Cheapest laser cutter with small kerf?

[David Wingate]

Hello, SMC folks. I've been reading around here for a long time, and just wanted to thank everyone for all of the wisdom that you share.

tl;dr: I'd like to find a laser cutter capable of cutting paper with a very small kerf and minimal burning. I'm a hobbyist, so price is the driving concern. I'd like to know what folks recommend.

Long version: I'm a hobbyist looking to buy a laser cutter for small-volume art projects. I've been able to prototype my designs on a machine at work (ULS PLS 4.75, 75W, 2.0" optics), with excellent results. I think that machine has spoiled me! But now that I'm trying to sell my designs, I can't use that cutter any more. So I need to buy my own.

However, when I've started looking at machines that I can afford, I've been disappointed in the results. Tried FSL (45W) and BOSS (150W), but the kerf was too big and I lost all of the detail on the project. (Yes, it's super detailed - I'm trying to maintain features that are ~0.25mm).

As far as I can tell, this is because the kerf of any glass-tube machine will be too large. I measured the kerf of the FSL machine at 0.02", but I think I need something that's more like 0.01" (with the ULS, I was getting more like 0.009").

I've looked into the big manufacturers -- Trotec, Epilog, ULS -- and while I think their machines could probably do what I want, they're just too expensive for me. My budget is ideally $5-6k. Maybe I could stretch to $8k.

So, I have two questions:

1) What's the cheapest machine for highly detailed vector engraving, with small kerf? I'm assuming I need a metal tube. Since I'll only be cutting paper, I think wattage is not an issue. I don't need to cut thick material, etc. This seems like the simplest possible case for a cutter!

2) Are there any brands I should be looking at that are capable of this kind of detailed work?

Would love any thoughts folks may have. Thanks in advance!

D

PS - I have attached several example images of what I've been able to achieve on the ULS machine. In all the photos, each circle is 35mm in diameter. In the first few images (with the penny), you can see some nicely detailed cuts + engraving (from the ULS) side-by-side with another test on a worse machine (note the lack of detail + charring). I included some additional images just to show the flow of the project - small circles are stacked together and encased in glass to create miniature ornaments that are about 1.5" in diameter.

[John Lifer]

Find a used Epilog Mini. Have seen several in your price range and being a small machine, it would fit your needs well.

[Howard Garner]

The Univeral Versa Laser should also work for this.

Howard Garner

[Doug Fisher]

Are you sure you are not using more power than you need? Also, a 1.5" lens might serve you better.

[Dave Sheldrake]

Kerf is a product of Incident beam diameter, focal length and M^2.... Excitation method helps on cheap vs expensive tubes but being glass is for a simple reason...it's non conductive in DC lasers

If you are looking for a metal tube that is what will make up most of the machine cost (RF tubes)

Failing that switch wavelengths

Drop to 532nm and you can get surprising results , going lower can help the actual cut mechanism as well based on the cut being photochemical vs photothermal (in many materials subject to their bandgap energies) and can be achieved with much lower actual raw power, start thinking 0.75 - 1 watt

[Bert Kemp]

Cut this out of paper on my Rabbit 60 watt you don't need 60 watts 40 even 30 will cut paper easyIMG_20180729_161805688_LL (Copy).jpg

[David Wingate]

Thanks for all of the replies. I've tried a 1.5" lens (on an FSL machine), and it didn't make a significant difference.

@dave sheldrake: I'm intrigued by the idea of changing wavelengths. How exactly does one drop to 532nm? I assume that involves a tube replacement?

[David Wingate]

Right! That's what I assumed - that paper ought to be the easiest possible case for laser cutters. That's why I was surprised when these machines couldn't seem to do an excellent job...

I like your results. Maybe I'll have to look at a Rabbit now...

[Bert Kemp]

I would suggest talking to Ray Scott at Rabbit Laser, maybe send him a file and some of the material you use and see how it works on it.

[Dave Sheldrake]

Thanks for all of the replies. I've tried a 1.5" lens (on an FSL machine), and it didn't make a significant difference.

@dave sheldrake: I'm intrigued by the idea of changing wavelengths. How exactly does one drop to 532nm? I assume that involves a tube replacement?

Totally different wavelength David, 532nm is green and the beam is a much thinner wavelength (it's 532nm wide) so the smallest focal spot you can achieve is orders of magnitude smaller, you cannot achieve a spot size smaller than the wavelength (well for practical purposes anyways although MIT have actually done it)

A CO2 (IR) beam can only be reduced to 10,640 nm, the Green is 532nm so your potential smallest spot size is 20 times (roughly) smaller diameter.Usually Green lasers are frequency doubled IR's but none of that really matters, what they do have is VERY high power density due to the smaller spot size

at 10,640nm the spot area is 89 um
at 532nm the spot area is 0.22 um

1 watt of input power in IR and you have 0.112 watts per Sq um
In green @ 1 watt you have 4.54 watts per Sq um