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DIY CNC Laser Cutter Power Question

StephenC

Junior Member
#1
Hi everyone!

This is my first time posting and I was hoping someone in the community could help me out with a quick question. As the title suggests I am making a cnc laser cutter so I can expedite prototyping and also have faster and more accurate foam board cutting. I have four questions (maybe just two if the 1st one has an answer haha).

1) Is there an online resource that lists what type/power laser is capable of cutting?
2) What type/power laser is required to 50% cut and 100% cut foam board?
3) What power would I have to increase to in order to cut balsa and 1/8" plywood?
4) Can you just have a more powerful laser than required and "dial" it down somehow or cut at a faster speed?

I have some experience with 3D printers and cnc milling machines so I am hoping to be able to apply my knowledge into my first "home" build of one of these machines. I would be ecstatic if anyone has additional advise or resources you can share.

Thank you everyone for your help. The resources Flite Test offers is absolutely amazing and I am excited to officially be a part of the community. Even though I have been stalking videos and the forums for some time now. lol


Cheers!

Stephen
 
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#2
Hi Stephen,
Welcome to the forums.

I've also toyed around with the idea of making something to cut foam and plywood.

How far along are you in your project?
Have you actually started purchasing pieces parts...or are you just in the planning stage?
What is your budget?

In regards to your question #4 you have the option to vary the lasers power settings, giving you a weaker to stronger cutting laser beam.
You also can vary the travel speed that the laser head moves at.

There are probably some charts on power settings and cutting speeds for various materials.
But in the end you'll need to just experiment by cutting test pieces using various power settings and head travel speeds.
 
#3
The speed you will be able to cut at is directly proportional to the power of the laser. You could probably cut foam with as little as 1W, but it would be painfully slow. If I remember correctly, the MesaRCFF group uses a 60W laser cutter, but I'm sure 20W would be fine.

I looked into this myself a couple of weeks ago, and determined that the lasers are ridiculously expensive and dangerous. I found that with a really high RPM (<7000rpm) and a very skinny bit (>1mm) foamboard cuts pretty cleanly. If you're looking to keep your price below many thousands, then I'd recommend looking into the milling alternative to lasers. You could probably use an EDF motor on 20-30V to get a very fast head-speed, because you won't have large lateral forces cutting foam.

There are also tangential cutters with a blade on the a-axis, but that's another level of complexity and tuning.
 
#4
On you question #2 here is a post from the Small Creek Forum:
http://www.sawmillcreek.org/showthread.php?188711-Laser-specs-to-cut-1-4-quot-Acrylic-and-Wood

They are discussing cutting acrylic and plywood.
From the discussion I would think that a 40 watt laser would cut 1/4inch foam and 1/8in plywood in a single pass with no problem.
40 watt tubes are expensive enough, and as you go up in wattage, the expense climbs dramatically with each step.

One thing to consider is that a laser cutter needs to be contained in a enclosed box so that the fumes are vented with a evacuation system to the outside. This is not just passive ventilation but you need a separate vacuum motor. Cutting wood is especially dirty. I guess you could cut in your garage with the garage door open...or outside.

Here's a comment off the forum post:
Quote:
Be sure to check and thoroughly clean the lens and mirrors. It doesn't take much smoke from cutting wood to accumulate enough crud on the optics to noticeably reduce cutting performance. I thought my tube was going bad, especially when the cuts started to look odd (like the beam was oval rather than round), but it turned out to just be a dirty lens."

So laser cutters present a whole set of issues...optic alignment and cleaning, fume vacuum system, and expensive tubes with a limited life.
The only thing you don't need that some CNC rotary router machines have, is a vacuum cutting table to hold down the pieces.
For the DIY hobby community, I'd bet there are 500 hobby CNC rotary router tables being made for every single hobby laser CNC table because of these very issues.

I too would recommend going the rotory cutter route...a CNC table using a dremel, a laminate cutter, or a small form factor router like the Bosh Colt or Makita compact Router.

Here's some websites to browse:
http://www.shapeoko.com/
www.openbuilds.com
 
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Balu

Moderator
Staff member
Admin
Moderator
#6
I wasn't able to cut 2.5 mm airplane grade plywood with a 40 W laser. It worked okish with a 60 W.
 
#7
My 40W laser from China / Ebay cuts 4mm plywood with two passes ... 2mm lite-ply with one high speed low power pass.

The power is adjustable from 0 to 100% in 1 and 10pt steps ..

Speed is adjustable from ultra slow to fast ...

Cutting wood is much easier to set-up than plastic or foam. Plastic melts and forms back often closing up / resticking parts together. Foam often the cu is so wide from foam melting. It takes care to do foam and plastic ..

I am drawing up a table over time to assist my setting up for each material - as they all need different combo's of speed and power.

There's a lot of crap spread about regarding the Chinese lasers - a lot of it sadly on specialist forums .. I gave up reading them after a while - and thought ... OK - I'l spend the money and find out the hard way.

Well - I bought a machine that was sold direct ex factory ... it has airfeed as well - that itself is a great advantage as it reduces overburn and flames ... I am totally sold on the machine ... it works .. it does what I want .. I just wish the working area was bigger !!

Here's a short thread about doing repairs to a Mig 3 that needed a new wing tip. Prevuously I would have cut by hand risking splitting the Lite Ply - but here I copied the good wing tip .. scanned into PC .. polylined and cut via the lser machine ... total time ? about 30mins. Repair completed that afternoon ...

http://www.wattflyer.com/forums/showthread.php?t=74855&highlight=laser

Here's an early run I did for a pal who sent me a template by email .. it was overpower and singed a bit - but it shows clearly ability ...


The reason the cutter goes all over the place when cuttiing isntead of one smooth op - the original template drawn up was in that sequence ... I didn't redraw to sort it - just used the raw poly info of the DXF file as supplied.

This machine allied with my bench saw .. my bench jigsaw ....... makes up a formidable tool set ...

The beauty is of course that my laser gear can be upgraded with longer guide bars to increase work space ... would need new cabinet of course - but at fraction of cost of bigger whole machine.

Nigel
 
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#8
100 watt Laser

I have built a 100 watt 4'x6' laser table. I also have purchased many sheets of DT foam and will be trying to cut the F-22.
I also have a 130 watt tube coming. I know I do not need that much power usually but as long as I can dial it back enough and still get the tube to fire I will have the power when needed. I have cut 3/4 inch thick hardwood in 1 pass with the 100 watt.(slow but cut it) 3mm birch ply was no problem at 40mm/sec.

I will post some results later in the week or weekend.