Good reason to buy 80 watt over 40 watt?

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Good reason to buy 80 watt over 40 watt?

Postby educa » Sun Jun 10, 2012 10:51 pm

I was wondering. Since I have to order my laser now (machine almost finished) what would be the reason to go for a laser of 80 watt instead of 40 watt.

I want to mostly cus tot following stuff


1) plywood upto 6 or maybe 8 mm
2) acrilyc upto 10mm
3) MDF upto 8mm

All would have to be done in 1 pass.

Is there a reason to buy a 80 watt tube for this or would 40 watt also do ?

Kind regards,
Bart
educa
 
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Re: Good reason to buy 80 watt over 40 watt?

Postby Liberty4Ever » Mon Jun 11, 2012 4:00 am

I use a 40W commercially manufactured laser to mostly cut rubbery materials - sheets of rubbery foam and Santoprene (a rubber plastic) tube with .125" thick walls. The foam sheets are cut in three passes at less than 100% laser power to avoid igniting it or charring it. The denser Santoprene tubing cuts and engraves a bit slow at 40W and could use more power, so I'm thinking of a 60W laser when I build. I'd probably opt for the 80W if the price didn't jump up so much between the 60W and 80W. I figure I can always reduce the power as needed.

The higher wattage tubes are quite a bit larger, so you'd need a large enclosure to house a larger tube.

On the plus side, most of the manufacturers claim longer life for the higher wattage laser tubes. Sometimes the life of a 40W tube is quoted as 1200 hours and the same manufacturer will quote up to 10,000 hours for an 80W tube. Of course, that only matters if you plan on doing more than 1300 hours of lasing. For comparison purposes, that's probably close to the time you'd put on a laser in a year if you were working full time as a laser operator. It's a lot of lasing.

I'm less familiar with the plywood you want to cut, although I've read that some plywood has a glue that lasers have a very difficult time cutting, so selecting laser friendly plywood would probably be more important that the laser power output. Assuming good plywood, I'd think 80W would be better than 40W, although plywood is a material that chars so I'd defer to someone with more plywood cutting experience than me.

For the thick acrylic, I think there's a fairly linear relationship between laser power and cut time. The 40W laser cuts thick acrylic and does a beautiful job with edges that are fire polished. They almost look like cast acrylic pieces. The laser is essentially vaporizing the acrylic, and there is a fine coating of white dust inside the laser. It seems like a good abrasive to me, so I'd keep that cleaned out of there. Fpr acrylic, I'd guess you'd see significantly faster cut times with a more powerful laser tube.

The manufacturers publish recommended settings for their lasers with different materials. That's almost certainly online. The VersaLaser charts I've seen list the settings (power as a percent of total power, pulses per inch) for each material. The trick is to look for the charts of your material, and if the power setting is less than 100% for a given model based on its maximum laser power output, then the laser power is determined by the material and a more powerful laser won't get the job done any sooner.

I did a little googling.

For 1/4" birch plywood
Power = 90
Speed = 2.6
PPI = 200

From: http://design-dev.ncsu.edu/facilities-r ... uggestions

That page also stated that up to three passes may be needed to cut through the plywood. Not sure of the wattage, but the fact that the power setting is less than 100% would indicate that thicker plywood could char if you tried to dump a lot of laser power into it and cut it in one pass.

The users manual for the VersaLaser I use has a chart that has settings for different lasers they make and I think they're 30W, 40W, 50W, 60W and 80W, or something like that. It'd be very handy when deciding what laser power you need to buy based on which jobs you anticipate doing the most. Apparently, from my one minute of googling, the Windows laser driver for newer VersaLaser machines incorporate the material selection as standard settings in the print driver, so users don't need to refer to charts.

If you cut thin materials like paper and card stock, a 40W laser is plenty and the speed seems limited by how fast the carriage can move.
Apparently, I didn't build that! :-)
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