reflection mirror from a old Hardrive disc

Discussions on optics for laser cutter/engravers

reflection mirror from a old Hardrive disc

Postby a542002 » Thu Jan 12, 2012 10:18 pm

Hi all
here are something I came up because the last of my reflection mirror was damaged.
I remembered the old days as we used old harddrive disc as mirror and because I have a lot of them laying around I took one appart and first try this with the dremel and a diamond cutting blade but it did not work out .
next I thought taking a metal snip and it realy worked great I cut a not quite round piece in the size of my mirrors out and put them, in the gantry holder
then I started a job where I could compare with one with the old mirrors
it worked the same like the goldplated mirrors.
here are a picture of the HD dis cut and the final mirorr also a sample engraving what shows no difference.
I did not have to adjust anythings
thats maybe some help if somebody runs out of new mirrors like me
greetings
walt
mirrorsample.jpg
thats the HD disc in progress
Attachments
mirrorpicture.jpg
thats the result exactly like with the goldplated mirror, just much cheaper
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Re: reflection mirror from a old Hardrive disc

Postby iGull » Thu Jan 12, 2012 10:54 pm

Nice one Walt !

Extremely useful tip.

Now, for your next trick, can you make a 50mm lens from an old beer bottle :lol:

Actually, I am in need of another piece of surface silvered mirror for a 'red dot' marker I'm working on - this is the answer.

Thanks for that.

Cheers

Neil
EMOs are a sign of weakness ...
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Re: reflection mirror from a old Hardrive disc

Postby Mark K » Fri Jan 13, 2012 4:33 pm

Walt,
Good hack.
If you have a non contact thermometer (IR) could you take the temperature of your gold mirror and your HDD mirror, then run a job and take both temperatures again? It would be interesting to see the difference in efficiency between the two mirrors.
Mark
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Re: reflection mirror from a old Hardrive disc

Postby mattrsch » Fri Jan 13, 2012 4:49 pm

That would be an interesting comparison, but you will need an IR thermometer with adjustable emissivity. The cheaper, non adjustable thermometers are set for about .95, which will cover most of your day to day materials. Polished gold's emissivity is way down in the .02-.03 range. Without the adjustment you will get a reading that is much colder than the gold actually is.
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Re: reflection mirror from a old Hardrive disc

Postby a542002 » Fri Jan 13, 2012 9:29 pm

Hi guys
I dont see any relation between the temperature at all I have engraved more then 25 hours now and there is no difference in performance.
the surface is coated with layers of cobalt and carbon.
I did not see any probleme but what is amazing that cleaning this is much easier as the gold plated mirrors practically indistructable.
greetings
walt
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Re: reflection mirror from a old Hardrive disc

Postby canadianavenger » Fri Jan 13, 2012 9:36 pm

while you may not notice it in your tests of running jobs, measuring the temperature will empirically tell us what losses [if any] happen with the swap. Interesting find nonetheless, I may do something similar on my re-build as interim mirrors.
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Re: reflection mirror from a old Hardrive disc

Postby a542002 » Tue Jan 17, 2012 10:56 am

Hi all
here are the picture from comparisson engraving with the different versions of the mirrors with HD disc mirrors
the engraving was set to 200mm/s 9% power ( 4mA)
the top one is with both mirrors gantry and head as the original goldplated mirrors
the second poic is with the gantry as HD disc mirror and the head original
the third one is with the head as HD disc mirror and the gantry the original
the fourth one is with both as HD disc mirror
there is no noticeable difference and not other probleme or differenc on the machine

greetings
walt
discmirror.JPG
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Re: reflection mirror from a old Hardrive disc

Postby twehr » Tue Jan 17, 2012 2:06 pm

Walt,
Have you tried a comparison doing cutting? Any loss of power will likely show up there. Maybe try the lowest power and fastest speed that will just barely cut a piece of 1/8" craft plywood. Then swap mirrors and try again at the same settings. If power is being lost, you will probably get a few wood fibers hanging on to the back side.

Even at that, if you discovered that you simply need to increase the power by 5% (or some other reasonable figure), it is still a great value. I plan to tear apart a HD and give it a try myself as soon as I get a few pressing tasks out of the way (the day job is killing me!).
tim
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Re: reflection mirror from a old Hardrive disc

Postby a542002 » Tue Jan 17, 2012 8:41 pm

Hi everybody
I just finished a new run making mirror out of old HD
a better way to cut them out is putting masking tape on both sides then clemped between two pices of 3/4 plywood then take the center drillbit out of a hole saw ( metall) clemp the plywood in a drillpress and at the lowest speed cut the mirror out . be carfull not to put to much pressure on the saw
greetings
walt
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Re: reflection mirror from a old Hardrive disc

Postby lasersafe1 » Fri Jan 20, 2012 2:48 pm

I have a power meter for CO2. If you want to send me a sample, for the cost of a stamp I can give you a definitive answer on the value of any loss as compared to a gold coated mirror (up to 35W).
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