Cut gobos using a laser cutter

[mundas]

Hello everyone,

 

In our fairly well-equipped school the Design and Technology department has recently acquired a laser cutter, which I'd love to use to cut our own gobos. The unfortunate thing is that the one they have cannot cut through metal, so I'm struggling to find a material which would be suitable http://www.blue-room.org.uk/public/style_emoticons/default/huh.gif

 

Has anyone had this situation before and can you suggest a material we might try??

 

This idea was mentioned briefly in a previous post in the Blue-Room forums.

 

Thanks in advance.

[adam2]

Are you certain that the laser cutter can not cut even thin metal ?

 

Many laser cutters that are intended for other materials will cut very thin stainless steel, I would give it a try. Unlike trying to cut unsuitable material with a physical cutting tool, trying unsuitable material in a laser cutter should not break anything.

[smalljoshua]

Apart from where the material is reflective and the feedback into the laser diode will cause a good amount of damage...

 

Some cutters will go though Anodised Aluminium, but if your Teachers say don't, don't as it could mean a large bill.

 

Josh

[Shez]

Agreed. They're funny things - we have one that will cut through moderately thick wood, leather etc but won't even cut aluminium foil...

[portytech]

What if you were to coat the metal with something to stop it being shiny. as far as I know the LASER cutter uses the concentrated beam of light to burn the material thus a shiny material will reflect the light thus reducing the effective energy of the beam. (There is actually a bit more to this but it involves photons and electrons and stuff)

 

Though any coating would have to be suitable. eg non flammable, and there would probably be the need for fume extraction.

 

Yep higher physics at work there.

[ImagineerTom]

...until the very first pass of the laser burns off the coating - then you're back to pointing a cutting beam at a reflective surface.

[the kid]

I don't know the exact numbers but the art dept were going to get one, the rep said that for paper, wood, plastics etc it was 500mw but for metal it starts at 5000mw.

[gyro_gearloose]

Actually its a little more complicated than that. Have a look here

[Jivemaster]

Sadly if you do not have permission to cut metal -for whatever reason, then you may NOT cut metal. End of story. School budgets often don't include expensive repairs!

 

Remember that a gobo will sit at the hottest part of the light beam so needs to be very heat resistant. Stainless steel is good aluminium can work. People can jury rig a gobo with foil from a take away meal container or thin sheet cut from a drinks can.

[themadhippy]

in days of old lithoplate was my weapon of choice

[LampTramp]

in days of old lithoplate was my weapon of choice

 

Wow! That's a blast from the past.. I remember sitting for ages cutting gobos at school cause we didn't have a budget to buy DHL gobos for shows.....

[Tomo]

Custom gobos are pretty cheap these days from the likes of Goboland, Rosco et al.

The cost is in the setup - first one might be £30 to £50, but further copies cost about the same as standard gobos.

 

Ok, if you want the gobo today or tomorrow or you want a glass one it's a bit pricey, but a steel gobo in a week or two is cheap.

[dbuckley]

The other possibility is to note that one can make gobos out of brass or copper, and the process for doing it is no different to making a PCB, except that one has to coat the metal with resist oneself, unless someone knows of a source of pre-sensitised brass or copper sheet. Schools often have the kit to make PCBs, especially the hard stuff like etching tanks with evil chemicals in them and a decent UV exposure box.

 

One can get spray-on resist such as Electrolube PRP (usually part number PRP200 for the 200ml spraycan) from the usual suspects, which was intended for coating non-presensitised PCB material, but that stuff went the way of the ark.

 

Rather than double-side coating the metal blank with resist, it should be possible to coat the non-exposed side with paint, lacquer or something similar.

 

The secret to making good PCBs (and by extension, gobos by the same method) is have a good master film, and Mega Electronics LaserStar film and a 600dpi laser are the right things to use.

 

If anyone has a go at this, do report how you get on.

[Cerbertech]

The other possibility is to note that one can make gobos out of brass or copper, and the process for doing it is no different to making a PCB, except that one has to coat the metal with resist oneself, unless someone knows of a source of pre-sensitised brass or copper sheet. Schools often have the kit to make PCBs, especially the hard stuff like etching tanks with evil chemicals in them and a decent UV exposure box.

 

One can get spray-on resist such as Electrolube PRP (usually part number PRP200 for the 200ml spraycan) from the usual suspects, which was intended for coating non-presensitised PCB material, but that stuff went the way of the ark.

 

Rather than double-side coating the metal blank with resist, it should be possible to coat the non-exposed side with paint, lacquer or something similar.

 

The secret to making good PCBs (and by extension, gobos by the same method) is have a good master film, and Mega Electronics LaserStar film and a 600dpi laser are the right things to use.

 

If anyone has a go at this, do report how you get on.

 

Did this many times when back at sixth form and university in the late 80's and early 90's. Takes practice to get the etch timing correct. and as stated image quality is everything although we were using Letraset and felt pens on plastic OHP slides as all the printers we had access to were dot matrix at the time.

[gyro_gearloose]

.....or the OP could just buy or hire a few Selecon Pacifics and print their own multicolour gobos on a desktop printer. Much cheaper and nowhere near as messy as etching your own gobos.