Extraction of fumes and cutting speeds

[plycoll]

Thanks for all the help & advice given so far, I feel I'm going in the right direction at last!
Any advice on the following please?
Cutting speeds & power.
I'm planning to make scale models of flat pack furniture with my 6th formers at school.
I am using 6mm Laser MDF and started by using the speed & power setting given in 'the chart', speed 2, power 98....result, burnt to a crisp! I need really tight 6mm slots.
I've been experimenting this afternoon and got as far as using drafting tape on both sides of the MDF, and this has kept the top & bottom scorch free....and speed 30, power 98, but with 10 passes.
Still pretty burnt on the sides but good, thin cuts resulting in tight fitting slots.
Tomorrow I'm going to try less power in the hope this might create even less burning on the sides.
Does this sound about right or is there a problem with the way my 6840 is outputting?

Extraction.
With all this testing there are a lot of fumes around from the Laser MDF. It is extracted outside with the pump on the machine but even so the workshop smells of burning wood & I can feel the effects on my chest. Is this normal? Is the extraction pump on the machine enough or do I require even more extraction? With the lid closed I'd hoped all the fumes would be taken outside but I don't think this is the case. Has any one suffered respiratory problems from cutting Laser MDF repeatedly in a confined space?

Any thoughts or suggestions?
Thanks.

[Spooky]

Hiya,

While a laser of 40 to 60 watts will cut 6mm mdf it's going to be close to the machines effective limit. The problem with MDF is carbon, as your laser pumps all that heat into the material Carbon builds up and it's a very good medium for sucking up laser radiation.The deeper it gets the more air you need at pressure to blow the carbon dust away.
I'm not a big fan of cutting thick materials with lasers.

Any kind of smoke, even fairly inert smoke from Laser MDF isn't going to do you any good medium term so extraction is pretty important.
As to has anybody suffered problems breathing wise? well I haven't personally heard of any but I'd be certain there HAVE been problems like that in some circumstances.

Bottom line is if you are feeling the effects then it would be a good idea to look at more powerful extraction no matter whether anybody else has had the same issue or not. (Machine mart do an extractor that is like a portable tornado)

If possible always try to keep the power of your machine under 90%, the Chinese power supplies are good but not as good as some of the western supplies so they can give out more power than the tube will take.A safe margin seems to be a top limit of 90%. If you need more effective power then reduce cutting speed rather than increase power over 90%.

hope that helps

best wishes

Dave

[WyeModels]

I know what you mean about the extraction it gets pretty wiffy and certainly notice it after 20 minutes cutting mdf and perspex, I am already extracting outside, but I could do with a better solution. Do you have a link to the machine mart extractors?

[Spooky]

http://www.machinemart.co.uk/shop/produ ... -extractor

Instant tornado

[WyeModels]

http://www.machinemart.co.uk/shop/produ ... -extractor

Instant tornado

the noise level sounds promising at 50/60db, I shall have to go and have a look at one.

[Spooky]

The standard extractor on the 1290 is 55 DBa so this isn't too bad

its a beast though, it's like a bloody jet turbine

[tweakie]

Plycoll,

The paper transfer tape used by vinyl sign makers is low tack, thin and ideal to apply to the work, before cutting, where the surface needs to be clear of any smoke discolouration. It comes in all widths and is not expensive to buy.

Tweakie.

[plycoll]

Thanks for the help and advice guys.