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CO2 laser - the learning curve


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Hi all,

 

Rather than clog up the Emblaser thread (or indeed, anyone else's thread) with stuff that's "almost relevant", I've started this thread. Please feel free to add anything about laser cutting, emphasis on gas lasers.

 

I'll cross reference where I think I should, please do so too if it helps. There's clearly a load of carry over between the machines.

 

Best

Simon

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Ok, so Phil (Brush Type 4 / Intentio) suggested that I do some proper trials, this was a good idea, and good discipline.

 

So I did, herewith some very boring photos.

 

post-20369-0-71274700-1460142090_thumb.jpeg

 

Brickwork, at speeds ranging from 150 to 300 mm/s, and currents ranging from 5 to 25mA, etched into MDF.

 

I made a mistake in my post about currents on the Emblaser thread - the meter only goes up to 30mA and when it's turned up full, it only does 25mA

 

Anyway, good results at 150/15, 200/20 & 200/25, 250/15 & 250/20. Even at 25mA 300mm/s seems too quick. Logically, you want to run as fast as you can (it takes over an hour to do an end panel) so 250/20 is looking favourite.

 

post-20369-0-02603100-1460142409_thumb.jpeg

 

Cutting, 2mm MDF. Various speeds & currents. Cleanest front at 15mm/s and 5mA, but it doesn't cut through. Best single cut, 10mm/s & 5mA or 5mm/s & 3mA. Slower and/or more power causes scorching, and a wider kerf.

 

post-20369-0-88668000-1460142666_thumb.jpeg

 

post-20369-0-08567700-1460142734_thumb.jpeg

 

post-20369-0-68714300-1460142777_thumb.jpeg

 

Multi-cut. Here I have to thank the Emblaser boys, as they only have 4W to play with - thus multiple cuts seem to be the order of the day.

 

I tried 10mm/s 3mA single and double cut, and 15mm/s, 3mA, single, double & triple cut.

 

The kerf on a 15mm/s triple cut is about 0.3 - 0.4mm compared with about 0.6mm on the double cut at 10mm/s so that looks like the best way to get a nice clean cut. You can check the kerf by cutting a piece out, flipping it over, and pushing it hard into the corner of the hole from which it came - thus the numbers above are twice the actual value.

 

Finally, I tried to see what difference focus makes. Not surprisingly, as you get away from the "nominally correct" value, the fuzzier the line gets. Marginally. Half a mm seems to make little difference, but more than that is not good.

 

post-20369-0-19433700-1460143420_thumb.jpeg

 

Hope this is of some interest to someone!

 

Best

Simon

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Good work Simon,

 

Your kerf is related to the focus so try and keep the focus adjusted for the thickness of the material or you'll have unpredictable results. Incorrect focus will widen the kerf and the cuts will begin to be less than square. Not always a problem but can show up on exposed corners. 

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Thanks Phil

 

Yes, that was precisely where I was going...

 

I managed to source 25 A4 sheets of 2.5 mm MDF yesterday, so I'll have another go at the end walls, perhaps later today.

 

How much difference do you find the focus makes? There can only be one point where it is focussed, and obviously the material is not infinitely thin, so it must be out of focus somewhere in the thickness. I guess the "range of acceptable focus" is pretty much the same sort of effect as "depth of field" in photography. My experiment yesterday suggested that more than a millimetre out would cause an increase in charring, and presumably kerf, and presumably that wasted energy is not cutting, just heating up the burnt edge.

 

Having sorted out cutting tiles from card, I wonder if I can cut several layers at one pass... Again, the depth of field will be relevant.

 

Thoughts & experiences very welcome!

 

Best

Simon

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Wessex Pictures. A4 pre-cut.

 

Don't know if it's somehow tougher than the 2mm stuff I already had, but it didn't cut with 4 runs at 3mA. Need to do more ramp tests. Strange because it etched perfectly at 250/20.

 

And I lost the datum between the etch layer and the cut layer. Spent an hour turning MDF & electricity into smoke, and didn't get it cut through to try the brickwork to see if the combs worked. Very frustrating.

 

I suppose I have plenty of material to run the ramps on, so it's an ill wind.

 

Best

Simon

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Well, I did a bit more, and after cleaning the lens, I got very good, consistent cuts in 2.5mm MDF at anything above about 5mA. 8 - 10 seems pretty good. More causes scorching, less than 5mA and it doesn't cut through.

 

post-20369-0-60200000-1460563235_thumb.jpeg

 

This image shows the cuts from the top, in a scrap already-etched piece of MDF

 

post-20369-0-57039800-1460563259_thumb.jpeg

 

The point here is how very fine the cut on the back is.

 

I applied this to the boilerhouse of the engine shed. The etch went very well, but despite being turbo-careful about aligning the models in Newlydraw, if you look carefully at the corner, you will see that the brick etch and the comb-joint do not quite match. It's well less than a millimetre, but it is visible, and annoying, and I need to find out what I'm doing wrong. Still, looking promising.

 

post-20369-0-34285700-1460563708_thumb.jpeg

 

The slates were done before, I haven't yet experimented with multiple cuts, or pre-coloured card.

 

And having made a bollox of the ventilators, I just cut some sleepers and point timbers from the 1/32 / 0.8mm ply. You'll see that I put an "L" of MDF on the laser bed to provide a solid & repeatable location for the material being cut. I just lasered it out, and stuck it down with double sided tape. The sleepers came out fine, but the back layer doesn't cut cleanly.

 

post-20369-0-93516700-1460563777_thumb.jpeg

 

Hoping to get a repeatable etch & joint sussed out at the weekend, and to make another end for the building. Maybe I'll try a row of brick s***houses just to do something quick, first. :)

 

Best

Simon

post-20369-0-16672000-1460566594_thumb.jpeg

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Hi Simon,

 

those sheets have rather coarse toelances, maybe they are thicker as assumed? It can be a scaling problem too. If you cut an rectangle 100x100 mm, do the dimensions exactly matching the drawing? 

Maybe you can cut the slots a little deeper with a sawblade?

 

Very interesting thread btw.

 

Michael

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Michael,

 

The sheet thicknesses are pretty much bang-on, according to my digital very-near, as are cut sizes. It's pretty accurate.

 

I could use the laser cut lines as "marking out" and the use the fretsaw, but it seems a better investment of my time to get this to work properly. Have a look at the building corners that Giles has achieved on the Emblaser thread (and of course, the commercially available products, such as Intentio) and you'll see what I'm trying to learn to do.

 

It is advised to keep an eye on the laser whilst its operating - but I can be painting another model, or doing CAD work, or even machining bits for my Rob Roy whilst it chatters away to itself - and its straight lines are straight, whereas mine...

 

Best

Simon

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Hi Simon, I'm sorry you've got problems with registration. Would it help if I sent you the DXF for the brick sh*thouse for you to try? The only thing is that it's designed for 2mm MDF, not 2.5.

 

PM me if it's of interest.

 

Good luck!

 

Giles

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Hi Simon, 

my point was to "rescue" the already existing parts... My very first laserkit (a tramway loco) had 17 mistakes, but it turned into a built model after manual reworking of the parts, because I had paid for them... The second attempt on this kit was much better...

 

Michael

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Michael

 

thanks for the thought - I have a deal of experience of making scrap parts over the years, by hand, with a drill, mill, lathe, and now with the laser, I just acquired another (expensive) tool to do it ...  :)

 

The waste is frustrating, but it's about 50p and an hour for each sheet, and I rue the hour more than the 50p, so I think I'd rather not invest a further hour of time in trying to make a poor part better. 

 

I know it can work, the software is horrid (Newlydraw) but the machine itself seems really quite good, so if I can establish a method that guarantees that the product is as good as the machine is physically capable of, then I can whack stuff out, right first time, every time, from then on.  Of course, getting to that particular Nirvana is not without it's frustrations!

 

thanks again

Simon

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Well, a bit of good progress yesterday.

 

Firstly a huge thank you to Giles who kindly shared the DXFs of his brick built outhouses with me, this saved an hour or two of drawing, and I was able to split the etch and cut layers into a pair of files. Before I did this, I drew a border frame around the image (and trimmed it back to an "L" with 5mm legs at each corner), which was copied onto both the etch image and the cut image.

 

I then etched a set of walls, before doing so, I ensured the laser had been reset to its datum position, which for reasons best known to its makers is top left, and the settings are X= -87, Y=0. The etch went well. Giles had drawn and patterned a brick, as an actual discrete rectangle, whereas I had drawn my other brickwork as a series of horizontal lines, and then the brick vertical mortar lines as short intersecting lines. The laser doesn't seem to care, and the mortar lines in Giles' brickwork is barely wider than mine. It etches in the same time anyway.

 

Once the etch was complete, I opened the cut layer drawing, and deliberately drove the laser (off) to a notional position miles from the datum, and then re-zeroed it on the datum, measurements as above. And hit "cut". With some success...

 

post-20369-0-44768400-1460894968_thumb.jpeg

 

post-20369-0-79471100-1460895471_thumb.jpeg

 

Need to flatten the slates somewhat!

 

So I think I have overcome the datum error, and I think I've got reasonable settings for cutting 2 & 2.5mm MDF, so I think I can proceed with the loco shed without too many problems. It's pretty much drawn, though I've still got the smoke hoods to do, and some bits & pieces.

 

There's the small matter of a baseboard...

 

Best

Simon

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As an aside, and maybe worthy of its own thread, there are a number of NC (numerical control) controller boards available, to replace or upgrade things like that in my laser. Some of these would also work with milling machines too.

 

There are specialist forums:

 

http://www.laserscript.co.uk/phpBB3/index.php?sid=2e500f49590f3bd0d37923ac972cab1a

 

 

There are driver boards & software:

 

http://smoothieware.org/laser-cutter-guide

 

http://www.chriscircuits.com/p/products.html

 

http://redmine.laoslaser.org/projects/laos/wiki

 

 

If there's interest, I'll ask the Mods to create a separate pinned thread

 

Best

Simon

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I'm so glad you've got to the bottom of your problem - its infuriating when you can't actually use your tool to do a real job!

 

A bit of paint and a roof make the outhouse look quite nice -I'll have to finish one of mine!

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Giles

 

I cocked-up in that I got the slates a bit wrong on the side you can't see in the photos...

 

I'll transfer my slate DXF to a computer with email and send you the file.

 

The slates are probably too big for a less important building, such as a brick-built-bog, but you can scale to suit.

 

Thanks again for your help

Simon

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Question to those etching MDF: what's the thinnest wall you can achieve in 2mm?

 

I'm doing some window frames and 0.6mm seems to be the thinnest I can reliably leave without simply burning away.

 

Is this "top of the class" or "could try harder"?

 

Repeated post in other thread

 

Best

Simon

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I hope I'm not too far off topic, but a glance at posts in this area seems to  cover home lasering .

 

 I've been lasering various materials  for both  repro  vintage  rolling stock, locos and accessories and also parts for  vintage cars.

  Mostly lasering but some materials have  H&S issues so e.g canvas bakelite. was NC milled and sprig copper contacts was  water jet cut . But all using the same  DXF  programs.

 

 In metals I have  used  aluminium, steel, stainless steel, spring steel, brass, tinplate etc depending on the application.   Attached pic of an Exley portsmouth motor coach in O gauge, laser cut but not yet pressed.

 Laser cutting can also be used in some cases to make the dies.

 When I had recommended this to  Vintage car people in UK I invariably get an answer that they can't afford to by an industrial laser cutter and feel that large companies won't take small jobs.

 

 I  don't have trouble  getting large companies to do my jobs, Paying cash is a great motivator. And prices are  quite cheap.

 But these days there is no reason that  a laser cutting company needs to be nearby. I  draw my own programs on Design View , and ancient  CAD program, so old it was originally the floppy discs that were actually floppy, Probably on a clockwork computer.  But very easy for someone like myself with no computer experience.

 

 So they could be  emailed anywhere in the world,a quote returned by email,, payment made by credit card and the  job posted to the buyer. and from an Englishman's point of view, they can be done in a country where there are exchange rate advantages

 Aluminium as you can see cuts very well, and for extremely fine jobs like  instrument needles I  get brass  or stainless which give an extremely clean cut.

post-29065-0-36105100-1461924966_thumb.jpg

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Ed

 

welcome to the thread - there's another bunch of laser enthusiasts on the "Emblaser" thread - I have only had my laser for a few weeks, still getting to grips with what it can do (and cannot do) and how to do the former, efficiently.

 

very interesting that you can get metal cut reasonably cheaply, I would certainly be interested at some point in having a go at that.  How does it compare with etching?

 

best

Simon

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Ed

 

welcome to the thread - there's another bunch of laser enthusiasts on the "Emblaser" thread - I have only had my laser for a few weeks, still getting to grips with what it can do (and cannot do) and how to do the former, efficiently.

 

very interesting that you can get metal cut reasonably cheaply, I would certainly be interested at some point in having a go at that.  How does it compare with etching?

 

best

Simon

Simon.

 I suppose the difference in method between etching and lasering is that the DXF file provides a road map for the laser to cut, or to follow. 

 Price  varies by material being cut , thickness of material, how many " starts" [ it cost s a little more to start a new hole or cut]

 The company programmer will take your drawing [ program]  and put in starting points and presumably other tech factors to do with speed of cut.

 For small delicate items they sometimes will leave them attached by a small bridge which can be broken off by hand.

 The place I am currently using also does folding by NC, very accurately, actually extraordinarily accurately

 I just need to mark in the fold lines on the program.

 Like every thing in industry, the first one is the most expensive, in bulk they get very cheap.  From their point of view it takes the same amount of time to pull a sheet of stock out and set it up on the machine whether cutting one or one hundred.

 One needs to ask for ' display' quality if the company is also doing industrial work.. This is so the workers don't drag the material from stock and scratch the  surface... not a problem if  cutting structural items but annoying for instruments and models.

 I think lasering gives a cleaner square cut to the edge, compared to etching I've seen.

   Formers to press or fold  can often be lasered as well, depending on the design of what you are making.

 

 For making punches [ in this case the sides of Exley seats]  where I would need many, I had the 2 parts of the die hot wire cut. Amazingly precise. When I went to pick up the pieces I said ''you've forgotten to cut it  it's only been drawn on the steel.'' Then he pushed the 2 halves apart.

 Limits with lasering is that they generally can't cut a hole of smaller diameter than the thickness of the material. But they can  laser etch an 'X' at the centre point so you can accurately drill.

 

 Somethig to consider with home lasering is that the commercial cutters won't  cut plastics and synthetics if they don't know the composition.  This is because of the danger of toxic emissions. These  can,  as an alternative, be water jet cut. 

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Thanks Ed,

 

I work in a business that uses some of these techniques, so I'm familiar with the principles, but it's all big hairy-a***d stuff, using 2 & 3mm steel. Even thicker at times. Not really "0 gauge"! We've been surprised at how bad some of the stuff has been, I suspect this is more to do with weld-induced distortion than any fault in the laser cutting or folding, but disappointing (and very costly in terms of delays and test failures) nonetheless.

 

I'm interested in the application of these kinds of things to the model world - your interest in instruments is much more like modelling - so I'll look into pricing etc when the need arises.

 

The warnings about cutting plastics are important. There are some that are quite toxic, and some will emit chlorine which will knacker your machine, and your lungs! On a more useful tack, the CO2 laser is brilliant with acrylics, whereas the blue LED won't touch it, absorption at different wavelengths is different. On that topic, we were looking into laser welding of plastics at work. I wonder...

 

 

Best

Simon

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Thanks Ed,

 

I work in a business that uses some of these techniques, so I'm familiar with the principles, but it's all big hairy-a***d stuff, using 2 & 3mm steel. Even thicker at times. Not really "0 gauge"! We've been surprised at how bad some of the stuff has been, I suspect this is more to do with weld-induced distortion than any fault in the laser cutting or folding, but disappointing (and very costly in terms of delays and test failures) nonetheless.

 

I'm interested in the application of these kinds of things to the model world - your interest in instruments is much more like modelling - so I'll look into pricing etc when the need arises.

 

The warnings about cutting plastics are important. There are some that are quite toxic, and some will emit chlorine which will knacker your machine, and your lungs! On a more useful tack, the CO2 laser is brilliant with acrylics, whereas the blue LED won't touch it, absorption at different wavelengths is different. On that topic, we were looking into laser welding of plastics at work. I wonder...

 

 

Best

Simon

Simon

 Fitzroy Loco Works uses laser cutting for the tinplate parts on their locomotives. On the Cock o' the North , the driving wheels were laser cut initially,in steel. Then the treads and flanges turned, and a home NC attachment on the mill/ lathe  profiled the spokes to the finished shape. I have to say it was amazing to watch being done post-29065-0-12919700-1462067294_thumb.jpgpost-29065-0-10082600-1462067312_thumb.jpgpost-29065-0-67571800-1462067330_thumb.jpgpost-29065-0-53917600-1462067354_thumb.jpgpost-29065-0-56796900-1462067498_thumb.jpg

 Attached some pics of  2 locos in the bare tin , so to speak . These were prototypes or try outs and the final end products had more detail. These were not intended as fine scale models but rather to be in the Basset Lowke tab and slot style but incorporating modern technology in the manufacture.

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Thanks Ed.

 

Mmm. Laser cut spokes for wheels. Rim insulation (or not) with turned tyres... I wonder. Probably can make those difficult-to-find wheels, but it's only going to be easy if there are no generated forms within the spokes. I'm thinking of a chamfer to the inside of the rim, between the spokes. This drives you to a casting (or moulding) approach, which effectively mimics the original.

 

I'm not into the tinplate personally, though there's some lovely stuff available. Your models look superb.

 

Thanks for this eye-opener.

 

Best

Simon

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Thanks Ed.

 

Mmm. Laser cut spokes for wheels. Rim insulation (or not) with turned tyres... I wonder. Probably can make those difficult-to-find wheels, but it's only going to be easy if there are no generated forms within the spokes. I'm thinking of a chamfer to the inside of the rim, between the spokes. This drives you to a casting (or moulding) approach, which effectively mimics the original.

 

I'm not into the tinplate personally, though there's some lovely stuff available. Your models look superb.

 

Thanks for this eye-opener.

 

Best

Simon

Simon

 

 Being made for coarse scale tinplate [ although that definition can be a bit hazy at times] these were made for 3 rail running. The group here  being of the opinion that so called 2 rail is unlikely to ever  find acceptance and its use is confined to clockwork drive and steam.

 

 However when I first saw the driving wheel as laser cut and turned , I shared your reservations about spoke profile.   But after turning the tread / flange, they were placed in  an indexing chuck of an NC mill [ attachment to a hobby lathe/mill]. The  cross section of a spoke is , shall we say oval, and the mill bit ran along the side of a spoke and milled      that edge to the profile. Then returned down the adjacent side to complete that spoke . The wheel was automatically rotated the required number of degrees and the process repeated for each spoke until the wheel was complete.  During which the operator could go off and have a coffee.

 The counterweights which vary from wheel to wheel [ OK axle to axle] were laser cut to suit and  JB welded on . Avoiding the incongruous look of Ace , BL etc having the same size weights everywhere.

 

 On a more general note , I went to  a large international manufacturing expo at Jeff's Shed last year. Noticeably most displays were from Chinese companies. There was an impressive array of NC punching , 5 axis NC milling machines , 3 D printers etc.

 One company had beautifully made mill vises. My own is a pretty cheap ordinary  item and I asked the price of one of their large good ones. " $ 45 " he said and I thought " great I'll take one."

 But my brother who was with me said " How are you going to carry that home in peak hour on a tram?".

 

 As for casting, it's horses for courses.  Lost wax casting gives a wonderful finish, but different companies have different methods and results. The local manufacturing jeweller gets perfect results but is limited by size of their centrifuge. Although my wife likes that they regularly send their wholesale catalogue of gold  castings out.

 Pressure lost wax didn't have the size limitations but they cast in aluminium bronze and silicon bronze which was  extremely hard to work and they bead blasted the ceramic off rather than chemically dissolved it.

 I think it's a matter of knowing all the options available  and picking the one that suits that job best.

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