part cut at a specific angle to the grain that’s What you will get...

The other thing is that with laser cutter you don’t crush or damage the edges of the wood and cause weaknesses that way - like you can with a scalpel.  Also the level of detail than can be achieved even on very light wood is astonishing and well beyond even what the most talented can achieve by hand...

Andrew
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« Reply #8 on: October 27, 2018, 10:17:34 AM »

To be fair, I understand what Buster is saying:  that an under-cambered wing rib will be least wide and therefore weakest in its rear half, and therefore he'd prefer to lay out his own ribs so that the grain is straightest (i.e. parallel) to the centre-line of the rear half, with the consequence then of the front half of the ribs having a little more cross-grain.  I personally wouldn't worry about this though.

There are virtues in both methods, but if one is building from a trad plan then hand-cutting ribs is normally the only option.  Hand-cut ribs aren't necessarily a disaster of crushing etc - scalpel slightly oversize and sand each stack of ribs to size in a simple jig... n'est pas?
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Bryanair
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« Reply #9 on: October 27, 2018, 10:46:55 AM »

I don't really see the point of having ribs laser cut for small models.  Much easier just to cut out a ply template and cut the ribs with a scalpel.  Where I think laser cutting scores is with larger models.  My latest 45inch project with a chord of 170mm required 46 full ribs and 60 riblets and I preferred to let someone else laser cut these.
Bryan
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Andrew Darby
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« Reply #10 on: October 27, 2018, 11:19:40 AM »

To be fair, I understand what Buster is saying:  that an under-cambered wing rib will be least wide and therefore weakest in its rear half, and therefore he'd prefer to lay out his own ribs so that the grain is straightest (i.e. parallel) to the centre-line of the rear half

But you can yo this with laser cutting too, you can angle the part to whatever angle to the grain you desire, it’s the choice of the human that sets the machine, not the machine itself.  in this way it is no different?  Ie the grain direction has absolutely nothing to do with the process per se.

I understand what you are saying with the profile, cutting through paper does tend to crush the edges of very light wood though (and blunts your blade) but if you cut notches with a scalpel, then there is a tendency to overcut in the corners leading to a weak point, just right for a crack to start.

Yeah you are right Bryan, just this afternoon I am cutting out a few ribs on a little 20” span model, first thing was find some hard stuff to make a template, and 30 mins later I have a set of identical ribs...

It’s all a matter of what floats your boat, and on what scale/size you are working...  Grin

Andrew
« Last Edit: October 27, 2018, 01:01:35 PM by Andrew Darby » Logged

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bjrn
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« Reply #11 on: October 27, 2018, 03:27:28 PM »

One advantage of having a cheap low power laser cutter is that I can cut identical fuselage formers with the grain at 90 deg from 1/32 sheet to make stronger 1/16th formers which is handy for my grandson’s slightly heavy handed building attempts.
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DavidJP
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« Reply #12 on: October 28, 2018, 10:41:42 AM »

Yes all absolutely true.  Laser cutting has its place.  A generation thing I think. 

I am probably 20mins from SLEC but do not make a lot of use of their laser service probably because I am currently building smaller models and also because I have been cutting out parts for model aeroplanes the old fashioned way for probably 70 years. And it seems almost automatic.  But when I built a 10ft span Minimoa it would have been useful.  All of them were different. 

The hard bit is producing the software which I do not do  often enough to become proficient.  SLEC will do this very reasonably but I have the old boys hang up about building the model, but of course kits are no different from laser cutting are they: although I don’t build from kits much either.
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che
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« Reply #13 on: November 08, 2018, 07:01:56 AM »

I've had a few sets of ribs laser cut in the UK and it's not a trivial job. In all cases I supplied my own CAD files but these themselves presented problems for some, despite the basic points/curves coming from commercial aeromodelling plotting software.

I also had issues with different balsa thickness. With 5mm material, even with some 1.5mm, there was a noticeable angle to the cut face where, presumably, some attenuation takes places and I have also noticed that circular holes come out quite oval in some cases. You also have to define (or consider) if the laser cuts to the middle of the drawn line or the outside as there is a thickness to the cut that needs to be accounted for in some cases; oh and the cut face is of course burnt so are you prepared to sand afterwards ? .

Finally, the wood provided is never quite what you specified and yes, you need to consider grain directions.

However, cutting 1mm wood to a non-critical (ie non contest model) airfoil is likely to be very successful if you either supply the material or specify harder than you think you need. I would strongly recommend you getting the company/individual to cut some test pieces of the actual parts beforehand so you can assess the quality.

CHE
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pedwards2932
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« Reply #14 on: November 08, 2018, 08:44:17 AM »

I tend to build models more than once so for me the time I use to trace out the parts and make cut files pays off later.  When I have to rebuild from a crash I can easily use my cut files and have my low power laser to cut replacement parts.  I have had several of my Cloudbusters flyaway and in 15 minutes I have all the parts to build another. I am kind of computer geek so part of my kick for this hobby is using the computer, laser, and 3D printer.  Tracing out the parts takes the most time for me so if I was only going to build it once it might not be worth it but still you get to fire up a LASER how cool is that. Grin
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fred
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« Reply #15 on: November 09, 2018, 12:36:37 PM »

I've tripped across a rarely mentioned issue with Laser cut bits;
 Too soft /light wood.  Odd to find this an issue .. but when you do it's a hair pulling one.
 It's far simpler for the cutters to standardise on a single wood density..
..because there is one less variable to deal with in the machine's setup.
Ease of production .. far offsetting the slight light wood upcharge costs
  Result is slight to no  chance of appropriate densities /woodgrains being fitted to the parts' strength / function in the build.
 A small point? maybe.  
But not one I'm  willing to forego.  Besides  I find hand cutting bits.. oddly relaxing.
 
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Andrew Darby
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« Reply #16 on: November 09, 2018, 01:19:36 PM »

It's far simpler for the cutters to standardise on a single wood density..
..because there is one less variable to deal with in the machine's setup.
Ease of production .. far offsetting the slight light wood upcharge costs

Errr no, I can’t agree.  The wood is pretty variable, the price is the price, the cost isn’t in the wood per se, it’s in the time taken or someone to hand select it, if you want a specific grade.  VMC have to grade it into bands, it can be silly light or pretty darn heavy.  When I designed the kits for them I separated the parts into sheets where the parts sheets fit into these bands.  Lightest for the sheets with ribs and formers etc, the very heaviest for “non flying parts” like pieces for the wing alignment jigs for the bipes and nose parts where you know the design will require nose weight.  They really do wish it was only one density but that just isn’t the case.

I've had a few sets of ribs laser cut in the UK and it's not a trivial job. In all cases I supplied my own CAD files but these themselves presented problems for some, despite the basic points/curves coming from commercial aeromodelling plotting software.

I also had issues with different balsa thickness. With 5mm material, even with some 1.5mm, there was a noticeable angle to the cut face where, presumably, some attenuation takes places and I have also noticed that circular holes come out quite oval in some cases. You also have to define (or consider) if the laser cuts to the middle of the drawn line or the outside as there is a thickness to the cut that needs to be accounted for in some cases; oh and the cut face is of course burnt so are you prepared to sand afterwards ? .

Finally, the wood provided is never quite what you specified and yes, you need to consider grain directions.

However, cutting 1mm wood to a non-critical (ie non contest model) airfoil is likely to be very successful if you either supply the material or specify harder than you think you need. I would strongly recommend you getting the company/individual to cut some test pieces of the actual parts beforehand so you can assess the quality.

CHE


The cut face should be pretty square, circles round, curves correct and sizes good IF, the people operating the machine know what they are doing.  You (as the person supplying the CAD data) must check whether they will compensate for the kerf, or you need to.

It’s like any machine tool like a lathe.  If you don’t know your speeds and feeds and how to set it up you won’t hit the tolerances or surface finishes expected.

I deal with “proper” big boy laser cutting too, on thick(ish) sheets of steel etc, and file formats and the way they convert to the normally required .DXF can be a problem even from professional drawing and drafting packages such as solidworks.

Before typing this I went and fetched a random piece of my stash of scrap odds and ends that I blag from VMC.  The picture shows the edge of a piece of 3/8” thick medium density sheet.  As you can see the edge is perfectly square (the very end isn’t as it is where I hacked it off to take the picture!)

But this is because they spend a good amount of time properly maintaining their machines (such things as laser focus etc) and know how to avoid some of the pitfalls, and make them perform to a suitable standard.

The point being not all manuafacturers are the same even though their advertised process is.

Andrew
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