Contura switch bad results revisited with picture

[brian257]

I have attached a picture of a rocker switch that I have been doing some test engraving on. I am using a cheapie Chinese K40 laser with the Lightobject DSP upgrade. This switch was already factory engraved. If you look at the winch symbol in the middle of the switch and the word "WINCH" engraved near the top (upside down) you can see that the engraving is perfect. The edges are very crisp and clear and the engraving depth is very shallow and completely consistent over the engraved area. It is also a good milky white and easy to read (switch is white translucent backlight plastic with a very thin black surface that is engraved through). For reference, the letters are little under an eighth of an inch tall.

Now when you look at the parts I engraved (words "ANCHOR LIGHT" and the light symbol you can see that my results are nowhere near as good. It looks like melted plastic and has been turned shiney and translucent instead of the milky white. The edges are nowhere near as crisp and defined. If you look at the very lightly engraved "LIGHT" at the bottom you can see that it was not enough power to go all the way through the black, but as soon as I use enough power to go through the black it engraves many times deeper than the factory engraving and gives me the melted translucent surface instead of the milky white (and I have cut the plastic and verified that it is milky white very deep, it is not just that I am engraving too deeply, just melting the plastic).

I have tried different speeds and power settings. I did some with a shorter focal length lens than this and got better results, but still not good.

Can anyone tell me why I am getting such bad results? I understand that I am not using a professional expensive laser, but is there anything I can change to at least get better results? Do I need a higher quality tube, do I need better quality optics, is it the difference between a glass tube and an RF tube, is it something with my settings? Any help would be greatly appreciated.

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[Tech_Marco]

I believe that regular CO2 laser is not the best candidate for doing this kind of engraving. I was told that there is another kind of laser, something call "violet laser" (translate from Chinese).

If you must do CO2 laser engraving with better engraving quality, you must use shorter focus lens like 38.5mm instead of 50.8mm. If you want even better, then you got to have beam expander but it won't be able to fit into the K40 due to the lack of space.


Marco

[brian257]

I have seen violet laser modules from 300mW to 1.5W. These are the low cost diode modules with built in adjustable focus lens selling from $50-$150 from China. I realize this is very low power, but what I am looking for is very shallow engraving in plastic. Do you think something like this would give me better results for this application than a CO2 laser?

[Axeman]

I've seen these lasers in the past used in a different application.

Many of the guys I had seen were using the Blu-Ray diodes to engrave wood pictures. They would have up to 2W lasers with huge heatsinks strapped to the housings and then would control them using PWM modules. They could get apparently up to 256 shades of grey using the PWM and modulating the power of the diode into the wood grain, making photo realistic pictures. It was stunning.

For your application, you could simply strap on a diode + any heat sinks or mounting hardware and Tee off of the DSP's "laser on" signal line to enable your diode to turn on instead. Use all of your original hardware and software, simply have a switch to decide between your standard laser beam or the Diode.

If I can find the forum that had lots of these guys talking about it I will post it. I thought about doing it myself actually, just to have the extra level of stuff you could do but I ended up going to school, so I haven't had the time to finish it up.

[Tech_Marco]

Good idea! How could I forget that this! I talked to the president from RD DSP and he told me that only high speed laser could handle '256 grayscale' engrave work like RF laser. He said that a standard CO2 laser tube was incapable to do the job because of latency from the beam.

I have 200mW green laser and 2Watt 808 infrared laser module not sure if I can use it for the job. I guess I need to find a focus lens to handle 532nm or 808nm instead of 10.6um from a CO2 laser.

May be I can come up some goodies

Marco

[brian257]

I just went ahead and bought the 1.5W unit since it was only something like $65.00. I found it on banggood.com and it comes with the power supply, big heat sink, focusable lens, and a cooling fan. I am sure it is just a blueray type laser diode. I don't expect to cut anything like the K40, but for the very fine low power engraving I need it just may give better results than the CO2. I had planned on just strapping it to by K40 to see what kind of results I get. If it works good I might just build a new stage for it. I will post the results when I get it. Probably will be a week or two since it is coming mail from China.

[swamidog]

I just went ahead and bought the 1.5W unit since it was only something like $65.00. I found it on banggood.com and it comes with the power supply, big heat sink, focusable lens, and a cooling fan. I am sure it is just a blueray type laser diode. I don't expect to cut anything like the K40, but for the very fine low power engraving I need it just may give better results than the CO2. I had planned on just strapping it to by K40 to see what kind of results I get. If it works good I might just build a new stage for it. I will post the results when I get it. Probably will be a week or two since it is coming mail from China.

those aren't bluray diodes. their multimode ~445nm diodes that were intended for video projector light engines. the issue to be aware of is fast axis vs. slow axis divergence. ideally, you would focus at the point where the spot is symmetrical or you risk an issue of horizontal marks having a different thickness from vertical marks.

[brian257]

Thanks. I will pay attention and see if the fast/slow axis is an issue. I have that problem with the CO2 on small text and I think that is due to the tube not turning on and/or off fast enough. I am assuming(hoping) that the diode will turn on and off much faster than the tube does.

[Tech_Marco]

You can engrave fine text on CO2 laser with 1) shorter focus lens, 2) use beam expander.

Marco

[Techgraphix]

I think the material is just not right to laser.. from its behavior, I should say it is some Polystyrene like plastic. if so, it doesn't matter how small your dotsize or how low your power is.. it will melt..

Kees

[Tech_Marco]

That is true. In China, they use different kind of laser to engrave plastic. It is some sort of 'blue way' and it is not CO2 but through semi-conductor type laser diode. I'm going to try the laser burner module and 'm currently looking for a focus lens. I believe that those laser won't work on ZnSe focus lens because of different wave spectrum.

Marco

[brian257]

Techgraphics, this switch is specifically made for laser engraving, but as Marco says, companies doing these switches are most likely not using CO2 lasers so how suitable to CO2 engraving they are I don't know.. I ordered the blue diode cheapie laser, but it has not arrived yet. Coming from China so may be another week.

Marco, I am using a 25.4mm focus lens. I can't fit in a beam expander since it is just a K40 machine. I sent you some of these switches probably five or six months ago. Did you ever get a chance to try them on a machine you have and see if you get better results?

If anyone else has a better quality machine that does good small engraving or something with an RF tube and they would like to try engraving a switch for me just give me an address and I will send a sample.

[brian257]

Finally got the new diode laser last week. I have been very busy so I have not had a chance to rig it up on the K40 yet and add a solid state relay to the output of the laser controller to turn the diode on and off yet. Should be fairly easy to mount it and get it turning on and off with the LO controller.

I did play with it a little just adjusting the focus and moving the beam around on the switch part by hand and from what I can see it looks like I am going to get good results. I can tell that the beam can focus down to a ridiculously small spot size as compared to the CO2. It also looks like the beam gives me a good white line on the switch without excessively melting it. Based on this being done by hand without a constant or ideal focal length and the motion being at some unknown rate I was surprised at how good the results looked.

I don't expect to get very good results with this diode for cutting, but for this one specialized application I think it is going to work better than the CO2. Might just wind up when I upgrade to a bigger CO2 laser that I have the diode mounted for fine engraving and the CO2 for cutting and fast engraving of bigger letters. Didn't get into it much, but looks like the controller will control two lasers. Would be great if the software can control two lasers and compensate with a fixed distance between the beams.

[DonL]

You can engrave fine text on CO2 laser with 1) shorter focus lens, 2) use beam expander.

Marco

I tried the shorter focal length lense and without any other mods to the K40 I got OK results engraving wood, I will post a photo after the upgrades.

This is a 4x4 inch block of pine and the photo was not very good, grainy from over compression.
as you can see by photo 2, the letters are about .6mm wide so that is pretty fine.

[DonL]

Techgraphics, this switch is specifically made for laser engraving, but as Marco says, companies doing these switches are most likely not using CO2 lasers so how suitable to CO2 engraving they are I don't know.. I ordered the blue diode cheapie laser, but it has not arrived yet. Coming from China so may be another week.

Marco, I am using a 25.4mm focus lens. I can't fit in a beam expander since it is just a K40 machine. I sent you some of these switches probably five or six months ago. Did you ever get a chance to try them on a machine you have and see if you get better results?

If anyone else has a better quality machine that does good small engraving or something with an RF tube and they would like to try engraving a switch for me just give me an address and I will send a sample.

It has been some months now, what did you find as a solution? I have a 500mw blue laser from China and it does a great job on items with a low flashpoint like wood, foam rubber, and plastic. There is no power setting, just speed. and it has more of a wratcheting stepper, id does not fly back and forth but rather more of a click,click,click... it does have a very fine dot size.