Hi,

I built my first CNC machine about a month ago, pretty much the same as the one at http://www.buildyourcnc.com.

I built it all from MDF because I can't afford the extruded aluminium that a lot of machines are made from.

Trouble is, when Im cutting along some wood the router tends to twist to the left. This is because the cutter is rotating anti-clockwise and a force exists between the cutter and the wood, etc. My only solution at the moment is to cut extremely small depths, with many slow passes until finished. Not ideal.


Im looking into using a laser on the gantry my router is currently attached to. Seen some 40W C02 laser tubes for about £150, which seems affordable.


I guess you can work out the laser cut depth by dividing the drilling rate by the feed rate. Drill rate is calculated at:

http://alumni.media.mit.edu/~yarin/laser/physics.html

but quite a few thermodynamic properties to look up for your material. Boiling point or melting point of 3/4" pine anyone?!?!?!?

I have 2 questions:

1. If the laser only cuts half the thicknes of my wood, could I just pass over it again to complete the full depth i require?

2.Could you use fibre optics rather than mirrors to direct laser energy from the source to the gantry?

Thanks for any help offered.

Regards
Adam

You're not going to cut 3/4" of wood with 40W and have anything recognizable come out of it... it just isn't going to happen. You also won't be able to use fiber with the wavelengths of a CO2 laser... you need to go to YAG wavelengths for that.

I cut 1/8" wood all day long with my 30 watt machine, 40 won't cut much more than that though. Unless you have 100-150 watts you won't be able to cut anything thicker than 1/2" or so. You can take multiple passes to cut through something, you will need to refocus every 1/16" or so and the result will never be as good as if you had enough power to cut through it in one pass.

My laser uses a printer driver to control the power and speed. I went through quite a bit of testing to determine the best speed/power settings for any given substrate. You won't find anything out there that will allow you to put in a substrate, laser power and speed and have it give you suggested settings, it just ain't out there... If it was, the person who created it would be very rich! That is the most difficult part of learning how to laser.

Gary