Been playing with me laser.

OK been working on doing some harrison M300 screw cutting plates.
Artwork was scanned in, cleaned up in CAD [ Cartoon Asisted Drawing ] then saved as a DXF and taken into the laser cutters software.

First off was a plate done out of the silver faced 1.6mm thick Rowmark type engraving plastic.




Came out really well but hard to get a good photo because of reflected light.
Plus points are it's easy to do and comes out nice. Cons are it scratches easily and will need to have a clear cover over it for workshop use.

Second try was it's possible to buy reversed engraving laminate and after trials using an old front number plate I got to thinking and just sprayed the back of a sheet of 3mm perspex with cheap silver rattle can paint from the hardware shop.

Image was reversed, burn onto the silver , then rattle canned black over this



Again came out well except for the reflected light .

Pro's are it's got to be the cheapest and fastest method, durable as you can't scratch the lettering.
Cons ? can't see any.

Last try was direct engrave onto stainless steel sheet. These Co2 lasers will engrave onto stainless but it's not a durable finish, scotchbrite will fetch it off easily.

Commercially there is some stuff called Ceemark which you spray on and it burns to onto the surface, it's a type of ceramic slurry made from ground up 3rd Ming Dynasty vases judging by it's price of £100 an aerosol [ no typo ]

After a bit of research on the web I came up with a link to some dry moly spray that works, bought a tin, £12 a pop and sprayed a stainless sheet up and then engraved on that.



Had problems with this one but overall pleased with the result.

Firstly because of the amount of heat going into this the plate bowed. The gobbled letters at the end of the main block are because i moved the plate trying to get a bit of tape on it to stop the bowing, which wasn't a good idea.

Lettering is thicker at the bottom of the lower block of lettering because the plate had risen up and reduced the focal length. Same at the top where the gear train numbers that were done first have missed the gears.

Best bit to form an opinion is the lettering in the middle and the feed legends towards the end.

As I say overall this is showing promise of a durable and workable system but needs to be secured to a large heat sink before cutting.

The moly has been burnt into the stainless plate and is a few thou deep, enough so that it won't scratch or wear off easily.

John S.

Hullo John,

Dont know how you illuminated subject but my thinking is along lines of something to diffuse the light source or even lighting aimed opposite direction and reflected back to subject, possibly with a mirror.

Rgds, John

Gert has a light box for doing photo's but to be honest point and click is good enough for me. My interest is in machining, everything else is peripheral.

That is very nice, very tidy. I would love to be able to do things like that.

Nice work John

Thanks for letting us learn at your expense !

MichaelG.

Hi John

Nice plates - bad 'photos - point and click just 'aint good enough! Yes the answer is to diffuse the light source. ( Photos could be a bit sharper too) Speak nicely to Gert and enrol her services in the light tent. As you well know the best work can be spoilt by lack of attention to detail. ( I still think the plates are good though and I guess it's better than good pictures of  bad plates).

Cheers

Norman

Edited By NJH on 26/11/2012 10:04:31

If the stuff is easily moveable take it outside on a cloudy day and take the pictures, that usually works for me.

But do not let the camera's built in flash operate!

Edited By V8Eng on 26/11/2012 13:12:31

The perspex one looks really good

_Paul_

Hi Sir John,

Have used celulose as a resist coat, laser off the paint then etch. Fill the etch with paint then wipe off the surface. Also useable for PCB's. Would agree with the comments about the "industry standard aerosol". We do a lot of perspex signs, as you say the backside paint then engrave and contrast coat works great. For illuminated signs you can paint a ground colour ( say red) then overcoat white then engrave through the lot. The white reflects back the light into the box giving more even and brighter lighting.

Your warping stainless might be down to too much power and too slow movement, it is always good to start low and work up rather than using cutting power but I have not used the molly route myself.

I am always very careful about just what gets exposed, few months back witnessed the effects of cutting PVC in a CO2 machine, everything was corroded and the control board was a write off.

It is a good idea to check the lens after blasting at something unusual, debris will significantly reduce power in some machines where the air assist is not so good.

Billy.

Photo tip FWIW

You need and old white bedsheet, then perhaps a dining chair that you can push the squab out or something to make a box frame. Drape the sheet over to form a white box. Direct some strong lights on the sides, cut a hole in the centre of the top sheet to point the camera down and shoot, do have a plain matt background (green is good)

It the way to take those tasty plates of food pix for example

Robin

A good light box can be made with crumpled up kitchen foil attached to all the inside surfaces of a large cardboard box.

If the object has a lot of shiny surfaces then place it in a cold fridge for a while and it will be less shiny when you take it out because of condensation ( Good for silver or plated objects) not precision machinery of course.

Outside, a muslin covered frame will filter the light and remove extreme dazzle points.

Clive

Edited By Clive Hartland on 27/11/2012 20:46:22

Informative post thanks for sharing with us. It's very useful for me.