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8321

Show"N"Tell ( What you have made with your CNC machine.) / Re: My first attempts at laser engraving.

« on: May 25, 2009, 09:27:34 AM »

Hi Mark,

Thanks for your input on this thread.
 
I have a 'Q Switch' on my YAG laser which does as you say bend the beam but It is too large for this project also it is designed specifically for 1064 nm and not a 655 nm red laser. I will check ebay more often to see if anything comes up.

After much experimentation I have now decided to use a shutter system for beam on/off which is driven by a small 4 position stepper motor (couldn't find a galvo without having to buy a disco light and stripping it for the parts) linked to the Z axis direction signal. It is quite fast in operation, performs like a galvo and seems OK. I am using PRF modulation of a 20nS pulse for control of the diode power output but am still experimenting with different pulse widths and modulation circuits.

To me, probably the most surprising thing about this project is that low power lasers do have useful applications with CNC machines.

Best regards,

Tweakie.

8322

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: May 25, 2009, 04:54:51 AM »

My Dad told me about Inches - they are best to be avoided.

Tweakie.

8323

Show"N"Tell ( What you have made with your CNC machine.) / Re: My first attempts at laser engraving.

« on: May 24, 2009, 06:35:45 AM »

Well Chris the results were not successful. I cut your pendant, before my wife had even noticed that the candles were missing from the lounge, it is nowhere near to your high quality of work but OK for my testing. I have concluded that with a point laser beam the heat generated is too localised to cause the type of surface reflow of the wax that is required. This does not mean that it is not possible but I think that the beam would have to be modified to more of a fan shape and of course that would require considerable power from a laser and well beyond my 150 mW.
My point beam is smaller than 0.1mm so in the test I used a step over of 0.1mm and the surface finish of the wax was not improved at all – in fact it was a lot worse. The microscope photos show the surface finish after machining and after laser treatment. It was a long shot but who knows it might have worked !.   

Tweakie.

8324

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: May 22, 2009, 12:57:40 PM »

No you don't  - you just love it !

Tweakie.

8325

Show"N"Tell ( What you have made with your CNC machine.) / Re: My first attempts at laser engraving.

« on: May 21, 2009, 07:28:52 AM »

As far as I can see the Z dwell is no problem as this can avoided by the Z inhibit function within Mach. The major problem here is that your existing toolpath makes multiple X passes between each Y move and you would probably end up producing laser marks to replace the tool marks. 

Tweakie.

8326

Show"N"Tell ( What you have made with your CNC machine.) / Re: My first attempts at laser engraving.

« on: May 21, 2009, 03:20:52 AM »

OK Chris, I see the application - brilliant idea. If you use modulation to control the laser (0 to 15kHz say) you will be able to have full command over the amount of radiated power from the laser for any feed rate that you choose. I have not seen modulation units for sale but it would be relatively easy to construct, I think, using a 555 timer or the like to create a variable PRF of a fixed width pulse. I will give this more thought and report back.

Tweakie.

8327

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: May 20, 2009, 07:08:18 AM »

You have just gotta get more sleep buddy.

Tweakie.

8328

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: May 19, 2009, 12:38:50 PM »

Thanks Chris - I can tell that it is 2 am. 

Tweakie.

8329

Show"N"Tell ( What you have made with your CNC machine.) / Re: Gertrude Gets Some!

« on: May 19, 2009, 07:50:12 AM »

Chris,

How and where do you now attach the sprue to pour the casting now that the hub has been removed ?.

Tweakie

 

8330

FAQs / Re: Laptop requirements with Mach 3

« on: May 19, 2009, 07:47:13 AM »

This is certainly a good forum with so many people sharing their ideas and solutions to problems.

Tweakie.