Drill a hole with a laser

[The Purple Death]

Hello,

TLDR: See bottom.
I've written this in long form for completeness. I'm sure I'd get a lot of questions otherwise.

So for some time I've had the option of getting a laser attachment for my 3D printer, but I never opted for that, because all I'd do with it is some engraving which wasn't as important as some of my other projects.
Well, recently I found myself needing to drill a lot of very very tiny holes in either very thin wood or very thin plastic (I'll have to try a few things to discover which is more optimal/workable). Holes that are 0.010mm-0.012mm in diameter. Now drill bits for such holes start in the hundreds of dollars (USD) for just one drill bit. As you might imagine, even if I used my 3D printer to hold the drill and do the drilling, I'd still probably break a few and so I'd end up spending thousands for these holes.

Then it occurred to me, I could use a laser to accomplish this! The problem is that most powerful blue lasers that I see people reviewing, visually appear to focus down to a few mm in size. That is to say, I'm orders of a magnitude off from the level of accuracy I require. Now I'll grant you, this could very well be a trick of the light. But still, I have no idea how to determine what the focus point size is for my laser at a given distance.

How do I get a blue laser to focus down to the size of 0.01mm-0.12mm?

Thanks!

 

[farbe2]

Focus size isnt a problem.
Its more "how deep do you want to drill" and "which color does your material have".

Often laser diodes dont burn holes that are round. Most diodes are elyptical in shape while some even aproach a rectangle.

There is also the problem of focusing. Which results in a cone like hole instead of a straight walled one like a drill would produce.
If that isnt a problem for your application, I would sugest using a beam formed sm diode to get a round hole. But it really depends on drill depth and absorbance of the material.

If you need say 5W blue to touch your material, you will only be able to drill a 10um hole for a depth of 10um. Thats not very deep.
Lower power diodes like a 405nm 1W sm diode will get you much deeper holes, something like 110um should be possible.
Still not very deep.

Story is much different for a 0,12mm hole, you are looking at roughly 13mm depth for the lower power diode and 1,3mm for the higher power ones.

So what is "very thin" for you? and whats plastic for you?

Forget about laserdrilling clear plastics with blue lasers.. the only laser capable of drilling clear plastic will get you at most a 0,5mm deep hole at 120um diameter.

 

[The Purple Death]

Focus size isnt a problem.
Its more "how deep do you want to drill" and "which color does your material have".

The main factor is that the material should be fairly tough, while being not electrically conductive. I could use thin paper, provided that I could stretch it so that it would be a flat plain. Likewise, I could use any sort of plastic wrap or other material. I know I'll have to experiment.

I could do almost any color in plastic. At the depths you suggested, I could only be using paper as a wood option. That would be brown paper or black. No point in buying white for use with a laser.

Often laser diodes dont burn holes that are round. Most diodes are elyptical in shape while some even aproach a rectangle.

Rectangular should work. Elliptical would be okay provided that it's really close to round.

There is also the problem of focusing. Which results in a cone like hole instead of a straight walled one like a drill would produce.
If that isnt a problem for your application, I would sugest using a beam formed sm diode to get a round hole. But it really depends on drill depth and absorbance of the material.

A cone could work. I'd have to play with changing the diameter of the holes.

If you need say 5W blue to touch your material, you will only be able to drill a 10um hole for a depth of 10um. That's not very deep.
Lower power diodes like a 405nm 1W sm diode will get you much deeper holes, something like 110um should be possible.
Still not very deep.

Why does laser power affect depth? Would a different color produce a deeper hole?

Story is much different for a 0,12mm hole, you are looking at roughly 13mm depth for the lower power diode and 1,3mm for the higher power ones. <snip>

The hole size is basically set in stone at 12um or smaller.

Thanks again!

 

[WizardG]

Given the parameters you've specified for the material and the size of the holes I think the BDR209 diode may be your best bet. It's a single mode diode that can be focused down to a very fine point and has enough power to punch holes in paper with ease. They can be touchy about current so I'd avoid anything over 6 or 7 hundred mA.

As to your question about how power affects depth, you're asking the wrong question. Our higher powered diodes are all multi-mode and won't focus as neatly as a single mode diode will. It's not the power, it's that multi-mode diodes have kinda sloppy beams.

 

[CurtisOliver]

Given the parameters you've specified for the material and the size of the holes I think the BDR209 diode may be your best bet. It's a single mode diode that can be focused down to a very fine point and has enough power to punch holes in paper with ease. They can be touchy about current so I'd avoid anything over 6 or 7 hundred mA.

As to your question about how power affects depth, you're asking the wrong question. Our higher powered diodes are all multi-mode and won't focus as neatly as a single mode diode will. It's not the power, it's that multi-mode diodes have kinda sloppy beams.

The BDR209 is a beast. So much single mode power with amazing beam specs and divergence.

 

[The Purple Death]

@WizardG , thanks, I should have recalled that.

So now I know that I should be looking for a diode SLD3237VF (that's what's in BDR209).

But what optics should I be using?

Being able to adjust the focus so that I can get a spot that is a few um in size is no ordinary feat. Granted, a cylinder is the shape my beam should be making, but from the replies so far,it seems that a cone shaped something is what I can expect.

Thanks!

 

[WizardG]

I'll let the laser CNC guys correct me but IIRC a longer focal length focusing lens will give you a longer 'blade'. The zone where the beam is narrow enough to do what you're after. But a shorter focal length lens can provide a smaller focused 'dot', but with a very short 'blade'. Being a single mode diode the BDR-209 can achieve very tight focus even with a G8 or G9 lens. Laser scrimshaw at its finest.

 

[CurtisOliver]

I'll let the laser CNC guys correct me but IIRC a longer focal length focusing lens will give you a longer 'blade'. The zone where the beam is narrow enough to do what you're after. But a shorter focal length lens can provide a smaller focused 'dot', but with a very short 'blade'. Being a single mode diode the BDR-209 can achieve very tight focus even with a G8 or G9 lens. Laser scrimshaw at its finest.

Yes. A longer focal will result in a wider beam waist but longer Rayleigh length and vice versa. It’s for that reason lens selection is quite important for laser processing. With CO2’s the typical lenses being used are 12.7mm (0.5”), 25.4mm (1”), and 50.8mm (2”). The 12.7mm lens is ideal for thin materials that require a high power density or need high resolution etching. 50.8mm is more ideal for thick materials as at least half the maximum energy density is maintained for a longer distance. But it’s not so good for fine engraving. This is the main reason most machines you’ll see are fitted with a 25.4mm lens as it’s a good all rounder.

Because you are now touching on guassian beam profiles we can actually go into why the BDR209 is a really good burner and it’s because of the M2 factor. M2 is the factor of how well a guassian beam can be focussed to its maximum physically allowed guassian beam for that wavelength. Single modes offer superior M2 factors to multimode diodes and therefore the beam waist is allowed to get smaller and the Rayleigh length can maintain the power density for longer.

 

[The Purple Death]

At the risk of sounding dense, how do I find the lenses that you suggest? Like what keywords or websites?

 

[WizardG]

DTR's Glass Lenses

Glass Collimating Lenses Installed in M9X0.5mm Threaded Barrels

dtrslasershop.com

I'd try the G8.

 

[farbe2]

Just a G8 won’t work. You will end up with a random spot diameter and an elyptical spot.

You need a lens system to form the beam to acceptable levels.
Expansion of the slow axis is needed to get the spot round first. Then a telescope to expand the beam to get your desired focal spot size and than a fixed pcx lens to focus your beam.

Do you have any constraints on how far away your laser module needs to be from your work?

Are you familiar with setting anamorphic prism pairs to form the beam?

As for material, kapton foil could be a good candidate as it’s designed to be electrical insulation.

 

[Eidetical]

Continuous lasers melt things. Because pulsed lasers vaporize, they're generally used for drilling holes. Your cheapest option is probably the conventional approach, even if you break a dozen drills. Pulsed lasers are used to drill pinholes easily down to 5 microns in stainless steel.

Deja vu?

 

[farbe2]

@Eidetical
Yes you are right, however everything pulsed will be very very expensive.
You would need 532, 1064 might already be too big of a spot - depending on drill depth.

However I would guess that you could also run the 405nm diode pulsed, won't result in higher peak powers but might be enough to reduce heat input and prevent melting. 2W CW (two diodes + PBS) could be good enough depending on material and processing speed requirements.

We definitely need more informations from the OP to check feasibility.

 

[Eidetical]

I'd look at an old ruby laser. Even a small one will poke such a hole into a razor blade. I made the video below over ten years ago.

 

[The Purple Death]

Just a G8 won’t work. You will end up with a random spot diameter and an elyptical spot.

You need a lens system to form the beam to acceptable levels.
Expansion of the slow axis is needed to get the spot round first. Then a telescope to expand the beam to get your desired focal spot size and than a fixed pcx lens to focus your beam.

Do you have any constraints on how far away your laser module needs to be from your work?

4 inches or closer. Theoretically, I can use a mirror to redirect the beam to another area (for just the laser diode and optics), thus eliminating any distance considerations.

Are you familiar with setting anamorphic prism pairs to form the beam?

No, but I'm willing to learn.

As for material, kapton foil could be a good candidate as it’s designed to be electrical insulation.

Thanks!

 

[The Purple Death]

@Eidetical
Yes you are right, however everything pulsed will be very very expensive.
You would need 532, 1064 might already be too big of a spot - depending on drill depth.

However I would guess that you could also run the 405nm diode pulsed, won't result in higher peak powers but might be enough to reduce heat input and prevent melting. 2W CW (two diodes + PBS) could be good enough depending on material and processing speed requirements.

We definitely need more informations from the OP to check feasibility.

The laser that we have selected, BDR209, is designed to be pulsed and at 2x the normal optical output power. I was assuming that we all knew that, but I guess not.