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Laser cut parts

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fly boy327/09/2018 12:46:27
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3535 forum posts
18 photos

Hi all, just received my first ever kit of laser cut parts, ribs, formers, etc. Very pleased indeed.Do I need to do any cutting to remove the parts from thier ply and balsa sheets ?, as they seem very tight, and could be damaged buy just pushing them through. Cheers

Levanter27/09/2018 12:48:55
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881 forum posts
436 photos

FB3

There will be little bridges of un-lasered wood. Cut these carefully and the parts should just drop out.

Levanter

Gary Murphy 127/09/2018 13:43:20
382 forum posts
14 photos

On a sidewards tack regarding laser cutting.

I have had a few "laser cut" and the cutting was not great, when you hear laser cut ,you would think near perfect.

I have noticed that on ply ,the cut was not entirely through and on thicker material the cut is not square.

I have just started buying some rubber powered wood kits, UGEARS is the brand. This as got to be the best laser cutting I have seen.

Not our branch of the hobby though

Peter Miller27/09/2018 13:51:40
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10313 forum posts
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I have had the odd laser cur kit of parts. Don't forget to sand off the black charred wood as it prevents the glue from working properly.

I prefer CNC cut wood.

Manish Chandrayan27/09/2018 14:19:41
606 forum posts
70 photos

Absolutely with you Peter!. Will take CNC routed parts any day over the laser cut yes

fly boy327/09/2018 14:26:31
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3535 forum posts
18 photos

Levanter, 100percent right, should have put my specs. on lol. Re Peters comment on C nC, could you please explain the difference to an old man. Thanks for charred wood cleaning info too. Cheers

Andy Meade27/09/2018 14:45:45
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2671 forum posts
681 photos

Both methods in fact use a CNC - a computer numerically controlled machine. The difference between machines is one uses a laser to burn or mark parts, the other is mechanically machined using a small router type bit to chase around the outline instead. Basically, a fast computer controlled milling machine.

 

Edited By Andy Meade on 27/09/2018 14:46:17

Manish Chandrayan27/09/2018 15:00:13
606 forum posts
70 photos

Yeah! the correct term is CNC routed parts

Bucksboy27/09/2018 15:57:15
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559 forum posts
106 photos

When I first started building from laser cut parts I was unsure how the charring would affect the glue. I tested numerous parts, some heavily charred, some sanded off. I then deliberately broke the joints, I couldn’t notice a jot of difference and consequently never bother about the charring, I glue them as they come. I use cyno a lot if this makes any difference.

John Stainforth27/09/2018 16:18:51
318 forum posts
38 photos

Generally laser cut parts are very accurate, but there are several problems.

(1) The cuts are very slightly tapered (narrower away from the laser), which means that many of the slots (in ply sheets at least) have to be filed slightly.

(2) The cuts are generally at right-angles to the wood, whereas as many of the cut surfaces need to be at slight angles from 90 to conform with the directions of spars and longerons etc. So this necessitates some sanding of the cuts in balsa or filing of cuts in ply.

(3) Most laser cut kits have a lot of tabs that fit into slots in other parts. These slots are designed to be the nominal thickness of the piece with the tabs. The problem is that wood thicknesses are *very* nominal, so that 1/8" sheets might actually come in thicknesses that vary from 0.12 to 0.13", say, and 3mm sheets of ply in thicknesses that vary from 2.8 to 3.2 mm, say. In the UK, balsa sheets are generally sold in fractions of an inch, and and ply in metric sizes, but I have found that sometimes the ply thicknesses are closer to the fractional inch sizes and v.v. for balsa sheets! This means that slots are often slightly too narrow or wide for the interlocking tabs. The slop in slots that are too wide is generally not serious, but the ones that are too narrow require some filing out, especially in ply pieces.

(4) The burnt surfaces. I am not convinced this is much of a problem with most modern glues. Anyway, by the time (1), (2) and (3) above have been dealt with, most of the cuts have had some filing or sanding that has removed most of the burnt surfaces.

So most laser cut parts require some (generally very minor) further "processing". When that has been done, everything fits together beautifully. Which is another way of saying that laser cut parts should always be dry-fitted together before getting the glue out!

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