Laser Cutting - Experience and ideas

[Fen End Pit]

As some on you may have seen from my blog http://www.rmweb.co.uk/community/index.php?/blog/186/entry-10885-first-attempts-with-a-laser-cutter/ that I've now got access to a laser cutter. I wanted to start a thread to collect peoples' experiences of laser cutting, the best way to to do things and the ideas on how to draw artwork to get the best results.

 

AndyY kindly extended the subject on the 3D printing and CAD group to cover laser cutting as we couldn't see another suitable area.

 

To kick things off here are the things I'm trying to get my brain around at the moment at the moment:-

 

What material to cut the majority of the building from?

Do I use an MDF, something commonly available like 3mm or do I use a plastic, maybe 1mm ABS?

 

What is the best approach for the corners?

Do I try to make a butt joint, but use a material thin enough that the brick closures are still correct? do I try to mitre the corners either by filing or even using a jig to hold the part at 45 degrees and then slice of the angle on the laser cutter? Do I try to cut every other brick out on the corners and dovetail the walls together?

 

What is the best approach to windows? If I use a thicker material like 3mm MDF for the walls do I have to make the windows to fit into the recess in the wall? If I use a thinner wall material do I have multiple layers to give window reveals?

 

Just how clever can you get with cutting depths and engraving? The cutter can also engrave a larger area so can I do things like the recesses in a paneled door using the engraving or do I have to use multiple layers of material? Can I also engrave certain bricks away to give a slightly less perfect wall finish and is it worth doing so?

 

So obviously the possibilities are huge and I'm really looking forward to playing about with it but if anyone has any advice to give me please do!

 

thanks

David Barham

[unravelled]

I have a basic laser cutter, and have been experimenting with materials and methods for the last year or so.

I put a couple of ideas into the 2012 challenge, box sash windows, http://www.rmweb.co.uk/community/index.php?/topic/62075-box-sash-windows/

and coach seating, http://www.rmweb.co.uk/community/index.php?/topic/58336-laser-cut-coach-seating/.

 

Regarding materials I have tried, MDF cuts well, but the cut I get is wider at the top surface than the bottom. This may cause problems with thicker materials, but might be reduced by tweaking settings.

Card and paper seem to cut cleanly.

The generic white styrene sheet sold by Modelzone cuts cleanly, but other samples have melted rather than cut cleanly. The clear sheets sold alongside styrene cut reasonably, but end up smoke marked, and are difficult/impossible to clean.

The best cutting material I have used is cast acrylic. I have use 0.5mm clear for the sash windows. It is a bit brittle, but easily cleans up after cutting. Unfortunately the common modelling  adhesives don't touch it, and it is expensive.

 

This is a attempt at an industrial window frame in paper

RIMG1044 by unravelled, on Flickr

 

I'll find some more pics and post some more later.

 

Thanks

 

Dave

[Beatty 139]

I have had my Laser for about 9 months now and have produced some very pleasing work on the machine, but to maintain the quality you will need to pay attention to cleaning and alinement of the machine, something that may be difficult within a group of people.

 

MDF is a good material to work with, I just wish I could source a supply in 1.5mm thick, Laser grade ply is lovely to work with but I don't think its avalible less that 4mm thick and normal ply 1/64" upwards will cut but you can find that it may be inconsistant and need to use a blade to ease parts out where a knot or such is in the middle ply.

 

Your CAD work is where you need to spend the time, get that right and you will have 'click' tiogether fits so build your off sets into mating parts I tend to work on about 0.06mm for best effect as I belive my machine cuts with about a 0.12mm line width. The laser on my machine cuts with about a 2^o taper to edges and has been said on thin sections you would never know but once your on 6mm MDF this becomes clear.

 

For Brickwork as my models are in Gauge 1 I have used a fingered edge and this works well when you source material that is the same thickness as a Headder for smaller scales I would have though the task becomes more difficult.

 

On the issue of mitering corners I can suggest you look for a small table top tilt arbour saw like the Proxxon one, I have tried making jigs and using the laser but its a fast path to insanity, best generate the angles required using CAD cut a template and set the saw blade to the template this way you can do the complex angles for hipped roofs with reasonable ease.

 

 

The Midland type 4 box is made from a mixture on Ply and MDF and also some yellow pine.

 

 

Again the Gauge 3 Midland covered goods wagon is produced from Ply and MDF, even the external straping has been cut from 1/64 ply and the wagon plates were home etched by coating brass sheet in primer using the laser to cut the paint away then etched in ferric chloride, an easy way to do one off etches.

 

Hope that helps

 

Andy

 

[meil]

Hobarts sell Laser grade ply down to 0.8mm.

[Beatty 139]

Thanks for that I will order some samples and see how it cuts, and suggestions on 1.6 / 1/16 MDF?

[Tim Horn]

I've used 1mm MDF on the chimney I'm messing about with at the moment. It uses interlocking bricks, but I'm still not happy with them. The ideal size would be 1.3mm thickness, as this is the size of the header bricks i'm doing in 4mm scale.

 

Cheers

Tim

 

 

 

 

 

[Beatty 139]

This is a chimney on a GCR platelayers hut before painting in 10mm scale done much the same way but with thicker materials

 

 

May I ask Tim where you source your thin MDF from as all the sheet material suppliers I have contacted can not offer me anything thinner than 2mm

 

Thanks

 

Andy

[Fen End Pit]

The 4D Model Shop in London do MDF in 1mm, 1.5mm and 2mm see http://www.modelshop.co.uk/mdf-384-c.asp

 

David Barham

[Beatty 139]

Many thanks David, I will give them a call and see if they can supply something larger than 250x500

[Rabs]

google threw up this one for thin MDF:

http://maplestreet.co.uk/advanced_search_result.php?keywords=mdf&osCsid=vugccktsv7qb3cqsudlvb75me7&x=0&y=0

 

Never used them myself

[Tim Horn]

Hi all,

 

I've used Maplestreet for the 1mm MDF http://maplestreet.co.uk/hobbies-catalogue-items-wood-p-4764.html?osCsid=qeogi6lvov4eknssqaopfqn413

 

Hobarts for 2mm mdf http://www.hobarts.com/store/laser-grade-p-312.html

 

and also Mindset for various sheet materials http://www.mindsetsonline.co.uk/index.php?cPath=418_6

 

I've yet to try any decent plastic equivalent sheet material, as I'm trying to get to grips with using the mdf at the moment!

 

Just trying to get one of the office ends done today, I thought I'd reduce the size and try doing a 2mm version

 

 

Cheers

Tim

 

 

 

 

 

[Tim Horn]

Back to the other end wall, I've tried the first cut out for the side door. I've used some printer card for both faces of the door with a sandwich of .25mm glazing.  Just need to tighten the measurements up on the edges, but I don't think I can tighten up the cut lines.

 

 

[Wild Boar Fell]

Hello Everyone,

As well as 3D printing, I have found laser cutting very interesting in scale modelling. I have had items laser cut since about April 2012 and have used it for a range of structures and object from small to large. I have found that the quality of laser cut items can be hugely impressive and very accurate. On items I have had window frames have been a fraction of a mm thick yet still strong enough to survive handling. I am currently wondering what I can get laser cut to go with the printed wagons.

 

Anyway here are a few photos of some of the laser cut buildings on my layout.

(Apologies for the photo quality, some are from my phone).

The terraced houses on the left were laser cut as was the engine shed on the right side.

One of 4 sheets of wood used to build the terraces.

The gate house in the bottom of the shot was cut too.

Finally the motive power depot (over 2ft long) was made of laminated interlocking sections with a drop in roof that was also cut (only the girder, ladder and smoke troughs weren't laser cut)

 

More photos are on my layout blog linked from my profile.

These Items were kindly cut for me by Ancorton Models (Formerly Miniscene).

 

Regards,

Wild Boar Fell

[Fen End Pit]

I've not been exactly too successful over the last few days. I managed to cut some very nice test walls in 3mm MDF and then I tried some experiments in painting them. I just made a complete mess.

 

The main problem is that the mortar cut in the MDF is very dark from the burning of the laser and I clearly need to paint this to a lighter mortar colour. I guess I've been impatient and not got out the air brush but trying to get a paint to brush into the mortar lines has been almost impossible. I also had a complete failure by using acrylics on the MDF and then it just absorbing water and bubbling up.

 

Please give me some advice!

 

 

I also ordered some .25mm, 5mm, 1mm and 1.5mm ABS and had a go at cutting this today. I tried various speeds and powers on the laser. It seems as if it is melting the ABS and particularly with the brickwork I end up with a raised edge around the engraved line. Any ideas? is this just the way it is with ABS? It seems to file down ok but the the lines are nowhere as fine as with the MDF or the coloured perspex I tried first. Bit disappointed as the ABS wasn't cheap.

 

 

more experimentation needed.

 

David Barham

[Tim Horn]

Hi David,

 

My limited testing and technical knowledge tells me that ABS melts rather than burns, so the laser melts and pushes the material either side of the beam, hence the raised edges. MDF will burn so the material is turned into smoke!

 

Experimenting is the only way of learning how stuff reacts to the laser. Using lower settings (speed and laser power) will help with cutting and mortar lines.  I've used Halfords spray can red primer to seal the MDF, I've just done a quick five minute paint job on this test section and it's come out ok. I've used artist acrylic paint fo the mortar and enamel blue paint for the blue bricks. Just rub the mortar paint off with IPA on kitchen roll on the faces of the bricks.

 

Just for the 1mm MDF cutting, I've used a speed of 30 out of 200 with a laser power set to 10.5% for the mortar lines, and cut through with speed of 6 out of 200 and a laser power of 20% (using a 40watt laser tube)

 

HTH

 

Cheers

Tim

 

[50031Hood]

These were the results that I got using brick-coloured card making my signal box in 2mm. By luck, the score lines used to create the mortar lines resulted in the beige colour without me having to do anything! The card was mounted onto 1mm clear acrylic - also laser cut - and the window frames made by laser cutting adhesive label paper.

[Fen End Pit]

<snip>   I've used Halfords spray can red primer to seal the MDF, I've just done a quick five minute paint job on this test section and it's come out ok. I've used artist acrylic paint fo the mortar and enamel blue paint for the blue bricks. Just rub the mortar paint off with IPA on kitchen roll on the faces of the bricks.

 

</snip>

Cheers

Tim

 

That looks superb, Which Halfords spray primer is that, a Acrylic one or an old cellulose one?

 

 

Thanks

David

[Tim Horn]

Thanks David, I've used the acrylic red primer, http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_203963_langId_-1_categoryId_165495

 

Seems to work ok.

 

Cheers

Tim

[Fen End Pit]

Thanks David, I've used the acrylic red primer, http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_203963_langId_-1_categoryId_165495

 

Seems to work ok.

 

Cheers

Tim

Thanks, next dumb questions:

1) Do you use the Halford's primer as the base 'red brick' colour or do you spraying a different colour on top of the primer.

2) When you put the acrylic mortar colour on are you leaving it dry before taking the excess off the brick surface with IPA or do you go in with the IPA almost immediately?

 

I think I've probably been cutting my mortar engraving too deep as it is almost 1mm out of the 3mm MDF. I guessing you are not as deep as you only use 1mm MDF!

 

I'll try and do some more experiments with corners over the next week or so. I've tried a mitre joint by cutting the 3mm MDF on a 45 degree jig. When I stuck it together the line was still quite dark where the 'sharp end' of the cut had been burned by the laser but when I glued and lightly ran some sandpaper of it and painted it the edge is actually pretty good. I also had a thought about cutting bricks out to interlock the edges. Using 1mm ply the width of the material doesn't quite match the size of a header in 4mm (and no-one does 1.3mm MDF!) so I've done a drawing where I use a stretcher which is 3mm 'as the bit that sticks out'. If I can make the cut work then the joint lines on the walls will accurately fall where the mortar lines would have been.

 

Thanks for the smashing photos!

 

David

[meil]

An Imperial header is generaly taken to be 106mm which together with an allowance of half a mortar joint (being on a corner) gives 111mm. At 1:76.2 scale that gives 1.45mm.

 

Which is as near as damit to 1.5mm.

[Tim Horn]

An Imperial header is generaly taken to be 106mm which together with an allowance of half a mortar joint (being on a corner) gives 111mm. At 1:76.2 scale that gives 1.45mm.

 

Which is as near as damit to 1.5mm.

 

 

Hi Meil, yes, 1.5mm, that's the size I draw them at and the stretchers average out at 3mm each. But I've found for the interlocking to work you need to use 1.3mm material. In my case, I've put a card backing onto the 1mm MDF. Bit of a pain, but workable at the moment until I have another look around for something more suitable.

 

David, don't worry too much about the depth of the mortar line as the mortar paint should fill this up. The red primer can be used for the brick colour if you want to as the white acrylic mortar paint tones the colour down quite a bit. Let the primer go off for a few hours, then paint the white paint on and take it off again straight away with kitchen roll wetted with IPA. Just play around with colours until you are happy!

 

 

Cheers

Tim

[Mike T]

Hi Meil, yes, 1.5mm, that's the size I draw them at and the stretchers average out at 3mm each. But I've found for the interlocking to work you need to use 1.3mm material. In my case, I've put a card backing onto the 1mm MDF. Bit of a pain, but workable at the moment until I have another look around for something more suitable.

 

David, don't worry too much about the depth of the mortar line as the mortar paint should fill this up. The red primer can be used for the brick colour if you want to as the white acrylic mortar paint tones the colour down quite a bit. Let the primer go off for a few hours, then paint the white paint on and take it off again straight away with kitchen roll wetted with IPA. Just play around with colours until you are happy!

 

Interlocking bricks TJH02 19th January 2012 Copyright Tim Horn.jpg

 

Cheers

Tim

Hi Tim

 

Searching around I have found 1.3mm card online but obviously don't know how it would cut. The other way mith mdf might be to use 1.5mm and make a jig to sand the back away 0.2mm at the joints?

 

Regards

 

Mike

[Tim Horn]

Cheers Mike.

 

I've got the 1.3mm card here, it cuts very nicely, but the cut looks more like a modern brick on close up photos. Great for new stuff, but not so for 150 year old bricks. That's me being picky though

 

The only other problem with the card is that it does warp alot more than the MDF when painted, but that can be cured with a different painting aproach.

 

You could probably run a sheet of 1.5 or 2mm through a plainer to get the thickness, bit messy though!

 

Cheers,

 

Tim

[Mike T]

Cheers Mike.

I've got the 1.3mm card here, it cuts very nicely, but the cut looks more like a modern brick on close up photos. Great for new stuff, but not so for 150 year old bricks. That's me being picky though

The only other problem with the card is that it does warp alot more than the MDF when painted, but that can be cured with a different painting aproach.

You could probably run a sheet of 1.5 or 2mm through a plainer to get the thickness, bit messy though!

Cheers,

Tim

Hi Tim

 

I did think of a planner/thicknesses but agree as you say messy so discounted that in favour of some sort of simple sanding jig?

 

Regards

 

Mike

[Fen End Pit]

So Tim. You commented that you felt you had 'sussed' the interleaving of the brickwork so I'd appreciate your views. I've got three different versions I'm playing with.

 

The first version one presumes a 1mm MDF and results in the last header actually having the joint half way down it. This doesn't seem like a good idea.

 

 

Then I found I could buy 1.5mm MDF which would seem to put the joint in the same place as the mortar line. I can imagine I might need to take maybe .1 or .2 of a millimetre off the back of the material so you wns up with some thickness to that mortar line but that seems possible. This would also mean only taking that material off the very e

 

 

Finally I also drew up a version where I interleaved the stretchers rather than the headers based on using 3mm MDF

 

 

I think I'm quite tempted by the 1.5mm and then I can make a building out of 3mm with a 1.5mm outside laminate. I could then make larger holes in the 3mm so that I could secure windows into a recess on the inside of the building.

 

 

Lots more things to try!

 

David