Author Topic: The Laser Project.  (Read 782233 times)

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Offline Ya-Nvr-No

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Re: The Laser Project.
« Reply #820 on: December 30, 2013, 08:42:20 AM »
Use some of that income you received for your cmm touch probe design.  ;)

Thou I  never seen it come to market. They just buy it to kill it ???

As far as the Ted 5000:
I installed a big central vacuum this past month for my shop and noticed that my projected electric bill will be going up.  :o
But being able to live dust free and work the winter months, priceless.  ;D
Really an education on the energy hogs and teaches you to shut things off or use timers. (Air compressors & Water Heaters,  :'()

Offline NODEGAMRA

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Re: The Laser Project.
« Reply #821 on: December 31, 2013, 07:15:43 PM »
Hi guys and thank you Tweakie for this great plug-in.
Total NOOB here and I am just getting started with laser engraving.
I have tested it by engraving simple shapes and it works perfectly.

I do have a question...
Is there any way to make the engraving from top to bottom, instead of bottom up?
 
Any info would be greatly appreciated.
Thank you.


Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #822 on: January 01, 2014, 03:12:00 AM »
Hi Nodegamra,

As it stands the pluglin is configured to only engrave from the bottom up.
Perhaps, at the next revision, I will consider adding selectable origins (centre and each corner) for the X0, Y0 starting position as, for me, a centre origin would be useful.

Armagedon  ;D

Tweakie.

 
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline texaspyro

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Re: The Laser Project.
« Reply #823 on: January 26, 2014, 01:31:20 AM »
I built a couple of laser diode heads for my desktop mini-mill.  One uses a 3 watt 445 nm multi-mode blue laser.  The other uses a 0.7 watt (driven at 0.5 watts max) 405 nm single-mode near-ultaviolet laser.  Single mode lasers can be focused to a smaller spot than multi-mode lasers.  My main application is cutting solder paste stencils.

Here is a Tweakie Bike cut from 0.032" bassword (0.063" balsa cuts the same) using the 405 nm laser.  Cutting was at 8"/minute.  Two passes were used to assure that the bits fell out... otherwise residual fibers can cause them to hang and punching them out can break things (particularly in balsa) due to the tiny features.

I converted Tweakies g-code to DXF and then converted the DXF to Mach3 gcode to control my laser.  Laser power is set via the "S" spindle speed word.  Spindle power mcodes control the laser power supply and coolant mcodes control the co-axial assist air (via a small 12V diaphragm pump).

The features in the DXF are 1mm wide.  After cutting,  the features measured 0.98mm...  works out to a kerf width of 0.0005" !  The laser lens is 4" from the cutting surface.  With a shorter throw,  the spot can supposedly be focused to 0.01mm

« Last Edit: January 26, 2014, 01:34:52 AM by texaspyro »

Offline Tweakie.CNC

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Re: The Laser Project.
« Reply #824 on: January 26, 2014, 02:14:32 AM »
Excellent work my friend, I look forward to seeing some pictures of more of the things you make.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline texaspyro

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Re: The Laser Project.
« Reply #825 on: January 26, 2014, 02:41:34 AM »
Here is a solder paste stencil cut in vellum paper.  The pads on the QFN20 packages are 0.5mm apart.  This one was cut without assist air.  The air really helps to reduce over-burn of the edges.  Without it the edges seem like they want to smolder some, expanding the size of the cutouts.  Sorry for the bad focus... it's all the camera will do.

With visible light lasers,  the color of the material greatly affects the cutting ability of the laser.  White or purple does not cut well at all (well being defined as faster feed rates and lower powers).  Red and black cuts well,  green a little less,  and yellow a little less.  Most cutting of stencil materials is in the 4"/minute and  1/3 to 1/2 power range.  Lower feed rates tend to work better since mill acceleration effects are minimized (i.e. small features cut the same as longer ones) and lower powers cut better (less over burn and longer laser life).  White papers cut very inconsistently...  some pads cut perfectly,  others hardly at all...  on the same sheet. 

Paper vellum (a translucent plasticized cotton paper) is one of the best materials that I have found for solder paste stencils.  It cuts very cleanly and is the proper thickness (0.003") and is very cheap (50 cents/square foot). It holds up well for small prototype runs.  I have also had good success using an orange colored copier paper from Staples.  It is a little over 0.004" thick and dirt cheap.   I can cut Kapton,  but not as well as vellum... plus it costs a bundle (over $15 sheet)  Mylar sucks...



Offline Fred27

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Re: The Laser Project.
« Reply #826 on: January 26, 2014, 03:42:27 PM »
I've never heard of vellum for solder stencils. That sounds interesting. I've successfully cut Mylar with a 40W CO2 laser (an eBay special with a Chris Circuits controller board) but it did suffer a little from the edges thickening where it melted. Covering with masking tape (both sides) before cutting and some gentle fine sanding afterwards helped and and it worked fine.

Incidentally, how do you control the laser power using the S command? I'm thinking of doing something similar to mine - maybe adding PPI control from gcode. I'm happy to custom design a controller but still not sure how best to get the setting from Mach3 to my board. Modbus seems to be a bit outdated and need serial in addition to parallel. PWM isn't really what I need. Getting into plug-in development seems a bit over the top. Ideally I just want some data sent via a parallel port pin. Any helpful hints?

Offline texaspyro

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Re: The Laser Project.
« Reply #827 on: January 26, 2014, 05:29:27 PM »
I am using a Flexmod P3 driver.  It has analog modulation.  I use the MACH3 spindle speed PWM feature to make an analog control voltage (via a Gecko G540 controller).  The Flexmod driver has pots that set the minimum and maximum laser diode current.  I have the minimum set to what the laser needs to just get cranking (around 5-10 mW output).  Spindle speed S0 produces 0V and S9000 produces max laser current.  Theoretically S5000 should be max power/5V output,  but probably due to light loading on the Flexmod input,  my laser power maxes out at somewhere between S6000 and S9000.

The laser power supply (a 9V regulated wall wart supply) is plugged into the mill controller spindle relay.  I use the spindle M-codes to switch the laser power supply ON/OFF and the coolant relay to control the air pump.  The Flexmod has a 7 second soft-start delay between applying power and allowing full laser output.  My gcode puts in an 8 second dwell after switching on the laser power supply and air pump.  That delay and the pump noise also provide some safety warning in case you forgot your laser goggles...

Offline texaspyro

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Re: The Laser Project.
« Reply #828 on: January 26, 2014, 06:07:23 PM »
I've never heard of vellum for solder stencils. That sounds interesting.

I have tried just about everything that looked like it might work for stencils (and a few that didn't).   So far the best results (cutting tiny features that hold up to the Toothbrush Scrubbing Test From Hell) have been with the vellum and the Bright Orange (24 lb?) copier paper from Staples.  They both seem to hold up will with use (but I've only done maybe a dozen boards with one stencil) and couldn't cut cleaner.  I have cut  0.15 mm pads spaced 0.15mm.

Something else that works very well cut-wise is self-stick vinyl.  But it makes nasty vapors.  Also the sticky had some advantages (keeps it in place on the board) and some dis-advantages (hard to align, particularly on larger boards).

I first found the vellum a Michael's on clearance...  and it looks like they have stopped carrying it.   I found the red vellum at Hobby Lobby.  This place also looks promising:  http://www.hyglossproducts.com/Vellum-Translucent-Paper-p/58203-1.htm

For very nice Kapton stencils for cheap try OSHSTENCILS.COM   Kapton stencils are good for several hundred boards.
« Last Edit: January 26, 2014, 06:10:11 PM by texaspyro »

Offline texaspyro

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Re: The Laser Project.
« Reply #829 on: January 27, 2014, 02:45:36 AM »
I did the "Engrave TWEAKIE in a grain of rice" test.   Not having any rice,  I marked a piece of Kapton.  I can read the 100 micron tall letters with a hand lens,  but the 50 micron ones will need a microscope.  I can tell there are individual letters, but can't make them out.  I could probably improve things with some proper attention to focusing.  the laser is just focused by (remaining) eye right now.