I am an optical and electrical engineer with a Sherline CNC mill in my home shop. Consulting is slow right now so I decided to design and build a ten watt CO2 (wavelength 10.6 microns) laser to strap onto my CNC mill.
I have designed optics for several large micromachines using UV excimer lasers so I feel that I have the optical design well in hand, even though this one is IR. Gas delivery and cooling are the challenge for me. Anyway, if it weren’t a challenge I wouldn’t learn anything or have any fun.
My plan is to focus the diffraction limited Gaussian beam to about 400 microns (0.016 inches) diameter at the center of a 3mm (1/8 inch) range (Z axis). This will produce an average of 8000 watts per square centimeter over the Gaussian spot with a peak of 16000 watts per square centimeter at the center of the Gaussian spot.
I expect full Gaussian beam divergence of 33.74mr (1.93 degrees). The defraction limited beam diameter will be less than 404um at the top and bottom of the 3mm Z range.
My little CNC mill can feed at 20 inches per minute on any combination of 3 axes.
My question is: What can I reasonably expect to cut or engrave with this laser and how long would these operations take to complete?
The laser will be operating CW (simple on/off switch from Gcode) and not pulse-synced to XY distance traveled so I don’t expect to have precision control over cut depth. How might this effect cutting? How might this effect engraving?
A 10 watt laser is on the small side. I’ve got a 30 watt and wish i had a 50. Power is a factor based on what materials your trying to engrave. Laser engraving is only x/y. Depth is fixed. Laser engraving can only engrave flat surfaces.
I’ve been looking at the cnc version of the sherline for another project I got in mind. Pretty slick little machines. I can’t invision what you have in mind but it sounds like you know what your talking about. It just seems to me that a small bit would have about the same precision as the laser but with more cutting power.
Its possible and it might be a fun project but I really don’t see the advantage.
I don’t really want to engrave or cut anything in particular. I really just want to design and build a CO2 laser…just for the experience. When done, I would replace the spindle on my CNC mill with the laser and focusing lens…just as a way to demonstrate doing something with a laser on a small CNC machine. Maybe I’ll just cut shapes out of some thin material.
I have had very little success at finding out what can be engraved or cut as a function of flunece. I chose 10 watts CO2 slow flow cuz that is about a 12 inch long package that weighs less than the 10 pound spindle and motor that the laser would replace. Might get away with forced air cooling but I’ll add water cooling if necessary.
I could build a 30 watt ot 50 watt laser but then everything would cost more, be larger, be heavier, be more complex. I can only get that serious if I can derive income somehow.
About your 30 watt laser, I presume it is a CO2 laser. Sealed or flowing gas? High voltage electrodes at the tube ends or RF along the sides of the tube or something else?
What size spot do you usually focus to? What materials can you engrave easily? What materials can you engrave with difficulty? What kind of materials can you not engrave?
Can you cut any material? If so, what materials and how thick?
Is your laser power or pulsing scaled with XY speed or is the power fixed once turned on?
Is that 6 inches per minute cutting through 1/4 inch acrylic?
To keep it simple (i.e. no turning mirrors), vertically oriented with the laser pointing down at the target.
The standard Sherline Z stage can move at 20 inches per minute carrying 10 pounds due to spindle and spindle motor. So up to 10 pounds of laser can be mounted in place of the spindle and spindle motor with no modification of the Z axis itself.
Much longer than 12 inches of tube or much heavier than 10 pounds and I would likely mount it horizontally behind or above the mill someplace. Then route the laser with mirrors until it is coming down the Z axis. The final focusing lens would be located about where you would normally have the chuck for an engraving bit, a few inches above the target surface.
I am a little concerned about debris falling on the lower window or mirror of a vertically oriented tube. But laser folks have said it is not likely to pose a problem. Also, I can remove the windows and mirrors for cleaning or replacement whenever I wish. The process of cleaning and aligning does not bother me. But replacing, if too often, could be expensive.
One way to reduce replacement cost is to use a 1 inch diameter sealing window or mirror where only 1/4 inch diameter is exposed to tube debris. This allows the dirty or damaged window or mirror to be rotated to a clean area rather than replaced. Smaller optics are slightly less expensive than 1 inch optics but not if you compare 6 small replacement optics to 1 larger optic rotated to 6 clean positions.