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[malcf]

I have recently bought a laser cutter and have been experimenting cutting styrene sheet 1.5mm thick, it has cut ok for the most of it leaving a slightly raised edge to the cut, I have experimented with speed and power settings but it is still there and also on very narrow sections say 1mm wide it melts away, I have cut the same profiles in 1.5 mm birch plywood and that is ok, it is looking like I will have to stay with the plywood unless someone can suggest another modelling material to try.

[carlmt]

Lasering styrene eh?  Welcome to my world!

When lasering styrene sheet - regardless of the thickness - you will always get a slightly raised edge.  You cannot eliminate this, much as you cannot eliminate getting a raised edge when cutting styrene with a knife.

As for the width?  Yes, especially with the thicker styrene sheets, two laser lines 1mm apart will obliterate what is between them.

Lasers are not 'ideal' for cutting styrene - please make sure you have decent extraction to atmosphere!!! - but they are great when producing repetitive and complex parts (cutting dozens of windows out?).

When cutting the wood, the properties of the material mean that it does not transmit the heat too far beyond the laser itself unlike the styrene which, as you have found, will melt away.

For straight, narrow, cuts of styrene it is better to use the knife and straight edge.

[TailUK]

We get out best results with styrene by repeat cuts.  Set the speed a little higher and go over it a couple or three  times.  Also use the colour sequence to separate cuts so they don't happen close together sequentially.  Both these measure ensure that not as much heat builds up in a small area.  The raised burr just wet and dries off like the burr on any material. 

[malcf]

  Thanks for the help guys it looks like I will have to have a reasonable width border around apertures etc the item I was trying to cut is the crane gantry for HMS Fearless I reckon I was expecting too much in styrene so it will be done out of 1.5 plywood, I have cut some samples and they are fine and reasonably strong.

[malcf]

Carl the ventilation is good in my workshop with the supplied Chinese fan unit but boy is it noisy and it sucks all the heat out of the room in no time at all I am lucky with the position of the workshop being at the bottom of the garden away from the neighbours houses  .

[carlmt]

We get out best results with styrene by repeat cuts.  Set the speed a little higher and go over it a couple or three  times.  Also use the colour sequence to separate cuts so they don't happen close together sequentially.  Both these measure ensure that not as much heat builds up in a small area.  The raised burr just wet and dries off like the burr on any material.

Hmmmm - That is a trick worth experimenting with!  Hadn't thought of that one. 

[Brian60]

I'm a little late in here possibly because i've been slumming in the UK for 10 days Anyway this is my technique.

I always use a bit of scrap styrene of the same thickness as I want to cut, then set the machine (I'm thinking you have a K40 variant?) to 5mAmps on the manual or around 10% on the digital variety. I push the speed to around 40mm/s and then cut a shape, circle, square or whatever. I remove the styrene and check the depth of cut, after you've owned one for sometime this becomes normal practice. Push it back in and make another pass over the first - recheck and make another pass etc until you cut through your styrene. This gives you the base to work to, so you can put in your workpiece and know that 'x' amount of passes at 'x' power and speed will cut what you desire. There is nothing worse than pulling out your workpiece and finding that some parts are cut while others are hung up - sometimes within mm's of each other on the same cut line, needing a pass with a scalpel blade, which kind of defeats the use of the laser!

On mine a setting of 5mAmps and40mm/s usually gets through 1.5mm styrene in 4 passes. You could of course up the power and do it in one, but I've found multi passes and low power give a cleaner cut. This happens because you are not over heating the styrene, I've also between cuts if its a complex shapes (think wheelhouse windows close together), put one of those freezer cool blocks on the styrene to cool it between passes.

[malcf]

Thanks Brian I will experiment this weekend in the shed , I don't reckon I will have much need for the freezer block in there but you never know btw its a red clone 60 watt/50 watt 700mm x 500mm Chinese model.

[madrob]

where would i buy a cheap laser cutter?
how thick a ply could you cut with one?

[malcf]

Hi I would suggest taking a look at this website and view the videos listed on it for a wealth of information about lasers, much more than I could ever type on here
http://rdworkslab.com/index.php

[carlmt]

Depending on how often you want to use your laser and what for, I would avoid 'cheap' ones.
 
Ours cost over £4k, but we have the comfort that the supplier is in the UK, has a call-out service and can provide spares and service back-up, usually within 48 hours.  The bed on ours will take a max sized sheet of 600mm x 300mm and cuts good quality ply up to 6mm thick with ease.  Could probably do thicker, but we have no need.  Use only good quality laser-able ply as ordinary ply can contain dodgy glue and voids within the plies....the dodgy glue will ruin your machine in time and the voids in the ply will cause it to fall apart when cut or burst into flame as the laser passes because the power to cut through a nominally uniform thickness would be suddenly too much for the correspondingly thinner wood.
With all laser cutters/engravers ensure you have an adequate means of ventilation as the fumes given off can be very unpleasant.

[Colin Bishop]

Not sure why the average modeller would need a cutter unlike commercial concerns such as Linkspan. For a one off model a knife should be adequate surely?

Colin

[carlmt]

Having the laser cutter is just the start - you will also need a computer with a drawing package on it that you know how to use.
The laser uses the vector drawings - usually dxf format - to 'read' the path it has to take.  This file is loaded into the laser cutter's software and read then sent to the machine.  If you don't have the drawing package or cannot use one, then a laser cutter is not going to be of much use.
If the job is a 'one off' then it would be cheaper in the long run to have a commercial firm cut the parts you need.

[Colin Bishop]

Yup, just because the technology is available it doesn't necessarily mean that it is the best solution in your particular case. Could just be overkill. There is a lot to be said for a steady hand and a Stanley knife.

Colin

[RAAArtyGunner]

Yup, just because the technology is available it doesn't necessarily mean that it is the best solution in your particular case. Could just be overkill. There is a lot to be said for a steady hand and a Stanley knife.

Colin

Correct, after all hand tools existed well before mechanical solutions were found and yes, in lots of cases the 'mechnaical' is not a patch on the hand tool method.

I always prefer to use hand tools even though I posses the mechanical option, better control and less damage if you slip up.

[Brian60]

I must own the cheapest cutter here, the ubiquitous K40 (£340 new, from Ebay). I find it ideal for model work, if I was running a business then one of the larger and much more expensive lasers would be my first call. But the K40 handles anything I can throw at it for modelling purposes.

It cuts styrene,
It cuts ply,
It cuts solid timber.
It cuts acrylic, both cast and sheet.
It will engrave on  all the above and also glass, marble, slate, brick any material really - bearing in mind some man made materials outgass some very toxic substances, so extractor units are a must.

Plywood I once cut a piece of 10mm thick just to see if it could - it did with multiple passes. Think of a laser like a saw blade. You push the saw and it removes a layer of timber as sawdust, pull the saw back and repeat, another layer of sawdust and the cut gets deeper.

The laser works in exactly the same way when doing multiple passes, except instead of producing sawdust, the material removed is vapourised and dissapears up the extractor as smoke and fumes.

Also unlike handtools as gunner mentions, what you draw on the computer, you get from the laser - it just doesn't make mistakes, no overcuts, loose joints or anything. As long as you can use a drawing program, Coreldraw for intance, you can get results from a laser cutter. The smaller laser like mine takes all sorts of files for import, dxf, cdr even bitmaps. Take a look at the tramp steamer in my byline, almost every part of this ship was done on the laser, the ships wheel which was only 5mm in diameter complete with spokes was cut, something I could never accomplish by hand alone.

The only drawback for me is that it doesn't cut metal (brass sheet for instance) but then neither do any of the mid priced lasers, for cutting metal you are looking to spend over 20 grand, now that is serious money in anyone's book!

[malcf]

I fully agree with your post Brian, the laser is just another string to my bow, I have an interest in computer controlled machines as we use them every day at work, In a couple  of years I will be retiring so I decided to purchase the laser while I can still afford it, hopefully by then I will be clued up on its abilities, I know I do not have to justify my purchase but it will be used on more than parts  for model boats etc, I have recently used it to engrave drinking glasses and stainless steel painted tumblers and a futuristic led table lamp.
The Chinese lasers require a bit of fettling to work at their best as the Chinese are not the best at setting them up properly more just assembling them and also things get thrown out of  alignment due to the journey from China to our shores and lastly don't expect any backup after your purchase other than Ebay and Paypal.

[Colin Bishop]

Looked up the K40 and can see the attraction although quality of the machines can apparently be a bit hit and miss depending on the sourcing. It is obviously handy for cutting out complex shapes and could be justified for a large project or someone who does a lot of building.

As someone who spent most of his career in an office environment including systems development, I like the contrast of using your own hands to build a model rather than making the components at one remove but it's horses for courses I suppose.

Colin

[JimG]

One point to remember about the cheap Chinese lasers is that the output power of the laser tube is less than that stated. The K40 is supposedly 40W but actually nearer 30W, the other common size of 50W is actually nearer 40W. While they can be made to output a power near to that stated it can only be done by overdriving the tube and drastically reducing its lifetime, already quite short for the cheap ones. The limitations of the eBay Chinese lasers and the cost of UK produced (in many cases actually upgraded Chinese ) lasers led me to making my own which is slowly being completed. 80W tube and cutting size will allow a 3foot long balsa sheet with up to 16 inches wide (4 x 4inch wide sheets) as my main use will be for aircraft.

Jim

[malcf]

Yes Jim my laser was stated as 60watt but if used at its maximum the tube life would be very short it actually has 50 watt of useable power this I learned luckily early on by watching  Russ's youtube videos that are in the link I posted.

[terry1956]

Adding a cheap air pump to push air around the laser cut area helps both with the burn mix’s and how deep you can cut. I use an pond air pump with the tube cable tied to the laser head.it all helps. I use the laser to mark out brass for etching. Works very well for that.

[malcf]

Terry I presume your laser cutter does not have a nozzle with air feed  through the end, They are available on the likes of ebay from china and they help to keep the lens clean by producing a positive downward jet of air, if you can get one to fit your machine it would help a lot or you could modify your own nozzle, I have been etching brass myself using the laser to burn away a coating of primer on the brass and have had good results more so by etching both sides of the brass but it is a bit tricky aligning both sides.

[JimG]

I have been etching brass myself using the laser to burn away a coating of primer on the brass and have had good results more so by etching both sides of the brass but it is a bit tricky aligning both sides.

I fitted a 1/16 ply surround to the cutting bed and used the laser to cut it to the size of the cutting area. This allows for repeat positioning when I have more than one sheet to cut. Useful for wing ribs and aircraft parts where a full sheet of balsa is needed.
Jim

[malcf]

Hi Jim what i meant was aligning both faces of the brass so i can burn away the pattern on both sides using a mirror image of the design, I am managing it at the moment as i am using the corner of the brass sheet as the datum point and can turn it over and locate in a jig like what you have suggested,I am relying on the brass stock i am using being the same width, a fraction out though will double creating an offset to the 2 sided etching, I find that double sided etching works best for me as i can obtain narrower etchings without as much edge erosion and is much faster.

[JimG]

Can you use a jig with a corner for alignment at the top left and bottom left of the bed. Set one side to cut with the brass aligned to the top, then align it with the bottom for the other side. Flipping the drawing to reverse it also flips the reference point. The firmware I use allows you to set the reference point it uses to start cutting to any of the 4 corners so the etch should be aligned on both sides.
Jim