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Mike Grudowski
06-27-2017, 1:14 PM
Hello all,

I am new to the forum and to laser cutting. I have a cheap k40 laser and I am wanting to replace the mirrors. I purchased these mirrors off of amazon. https://www.amazon.com/gp/product/B01DP2FNQ0/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1 (https://www.amazon.com/gp/product/B01DP2FNQ0/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1) They worked for a few seconds and then they shattered. I had the laser at about half power. Where these they wrong type of mirrors or where they just cheap. Can anyone direct me to some cost effective mirrors that should work with the k40. Thank you so much in advance for any help that you may be able to provide.

Mark Canada
06-27-2017, 1:23 PM
They should have been fine - did you clean them before installation? Maybe they had some residue on them when shipped or from handling as you installed them?

Mike Grudowski
06-27-2017, 1:32 PM
I cleaned them with rubbing alcohol and a cloth like what you use on your glasses. I did this on the old mirrors with no issues.

Gary Hair
06-27-2017, 1:50 PM
Either the rubbing alcohol or the cloth could have left a film. It's best to use lens cleaning tissues and acetone. I have 10+ year old lenses that I have cleaned this way on a regular basis and they look as good as new.

Bill George
06-27-2017, 1:51 PM
You might try the K40 group on FaceBook I think your the only one using that machine here. This is really not a hobby / build Forum.

Mike Grudowski
06-27-2017, 1:57 PM
Thanks will do

Gary Hair
06-27-2017, 2:13 PM
You might try the K40 group on FaceBook I think your the only one using that machine here. This is really not a hobby / build Forum.

If you chased away all of the hobbyists this place would be a veritable ghost town. I don't think that's the intent of this forum and it's certainly not your call. Not that I want to read about a bunch of K40 problems, but no matter what brand/model machine it goes on, if it's a low powered CO2, the lenses all need the same maintenance.

Mark Canada
06-27-2017, 2:15 PM
Even if there was a film left by a low purity IPA or dirty lens cloth, it shouldnt be bad enough to pop the mirror THAT fast. Considering how smokey i've seen lenses on 100W lasers without popping them.

Might be worth spending a little more on the next set of lenses.. maybe the substrate the gold was deposited on was inferior, or the plating was...

Dave Sheldrake
06-27-2017, 2:41 PM
K9 mirrors are the worst it's possible to buy, they are usually poor quality glass that is PVD'd with gold, Next up is Si mirrors, then Mo if you really want tough one's

Copper and exotics Like Ge are a waste of money on normal home user machines

Kev Williams
06-27-2017, 3:06 PM
I'm curious about: "they" shattered-- it would be a trick to have all 3 mirrors break at or near the same time. Rapid heating and cooling I guess would do it...

John Lifer
06-27-2017, 4:22 PM
Kev, kind of curious also. I mean, shattered? Granted they were only $8 each...... In too tight? Backwards? or did he clean the gold plating off of them :)

Mike Grudowski
06-27-2017, 5:13 PM
I'm curious about: "they" shattered-- it would be a trick to have all 3 mirrors break at or near the same time. Rapid heating and cooling I guess would do it...


Here is a picture of one.

362822

Mark Canada
06-27-2017, 5:37 PM
Wow, it looks like the gold was blown right off the centre and then the glass was heated rapidly by the whole beam. It looks like there is a very clear centre with no gold?

I wonder if the gold deposition was too thin, allowing the beam to directly heat the glass, but enough beam still reflected to do the same to the other mirrors. Crazy.

Dave Sheldrake
06-27-2017, 8:08 PM
badly adhered PVD plating, not uncommon with K9's

Matt McCoy
06-27-2017, 8:12 PM
If they all shattered, did the mirrors break in reverse order (e.g., mirror 3, mirror 2, then mirror 1)?

John Lifer
06-27-2017, 8:16 PM
Wow, guess I'd better by the $11.39 ones:D

Clark Pace
06-27-2017, 8:21 PM
You might try the K40 group on FaceBook I think your the only one using that machine here. This is really not a hobby / build Forum.

Be nice! I think we can be helpful! Don't be laser snobby!

Bill George
06-27-2017, 8:23 PM
If you chased away all of the hobbyists this place would be a veritable ghost town. I don't think that's the intent of this forum and it's certainly not your call. Not that I want to read about a bunch of K40 problems, but no matter what brand/model machine it goes on, if it's a low powered CO2, the lenses all need the same maintenance.

And so would he better off asking on a dedicated Forum for the K40 or here Gary?

In fact you advocated for separate Forum for Chinese machines back over on the never ending Glow Forge discussion.
it's just a statement of fact, and why I would advocate for a separate forum for Chinese lasers as a way to better serve each group.

Gary Hair
06-28-2017, 10:31 AM
And so would he better off asking on a dedicated Forum for the K40 or here Gary?

In fact you advocated for separate Forum for Chinese machines back over on the never ending Glow Forge discussion.
it's just a statement of fact, and why I would advocate for a separate forum for Chinese lasers as a way to better serve each group.

When he asked about a mirror there was no need to tell him to go away and seek advice from a K40 forum. I do, however, advocate for separate forums for machine specific issues.

Clark Pace
06-28-2017, 11:15 PM
And so would he better off asking on a dedicated Forum for the K40 or here Gary?

In fact you advocated for separate Forum for Chinese machines back over on the never ending Glow Forge discussion.
it's just a statement of fact, and why I would advocate for a separate forum for Chinese lasers as a way to better serve each group.


It's not what was said. It was how it was said. If it were me I would have said.

"Perhaps we can help, but there is a forum that deals specifically with the k40 machines. You can try there also."

And then provide a link if you had it.

Bill George
06-29-2017, 4:27 PM
Hello all,

I am new to the forum and to laser cutting. I have a cheap k40 laser and I am wanting to replace the mirrors. I purchased these mirrors off of amazon. https://www.amazon.com/gp/product/B01DP2FNQ0/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1 (https://www.amazon.com/gp/product/B01DP2FNQ0/ref=oh_aui_detailpage_o01_s01?ie=UTF8&psc=1) They worked for a few seconds and then they shattered. I had the laser at about half power. Where these they wrong type of mirrors or where they just cheap. Can anyone direct me to some cost effective mirrors that should work with the k40. Thank you so much in advance for any help that you may be able to provide.
Since you purchased on Amazon did you try to contact either them or the vender? Perhaps you got a bad set and I have had good luck with Amazon getting things right. It does say for K40 machines so there is no good reason why they won't work. BTW there is over 800 users on the FaceBook K40 group I found and there might be other groups (yes the other has over 2,000 members!) perhaps they would have suggestions, that you won't find here? I just joined the last one and there are some very good posts. It is the Chinese K40 Laser Group.

Bert McMahan
06-29-2017, 4:52 PM
Sorry if this is a silly question, but are you sure you installed them the right way around? The shiny side should be directly towards the beam (not like a normal mirror where the shiny part is *under* the glass).

Bill George
06-29-2017, 6:40 PM
Sorry if this is a silly question, but are you sure you installed them the right way around? The shiny side should be directly towards the beam (not like a normal mirror where the shiny part is *under* the glass).

Interesting thought Bert, wonder why nobody else suggested and since I have never replaced a mirror I just learned something.

Kev Williams
06-30-2017, 2:57 AM
I just checked my Triumph spare mirrors, the back side is a dull silver-gray. The GCC spare mirrors have near black backs. The mirror that used to be above the lens in my LS900 is virtually identical to look at on both sides! I turned it around once, figuring it was 2-sided on purpose to save me from buying a spare! Bonus!

Nope- ... at full power it would barely mark Rowmark.

This reminds me of when I made a mirror out of a hard drive platter. Took my LS900 about 5 minutes to burn a hole thru it!
check out the beam spot in the mirror :)
362932

This is one way to tell if your beam is in alignment :D
362933

found out I made it from the wrong type of drive platter, oops... But I'm still trying to figure out how I was able to cut out this mirror in the first place, since it's GLASS!