Newbie needs advice from the pros

[SgtSage]

Hello All,

I have recently decided to start my first laser project. It will be a laser cutter/etcher project that will be largely made with parts from OpenBuilds Part Store. It's a open source website that has a lot of CNC, 3D printer and laser builds. I'm largely a embedded electronics guy and I'm weak in the mechanical sense so this has helped out a lot.

Anyway, the part that is the newest(and probably the scariest for me) is the laser. I've dumped a lot of time into figuring out which laser I'm going to use and how to use it. This site has actually been a lot of help to me. I've read through the "I want to build a laser" thread a few times and feel like I have the basics down. I really do appreciate the info that has been put into these forms, it's helped out a lot

The main part of this post is actually a question about laser safety. I want to be practicing best possible laser safety. I'm planning on using a 2W 455nm M140 M-Type diode laser, more then likely it will be purchased from DTR's laser shop (with the a copper host and G-2 lens). I already have earmarked a pair of Eagle Pair 190-540nm Slip Over Laser Safety Goggles that I will make sure to wear 100% of time time the laser is powered on(probably more accurate anytime the laser cutter is powered on). Currently I have not ordered the structural materials for the laser cutter as I'm waiting for parts to come back it stock. Though, I do have a 3D CAD mock-up of what I think it will probably be.

In the attached Figure 1, I have what I was originally planning. Although because of safety concerns I've seen in these forums I'm thinking of redesigning it. I'm worried that when then laser is cutting, there will be scattering/reflections on the horizontal plane. I've read that I can put colored plexi glass to act as walls, but I'm confused about how this can be considered safe when a pair of good safety goggles can be $50-100 and a pane of plexi glass will only be $5. To me it seems that using plain plexi glass will do almost nothing because it does not have any OD level protection. Would it be far safer(granted less visually appealing, but worth it because I love being able to see) to use something that is not opaque like wood?

In the attached Figure 2, I did another mock up with something on the 4 walls to protect against the scattering/reflections of the laser. I also ended up adding a full cube frame for better stability. Even after this I'm still kinda worried about how the top is open. So I'm thinking about expanding some of the rails and designing a top hatch so the laser cutter would be encased.

Although, I stared to hear things about how smoke is bad for the laser. I've seen a lot of builds that incorporate fans into the bottom walls of the structure to create air flow, but it seems like a odd concept for me that I feel like I need help with. First, wouldn't putting a few fans into the enclosed box just giving the laser a chance to escape which would just void the point of having it in a box? Second, how does smoke hurt the laser? Is it the fact that when cutting materials which produce smoke(such as etching wood), the laser will reflect off of the smoke back into the lens and housing of the laser causing it damage? Or are fans just there to pull/push air from/onto the heat sink of the laser to keep it from overheating?

I guess the overall point is, am I being overly paranoid about this in terms of building the laser cutting into a box or would it be fine with just walls and no lid?

Sorry for the novel, but thank you for any help and time,
Sage


TL;DR: Starting a laser cutter/etcher project, need suggestions on laser safety with laser scattering and reflection. What type of materials other than safety goggles should I be using? Is it worth it designing it totally enclosed?

 

[Teej]

What are you going to be cutting/etching?

You can actually buy OD rated panels, with specs similar to the safety goggle specs. That way, you can build a containment similar to the Plexiglas version you had in mind, but with those instead.

Laser Acrylic Sheeting

For example

 

[doubleone44]

Just a bit of laser diode advice:
If you are planning to do small spots, get the 405nm diode from DTR (BDR-209). It's a bit more expensive, and seemingly lower in power, but due to it's beam characteristics it can make much smaller spots with a lot higher power density, for faster and easier cutting.

 

[diachi]

You'd be fine with coloured plexiglass, similar to the orange "UV Protective" polycarbonate eye glasses you see all over the place. If everything is securely fastened onto the frame and the laser can only point downwards you don't need to worry about direct beams penetrating the walls, only specular reflections which shouldn't be an issue. Unless you're using a mirror for the base of your engraver ... Or spend the extra cash and get OD rated panels ... I wouldn't worry too much though. Some may disagree. Could also just go with some thin Aluminum plate (2-3mm) walls and an orange plexiglass or polycarbonate lid.

As for smoke and fans - you can still use fans with your enclosure, you'd just want to build some sort of light trap around them so that air can flow but light cannot escape. One way you could do this is to mount fans to the bottom of the case, then have a "raised floor" where the material you are etching will sit. Around the raised floor you could have a gap for airflow that would allow smoke to get sucked out of the bottom but would trap most of the light. There are other ways to do this, but that's the general idea.

Smoke is bad for the optics, it can fog up your lens with various contaminants depending on what you are etching. This results in a beam with lots of "speckle", reduced beam quality and reduced output power. In the end your engraver won't work as well as it once did without cleaning the optics.

With a powerful enough laser you can burn or even crack the lens. I don't see that being an issue at 2W with a glass lens.

You will need a heatsink for that diode. I'd get one with an attached fan too.

 

[SgtSage]

What are you going to be cutting/etching?

You can actually buy OD rated panels, with specs similar to the safety goggle specs. That way, you can build a containment similar to the Plexiglas version you had in mind, but with those instead.

Laser Acrylic Sheeting

For example

Good to know. But at that price point, I might just go with thin wood walls or what ever I end up finding at Lowes/Home Depot.

Just a bit of laser diode advice:
If you are planning to do small spots, get the 405nm diode from DTR (BDR-209). It's a bit more expensive, and seemingly lower in power, but due to it's beam characteristics it can make much smaller spots with a lot higher power density, for faster and easier cutting.

Hmm, that seems like it might be better for more detailed work but wouldn't that limit the depth/power I would be able to cut? I was thinking of being able to cut thin balsa word and various types of paper(cardboard/presentation board/different weights of cardboard stock).

You'd be fine with coloured plexiglass, similar to the orange "UV Protective" polycarbonate eye glasses you see all over the place. If everything is securely fastened onto the frame and the laser can only point downwards you don't need to worry about direct beams penetrating the walls, only specular reflections which shouldn't be an issue. Unless you're using a mirror for the base of your engraver ... Or spend the extra cash and get OD rated panels ... I wouldn't worry too much though. Some may disagree. Could also just go with some thin Aluminum plate (2-3mm) walls and an orange plexiglass or polycarbonate lid.

Yeah, Teej mentioned the OD rated panels but I'd rather not spend that much extra cash and just go with the thin wood/aluminum plate walls and the plexiglass you mentioned. Do you have a favorite source for the plexiglass or poly-carbonate?

As for smoke and fans - you can still use fans with your enclosure, you'd just want to build some sort of light trap around them so that air can flow but light cannot escape. One way you could do this is to mount fans to the bottom of the case, then have a "raised floor" where the material you are etching will sit. Around the raised floor you could have a gap for airflow that would allow smoke to get sucked out of the bottom but would trap most of the light. There are other ways to do this, but that's the general idea.

Good ideal! I didn't think of that really at all, i'll try a rework of the design and let you know what I come up with.

Smoke is bad for the optics, it can fog up your lens with various contaminants depending on what you are etching. This results in a beam with lots of "speckle", reduced beam quality and reduced output power. In the end your engraver won't work as well as it once did without cleaning the optics.
With a powerful enough laser you can burn or even crack the lens. I don't see that being an issue at 2W with a glass lens.

Do you have a preferred lens or is the G-2 a good one?

You will need a heatsink for that diode. I'd get one with an attached fan too.

Already planned that out. What ever diode i'm going to buy, i'm going to get it with a copper host then I'm planning on putting it in a large heat sink from z-bolt[/COLOR]