Because 670nm is smaller than 0.005mm, 0.00067mm to be exact.
That 0.00067 is the smallest possible spot size, you’ll never achieve that due to blah blah blah. 0.005mm is very good.
Their description gives the hint:
“A highly focused red light laser diode is moving step-wise alongside that drum, driven by a precise stepper motor with worm and gear drive.”
They’re using a lens with a very small focus length, say 10mm or so. Shorter the lens, the smaller the dot, but also has a very small depth of field. There is only a small distance from the lens where the spot size is at is smallest (the beam is hourglass shaped).
Using a scanning mirror means the distance between the lens and the film varies, so the spot varies in size too; they use a stepper to move the laser back & forth to keep the beam in focus and have a consistent spot size.
You also need to read the fine print, especially where it talks about the gaps between two lines. They state 0.01mm (ie twice the line size) and that’s because the lines aren’t solid, they have blurry edges due to scatter. If you try to draw two lines close to each other the blurry edges overlap and you get one thick line.
Tony
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
Sent: Sunday, 21 December 2014 4:17 AM
To:
Homebrew_PCBs@yahoogroups.comSubject: RE: [Homebrew_PCBs] Re: laser ablation of paint on copper clad
The Bungard photoplotter uses a red 670nm laser diode. The spot size is 0.005mm/0.0002inches which produces 5,000 dpi resolution. How is a 0.005mm spot size achieved with a laser diode?
http://bungard.de/index.php?option=com_content&view=article&id=43&Itemid=60&lang=englishJeff
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, December 20, 2014 5:02 AM
To:
Homebrew_PCBs@yahoogroups.comSubject: RE: [Homebrew_PCBs] Re: laser ablation of paint on copper clad
They’re YAG lasers, so yeah $$$$$ is right.
Spot size starts with wavelength, smaller wavelength = small spot, so UV < Visible < IR.
A YAG will be 1/10th the size of the typical IR CO2 lasers simply due to frequency of the light.
A lens with a short focus is next, a problem there is scanning and short focus don’t get along well.
“How big is the spot” varies depends on a lot of variables, including defining just what the spot itself actually is (scatter etc).
Save your pennies and get one of these:
http://www.youtube.com/watch?v=mzmjGz0_joM. My reaction to seeing that was “That’s awesome!” – most lasers can’t etch copper, indeed some systems use copper mirrors for that reason.
Tony
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
Sent: Saturday, 20 December 2014 5:40 AM
To:
Homebrew_PCBs@yahoogroups.comSubject: Re: [Homebrew_PCBs] Re: laser ablation of paint on copper clad
HI, jeff
On this page :
http://www.beamtech-laser.com/en/proInfo.aspx?m=20101216100729203892 <
http://www.beamtech-laser.com/en/proInfo.aspx?m=20101216100729203892&n=20101222115304745038&protype=20101216101714765927> &n=20101222115304745038&protype=20101216101714765927
they speak of that kind of laser spot resolution.
But only by the looks of it I think its going to be a $$$$$$ digit number ...LOL
camillus
On 12/19/2014 10:43:29 AM, jeff.heiss@... [Homebrew_PCBs] <homebrew_pcbs@yahoogroups.com> wrote:
The Bungard drum plotter has laser spot size of 0.005mm/0.0002inches. This is a resolution of 5,000 dpi. The laser inside is a red 670nm laser. How do they achieve this? What laser and lenses are used?
Is red sensitized photoresist film common? Where can it be purchased?
Photoplotter <http://bungard.de/index.php?option=com_content <http://bungard.de/index.php?option=com_content&view=article&id=43&Itemid=60&lang=english> &view=article&id=43&Itemid=60&lang=english>
<http://bungard.de/index.php?option=com_content <http://bungard.de/index.php?option=com_content&view=article&id=43&Itemid=60&lang=english> &view=article&id=43&Itemid=60&lang=english> Image removed by sender. image
<http://bungard.de/index.php?option=com_content <http://bungard.de/index.php?option=com_content&view=article&id=43&Itemid=60&lang=english> &view=article&id=43&Itemid=60&lang=english> Photoplotter
Filmstar-Plus is the name of the next generation of our bitmap photoplotter series. Optimized for inhouse production of high end film layouts at reasonable p...
<http://bungard.de/index.php?option=com_content <http://bungard.de/index.php?option=com_content&view=article&id=43&Itemid=60&lang=english> &view=article&id=43&Itemid=60&lang=english> View on bungard.de
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Jeff
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